Apparatus and method for mounting electronic components

After detection of contact between respective solder bumps of an electronic component, sucked and held by a suction nozzle of a head tool, and respective solder portions of a circuit board, the solder bumps and the solder portions are melted by heating. Releasing of the electronic component from suction and holding by the suction nozzle of the head tool is performed, not at a time during solder melting, but at a time after the solder is melted, cooled and solidified. Thus, an electronic component mounting method and apparatus capable of mounting high-end electronic components having narrow-pitched bumps are provided.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for mounting electronic components onto a circuit board. More particularly, the invention relates to an electronic component mounting method and apparatus that makes it possible to mount such electronic components as IC chips having narrow pitched bumps onto a circuit board by performing a flip chip bonding method.

As electronic component mounting methods of this type, there have conventionally been known various methods. As an example of a conventional electronic component mounting method corresponding to the flip chip bonding method, is a method including steps of temporarily bonding a plurality of electronic components onto a circuit board and thereafter subjecting the electronic components collectively to reflow soldering, thus achieving electronic component mounting, (hereinafter, described as a collective reflow mounting method) as shownFIGS. 22A-22D.

As shown inFIG. 22A, solder paste is fed by printing or the like onto pads84a, which are a plurality of electrodes on a top surface of a plate-like circuit board84, so that solder portions82are formed on the pads84aof the circuit board84, respectively.

Next, inFIG. 22B, an electronic component81, to which solder bumps81bare bonded at a plurality of electrodes81aprovided on a bonding surface of the electronic component81, is sucked and held at its rear surface, which has no electrodes81athereon, by a tool83. After a positional alignment that makes the solder bumps81bof the electronic component81bondable with the solder portions82on the circuit board84, respectively, the solder bumps81bof the electronic component81are pressed against the solder portions82of the circuit board84, respectively, thereby achieving their temporary bonding. For mounting of a plurality of electronic components81onto the circuit board84, these working steps are iteratively performed so that respective electronic components81are mounted onto the circuit board84. It is noted here that the terms, “temporary bonding,” refer to a bonding process such that the electronic component81and the circuit board84are releasable from their bonding by applying external force to the electronic component81or the circuit board84without breaking the electronic component81or the circuit board84.

Thereafter, the circuit board84, to which the electronic components81have been temporarily bonded, is conveyed to a reflow soldering working section. As shown inFIG. 22C, the electronic components81and the circuit board84are heated by a heat source in the reflow soldering working section, by which the solder portions82and the solder bumps81bare melted. In a case where a plurality of electronic components81are temporarily bonded to the circuit board84, those electronic components81are collectively subjected to heat so as to melt the solder in this reflow soldering working section.

Thereafter, as shown inFIG. 22D, with the circuit board84removed from the reflow soldering working section, molten solder is cooled and solidified, thereby achieving primary bonding of the electrodes81aof each electronic component81to the pads84aof the circuit board84, respectively, via the solder, by which the electronic components81are collectively mounted onto the circuit board84. It is noted here that the terms, “primary bonding,” refer to a bonding process that is performed by melting the solder with heat applied to the temporarily bonded electronic component81and circuit board84, and by thereafter solidifying the solder, and this makes it hard to release a resulting bonded state by applying external force to the electronic component81or the circuit board84.

In such a collective reflow mounting method, a multiplicity of electronic components81, after their temporary bonding, can be subjected to collective melting of solder, by which the electronic components81can be finally bonded and thereby mounted to the circuit board84. This allows for electronic-component mounting operations to be efficiently achieved. As a result, it has been a case in that costs of mounting the electronic components81onto the circuit board84can be reduced.

However, for such a method, which includes steps for temporarily bonding of the electronic components81to the circuit board84, and thereafter performing their primary bonding by melting the solder, there is a need for conveying the circuit board84, to which the electronic components81have been temporarily bonded, to the reflow soldering working section. During this conveyance, a bonding position of each electronic component81relative to the circuit board84might be shifted due to vibrations or the like caused by the conveyance, in which case reflowing of the solder in such a shifted state might result in defective bonding of the electronic components81to the circuit board84. Such shifts of the bonding positions as would occur in the collective reflow mounting method would not matter for electronic components to which high precision for their bonding positions is not required, such as general-purpose electronic components. However, for some electronic components, such as IC chips, to which particularly high precision for their bonding positions is required, this would matter.

As an example of a conventional electronic component mounting method corresponding to a flip chip bonding method intended to solve such issues of the collective reflow mounting method as described above, a method including the step of simultaneously heating and pressing electronic components onto a circuit board to thereby subject the electronic components individually to reflow soldering, thus achieving electronic component mounting, (hereinafter, described as a conventional local reflow mounting method) is shownFIGS. 23A-23D.

As shown inFIG. 23A, solder paste is fed by printing or the like onto pads94a, which are a plurality of electrodes on a top surface of a plate-like circuit board94, so that solder portions92are formed on the pads94aof the circuit board94, respectively.

Next, as shown inFIG. 23B, an electronic component91to which solder bumps91bare bonded at a plurality of electrodes91aprovided on a bonding surface of the electronic component91, is sucked and held at its rear surface, which has no electrodes91athereon, by a tool93. After performing a positional alignment that makes the solder bumps91bof the electronic component91bondable with the solder portions92on the circuit board94, respectively, the solder bumps91bof the electronic component91are, while heated, pressed against the solder portions92of the circuit board94, respectively, by which the solder portions92and the solder bumps911bare melted.

Next, as shown inFIG. 23C, while solder is maintained in a molten state, suction and holding of the electronic component91by the tool93is released. As a result of this, a self alignment effect by surface tension of the molten solder is obtained.

Thereafter, as shown inFIG. 23D, by solidifying the molten solder, the electrodes91aof the electronic component91are bonded to the pads94aof the circuit board94, respectively, via the solder, by which the electronic component91is individually mounted onto the circuit board94. In addition, for mounting of a plurality of electronic components91onto the circuit board94, these working steps are iteratively performed so that respective electronic components91are mounted onto the circuit board94, individually.

In such a local reflow mounting method, the electronic component91is sucked and held by the tool93, the solder bumps91bof the electronic component91are pressed against the solder portions92of the circuit board94while the solder bumps91band the solder portions92are heated, respectively, by the tool93, and thereafter suction and holding of the electronic component91by the tool93is released while the solder is in the molten state. As a result, a self alignment effect by the surface tension of the molten solder is obtained. Thus, even with more or less poor precision of a bonding position of the electronic component91by the tool93, a precision of a bonding position that would not result in defective bonding eventually could be obtained by the self alignment effect.

However, in a case of high-end electronic components of narrowed bump pitches, from among such electronic components as IC chips, with their bump pitch being as narrow as, for example, not more than 150 μm, it is required for electronic components having bumps of such narrow pitches to meet a high precision for a bonding position of, for example, ±5 μm, which would concern a bonding-position shift amount of an electronic component due to a vacuum break blow occurring at releasing of the suction and holding of the electronic component during solder melting, more than the self alignment effect would be concerned in the local reflow mounting method. Therefore, the above-described electronic component mounting performed by the local reflow mounting method, in which suction and holding of an electronic component by the tool is released during a solder's molten state, has had an issue of incapability of mounting high-end electronic components which have bumps of such narrow pitches as shown above and to which high precision for a bonding position is required.

Accordingly, an object of the present invention is to solve the above-described issues and provide an electronic-component mounting method and apparatus which are capable of mounting high-end electronic components having narrow-pitch bumps, and moreover, which are intended for mounting of electronic components onto a circuit board on which general-purpose electronic components and high-end electronic components are to be mixedly mounted. The method and apparatus allow both productivity and quality to be satisfied by changing a method to be used for individual electronic components depending on precision of a bonding position required for individual electronic components.

SUMMARY OF THE INVENTION

In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a method for mounting an electronic component, comprising, while a plurality of electrodes of an electronic component held by a component holding member and a plurality of electrodes of a circuit board are in contact with bonding members interposed therebetween: heating and thereby melting the bonding members; cooling and thereby solidifying the bonding members; and thereafter releasing the electronic component from suction and holding by the component holding member.

According to a second aspect of the present invention, there is provided a method for mounting an electronic component, comprising:

sucking and holding an electronic component, having a plurality of electrodes, by a component holding member;

performing positional alignment so that the electrodes of the electronic component and a plurality of electrodes of a circuit board become bondable with each other;

moving down the component holding member with the electronic component sucked and held thereon;

while the electrodes of the electronic component and the electrodes of the circuit board are kept in contact with bonding members, respectively, interposed therebetween, heating and thereby melting the bonding members, and cooling and thereby solidifying the bonding members; and

thereafter releasing the electronic component from suction and holding by the component holding member.

According to a third aspect of the present invention, there is provided the method for mounting an electronic component according to the second aspect, wherein the bonding members are preliminarily fed at least either onto respective electrodes of the electronic component or onto respective electrodes of the circuit board.

According to a fourth aspect of the present invention, there is provided the method for mounting an electronic component according to the second aspect, wherein the bonding members are solder.

According to a fifth aspect of the present invention, there is provided the method for mounting an electronic component according to the second aspect, wherein flux is preliminarily fed onto respective electrodes of the electronic component, or onto respective electrodes of the circuit board, or onto the bonding members.

According to a sixth aspect of the present invention, there is provided the method for mounting an electronic component according to the second aspect, wherein the bonding members are solder bumps formed on respective electrodes of the electronic component, or solder bumps formed on the respective electrodes of the electronic component and solder portions formed on respective electrodes of the circuit board.

According to a seventh aspect of the present invention, there is provided a method for mounting an electronic component, comprising:

sucking and holding an electronic component, having a plurality of electrodes, by a component holding member;

performing positional alignment so that the electrodes of the electronic component and a plurality of electrodes of a circuit board become bondable with each other via bonding members interposed therebetween;

moving down the component holding member with the electronic component sucked and held thereon;

detecting contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween;

after detection of this contact, heating and thereby melting the bonding members; and

cooling and thereby solidifying the bonding members.

According to an eighth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein the detection of the contact is fulfilled by detecting that a load, which is actually generated upon contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding member interposed therebetween, exceeds a contact load which is expected to be generated upon the contact.

According to a ninth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein under such control of the component holding member that the component holding member is moved down in very small steps, in response to a load actually generated upon contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween, the detection of contact is fulfilled by detecting that the load actually generated upon the contact exceeds a contact load which is expected to be generated upon the contact.

According to a tenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising releasing suction and holding of the electronic component by the component holding member after solidification of the bonding members.

According to a eleventh aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein the bonding members are preliminarily fed at least either onto respective electrodes of the electronic component or onto respective electrodes of the circuit board.

According to a twelfth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein the bonding members are solder.

According to a thirteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein flux is preliminarily fed onto respective electrodes of the electronic component, or onto respective electrodes of the circuit board, or onto the bonding members.

According to a fourteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, wherein the bonding members are solder bumps formed on respective electrodes of the electronic component, or solder bumps formed on the respective electrodes of the electronic component and solder portions formed on respective electrodes of the circuit board.

According to a fifteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising:

detecting contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members interposed therebetween;

deciding whether or not an elongation-amount correction of the component holding member by heating is performed;

if the elongation-amount correction of the component holding member is performed, then melting individual bonding members between the electrodes of the electronic component and the electrodes of the circuit board by this heating, while causing the component holding member to be moved up, based on data concerning elongation-amount variations of the component holding member by the heating; and if the elongation-amount correction of the component holding member is not performed, then melting the bonding members between the electrodes of the electronic component and the electrodes of the circuit board by heating;

after a start of cooling of molten bonding members, deciding whether or not a shrinkage-amount correction of the component holding member by the cooling is performed; and

if the shrinkage-amount correction of the component holding member is performed, then solidifying individual bonding members between the electrodes of the electronic component and the electrodes of the circuit board by the cooling, while causing the component holding member to be moved down, based on data concerning shrinkage-amount variations of the component holding member by the cooling; and if the shrinkage-amount correction of the component holding member is not performed, then solidifying the bonding members between the electrodes of the electronic component and the electrodes of the circuit board by cooling.

According to a sixteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising:

detecting contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members interposed therebetween; and

melting individual bonding members between the electrodes of the electronic component and the electrodes of the circuit board by heating, while causing the component holding member to be moved down, based on data concerning elongation-amount variations of the component holding member by the heating.

According to a seventeenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising:

after a start of cooling of molten bonding members,

solidifying individual bonding members between the electrodes of the electronic component and the electrodes of the circuit board by the cooling, while causing the component holding member to be moved down, based on data concerning shrinkage-amount variations of the component holding member by the cooling.

According to an eighteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising:

after detection of contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members interposed therebetween,

maintaining a load, which is actually generated between the electrodes by this contact, at a generally constant level; and

after a start of melting of the bonding members by heating, releasing maintaining of the actually generated load and maintaining a contact height position of the electronic components relative to the circuit board at a generally constant position.

According to a nineteenth aspect of the present invention, there is provided the method for mounting an electronic component according to the eighteenth aspect, wherein the start of the melting of the bonding members is a time when a decrease of the load generated between the electrodes by the contact is detected.

According to a twentieth aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, further comprising:

after sucking and holding of the electronic component by the component holding member,

making the bonding members preliminarily fed onto respective electrodes of the electronic component uniform in feed height, and

performing positional alignment between the electronic component and the circuit board so that the electrodes of the electronic component and the electrodes of the circuit board become bondable with each other.

According to a twenty-first aspect of the present invention, there is provided the method for mounting an electronic component according to the seventh aspect, for use in a case where two types of electronic components, a first electronic component and a second electronic component, are mounted onto the circuit board, wherein the second electronic component is required to be mounted to the circuit board with a higher bonding position precision than that required for the first electronic component, the method further comprising:

sucking and holding the first electronic component by a component holding member;

performing a positional alignment so that a plurality of electrodes of the first electronic component and a plurality of electrodes of the circuit board become bondable with each other via bonding members interposed therebetween;

moving down the component holding member with the first electronic component sucked and held thereon, and pressing respective electrodes of the first electronic component and respective electrodes of the circuit board, with the bonding members interposed therebetween, to fulfill temporary bonding;

heating and thereby melting the bonding members between temporarily bonded respective electrodes of the first electronic component and respective electrodes of the circuit board, cooling and thereby solidifying the bonding members to fulfill final bonding, and mounting the respective electrodes of the first electronic component to the respective electrodes of the circuit board via the bonding members interposed therebetween; and

thereafter mounting the second electronic component onto the circuit board which has a plurality of electrodes bondable with electrodes of the second electronic component, respectively, and on which the first electronic component has been mounted.

According to a twenty-second aspect of the present invention, there is provided an apparatus for mounting an electronic component by sucking and holding an electronic component by a component holding member and bonding a plurality of electrodes of the electronic component and a plurality of electrodes of a circuit board to each other via bonding members interposed therebetween, the apparatus comprising:

a suction-and-holding mechanism for sucking and holding the electronic component onto the component holding member;

an up-and-down moving mechanism for moving up or down the component holding member;

a frame section for placing the circuit board thereon;

a heating mechanism for heating the bonding members;

a cooling mechanism for cooling the bonding members; and

a control part which is capable of controlling the suction-and-holding mechanism, the up-and-down moving mechanism, the heating mechanism and the cooling mechanism, and which performs: while controlling the up-and-down moving mechanism so that the electronic component sucked and held by the component holding member is kept in contact with the circuit board, controlling the heating mechanism for heating and thereby melting the bonding members; thereafter controlling the cooling mechanism for cooling and thereby solidifying the bonding members; and, after solidification of the bonding members, controlling the suction-and-holding mechanism for releasing the suction and holding of the electronic component.

According to a twenty-third aspect of the present invention, there is provided an apparatus for mounting an electronic component by sucking and holding an electronic component by a component holding member, and, while keeping a plurality of electrodes of the electronic component and a plurality of electrodes of a circuit board in contact with bonding members interposed therebetween, heating and thereby melting the bonding members, thus bonding the electrodes of the electronic component onto the electrodes of the circuit board, respectively, via the bonding members interposed therebetween, the apparatus comprising:

a suction-and-holding mechanism for sucking and holding the electronic component onto the component holding member;

an up-and-down moving mechanism for moving up or down the component holding member;

a frame section for placing the circuit board thereon;

a heating mechanism for heating the bonding members;

a cooling mechanism for cooling the bonding members; and

a control part which is capable of controlling the suction-and-holding mechanism, the up-and-down moving mechanism, the heating mechanism and the cooling mechanism, and which performs: controlling the heating mechanism for heating and thereby melting the bonding members, and thereafter controlling the cooling mechanism for cooling and thereby solidifying the bonding members, and moreover; controlling the suction-and-holding mechanism for sucking and holding the electronic component by the component holding member even during melting of the bonding members by the heating mechanism; and after cooling and solidification of the bonding members by the cooling mechanism under control of the control part, causing the electronic component to be released from the suction and holding of the suction-and-holding mechanism.

According to a twenty-fourth aspect of the present invention, there is provided an apparatus for mounting an electronic component by sucking and holding an electronic component by a component holding member, putting a plurality of electrodes of the electronic component and a plurality of electrodes of a circuit board into contact with bonding members interposed therebetween, and heating and thereby melting the bonding members, thus bonding the electrodes of the electronic component and the electrodes of the circuit board with each other, respectively, via the bonding members interposed therebetween, the apparatus comprising:

a suction-and-holding mechanism for sucking and holding the electronic component onto the component holding member;

an up-and-down moving mechanism for moving up or down the component holding member;

a load detecting section for detecting a contact load generated between the electrodes of the electronic component and the electrodes of the circuit board upon contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween, with the contact resulting from moving down, by virtue of the up-and-down moving mechanism, the component holding member that is sucking and holding the electronic component by the suction-and-holding mechanism;

a heating mechanism for heating the bonding members;

a cooling mechanism for cooling the bonding members heated by the heating mechanism; and

a control part which is capable of controlling the suction-and-holding mechanism, the up-and-down moving mechanism, the load detecting section, the heating mechanism and the cooling mechanism, and which performs: after detection of a contact load by the load detecting section, causing the bonding members to be melted by heating performed by the heating mechanism; and thereafter causing the bonding members to be cooled and solidified by the cooling mechanism, and moreover which is capable of controlling up-and-down movement operations of the component holding member by the up-and-down moving mechanism in response to the contact load detected by the load detecting section during a period from the contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members interposed therebetween until the melting of the bonding members.

According to a twenty-fifth aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-fourth aspect, wherein the detection of a contact load is fulfilled by the control part by detecting that a load which is actually generated upon the contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween, and which is detected by the load detecting section, exceeds a contact load which is expected to be generated upon the contact.

According to a twenty-sixth aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-fourth aspect, wherein the detection of the contact load is fulfilled by the control part by detecting that a load generated as a result of moving down the component holding member in very small steps by the up-and-down moving mechanism in response to a load actually generated upon the contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween, and which is detected by the load detecting section, exceeds a contact load which is expected to be generated upon the contact.

According to a twenty-seventh aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-fourth aspect, wherein the control part performs: maintaining the suction and holding of the electronic component to the component holding member by the suction-and-holding mechanism even during the melting of the bonding members by the heating mechanism; and after the solidification by the cooling of the bonding members by the cooling mechanism, under control of the control part, releasing the electronic component from the suction and holding to the component holding member by the suction-and-holding mechanism.

According to a twenty-eighth aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-fourth aspect, wherein during a period from when the electrodes of the electronic component and the electrodes of the circuit board are aligned with each other, with the bonding members interposed therebetween, until the component holding member sucking and holding the electronic component is moved down,

the control part sets a load detected by the load detecting section to a load-zero point in the load detecting section.

According to a twenty-ninth aspect of the present invention, there is provided an apparatus for mounting an electronic component by sucking and holding an electronic component by a component holding member, putting a plurality of electrodes of the electronic component and a plurality of electrodes of a circuit board into contact with bonding members interposed therebetween, and heating and thereby melting the bonding members, thus bonding the electrodes of the electronic component and the electrodes of the circuit board with each other, respectively, via the bonding members interposed therebetween, the apparatus comprising:

a suction-and-holding mechanism for sucking and holding the electronic component onto the component holding member;

an up-and-down moving mechanism for moving up or down the component holding member;

a load detecting section for detecting a contact load generated between the electrodes of the electronic component and the electrodes of the circuit board upon contact between either the electrodes of the electronic component or the electrodes of the circuit board and the bonding members respectively interposed therebetween, with the contact resulting from moving down, by the up-and-down moving mechanism, the component holding member that is sucking and holding the electronic component by the suction-and-holding mechanism;

a heating mechanism for heating the bonding members; and

a cooling mechanism for cooling the bonding members heated by the heating mechanism, wherein

the component holding member comprises a component-holding-member tip portion and a component-holding-member body portion,

the component-holding-member tip portion comprises the suction-and-holding mechanism, the heating mechanism, the cooling mechanism and a shaft portion,

the component-holding-member body portion comprises a support portion for supporting the component-holding-member tip portion, and the load detecting section fitted to the support portion,

centers of the suction-and-holding mechanism, the heating mechanism, the shaft portion and the load detecting section are placed coaxially on an identical axis, and their identical axis is placed parallel to an axis of up-and-down operations of the component holding member caused by the up-and-down moving mechanism, and

the load detecting section is capable of detecting a load of the component-holding-member tip portion acting toward the shaft portion by an arrangement such that an end portion of the shaft portion in the component-holding-member tip portion is pressed against a load-detecting surface of the load detecting section by an elastic member fitted to the support portion and supporting the shaft portion.

According to a thirtieth aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-ninth aspect, wherein the component holding member further includes a pressing mechanism for pressing the electronic component against the circuit board,

the pressing mechanism has two pneumatic cylinders different in inner diameter from each other,

out of the two pneumatic cylinders, one pneumatic cylinder is provided in the component-holding-member body portion and the other cylinder is provided in the component-holding-member tip portion, and wherein

the component holding member is so constituted as to have a pressing function for pressing the electrodes of the electronic component sucked and held by the suction-and-holding mechanism and the electrodes of the circuit board against the bonding members interposed therebetween, by selecting and actuating one pneumatic cylinder of an inner diameter suited to a contact load, from among the two pneumatic cylinders, to move down the component-holding-member tip portion on the identical axis,

at least one pneumatic cylinder, out of the two pneumatic cylinders, includes a restricting mechanism for mechanically restricting operations of the at least one pneumatic cylinder, and

the restricting mechanism restricts operations of the at least pneumatic cylinder in a state that the at least one pneumatic cylinder presses the other pneumatic cylinder, thereby restricting operations of the pneumatic cylinders so that the pressing function of the component holding member is restricted.

According to a thirty-first aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the thirtieth aspect, wherein the restricting mechanism provided in the at least one pneumatic cylinder includes a cylindrical guide and a columnar rod disposed inside the guide, is provided with a groove-like recessed portion formed on an outer circumference of a columnar side face of the rod, a hole formed on the cylindrical side face of the guide at a position that can be coincident with the recessed portion of the rod, and a bar member which extends through the hole of the guide and which is fittable inside the recessed portion of the rod, and wherein

the restricting mechanism exerts an operational restriction on the at least one pneumatic cylinder by making the bar member extend from outside of the guide through the hole of the guide and further into the recessed portion of the rod.

According to a thirty-second aspect of the present invention, there is provided the apparatus for mounting an electronic component according to the twenty-fourth aspect, wherein out of the two pneumatic cylinders different in inner diameter from each other in the pressing mechanism, a large cylinder having a larger inner diameter is provided in the component-holding-member body portion, and a small cylinder having a smaller inner diameter is provided in the component-holding-member tip portion, and wherein

centers of the large cylinder and the small cylinder are placed coaxially on an identical axis,

the large cylinder includes the restricting mechanism,

in the component-holding-member body portion, the guide of the large cylinder is fitted to an end portion of the support portion and the rod of the large cylinder is fitted to the load detecting section, and

in the component-holding-member tip portion, the guide of the small cylinder is fitted to the end portion of the shaft portion and the rod of the small cylinder is set so as to be contactable with the load-detecting surface of the load detecting section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, embodiments of the present invention are described in detail with reference to the accompanying drawings.

First Embodiment

An electronic component mounting method and apparatus according to the present invention relate to an electronic component mounting method and apparatus including steps of placing a plurality of electrodes of an electronic component and a plurality of electrodes of a circuit board into a state of contact with bonding members interposed therebetween, and causing the bonding members to be individually melted and solidified so that the electronic component is bonded to the circuit board via the bonding members therebetween. An electronic component mounting method and apparatus according to the first embodiment of the invention is described in detail with reference to the accompanying drawings.

As shown inFIG. 1, referring to an electronic component mounting apparatus201, a head tool3, which is an example of a component holding member for performing electronic component mounting, is fixed to a nut portion of an X-direction moving mechanism22. The X-direction moving mechanism22rotates a ball screw shaft by a motor so that the head tool3fixed to the nut portion, screwed to the ball screw shaft, is moved in an X1direction rightward of an X direction shown in the figure or an X2direction leftward thereof. Also, as shown inFIG. 3, which is a schematic sectional view of the head tool3, the electronic component mounting apparatus201includes an up/down moving unit21, which is an example of an up/down moving mechanism, for moving down or up the head tool3. The head tool3further comprises: a suction nozzle11, which is an example of a suction-and-holding mechanism, for sucking and holding an electronic component at its tip portion; a ceramic heater12, which is an example of a heating mechanism, for heating the suction nozzle11to thereby heat the electronic component sucked and held by the suction nozzle11; and a cooling blow nozzle19, which is an example of a cooling mechanism, for cooling the electronic component heated by the ceramic heater12. In this case, although the heating mechanism is given here by the ceramic heater12provided on the head tool3as an example, another case may be one in which the electronic component mounting apparatus includes, instead of the ceramic heater12, a heating part provided on a frame section on which a circuit board is to be placed, or a heating part that performs heating by blowing hot air against an electronic component and the circuit board. It is noted that structure of the head tool3will be described in detail later.

Referring toFIG. 1, a slide base6is fixed to a nut portion of a Y-direction moving mechanism23. The Y-direction moving mechanism23rotates a ball screw shaft by a motor so that the slide base6fixed to the nut portion, screwed to the ball screw shaft, is moved in a Y1direction rightward of a Y direction shown in the figure or a Y2direction leftward thereof. A plurality of electronic components1are fed to a component tray5fixed on the slide base6, and a circuit board4is positioned and fixed to a stage7, which is an example of a frame section fixed on the slide base6. In addition, the X direction and the Y direction inFIG. 1are perpendicular to each other.

The electronic component mounting apparatus201further includes a control part9which is a control part for performing control of individual constituent parts in the electronic component mounting apparatus201. Moving operation of the up/down moving unit21, moving operation of the X-direction moving mechanism22, moving operation of the Y-direction moving mechanism23, sucking and holding operation of the suction nozzle11of the head tool3, and heating operation of the ceramic heater12of the head tool3are controlled by the control part9.

FIGS. 2A-2Fare schematic sectional views of the electronic component1and the circuit board4, schematically showing the electronic component mounting method according to the first embodiment. As shown inFIG. 2B, rectangular-plate like shaped electronic component1has a multiplicity of electrodes1aon a bonding surface of the electronic component1, and solder bumps1b, which are bonding members, have preliminarily been formed on the electrodes1a, respectively. Also, as shown inFIG. 2A, rectangular-plate like shaped circuit board4has pads4a, which are a multiplicity of electrodes, on a top surface of the circuit board, and solder, which corresponds to bonding members, has preliminarily been fed by printing or the like so that solder portions2are formed on the pads4a, respectively. The pads4aof the circuit board4are placed at positions corresponding to the electrodes1aof the electronic component1, respectively, so that the electrodes1aof the electronic component1and the pads4aof the circuit board4can be bonded together. In this case, the electronic component1is, for example, a high-end electronic component to which high precision of a bonding position is required, such as a high-end IC chip having a 150 μm or less bump pitch, which is an interval pitch of the solder bumps1bformed on the electrodes1aof the electronic component. In addition, the circuit board4may be any one of such circuit boards as resin boards, paper-phenol boards, ceramic boards, glass epoxy boards and film boards, or such circuit blocks as single layer boards or multilayer boards, or such object articles having circuits formed thereon as component parts, casings or frames.

Next, the method for mounting the electronic component1onto the circuit board4by using the electronic component mounting apparatus201is explained.

First, referring toFIG. 1, the slide base6, to which is fixed the component tray5with a multiplicity of electronic components1fed thereto and placed thereon, is moved in the Y1or Y2direction by the Y-direction moving mechanism23, and moreover the head tool3is moved in the X1or X2direction by the X-direction moving mechanism22, by which the head tool3is aligned with one electronic component1placed in the component tray5so that this electronic component1becomes suckable by the suction nozzle11provided at the tip portion of the head tool3. Thereafter, the head tool3is moved down by the up/down moving unit21, thereby sucking and holding the electronic component1at its rear surface, that has no electrodes1a, by the suction nozzle11of the head tool3. Then, the head tool3is moved up by the up/down moving unit21, and the electronic component1is removed from the component tray5. It is noted that although the electronic component1is placed with its rear surface up in the component tray5in the above-described case, a case may be that the electronic component1is placed with its rear surface down, in which case also, suction and holding of the electronic component1at its rear surface by the suction nozzle11is enabled by providing an inversion mechanism for inverting the electronic component1before the suction and holding of the electronic component1to the suction nozzle11of the head tool3. In addition, a case may also be that with a wafer feed section provided, the electronic components1are fed from wafers instead of a feed of the electronic components1from the component tray5.

Next, referring toFIG. 1, the slide base6, to which is fixed the stage7with the circuit board4fixed thereon, is moved in the Y1or Y2direction by the Y-direction moving mechanism23, and moreover the head tool3with the electronic component1sucked and held thereto is moved in the X1or X2direction by the X-direction moving mechanism22, by which the electronic component1and the circuit board4are aligned with each other, as shown inFIG. 2B, so that the solder bumps1bformed on the electrodes1aof the electronic component1become bondable to the solder portions2on the pads4aof the circuit board4, respectively.

Thereafter, as shown inFIG. 2C, the head tool3is moved down by the up/down moving unit21, by which the solder bumps1bof the electronic component1sucked and held by the suction nozzle11are put into contact with the solder portions2, respectively, of the circuit board4fixed to the stage7.

After this contact, as shown inFIG. 2D, the suction nozzle11is heated by the ceramic heater12of the head tool3so that the solder bumps1bof the electronic component1sucked and held by the suction nozzle11, as well as the solder portions2of the circuit board4kept in contact with these solder bumps, are heated. Further, a heating temperature for the suction nozzle11by the ceramic heater12is increased to a temperature not less than a melting point of solder forming the solder bumps1band not less than a melting point of solder forming the solder portions2, and thus the solder bumps1band the solder portions2are melted. As to an atmosphere for such melting process, whereas the melting process is performed in air of an environment under which the electronic component mounting apparatus201is installed (e.g., clear air), a case may alternatively be that the atmosphere is an inert gas atmosphere (e.g., N2 atmosphere) to obtain a successful molten state.

Thereafter, as shown inFIG. 2E, with the heating by the ceramic heater12stopped, molten solder is subjected to cooling by blows from the cooling blow nozzle19, with the solder being thereby solidified so that the electrodes1aof the electronic component1and the pads4aof the circuit board4are bonded together, respectively, via the solder. Alternatively, the solder may also be solidified by natural cooling of the molten solder, instead of the forced cooling of the molten solder by the cooling blow nozzle19.

Thereafter, as shown inFIG. 2F, the sucking and holding of the electronic component1by the suction nozzle11at the tip portion of the head tool3is released, and the head tool3is moved up by the up/down moving unit21. In addition, for mounting of a plurality of electronic components1onto the circuit board4, these working steps are iteratively performed for each electronic component1so that respective electronic components1are mounted onto the circuit board4.

Although the above description has been made for a case where the bonding members are the solder bumps1bpreliminarily formed on the electrodes1aof the electronic component1as well as the solder portions2preliminarily formed on the pads4aof the circuit board4, the bonding members may also be only the solder bumps1bpreliminarily formed on the electrodes1aof the electronic component1.

Furthermore, flux that can remove surface oxide films at individual bonding portions and enhance wettability of molten solder may preliminarily be supplied by coating the flux onto the electrodes1aof the electronic component1or onto the pads4aof the circuit board4, or onto the solder bumps1bor the solder portions2, which are both the bonding members. In addition, depending on a type of flux supplied by coating, there are some cases where the flux supplied by coating is removed by cleaning after mounting of the electronic component1onto the circuit board4.

Next, the structure of the head tool3in the electronic component mounting apparatus201is explained in detail with reference toFIG. 3, which is a sectional view schematically showing the structure of the head tool3.

Referring toFIG. 3, the head tool3includes a head-tool tip portion3afor performing sucking and holding, and heating or other operations on the electronic component1, and a head-tool body portion3bfor supporting the head-tool tip portion3aand exercising up-and-down operations on the head tool3.

The head-tool tip portion3aincludes, as viewed from its tip side, the suction nozzle11capable of sucking and holding the electronic component1, the ceramic heater12for heating the electronic component1sucked and held by the suction nozzle11, a water jacket13which is a cooling part for intercepting heat so that heat derived from the ceramic heater12is not transferred to the head-tool body portion3b, and a shaft17which is an example of a shaft portion fitted to an upper portion of the water jacket13. The cooling blow nozzle19for cooling by blowing the electronic component1heated by the ceramic heater12is further fitted around a periphery of a lower-portion of the shaft17.

The head-tool body portion3bincludes a frame16, which is an example of a support portion, for supporting the head-tool tip portion3aand a load cell14, which is an example of a load detector portion on the frame16.

The frame16, which is formed of a rigid body into a generally U shape, includes an upper frame16afor supporting the load cell14, a lower frame16bfor supporting the shaft17of the head-tool tip portion3avia a self-weight balancing spring15, which is an example of an elastic member, fitted to a lower portion of an annular-protrusion shaped spring holder portion18provided at a side portion of the shaft17so as to surround an outer periphery of the shaft17, and a cylindrical-shaped intermediate frame16cfor supporting the upper frame16aand the lower frame16b. The lower frame16bfurther serves for guiding up-and-down motions of the shaft17.

The shaft17has a stepped portion17cnearly intermediate of its axial direction, wherein with the stepped portion17cserving as a boundary, the shaft17has a shaft lower portion17bsmaller in diameter than a shaft upper portion17a. Further, this shaft lower portion17bextends through a hole16dformed in the lower frame16bsupporting the shaft17via the self-weight balancing spring15, wherein the hole16dof the lower frame16bis formed so as to be capable of guiding up-and-down motions of the shaft17, and is smaller in diameter than the shaft upper portion17a. As a result of this, the shaft17can be guided by the hole16dof the lower frame16bto move up and down while supported by the lower frame16bvia the self-weight balancing spring15. Also, even if the self-weight balancing spring15has become no longer capable of supporting the shaft17due to damage or the like, a peripheral portion of the hole16dof the lower frame16bcan support the shaft17by the stepped portion17cof the shaft17so that the shaft17is prevented from falling off.

Further, the shaft lower portion17bhas a ball-spline outer ring and a shaft, and the lower frame16bhas a bearing inside the hole16d, wherein the ball-spline outer ring is fitted inside the bearing. Thus, the shaft17can be rotated about its axis while being supported by the lower frame16b, and also be made to move up-and-down in an axial direction.

The intermediate frame16cis cylindrical at both ends, which ends are fixed to nut portions21bof the up/down moving unit21. Rotating a ball screw shaft21a, screwed to the nut portions21b, by a motor21min the up/down moving unit21causes the intermediate frame16cto be operated so as to move up and down, by which the frame16is operated to move up and down, by which the head tool3as a whole is operated to move up and down.

Also, the suction nozzle11, the ceramic heater12, the water jacket13, the shaft17and the load cell14have their centers positioned coaxially on one axis that is positioned parallel to the axis of up/down operations. Thus, by the up/down operations performed by the up/down moving unit21, the suction nozzle11, the ceramic heater12, the water jacket13, the shaft17and the load cell14are up-and-down movable on the same axis.

Further, an upper end of the shaft17in the head-tool tip portion3ais pressed into contact with a load-detecting surface, which is a lower surface of the load cell14, by the self-weight balancing spring15, which is fitted to the lower frame16bto support the shaft17via the spring holder portion18, thus making it possible for the load cell14to detect a load that acts upwardly of the shaft17of the head-tool tip portion3a.

Also, the cooling blow nozzle19fitted to the periphery of the shaft lower portion17b, which is a lower periphery of the shaft17, is formed around both sides of the water jacket13and the ceramic heater12, which are positioned under the shaft17. Further, the tip of the cooling blow nozzle19is directed toward an electronic-component suction and holding surface, i.e. lower surface, of the suction nozzle11, so that a blow from the cooling blow nozzle19can cool the electronic component1sucked and held by the suction nozzle11.

The control part9controls sucking operation of the suction nozzle11, heating operation of the ceramic heater12and moving operation of the up/down moving unit21, and a load detected by the load cell14is outputted to the control part9.

Now a control system diagram for the electronic component mounting apparatus201is shown inFIG. 11. Referring to the electronic component mounting apparatus201, the control part9controls operations of individual constituent parts of the electronic component mounting apparatus201, i.e., up/down operations of the up/down moving unit21by the motor21m, heating operation of the ceramic heater12, cooling operation of the cooling blow nozzle19, sucking operation of the suction nozzle11, moving operation of the X-direction moving mechanism22by a motor, and moving operation of the Y-direction moving mechanism23by a motor, and further a load detected by the load cell14is outputted to the control part9. As a result of this, the constituent parts, which are controlled parts for the control part9, are controlled correlatively by the control part9, by which mounting of the electronic components1onto the circuit board4is fulfilled in the electronic component mounting apparatus201.

Next, a method for detecting a contact load generated upon contact between the electronic component1and the circuit board4, by the load cell14in the head tool3, is explained.

After alignment between the electronic component1and the circuit board4, while the electronic component1is kept sucked and held by the suction nozzle11, the head tool3is moved down by the up/down moving unit21, by which the solder bumps1bof the electronic component1are put into contact with the solder portions2of the circuit board4, respectively. In this state, there arises a contact load between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, wherein this contact load causes the upper end of the shaft17of the head-tool tip portion3a, in contact with the load-detecting surface of the load cell14of the head tool3, to push up the load-detecting surface of the load cell14, resulting in the contact load being detected by the load cell14.

By detecting the contact load in the load cell14in this way, occurrence of contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4is detected. Moreover, the contact load detected by the load cell14is outputted to the control part9, while the up/down moving unit21is controlled by the control part9so as to obtain a contact load preset in the control part9, the head tool3is moved down to a small amount by the up/down moving unit21, and the up/down moving unit21is controlled so that the contact load detected by the load cell14becomes a preset contact load.

As to the electronic component mounting method according to the first embodiment which is constituted and performed by the mounting procedure as described above (hereinafter, this method will be referred to as a local reflow mounting method of the first embodiment, since melting, i.e., reflow is performed individually for each electronic component), its mounting procedure is comprehensively given in a flowchart shown inFIG. 4. It is noted that operational instructions at individual steps are implemented by the control part9.

At step SP1inFIG. 4, the electronic component1is sucked and held by the head tool3. At step SP2, a positional alignment between the electronic component1and the circuit board4is performed so that the solder bumps1bformed on the electrodes1aof the electronic component1and the solder portions2formed on the pads4aof the circuit board4become bondable with each other. Thereafter, at step SP3, the head tool3is moved down while maintaining sucking and holding of the electronic component1. At step SP4, contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4is detected by the load cell14of the head tool3. Further, at step SP5, by heating of the electronic component1with the ceramic heater12of the head tool3, the solder bumps1bof the electronic component1and the solder portions2of the circuit board4are melted. Subsequently, at step SP6, cooling by blow of the cooling blow nozzle19onto the molten solder is started. At step SP7, the molten solder is solidified so that the electrodes1aof the electronic component1are bonded to the pads4bof the circuit board4, respectively, via the solder. Subsequently, at step SP8, suction and holding of the electronic component1by the head tool3is released. In addition, for mounting of a plurality of electronic components1onto the circuit board4, these steps SP1to SP8as described above are iteratively performed for each electronic component1to fulfill mounting of these respective electronic components1. Further, in other cases, cooling of the molten solder at step SP6may be implemented by natural cooling instead of cooling by blow of the cooling blow nozzle19.

Next, in a case where correction of an elongation amount and shrinkage amount of the head tool3due to heat is performed, this correction operation is explained.

After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, when the suction nozzle11is heated by the ceramic heater12of the head tool3so that the solder bumps1band the solder portions2are melted, at least the head-tool tip portion3ain the head tool3is elongated in the up/down direction under an effect of heat derived from the ceramic heater12, and further, when heating by the ceramic heater12is stopped, the head-tool tip portion3ais shrunk in the up/down direction with an effect of heat being eliminated. Because of such up/down elongation and shrinkage of the head-tool tip portion3a, during a period from contact to bonding of the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, it may become, in some cases, difficult to maintain generally constant a rear-face height of the electronic component1having the electrodes1akept in contact with the electrodes4aof the circuit board4via the solder portions2and the solder bumps1b. As a result, in some cases, there occur bump crushes or the like, making it difficult to achieve a stable bonding quality of electronic components depending on a required bonding precision.

With a view to fulfilling reliable rear-face height control for the electronic components1, the elongation-amount and shrinkage-amount correction of the head-tool tip portion3ais performed during the following procedure. That is, variation data of elongation amount and shrinkage amount due to heat of the head-tool tip portion3aare preliminarily set to a memory in the control part9, and the control part9performs control over the ceramic heater12, the up/down moving unit21and the cooling blow nozzle19. During heating by the ceramic heater12, the head tool3is moved up gradually by the up/down moving unit21based on the variation data of elongation amount of the head-tool tip portion3adue to the heating. After a stoppage of the heating by the ceramic heater12, and during cooling by the cooling blow nozzle19, the head tool3is moved down gradually by the up/down moving unit21based on the variation data of shrinkage amount of the head-tool tip portion3adue to the cooling. Thus, the correction of elongation amount and shrinkage amount of the head-tool tip portion due to heat is fulfilled. As a result of this, the rear-face height of the electronic component1sucked and held by the suction nozzle11of the head tool3can be maintained constant during a period from contact to bonding between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4. Otherwise, the correction of elongation amount or shrinkage amount of the head tool3due to heat may alternatively be a correction of only either one of the elongation-amount correction or the shrinkage-amount correction, wherein a decision as to whether the correction is performed or not is made depending on the required bonding precision of the electronic component1onto the circuit board4, or a number of solder bumps1bformed on the electrodes1aof the electronic component1.

A procedure for the correction operation of elongation amount and shrinkage amount of the head tool3due to the heat constituted as shown above is comprehensively shown inFIG. 5.FIG. 5is a flowchart showing the procedure of the correction operation in which steps associated with the correction operation of elongation amount and shrinkage amount of the head tool3due to heat are added between step SP4and SP7in the flowchart ofFIG. 4showing the mounting procedure of the electronic component mounting method according to the foregoing embodiment. It is noted that operational instructions and decisions at individual steps are implemented by the control part9.

After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4is detected at step SP4inFIG. 5, temperature increase of the suction nozzle11is started by heating performed by the ceramic heater12at step SP10. Next, at step SP11, it is decided whether or not the correction of elongation amount of the head tool3due to heat is performed. If the elongation-amount correction is performed, it is decided at step SP12whether or not a waiting for a start of the elongation-amount correction for the head tool3is performed. In a case where waiting for the start of the elongation-amount correction is performed, the start of the elongation-amount correction for the head tool3is kept in a standby state for a set time period at step SP13. In a case where waiting for the start of the elongation-amount correction is not performed, on the other hand, step SP13is not performed and, subsequently, at step SP14, the head tool3is moved up gradually based on variation data of elongation amount of the head tool3due to heat. At step SP5, the solder bumps1bof the electronic component1and the solder portions2of the circuit board4are melted by heating performed by the ceramic heater12. Otherwise, the stand-by operation of the starting of the elongation-amount correction for the head tool3at step SP13may alternatively be that the standby state is maintained until a temperature of the suction nozzle11, heated by the ceramic heater12, increases beyond a set temperature, instead of maintaining the standby state for a set time period as described above.

Meanwhile, if it is decided at step SP11that the elongation-amount correction is not performed, then step SP5is performed without performing steps SP12to SP14.

Thereafter, at step SP6, cooling of the molten solder is started. Next, at step SP15, it is decided whether or not the correction of shrinkage amount of the head tool3due to the cooling is performed. If the shrinkage-amount correction is performed, it is decided at step SP16whether or not waiting for a start of the shrinkage-amount correction for the head tool3is performed. In a case where waiting for the start of the shrinkage-amount correction is performed, the start of the shrinkage-amount correction for the head tool3is kept in a standby state for a set time period at step SP17. In a case where waiting for the start of the shrinkage-amount correction is not performed, on the other hand, step SP17is not performed and, subsequently, at step SP18, the head tool3is moved down gradually based on variation data of shrinkage amount of the head tool3due to the cooling. At step SP7, the melted solder is solidified by the cooling. Otherwise, the stand-by operation of the starting of the shrinkage-amount correction for the head tool3at step SP17may alternatively be that the standby state is maintained until a temperature of the suction nozzle11, heated by the ceramic heater12, decreases below a set temperature, instead of maintaining the standby state for a set time period as described above.

Meanwhile, if it is decided at step SP15that the shrinkage-amount correction is not performed, then step SP7is performed without performing steps SP16to SP18.

Next described is a case where a constant contact load control by the head tool3is performed after detection of contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, and additionally, tip position control of the suction nozzle11is performed after melting of the solder bumps1band the solder portions2.

After detection of contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, the up/down moving unit21is controlled by the control part9so that a contact load detected by the load cell14becomes a preset contact load, and a constant load is applied to the electronic component1and the circuit board4by the head tool3, resulting in a constant-load control state by the head tool3. However, in a state that the solder bumps1bof the electronic component1and the solder portions2of the circuit board4have been melted by heating of the suction nozzle11by the ceramic heater12, if the head tool3remains in the constant-load control state as described above, then a tip position of the suction nozzle11would lower, giving rise to a problem in that molten solder bumps1band solder portions2would be excessively crushed.

In order to solve these and other problems, with a view to reliable achievement of a rear-face height control for the electronic component1after melting of respective solder pieces, i.e., positional control for a contact height of the electronic component1with the circuit board4, several steps are performed, including: effectuating the constant-load control state by the head tool3after the start of temperature increase of the suction nozzle11by heating performed by the ceramic heater12; performing load detection by the load cell14; and, upon a decision that a detection of decrease of this detected load is regarded as a start of melting of the respective solder pieces, switching from the constant-load control of the head tool3to the positional control for making a tip-height position of the suction nozzle11constant, by which even in a molten state of the respective solder pieces, the tip height position of the suction nozzle11can be made constant, thus allowing the rear-face height control for the electronic component1to be achieved reliably.

A procedure for the constant-load control of the head tool3and the tip-height-position control operation of the suction nozzle11constituted as shown above is comprehensively shown inFIG. 6.FIG. 6is a flowchart showing a procedure for operations of the constant-load control of the head tool3and the tip-height-position control of the suction nozzle11between step SP4and SP6in the flowchart ofFIG. 4showing the mounting procedure of the electronic component mounting method according to the foregoing embodiment. It is noted that operational instructions and decisions at individual steps are implemented by the control part9.

After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4is detected at step SP4inFIG. 6, temperature increase of the suction nozzle11is started by heating performed by the ceramic heater12at step SP10. Next, at step SP5a, move-down operation of the up/down moving unit21is controlled in small steps, by which constant-load control of the head tool3is performed, resulting in a state that a constant load is applied to the electronic component1and the circuit board4by the head tool3. During this constant-load control, a load actually generated in the load cell14is detected, wherein if a decrease of the detected load is detected at step SP5bas a result of the decrease of the load detected in the load cell14, then it is decided that the melting of the solder pieces has been started, and a control mode is switched from the constant-load control of the head tool3to the constant tip-height-position control of the suction nozzle11at step SP5c. At step SP5d, up/down operation of the up/down moving unit21is limited, by which a rear-face height of the electronic component1sucked and held by the suction nozzle11, whose tip height position has been made constant, is made constant. At step SP5e, the constant tip-height-position control of the suction nozzle11is performed until temperature increase of the suction nozzle11, due to a stopping of heating of the ceramic heater12, is completed. If the temperature increase of the suction nozzle11is completed at step SP5e, cooling of the molten solder pieces is started at step SP6.

Meanwhile, if a decrease of the load detected in the load cell14is not detected at step SP5b, then it is decided that melting of the solder pieces has not yet been started. It is decided at step SP5fwhether or not the temperature increase of the suction nozzle11has been completed due to a stopping of heating by the ceramic heater12, wherein if it has not yet been completed, the program returns again to step SP5aand the constant-load control of the head tool3is continued. If it is decided at step SP5fthat the temperature increase of the suction nozzle11has been completed, due to a stopping of heating by the ceramic heater12, then a control mode is switched from the constant-load control of the head tool3to the constant tip-height-position control of the suction nozzle11at step SP5g. The rear-face height of the electronic component1sucked and held by the suction nozzle11, whose tip height position has been made constant, comes to a specified height at step SP5h, and cooling of the molten solder pieces is started at step SP6.

During step SP4, upon detection of contact between the solder bumps1bof the electronic component1and the solder portions of the circuit board4, there are some cases where some of the solder bumps1band the solder portions2are not in contact with one another because of variations in a formation height of the solder bumps1band the solder portions2. An example is an electronic component1on which as many as one thousand or more bumps are formed. In such a case, when the electronic component1is heated as it is, there would occur a problem in that non-contacted solder portions2do not conduct heat from the solder bumps1b, and therefore are not melted.

With respect to such a problem, in the constant-load control of the head tool3at step SP5a, the constant load is set to a load not less than a contact load for contact detection, and the set load is, under constant control, applied to the electronic component1and the circuit board4. By so doing, even if some of the solder bumps1band the solder portions2are not in contact with one another because of variations in a formation height of the solder bumps1band the solder portions2as described the above, upon detection of contact between the solder bumps1bof the electronic component1and the solder portions of the circuit board4, it is implementable to enhance contactability between the solder bumps1band the solder portions2by applying the above-mentioned constant load, by which all the solder pieces can be melted reliably.

Next described is a case where a load zero setting of the load cell14of the head tool3is performed.

Heat generated by heating of the ceramic heater12of the head tool3is transferred by heat conduction from individual constituent parts of the head tool3or heat conduction through ambient air of the head tool3, so that the self-weight balancing spring15fitted to the spring holder portion18of the shaft17at the head-tool tip portion3achanges in its spring characteristics under influence of this heat. This results in a change of a pressing load in the load cell14generated by the self-weight balancing spring15, which has changed in its spring characteristics, pressing the shaft17against the load-detecting surface of the load cell14. Further, this pressing load in the load cell14by the self-weight balancing spring15also changes due to secular changes in the spring characteristics of the self-weight balancing spring15depending on duration of use of the head tool3. By this change in the pressing load in the load cell14due to the change in the spring characteristics of the self-weight balancing spring15, there occurs a difference between an actual pressing load upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4and a contact-load value detected by the load cell14, resulting in a problem that an actual contact load cannot be controlled in accordance with a preset contact load.

In such a case, after the electronic component1sucked and held by the head tool3is aligned so as to be bondable with the circuit board4, a pressing load, with which the shaft17at the head-tool tip portion3ais pressed against the load-detecting surface of the load cell14by the self-weight balancing spring15in a noncontact state of the electronic component1and the circuit board4, is detected by the load cell14, and this detected pressing load is outputted to the control part9. In the control part9, this pressing load is set as a load-zero point in the load cell14. Subsequently, the head tool3is moved down, so that mounting of the electronic component1onto the circuit board4is performed. All these steps are performed under control of the control part9.

Therefore, even in a case where a pressing load by the shaft17at the head-tool tip portion3achanges in the load cell14because of changes of the spring characteristics of the self-weight balancing spring15under influence of heat or secular changes, a pressing load detected in the control part9is set to a load-zero point in the load cell14each time alignment between the electronic component1and the circuit board4is performed, which eliminates any difference between an actual contact load upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, and a detected value of a load detected by the load cell14, thus allowing control of the actual contact load in accordance with a preset contact load to be achieved.

Next described is a method for controlling up/down movement operations of the head tool3to thereby control a contact load to a preset contact load, based on detection of a contact load due to the head tool3upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4by virtue of the load cell14of the head tool3, with reference to contact-load control operation flowcharts shown inFIGS. 7 and 8on a basis of a working example. It is noted that operational instructions and decisions at individual steps are implemented by the control part9.

After alignment between the electronic component1and the circuit board4, the head tool3sucking and holding the electronic component1starts to be moved down by the up/down moving unit21at step SP3. During this downward movement of the head tool3, it is decided at step SP21whether or not a preset contact load is beyond 450 g. If the preset contact load is beyond 450 g, an initial detected load due to contact is set to 200 g at step SP22. If the preset contact load is not more than 450 g, the initial detected load due to the contact is set to 100 g at step SP23. Next, at step SP24, the solder bumps1bof the electronic component1and the solder portions2of the circuit board4come into contact with each other, wherein a set initial detected load is detected by the load cell14. Then, at step SP25, the head tool3that has been moving down is stopped so as to be kept in an operation standby state for 200 ms; that is, kept in a static state so as to eliminate any effects on the detected load of the load cell14by the head tool3moving down by a small overshoot after a stop operation of the head tool3, i.e., by the head tool3moving down by a small amount after a move-down operational instruction from the control part9to over a period from deceleration of a move-down speed of the head tool3until its stopping.

Next, it is decided at step SP26whether or not a current load detected by the load cell14is beyond the preset contact load −100 g, wherein it is decided how close the current load is to the preset contact load.

If it has been determined at step SP26that the current load is over the preset contact load −100 g, the head tool3is subjected to a static state for 200 ms at step SP27. Further, at step SP28, it is decided whether or not the current load is not less than the preset contact load −50 g. If the current load is less than the preset contact load −50 g, the head tool3is moved down by 1 μm by the up/down moving unit21at step SP29, and the head tool3is subjected to a static state for 200 ms at step SP27. Thereafter, it is decided again at step SP28whether or not the current load is not less than the preset contact load −50 g. This operational loop is iteratively performed until the current load becomes not less than the preset contact load −50 g.

If the current load is not less than the preset contact load −50 g at step SP28, then the head tool3is kept in a static state for a preset time period at step SP30, wherein control of a contact load between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4toward the preset contact load is completed. Then, a result at step SP4is that contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4has been detected. It is noted here that the preset contact load −50 g, which is a decision criterion in step SP28, is a contact load which is expected to occur upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4. When a current load, which is a load that actually occurs upon contact, becomes not less than a contact load that is expected to occur upon contact, generally all of the solder bumps1bof the electronic component1and generally all of the solder portions2of the circuit board4come into a contact state, thus resulting in detection of contact.

Otherwise, if the current load is not more than the preset contact load −100 g at step SP26, it is further decided at step SP31whether or not the current load is beyond the preset contact load −500 g, wherein if not, it is further decided at step SP32whether or not the current load is beyond the preset contact load −1000 g in a stepwise manner. If the current load is not more than the preset contact load −1000 g at step SP32, a load difference between the current load and the preset contact load is converted into a movement distance of the head tool3at step SP33. Also, in a case where the current load has satisfied the condition of step SP31, the movement distance of the head tool3is set to 1 μm at step SP34. In a case where the current load has satisfied the condition of step SP32, the movement distance of the head tool3is set to 2 mm at step SP35. Thereafter, at step SP36, the head tool3is moved down by the up/down moving unit21to an extent corresponding to movement distance of the head tool3in either case as shown above. At step SP37, the head tool3is stopped and kept in a static state for 50 ms. Thereafter, it is decided again at step SP26whether or not the current load is beyond the preset contact load −100 g. The loop of these operations is iteratively performed until this condition of step SP26is satisfied.

In the contact-load control method performed by the operations as described above, the head tool3is controlled for its minute move-down operation. Respective movement distances of the head tool3under respective operational conditions are set based on a relationship between an up/down minimum movable distance of the head tool3by the up/down moving unit21and a load per head-tool unit movement that can be generated by this minimum movable distance. In the above working example, the minimum movable distance is 1 μm, and the load per head-tool unit movement is 100 g/μm. Accordingly, for example, the difference of 100 g between preset contact load and current load, which is the condition of step SP26, is set based on the load per head-tool unit movement. Also at step SP29, step SP34and step SP35, movement distances of the head tool3, 1 μm and 2 μm, are set based on minimum movable distances, respectively.

It is noted that loads, times, distances or other numerical values in the above description are those as an example in this embodiment, and this embodiment is not limited to these numerical values.

Next described is a case including a step of performing a reshaping operation of the solder bumps1bof the electronic component1by the head tool3.

After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, when the suction nozzle11is heated by the ceramic heater12of the head tool3so that the solder bumps1band the solder portions2are melted, the head tool3sucking and holding the electronic component1is subjected to micro-vibrational operations in the up/down or sideways directions so that solder wettability between these molten solder bumps1band solder portions2can be improved and that quality of bonding for the electronic component1and the circuit board4can be made successful. As a pattern of this vibrational operation in the reshaping operation performed by the head tool3, as shown inFIGS. 9A-9D, such patterns are available as a cross type (seeFIG. 9A), an O type (seeFIG. 9B), and 8-letter types (seeFIGS. 9C and 9D) ones as have been used in conventional electronic component mounting methods. Further, as parameters to be used for respective vibrational operations in the reshaping operation performed by the head tool3, a number of reshaping-operation up/down moves for moving up and down the head tool3during the reshaping operation is 0 to 20 times as an example, an operating speed for moving up and down the head tool3during the reshaping operation is 0.1 to 9.9 seconds as an example, an operating amount, that is a movement amount for moving up and down the head tool3in the reshaping operation, is −99 to 99 μm as an example, and a number of reshaping vibrational operations for vibrating the head tool3in the X and Y directions during the reshaping operation is 0 to 200 times as an example.

Next, with regard to a case where electronic components are mounted onto a circuit board by compositely performing individual operations of the head tool3as described above, time charts showing time-varying states of a control height of the head tool3, tip height of the suction nozzle11of the head tool3and temperature of the suction nozzle11of the head tool3are shown inFIGS. 10A,10B and10C, respectively. It is noted here that the control height of the head tool3refers to a relative height position of up/down movement control of the head tool3by the up/down moving unit21, and the tip height of the suction nozzle11of the head tool3refers to a relative tip height of the suction nozzle11. It is also noted that time axes, which are the horizontal axes inFIGS. 10A-10C, are given as the same time axis so as to allow comparisons among respective variation states.

First, during a period from time origin t0to t1inFIGS. 10A-10C, the control height of the head tool3as well as the tip height of the suction nozzle11fall in similar variation states along with downward movement of the head tool3by the up/down moving unit21. In this case, since heating by the ceramic heater12has not yet been started, temperature has been maintained in a constant state.

Subsequently, during a period from time t1to t2, the electronic component1and the circuit board4come into contact with each other at time t1, and heating of the suction nozzle11is started by the ceramic heater12, by which temperature of the suction nozzle111is increased. Since a correction operation of elongation amount of the head tool3due to this temperature increase is performed, the control height of the head tool3is increased as previously set. The head tool3that has been subjected to the elongation-amount correctional operation becomes constant in the tip height of the suction nozzle11. During this period from time t1to t2, solder melting is started.

Subsequently, during a period from t2to t4, the temperature of the suction nozzle11is controlled by heating of the ceramic heater12so as to be maintained at a constant temperature. Also, the control height of the head tool3as well as the tip height of the suction nozzle11are both maintained at a constant level. However, during the period from time t2to t3, since a reshaping operation of the solder bumps1bof the electronic component1by the head tool3is performed, the head tool3performs micro-vibrational operations, so that both the control height of the head tool3and the tip height of the suction nozzle11of the head tool3move up and down in micro steps.

Subsequently, during the period from time t4to t5, cooling of molten solder is started, and the temperature of the suction nozzle11falls. Since a correctional operation of shrinkage amount of the head tool3due to this cooling is performed, the control height of the head tool3is lowered as previously set. The head tool3that has been subjected to the shrinkage-amount correctional operation becomes constant in the tip height of the suction nozzle11. During this period from time t4to t5, the molten solder is solidified.

Finally, at time t5, suction and holding of the electronic component1by the suction nozzle11of the head tool3is released, and thereafter the head tool3is moved up by the up/down moving unit21, so that the control height of the head tool3as well as the tip height of the suction nozzle11go up in similar variation states.

Further, a working example which is more concretely embodied according to a modification example of the embodiment of operations of the head tool3as described above is described below. Also, time charts showing time-varying states of the tip height of the suction nozzle11of the head tool3, temperature of the suction nozzle11, and load detected by the load cell14under loading by the electronic component1and the circuit board4due to downward movement of the head tool3, respectively, are shown inFIG. 25. Further, schematic explanatory views showing states of the electronic component1and the circuit board4at singular time points of the time charts ofFIG. 25are shown inFIGS. 24A-24E, respectively. In addition, inFIG. 25, the horizontal axis is given as a time axis, wherein times Ta-Th are shown as respective singular time points in the above-mentioned varying states, while the vertical axis shows the tip height of the suction nozzle11, the temperature of the suction nozzle11and the load detected by the load cell14, in an order from above to below.

First, as shown inFIG. 24A, after the electronic component1sucked and held by the suction nozzle11is aligned with a mounting position of the circuit board4, the head tool3is moved down so that the suction nozzle11is moved down to a search start height as its tip height (time Ta inFIG. 25). It is noted here that the term “search start height” refers to a height at which detection of contact between individual solder bumps1bof the electronic component1and individual solder portions2of the circuit board4, respectively, is started by load detection of the load cell14. Also, the temperature of the suction nozzle11is maintained at a temperature of, for example, about 100° C. by being heated by the ceramic heater12so that temperatures that do not cause melting of the individual solder bumps1bof the electronic component1can be maintained with a view to reducing as much as possible a temperature increase time for later solder melting. Thereafter, the head tool3is moved down at a move-down speed previously set in the control part9or the like, by which the suction nozzle11is moved down.

When the suction nozzle11is moved down, some of the solder bumps1bof the electronic component1come into contact with the solder portions2of the circuit board4, as shown inFIG. 24B, wherein a load due to this contact is detected in the load cell14. When this detected load has reached a preset contact load (e.g., 1 N), it is decided that contact between the solder bumps1band the solder portions2has been detected, wherein contact load detection is ended (time Tb inFIG. 25). This occurrence of contact between some of the solder bumps1band some of the solder portions2is due to the fact that, for example, the individual solder bumps1bof the electronic component1are formed of high-temperature solder, varying in their formation height in some cases. Further, since the individual solder portions2are formed by plating with, for example, eutectic solder on the pads4aof the circuit board4, respectively, the solder portions2may also vary in their formation height in some cases. Otherwise, another case may be one in which the individual solder portions2are formed by printing with solder paste, instead of being formed by plating as shown above. Accordingly, in a state that contact has been detected, this case is not that all the solder bumps1band all the solder portions2are necessarily in contact with each other, but that, for example, only some solder portions2bthat are highest in formation height are in contact, as shown inFIG. 24B.

Subsequently, a temperature of the suction nozzle11is increased so that the individual solder portions2are melted. However, if the temperature of the suction nozzle11is increased in such a contact-detected state, heat would not be transferred to solder portions2that should be put into contact with solder bumps1bother than the above-mentioned some solder bumps1b, wherein this solder is not melted, thereby causing higher positionability of occurrence of defective bonding. Therefore, after contact detection, the suction nozzle11is further moved down so that a further load generated by this downward movement is added to the foregoing contact load, as shown inFIG. 24C, by which the solder bumps1bof higher formation heights that have previously been in contact are plastically deformed by the load so that all the solder bumps1bare put into contact with the solder portions2, respectively (time Tb-Tc). A load value necessary in further adding a load as shown above depends on a number of the solder bumps1b. For example, assuming that the number of solder bumps1bis one hundred and that a load of 0.03 N is applied to each one solder bump1b, then a total load of 3 N is set as a target load for increasing of the load. Also in performing this load increase, the head tool3is moved down by a minimum movable distance for move-down of the head tool3, and moreover while a resulting load increment is being measured by the load cell14, the head tool3is moved down by a specified amount so as to reach a target load. For example, with a minimum resolution of 1 μm as the minimum movable distance and with a load increment of 1 N corresponding thereto, the head tool3is moved down in steps of 1 μm while a detected load is checked. In the case ofFIG. 25, with a setting that the tip height position of the suction nozzle11upon a detection of contact is Hc, the tip height position is first lowered and positioned to Hc-1 μm, and further lowered and positioned to Hc-2 μm, thus stepwise downward movement is performed. Further, during a period from a downward movement of the head tool3to a check of the load value, a wait time of a certain time interval is provided. This is intended to stabilize the load value by a certain time lapse, since plastic deformation of the individual solder bumps1bis not completed instantaneously but needs a certain time lapse for the plastic deformation to be stabilized. Further, the load is checked again after the elapse of the specified time period even after the target load is reached, wherein if it is verified that the detected load has reached the target load, then a temperature increase of the suction nozzle11by heating of the ceramic heater12is performed.

Thereafter, the individual solder portions2of the circuit board4are heated by the temperature increase of the suction nozzle11via the individual solder bumps1b, by which melting of the individual solder portions2is started (time Tc-Td). In this case, if the solder portions2are formed of a eutectic solder having a melting point of 183° C., the temperature increase of the suction nozzle11is performed with a target temperature (e.g., 200° C.) which is slightly higher than a melting point and which is lower than a melting point of high-temperature solder from which the individual solder bumps1bof the electronic component1are formed. Also, in a case where the tip height of the suction nozzle11is maintained as it is during this temperature increase, the tip of the suction nozzle11would be elongated along with the temperature increase, thus causing the load detected in the load cell14to be increased. In this connection, elongation amount of the suction nozzle11depends on its material and temperature increments, and therefore effects of elongation on the load can be reduced by selecting a material hard to elongate due to heat as the material, or by setting the temperature upon contact detection to a highest possible temperature so that a temperature variation against a melting temperature is reduced. Furthermore, a case may be another one in which a load upon contact detection is set to a somewhat lower one in view of a load increase due to elongation of the suction nozzle11during temperature increase. Still also, a case may be another one including a controlling step in which the tip height position of the suction nozzle11is moved up according to a temperature of the suction nozzle11with a view to suppressing any load increases, due to such temperature increases, as much as possible. In such a case, an elongation amount of the suction nozzle11corresponding to an incremental temperature of 1° C. is preliminarily set in the control part9or the like as data, and the suction nozzle11is moved up according to a temperature increment from the temperature at contact detection (e.g., 100° C.), thus allowing a load increase due to a temperature increase to be suppressed.

Further, since the suction nozzle11is under the control of holding its tip height position, the height position of the electronic component1remains as it is at the moment of the melting of the solder portions2, wherein the solder portions2are melted so that no solid substances are present between the individual pads4aof the circuit board4and the individual solder bumps1b, thus the load detected by the load cell14abruptly decreases toward zero (time Td-Te). In this case, since the circuit board4or the electronic component1is more or less flexed by a load effectuated just before melting of the individual solder portions2, the electronic component1is moved (lowered) in such a direction as to slightly sink toward the circuit board4side at the moment that the load has become zero. Accordingly, not that a gap is left by an extent corresponding to a formation thickness of the solder portions2which has been present between the individual pads4aof the circuit board4and the individual solder bumps1b, but that tips of the individual solder bumps1bare sunk into their corresponding solder portions2, respectively, so that the above-noted gap is reduced. Further, the more the load that has been present just before the melting of the solder portions2becomes larger, the more the gap tends to become smaller. With the load too large, sinkage larger than the gap may occur, so that the solder bumps1band the pads4aof the circuit board4are kept in direct contact with each other even after melting of the solder portions2, leading to occurrence of a phenomenon that the detected load does not become zero. Also, with too large a load and with the melting of the solder portions2in rapid progress, the electronic component1may sink as if it were struck against the circuit board4at the moment when the solder portions2have been melted, which may then cause molten solder to spatter, giving rise to short-circuiting faults. Even for prevention of occurrence of such various problems due to abrupt decreases in load caused by melting of the solder portions2, maintaining at a proper value the load that exists just before the melting of the solder portions2is a significantly important factor in terms of bonding stability between the electronic component1and the circuit board4.

Thereafter, melting of the solder portions2is started. When a temperature of the suction nozzle11has reached a target temperature (time Te), this state is maintained for a specified time period. As a result of this, as shown inFIG. 24D, molten solder portions2are formed into fillets by their surface tension between the individual solder bumps1band the individual pads4aof the circuit board4so as to partly cover outer peripheries of the individual solder bumps1b.

In a case where the above-noted gap has occurred between the solder portions2and the pads4aas a result of melting of the solder portions2, the suction nozzle11is moved down so that tips of the solder bumps1band the pads4aare put into contact with each other, respectively. This is so as to achieve that the gap between the surface of the circuit board4and the electronic component1becomes equal to a formation height of the individual solder bumps1bas much as possible at a time of completion of bonding. By performing such an operation, bonding strength of the electronic component1onto the circuit board4can also be enhanced. In more detail, in a state that the load has become zero as a result of melting of the individual solder portions2, the suction nozzle11is moved down until a load is detected by the load cell14, and then, conversely, the suction nozzle11is moved up to an extent corresponding to the above-noted minimum resolution (e.g., 1 μm) from a position where the load is detected, so that a load to be detected again is returned to zero (time Tf). After performing such an operation, a time period required for stabilizing re-melted individual solder portions2is awaited, and then a heating temperature of the suction nozzle11by the ceramic heater12is lowered (time Tf-Tg).

Thereafter, when a temperature of the suction nozzle11has become lower than the melting point of the eutectic solder, the molten solder portions2begin to solidify. Once the temperature has lowered to a secure-solidification temperature (e.g., 150° C.), suction and holding of the electronic component1by the suction nozzle11is released (time Tg). In addition, before this solidification of the solder portions2, elongation of the suction nozzle11due to heat would restore along with a temperature drop of the suction nozzle11, thereby giving rise to a force that would peel off the electronic component1from the circuit board4by the suction nozzle11. In order to prevent an occurrence of such force, it is also possible to perform a control operation for moving down the suction nozzle11along with a temperature decrease of the suction nozzle11so that a tip height position of the suction nozzle11is maintained at a fixed height position. It is yet also that suction and holding of the electronic component1is released at a point in time when the temperature of the suction nozzle11has become slightly lower than the melting point of the eutectic solder, in which state the temperature of the suction nozzle11is lowered to a temperature at which the solder portions2are securely solidified.

Thereafter, as shown inFIG. 24E, the head tool3is moved up so that the suction nozzle11is moved up (time Th), wherein bonding of the electronic component1onto the circuit board4is completed.

Next described is a case which includes a step of performing a leveling operation such that solder bumps1bof electronic component1are made uniform in their height with one another before the electronic component1is put into association with circuit board4.

With nonuniformities of their height included in the solder bumps1bbonded to electrodes1aof the electronic component1, when the solder bumps1bof the electronic component1and solder portions2of the circuit board4are put into contact with each other, a contact load control would be affected by these nonuniformities of height of the solder bumps1b, so that suction and holding to a predetermined rear-face height of the electronic component1could not be achieved by head tool3. If solder is melted in a state as it is and the electronic component1is bonded to the circuit board4, there would arise a problem in that individual electronic components1of the circuit board4could not be made uniform in their height.

In order to solve such a problem, before a mounting operation of the electronic component1onto the circuit board4by the head tool3, a leveling operation for making uniform a height of the solder bumps1bof the electronic component1is performed, and thereafter the mounting operation of the electronic component1onto the circuit board4is performed.

In the electronic component mounting apparatus201ofFIG. 1, a leveling stage8is fixed to the slide base6that can be moved by the Y-direction moving mechanism23in the Y1or Y2direction as viewed in this figure. After an electronic component1is sucked and held by the suction nozzle11of the head tool3, and before a positional alignment is performed so that the solder bumps1bof the electronic component1can be bonded with the solder portions2of a circuit board4, respectively, the slide base6, to which the leveling stage8is fixed, is moved in the Y1or Y2direction by the Y-direction moving mechanism23, and moreover the head tool3is moved in the X1or X2direction by the X-direction moving mechanism22, by which the electronic component1sucked and held by the suction nozzle11of the head tool3is aligned with a top surface of the leveling stage8. Thereafter, the head tool3is moved down by the up/down moving unit21so that the solder bumps1bof the electronic component1sucked and held by the suction nozzle11of the head tool3are put into contact with the top surface of the leveling stage8. It is noted that this top surface of the leveling stage8is formed of a glass plate or the like having a smooth flat surface. In this state, a contact load generated by this contact is detected by the load cell14of the head tool3, and further the up/down moving unit21is controlled according to this detected contact load so that the head tool3is moved down in small steps by the up/down moving unit21, by which the contact load is controlled so as to become a preset contact load. The solder bumps1bof the electronic component1are pressed against the top surface of the leveling stage8with the above controlled contact load, by which the solder bumps1bare made uniform in height. Thereafter, the head tool3is moved up by the up/down moving unit21, by which a positional alignment between the electronic component1and the circuit board4is performed so that the solder bumps1bof the electronic component1sucked and held by the suction nozzle11of the head tool3become bondable with the solder portions2of the circuit board4, respectively. Then, a mounting operation of the electronic component1onto the circuit board4is performed.

According to this first embodiment, various effects as shown below can be obtained.

First of all, according to the first embodiment, after the solder bumps1bof the electronic component1are put into contact with the solder portions2of the circuit board4, respectively, the solder bumps1band the solder portions2are melted by heating, while kept in that contact state, and thereafter solidified by cooling, by which the electrodes1aof the electronic component1and the pads4aof the circuit board4are bonded together with bonding members interposed therebetween. That is, working processes from contact to bonding between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4are performed at the same place. Thus, it can be made unnecessary to perform a step of conveying a circuit board to a reflow soldering working section with an electronic component temporarily bonded thereto, which is a step that would conventionally be performed after temporary bonding of the electronic component to the circuit board, and before primary bonding of the electronic component to the circuit board by collectively melting solder bumps and solder portions, as would be involved in a conventional collective reflow mounting method. Therefore, occurrence of any bonding-position shifts of the electronic component relative to the circuit board, as would occur during this conveyance, can be eliminated, making it possible to enhance a bonding quality of the electronic component onto the circuit board.

Also, after the solder bumps1bof the electronic component1sucked and held by the suction nozzle11of the head tool3and the solder portions2of the circuit board4are put into contact with each other, a timing for melting the solder bumps1band the solder portions2by heating and for releasing the electronic component1from suction and holding by the suction nozzle11of the head tool3is set not to such a timing that this releasing is performed during melting of solder as in the conventional local reflow mounting method, but to a timing that the releasing is performed after the solder is melted, cooled and solidified. That is, electronic-component mounting is not performed based on obtainment of a self alignment effect by surface tension of molten solder as in the conventional local reflow mounting method, but mounting of the electronic component1onto the circuit board4is performed at a contact position positioned by the head tool3. As a result of this, there can be eliminated any bonding position shifts of the electronic component1due to a vacuum break blow occurring to the suction nozzle11when the electronic component1is released from suction and holding by the suction nozzle11of the head tool3. Consequently, it becomes possible to achieve mounting onto a circuit board of such electronic components as high-end IC chips of narrowed bump pitches, for example as narrow as150μm or less bump pitches, in which case bonding position shifts of an electronic component due to a vacuum break blow at the suction nozzle would matter rather than obtainment of the self alignment effect.

Also, in the head tool3, by the arrangement that the upper end of the shaft17at the head-tool tip portion3ais pressed in contact against the lower surface, i.e. load-detecting surface, of the load cell14by the self-weight balancing spring15fitted to the lower frame16band the spring holder portion18of the shaft17to support the shaft17, it becomes possible to detect a load that acts upwardly of the head-tool tip portion3ain the load cell14.

As a result, by a contact load generated between the solder bumps1bof the electronic component1sucked and held by the head tool3and the solder portions2of the circuit board4upon contact therebetween, the upper end of the shaft17of the head-tool tip portion3apushes up the load-detecting surface of the load cell14, thus making it possible to reliably detect the load by the load cell14.

Consequently, by this detection of the contact load, it becomes possible to detect in the control part9the fact that the solder bumps1bof the electronic component1and the solder portions2of the circuit board4have come into contact with each other. Furthermore, the up/down moving unit21is controlled based on the detected contact load, and the head tool3is moved down in small steps by the up/down moving unit21, so that an actual contact load can be more accurately controlled so as to meet a preset contact load. Thus, in a case where mounting to the circuit board is iteratively performed for a plurality of electronic components, individual electronic components can be put into contact with the circuit board constantly with the preset contact load, so that a stable bonding quality of electronic components to the circuit board can be achieved.

Here are described working effects based on embodiments in a case where both an elongation-amount correction and a shrinkage-amount correction of the head tool3are performed, a case in which either one of the elongation-amount correction or the shrinkage-amount correction is performed, and a case in which neither the elongation-amount correction nor the shrinkage-amount correction is performed.

After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, the head-tool tip portion3ais elongated in the up/down direction under an effect of heat derived from the ceramic heater12, by which a contact load generated between the electronic component1and the circuit board4is affected. An influence load on the contact load by this elongation of the head-tool tip portion3ais about 3 kg. Based on this influence load, working effects by the above-mentioned various combinations of the elongation-amount correction and the shrinkage-amount correction of the head-tool tip portion3aare explained below.

First, in a case where the electronic component1is an IC chip having electrodes1aof not less than 1000 bumps, and where neither an elongation-amount correction nor a shrinkage-amount correction of the head tool3is performed, if the electronic component1is an IC chip having electrodes1aof 2000 bumps as an example, then an influence load of about 3 kg due to elongation of the head-tool tip portion3ais equivalent to about 1.5 g per bump. After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, the influence load due to the head-tool tip portion3ais taken as a contact load by using the elongation amount of the head-tool tip portion3a, where a proper contact load of about 1.5 g per bump can be generated, thus making it possible to reduce nonuniformities in melting height of the solder bumps1band the solder portions2.

Next, in a case where the electronic component1is an IC chip having a gap width as narrow as 50 μm or less between adjacent solder bumps1bformed at the electrodes1a, and where only an elongation-amount correction of the head-tool tip portion3ais performed and a shrinkage-amount correction is not performed, the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, which are pressed into contact with each other at a preset proper contact load resulting from an elongation-amount correction of the head-tool tip portion3a, are melted and thereafter these molten solder pieces are solidified by cooling while the head tool3is shrinking. That is, the molten solder is solidified by being elongated to an extent corresponding to a shrinking amount of the head-tool tip portion3adue to the cooling. Therefore, the solder bumps1band the solder portions2after the melting and the solidification can be formed into a Japanese hand drum shape, thus making it possible to prevent contact between adjacent solder bumps.

Next, in a case where the electronic component1is an IC chip having electrodes1aof not less than 1000 bumps and where an elongation-amount correction of the head-tool tip portion3ais not performed and only a shrinkage-amount correction is performed, if the electronic component1is an IC chip having electrodes1aof 2000 bumps as an example, then an influence load of about 3 kg due to elongation of the head-tool tip portion3ais equivalent to about 1.5 g per bump. After contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, the influence load due to the head-tool tip portion3ais taken as a contact load by using an elongation amount of the head-tool tip portion3a, where a proper contact load of about 1.5 g per bump can be generated. By this contact load, the IC chip is pushed in to a specified extent, and further shrinkage-amount correction of the head tool3is performed. Thus, solder of the IC chip can be solidified while a tip position of the suction nozzle11of the head tool3is kept constant, thereby making it possible to enhance control precision for a final IC-chip rear-face height after solder cooling.

Furthermore, in a case where the electronic component1is an IC chip having electrodes1aof less than 1000 bumps, and where both an elongation-amount correction and a shrinkage-amount correction of the head-tool tip portion3aare performed, if the electronic component1is an IC chip having electrodes1aof 100 bumps as an example, then an influence load of about 3 kg due to elongation of the head-tool tip portion3ais equivalent to about 30 g per bump. In this case, without performing the elongation-amount correction, an excessive load would be applied to the solder bumps1b, thereby causing bump crushes to occur. Thus, elongation-amount correction and shrinkage-amount correction of the head-tool tip portion3aare performed so as to enable bonding free from bump crushes.

Consequently, from the individual cases as described the above, it becomes possible to obtain required bonding qualities of electronic components, depending on whether both an elongation-amount correction and a shrinkage-amount correction of the head-tool tip portion3aare performed, or whether only either one of the elongation-amount correction or the shrinkage-amount correction is performed, or whether neither the elongation-amount correction nor the shrinkage-amount correction is performed, according to a number of solder bumps1bformed at the electrodes1aof the electronic component1to be mounted, or to bonding precision required for the electronic component1.

Also, in a case where a standby operation for start of an elongation-amount correction operation is performed during a time period from a start of temperature increase of the suction nozzle11at step SP10until a start of an elongation-amount correction operation of the head tool3at step SP14, even if an elongation amount of the head tool3is affected by, for example, nonuniform heat transfer or thermal disturbance or the like, during an initial stage of heating, to the suction nozzle11, such effects during this initial stage can be eliminated by the standby operation, and thereafter the elongation-amount correction operation of the head tool3can be performed. In addition, working effects similar to the foregoing can be obtained also with a shrinkage-amount correction of the head tool3.

It is noted that numerical values of various loads in the above description are those as an example in this embodiment, and this embodiment is not limited to these numerical values.

Furthermore, after start of temperature increase of the suction nozzle11by heating by the ceramic heater12, a load detection is performed by the load cell14as a constant-load control state by the head tool3. By deciding a decrease of this detected load as a start of solder melting, a control mode is switched from a constant-load control state of the head tool3to a positional control in which a tip height position of the suction nozzle11is maintained constant, thus making it possible to maintain the tip height position of the suction nozzle11even during melting of solder. As a result of this, when the solder bumps1bof the electronic component1and the solder portions2of the circuit board4are melted, molten solder bumps1band solder portions2can be prevented from crushing due to lowering of the tip position of the suction nozzle11. Thus, it becomes possible to reliably perform rear-face height control of an electronic component even during solder melting.

Further, during constant-load control of the head tool3as described above, with a constant load set to a load higher than a contact load upon contact detection, this load is controlled so as to be constant, and applied to the electronic component1and the circuit board4. Thus, even in such a case where some of the solder bumps1band the solder portions2are in a noncontact state due to nonuniformities in a formation height of the solder bumps1band the solder portions2upon detection of contact between the solder bumps1bof the electronic component1and the solder portions of the circuit board4, applying the constant load as described above makes it possible to enhance contactability between the solder bumps1band the solder portions2, respectively, so that all solder pieces can be securely melted, and thus that bonding reliability between the electronic component and the circuit board can be enhanced.

Furthermore, after the electronic component1sucked and held by the suction nozzle11of the head tool3is aligned so as to be bondable to the circuit board4, a pressing load, with which the shaft17at the head-tool tip portion3ais pressed against the load-detecting surface of the load cell14by the self-weight balancing spring15, is detected by the load cell14, and this detected pressing load is outputted to the control part9. In the control part9, this pressing load is set as a load-zero point in the load cell14. Thus, even in a case where the pressing load by the head-tool tip portion3achanges in the load cell14because of changes of spring characteristics of the self-weight balancing spring15under influence of heat or the like, there are no differences between an actual contact load upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, and a detected value of a contact load detected by the load cell14, thus allowing control of the actual contact load according to the preset contact load to be achieved. Thus, in a case where mounting to a circuit board is iteratively performed for a plurality of electronic components, individual electronic components can be put into contact with the circuit board constantly with the preset contact load, so that a stable bonding quality of electronic components to the circuit board can be achieved.

Furthermore, after contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, and during melting of the solder bumps1band the solder portions2, the head tool3performs a reshaping operation of the solder bumps1bof the electronic component1, by which mutual wettability of the solder bumps1bof the electronic component1and the solder portions2of the circuit board4in a molten state can be improved. Thus, solderability onto the electrodes1aof the electronic component1and the pads4aof the circuit board4can be made successful, and bonding reliability between an electronic component and the circuit board can be enhanced.

Furthermore, before the electronic component1is put into contact with the circuit board4, a leveling operation for making uniform a height of the solder bumps1bof the electronic component1is performed. By so doing, even in a case where the solder bumps1bof the electronic component1have nonuniformities in terms of formation height, these nonuniformities can be eliminated so that the solder bumps1bcan be made uniform in height. As a result, upon contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4, influences on a contact load control due to nonuniformities of the formation height of the solder bumps1bcan be eliminated, so that controllability on the contact load can be made successful, and so that the contact load can be applied to the solder bumps1bmore uniformly. Consequently, the electrodes1aof the electronic component1and the pads4aof the circuit board4can be bonded together with solder interposed therebetween reliably with a more uniform contact load, and a stabler bonding quality between the electronic components and the circuit board can be achieved.

Furthermore, in such a case as a rear-face height precision of the electronic component1, after bonding of the electronic component1to the circuit board4, is required, a leveling operation is performed so that the solder bumps1bof the electronic component1are made uniform in formation height. By so doing, it becomes possible to stabilize a rear-face height of the electronic component1after its mounting onto the circuit board4. It is noted that this leveling operation, when applied to electronic components1having, for example, at least 1000 solder bumps1b, allows a stabler bonding quality to be achieved, and hence be effective.

Second Embodiment

It is noted that the present invention is not limited to the above-described embodiment and may be embodied in other various modes. For example, an electronic component mounting method according to a second embodiment of the invention is an electronic component mounting method for mixedly mounting a plurality of types of electronic components onto a circuit board during different methods.

A first electronic component, which is one type of an electronic component from among the plurality of types of electronic components, is a general-purpose electronic component which is unlikely to incur defective bonding of the electronic component onto a circuit board due to a bonding position shift by virtue of its large bump pitch at which solder bumps are formed at electrodes of the electronic component, respectively, in the conventional collective reflow mounting method even if the bonding position shift of the electronic component with respect to the circuit board has occurred during a process in which the circuit board with the electronic component temporarily bonded thereon is conveyed to the reflow soldering working section. The first electronic component is, for example, a general-purpose electronic component31having a bump pitch of at least 150 μm of bumps formed on individual electrodes of the general-purpose electronic component. Further, a second electronic component, which is another type of electronic component, is a high-end electronic component which is required to meet such a high precision for a bonding position that the above-mentioned bonding position shift would incur defective bonding of the electronic component onto a circuit board in the conventional collective reflow mounting method. The second electronic component is, for example, a high-end electronic component41such as a high-end IC chip having a bump pitch of at most 150 μm or less required to meet a bonding position precision of 5 μm. With these electronic components, a plurality of general-purpose electronic components31are mounted onto the circuit board by a collective reflow mounting method, and thereafter the high-end electronic components41are mounted onto the circuit board by a local reflow mounting method of the foregoing first embodiment.

The electronic component mounting method according to the second embodiment of the invention is described in detail below with reference toFIGS. 12A to 12DandFIGS. 13E to 13H.

As shown inFIG. 12A, a rectangular-plate shaped circuit board34has a plurality of electrodes, pads34aand34b, on its top surface, wherein the pads34aare bondable to general-purpose electronic components31and the pads34bare bondable to high-end electronic components41. Flux is fed by a feed nozzle35onto the pads34aof the circuit board34, which are bondable to the general-purpose electronic components31, so that flux portions32are formed on the pads34a, respectively.

Next, inFIG. 12B, general-purpose electronic component31, on which solder bumps31b, serving as bonding members, are formed on the plurality of electrodes31aand which has a rectangular-plate shape, is sucked and held at its rear surface which has no electrodes by a tool33as an example of a component holding member. Then, the general-purpose electronic component31is aligned with the circuit board34so that the solder bumps31bof the general-purpose electronic component31becomes bondable to the flux portions32formed on the pads34aof the circuit board34, respectively. Thereafter, the tool33sucking and holding the general-purpose electronic component31is moved down so that the solder bumps31bof the general-purpose electronic component31are pressed against the pads34aof the circuit board34via the flux portions32, and thus are temporarily bonded. For each of the general-purpose electronic components31, these working steps are iteratively performed, by which the general-purpose electronic components31are temporarily bonded to the circuit board34.

Next, the circuit board34, to which the general-purpose electronic components31are temporarily bonded, is conveyed to a reflow soldering working section, where as shown inFIG. 12C, the general-purpose electronic components31and the circuit board34are heated by a heat source in the reflow soldering working section, by which the solder bumps31bof the respective general-purpose electronic components31are melted.

Thereafter, as shown inFIG. 12D, the heated general-purpose electronic components31and circuit board34are cooled, by which the molten solder bumps31bof the general-purpose electronic components31are solidified, so that the electrodes31aof the general-purpose electronic components31are finally bonded to the pads34aof the circuit board34, respectively, via the solder bumps31b; thus the general-purpose electronic components31are collectively mounted onto the circuit board34.

Next, as shown inFIG. 13E, flux is fed by a nozzle45onto the pads34b, that are bondable to high-end electronic component41, in the circuit board34with the general-purpose electronic components31mounted thereon, by which flux portions42are formed on the pads34b.

Next, as shown inFIG. 13F, the rectangular-plate shaped high-end electronic component41, on which solder bumps41bare formed on the plurality of electrodes41aand which has a rectangular-plate shape, is sucked and held at its rear surface which has no electrodes41aby a suction nozzle11of head tool3. Then, the high-end electronic component41is aligned with the circuit board34so that the solder bumps41bof the high-end electronic component41becomes bondable to the pads34bof the circuit board34via the flux portions42, respectively.

Thereafter, as shown inFIG. 13G, the suction nozzle11of the head tool3sucking and holding the high-end electronic component41is moved down so that the solder bumps41bof the high-end electronic component41are put into contact with the pads34aof the circuit board34via the flux portions42. After this contact, the solder bumps41bof the high-end electronic component41, which are in contact with the flux portions42of the circuit board34, respectively, are heated and thereby melted by ceramic heater12of the head tool3. Thereafter, heating by the ceramic heater12is stopped, and then the molten solder is subjected to cooling by blows from cooling blow nozzle19, thereby the molten solder bumps41bare solidified, so that the electrodes41aof the high-end electronic component41and the pads34bof the circuit board34are bonded to the solder bumps41b, respectively. Otherwise, the solder may also be solidified by natural cooling of the molten solder instead of the forced cooling of the molten solder by the cooling blow nozzle19.

Thereafter, as shown inFIG. 13H, the sucking and holding of the high-end electronic component41by the suction nozzle11of the head tool3is released, and the head tool3is moved up.

Through the electronic component mounting method as described the above, the general-purpose electronic components31and the high-end electronic component41are mixedly mounted onto the circuit board34.

Although the above description has been made for a case where the bonding members are the solder bumps1bpreliminarily formed on the electrodes31aof the general-purpose electronic components31as well as the solder bumps41bpreliminarily formed on the electrodes41aof the high-end electronic component41, the bonding members may also be only the solder bumps preliminarily formed on the electrodes31aof the general-purpose electronic components31, the solder bumps preliminarily formed on the electrodes41aof the high-end electronic component41, and the solder portions preliminarily formed on the pads34aand34bof the circuit board34.

Furthermore, the flux may also be fed onto the electrodes31aof the general-purpose electronic components31, or onto the electrodes41aof the high-end electronic component41, or onto the pads34aand34bof the circuit board34, or onto the solder bumps or solder portions, which are the bonding members, whichever the case may be, and otherwise, in another case flux is not fed. In addition, depending on the type of the flux supplied by coating, there are some cases where the flux supplied by coating is removed by cleaning after mounting of the general-purpose electronic components31and the high-end electronic component41onto the circuit board34.

According to the second embodiment as described above, in such cases as the general-purpose electronic components31having a bump pitch of at least 150 μm of bumps formed on individual electrodes of the electronic components, and the high-end electronic component41having a pitch of at most 150 μm of its bumps, are mixedly mounted on the circuit board34, the general-purpose electronic components31, for which high precision for a bonding position is not required, are first mounted onto the circuit board34by the conventional collective reflow mounting method, and thereafter the high-end electronic component41, for which high precision for a bonding position is required, is mounted by the local reflow mounting method of the first embodiment onto the circuit board34, on which the general-purpose electronic components31have been mounted.

In the mounting method of the general-purpose electronic components31onto the circuit board34, even in a case where a bonding position shift of the general-purpose electronic components31with respect to the circuit board34has occurred during conveyance of the circuit board34, with the general-purpose electronic components31temporarily bonded thereon, to the reflow soldering working section, since the solder bumps31bformed on the electrodes31aof the general-purpose electronic components31are formed so as to be have a bump pitch not less than 150 μm, a bonding position shift is unlikely to incur defective bonding of the general-purpose electronic components31to the circuit board34. Further, in the mounting method of the general-purpose electronic components31onto the circuit board34, it is not required to enhance bonding position precision, but rather to suppress mounting costs.

Accordingly, the general-purpose electronic components31, after being temporarily bonded onto the circuit board34, can be finally bonded and mounted onto the circuit board34by collectively melting their solder, thus allowing mounting work to be performed efficiently. Thus, costs associated with mounting of the general-purpose electronic components31onto the circuit board34can be suppressed.

On the other hand, the high-end electronic component41is sucked and held by the suction nozzle11of the head tool3from contact between the solder bumps41bof the high-end electronic component41and the flux portions42of the circuit board34until solidification of the solder after its melting; thus the high-end electronic component41is prevented from occurrence of bonding position shifts, so that the high-end electronic component41can be mounted onto the circuit board34with high precision for its bonding position.

Consequently, in the electronic component mounting method for cases in which the general-purpose electronic components31and the high-end electronic component41are mixedly mounted onto the circuit board34, it becomes possible to obtain successful results in both productivity and quality by switching a method for individual electronic components depending on a bonding position precision required for the individual electronic components.

Third Embodiment

Further, the mounting apparatus to be used for the electronic component mounting method according to a third embodiment of the invention is an electronic component mounting apparatus in which the head tool further includes a pressing mechanism for pressing an electronic component against a circuit board, wherein the electronic component mounting apparatus employs a head tool that has two large-and-small pneumatic cylinders as an example of the pressing mechanism and that is usable also for local reflow mounting apparatuses, and wherein electronic component mounting can be performed by the local reflow mounting method according to the first embodiment with the electronic component mounting apparatus having this head tool, and moreover the electronic component mounting apparatus is adaptable to local reflow mounting methods.

Structure of this head tool is explained in detail. Referring toFIG. 14, a head tool50comprises a head-tool tip portion50afor performing suction and holding, heating or other operations on electronic component1, and a head-tool body portion50bfor supporting the head-tool tip portion50aand exercising up-and-down operations on the head tool50, wherein the head-tool tip portion50ahas a small cylinder58and the head-tool body portion50bhas a large cylinder61, respectively, coaxially.

InFIG. 14, the head-tool tip portion50aincludes, as viewed from its tip side, a suction nozzle51capable of sucking and holding the electronic component1, a ceramic heater52for heating the electronic component1sucked and held by the suction nozzle51, a water jacket53for performing thermal interception so that heat derived from the ceramic heater52is not transferred to the head-tool body portion50b, a shaft57fitted to an upper portion of the water jacket53, and the small cylinder58provided at an upper portion of the shaft57, wherein the cooling blow nozzle70, for cooling the electronic component1heated by the ceramic heater52, is further fitted at a lower-portion periphery of the shaft57.

Also inFIG. 14, the head-tool body portion50bcomprises a frame56for supporting the head-tool tip portion50a, the large cylinder61provided at an upper portion of the frame56, and a load cell54fitted to a lower portion of the large cylinder61.

The frame56, which is formed of rigid body into a generally U shape, comprises an upper frame56awhere the large cylinder61is provided, a lower frame56bfor supporting the shaft57of the head-tool tip portion50avia a self-weight balancing spring55which is an elastic member fitted to a lower portion of an annular-protrusion shaped spring holder portion68provided at a side portion of the shaft57so as to surround an outer periphery of the shaft57. The lower frame56bfurther serves for guiding up-and-down motions of the shaft57, and the frame56further comprises a cylindrical-shaped intermediate frame56cfor supporting the upper frame56aand the lower frame56b.

The shaft57has a stepped portion57cnearly intermediately of its axial direction, wherein with the stepped portion57cserving as a boundary, the shaft57has a shaft lower portion57bsmaller in diameter than a shaft upper portion57a. Further, this shaft lower portion57bextends through a hole56dformed in the lower frame56bsupporting the shaft57via the self-weight balancing spring55, wherein the hole56dof the lower frame56bis formed so as to be capable of guiding up-and-down motions of the shaft57and is smaller in diameter than the shaft upper portion57aof the shaft57. As a result of this, the shaft57can be guided by the hole56dof the lower frame56bto move up and down via the self-weight balancing spring55. Also, even if the self-weight balancing spring55has become no longer capable of supporting the shaft57due to damage or the like, a peripheral portion of the hole56dof the lower frame56bcan support the shaft57by the stepped portion57cof the shaft57so that the shaft57is prevented from falling off.

Further, the shaft lower portion57bhas a ball-spline outer ring and a shaft, and the lower frame56bhas a bearing inside the hole56d, wherein the ball-spline outer ring is fitted inside the bearing. Thus, the shaft57can be rotated about its axis while being supported by the lower frame56b, and also moved up-and-down in an axial direction.

The intermediate frame56cis cylindrical at both ends, which are fixed to nut portions21bof up/down moving unit21. Rotating a ball screw shaft21a, screwed to the nut portions21b, by a motor21min the up/down moving unit21causes the intermediate frame56cto be operated to move up and down, by which the frame56is operated to move up and down, by which the head tool50as a whole is operated to move up and down.

Also, the small cylinder58includes a cylindrically-shaped guide60formed at the shaft upper portion57aof the shaft57, and a columnar-shaped rod59disposed inside the guide60and guided by an interior of the guide60to move up and down within the guide60, wherein compressed air can be supplied and exhausted to a compressed air supply chamber65surrounded by an inner surface of the guide60and a lower surface of the rod59.

Also, the large cylinder61includes a cylindrically-shaped guide63formed at an end portion of the upper frame56a, and a columnar-shaped rod62disposed inside the guide63and guided by an interior of the guide63to move up and down within the guide63, and further the rod62has a lower end of a narrow-neck portion62b, i.e., its lower portion, fitted to an upper surface of the load cell54. The large cylinder61further includes a compressed air supply chamber66surrounded by the inner surface of the guide63and the upper surface of the rod62, so that compressed air can be supplied and exhausted to the compressed air supply chamber66.

Also, the suction nozzle51, the ceramic heater52, the water jacket53, the shaft57, the guide60of the small cylinder58, the rod59, the load cell54, the guide63of the large cylinder61and the rod62are positioned coaxially on one axis, so that the rod62of the large cylinder61and the rod59of the small cylinder58move up and down on this same axis. Further, since this axis is positioned so as to be parallel to an axis of up/down operations of the up/down moving unit21, individual constituent parts of the head tool50positioned coaxially as described above are up-and-down movable on the same axis by the up/down operations of the up/down moving unit21.

Further, an upper end of the rod59of the small cylinder58in the head-tool tip portion50acan be put into contact with a load-detecting lower surface of the load cell54at the head-tool tip portion3awhich is supported on the lower frame56bvia the self-weight balancing spring55. Thus, when the upper end of the rod59of the small cylinder58makes contact with the load cell54, this contact enables the load cell54to detect a load that acts upwardly on the load-detecting lower surface of the load cell54.

Further, in the large cylinder61, the rod62has a trench-like recess portion62ain an outer periphery of its columnar-shaped side face, which is an axially central portion of the rod62, while the guide63has on its cylindrical-shaped side face a hole63aat a position where the guide63is fittable into the recess portion62aof the rod62. Further, a bar-shaped stopper64, which is an example of a bar member that can pass through this hole63aof the guide63, is formed so as to be fittable into the recess portion62aof the rod62through the hole63aof the guide63from outside of the guide63by a stopper driving cylinder67, which is an example of a bar-member drive mechanism provided outside the guide63. The rod62of the large cylinder61can be restricted in its up-and-down motions by a driving operation of the stopper driving cylinder67for making the stopper64pass through the hole63aof the guide63and thereby fitted into the recess portion62aof the rod62, and an example of a restricting mechanism for restricting operations of the rod62of the large cylinder61is constituted as described above. It is noted that an inner axial width of the recess portion62aof the rod62is set slightly larger than an axial width of the stopper64, so that the rod62having the recess portion62a, in a state that the stopper64is fitted inside the recess portion62a, i.e., in a state that the rod62is restricted in its up-and-down motions, is enabled to move up and down to a little extent corresponding to an extent by which the inner axial width of the recess portion62ais larger than that of the stopper64.

Also, the large cylinder61, the small cylinder58and the stopper driving cylinder67are connected respectively to compressed-air supply and exhaust sections69A,69B and69C, each of which is an example of a compressed-air supply and exhaust mechanism. Each of the compressed-air supply and exhaust sections69A,69B and69C is made up of an air supply portion for supplying compressed air, an air exhaust portion for exhausting compressed air, a switching valve for switching between air supply from the air supply portion and air exhaust from the air exhaust portion, and an air supply-and-exhaust line for compressed air connected from the switching valve to the cylinders, respectively.

Also, the cooling blow nozzle70fitted on the periphery of the shaft lower portion57b, which is a lower periphery of the shaft57, is formed so as to surround both sides of the water jacket53and the ceramic heater52, which are positioned under the shaft57. Further, a tip of the cooling blow nozzle70is directed toward an electronic-component suction and holding surface, i.e. lower surface, of the suction nozzle51, so that a blow from the cooling blow nozzle70can cool electronic component1sucked and held by the suction nozzle51.

Control part9controls a sucking operation of the suction nozzle51, a heating operation of the ceramic heater52, supply-and-exhaust operations of the compressed-air supply and exhaust sections69A to69C connected to the large cylinder61, the small cylinder58and the stopper driving cylinder67, respectively, and a moving operation of the up/down moving unit21, and a load detected by the load cell54is outputted to the control part9.

Next, operation of the head tool3in this third embodiment is explained with reference toFIGS. 14 and 15.

First, in a case where the head tool3is used in the local reflow mounting method of the first embodiment, referring toFIG. 14, compressed air is supplied to the compressed air supply chamber65in the small cylinder58by the compressed-air supply and exhaust section69A, so that the rod59is moved within the guide60upwardly along the inner surface of the guide60by pressure of this supplied compressed air, thereby bringing the upper end of the rod59into contact with the lower surface of the load cell54. Further, the rod62in the large cylinder61is pushed up via the load cell54, so that the rod62is moved within the guide63upwardly along the inner surface of the guide63. When this is done, the stopper64for restriction of the up-and-down motions of the rod62of the large cylinder61is not fitted inside the recess portion62aof the rod62; thus the stopper64is in the OFF state, and the rod62is in a state that the rod62is freely up-and-down movable within the guide63along the inner surface of the guide63.

Next, after the upper surface of the rod62of the large cylinder61pushed up and moved upwardly is brought into contact with an inner upper surface of the guide63, and the rod62having reached an upper end of its up-and-down motion along the inner surface of the guide63, OFF-state stopper64for restriction of the up-and-down motions of the rod62of the large cylinder61is fitted into the recess portion62aof the rod62while made to pass through the hole63aof the guide63by supplying compressed air to the stopper driving cylinder67by the compressed-air supply and exhaust section69C, as shown inFIG. 15; thus causing the stopper64to be brought into the ON state.

Thereafter, supply of the compressed air to the compressed air supply chamber65in the small cylinder58by the compressed-air supply and exhaust section69A is stopped, compressed air is exhausted from the compressed air supply chamber65in the small cylinder58by the compressed-air supply and exhaust section69A while compressed air is supplied to the compressed air supply chamber66in the large cylinder61by the compressed-air supply and exhaust section69B. Thus, by pressure of the compressed air supplied to the compressed air supply chamber66, the rod62of the large cylinder61is pushed down, so that the load cell54fitted to the lower end of the narrow-neck portion62b, which is a lower portion of the rod62, is moved downwardly, by which the rod59of the small cylinder58with its upper end in contact with the lower surface of the load cell54is pushed down via the load cell54and moved downwardly.

Thereafter, the lower end of the rod59of the small cylinder58comes into contact with an inner lower end of the guide60, so that the rod59comes into a structure integrated with the shaft57forming the guide60as a result of this contact. Further, by the rod59being pressed downwardly, the head-tool tip portion50ain its entirety supported by the lower frame56bvia the self-weight balancing spring55is pushed down, resulting in a state that the self-weight balancing spring55is compressed by this press-down load. Then, in the large cylinder61, the inner upper surface of the recess portion62aof the pushed-down rod62comes into contact with the upper portion of the stopper64, and in this contact position, the rod62is pressed downwardly and fixed by pressure of the compressed air supplied to the compressed air supply chamber66. It is noted that for relaxation of impact upon contact between the rod62and the stopper64, a quantity of compressed air supplied to the compressed air supply chamber66in the compressed-air supply and exhaust section69B is controlled stepwise by a load detected by the load cell54.

Now a relationship between the inner axial width of the recess portion62aof the rod62and the axial width of the stopper64is explained here in further detail. The relationship of these two widths is as follows. That is, after performing steps such that the rod59of the small cylinder58is pushed up and moved upwardly within the guide60along the inner surface of the guide60, by which the rod62of the large cylinder61is pushed up via the load cell54and moved upwardly within the guide63along the inner surface of the guide63, and when the rod62has been moved until the upper surface of the rod62comes into contact with the inner upper surface of the guide63, the stopper64is fittable within the recess portion62aof the rod62. Moreover, after that, the rod62of the large cylinder61is pushed down and moved downwardly within the guide63along the inner surface of the guide63, by which the rod59of the small cylinder58is pushed down via the load cell54and moved downwardly within the guide60along the inner surface of the guide60until the lower end of the rod59comes into contact with the inner lower end of the guide60, and the rod59is further pressed, by which it becomes possible to obtain a state that the self-weight balancing spring55is compressed by this pressing force with which the self-weight balancing spring55is pressed, in which state the inner upper surface of the recess portion62aof the rod62is brought into contact with the upper portion of the stopper64.

In the head tool50in such a state as described above, the electronic component1is sucked and held to the suction nozzle51, and positional alignment between the electronic component1and the circuit board4is performed. Thereafter, while the electronic component1is kept sucked and held by the suction nozzle51, the head tool50is moved down by the up/down moving unit21, by which the solder bumps1bof the electronic component1are put into contact with the solder portions2of the circuit board4, respectively. In this state, by a contact load that occurs, the upper end of the rod59of the small cylinder58formed into an integral structure with the shaft57at the upper portion of the head-tool tip portion50apresses the load-detecting surface of the load cell54, so that a contact load is detectable in the load cell54.

By detecting the contact load in the load cell54in this way, occurrence of contact between the solder bumps1bof the electronic component1and the solder portions2of the circuit board4is detected. Moreover, the contact load detected by the load cell54is outputted to the control part9, while the up/down moving unit21is controlled by the control part9so as to obtain a contact load preset in the control part9. Thus, the up/down moving unit21is controlled so that the contact load detected by the load cell54becomes a preset contact load.

Next, in a case where the head tool50is used in the local reflow mounting method of the prior art, referring toFIG. 15, in the head tool50in a state of use in the local reflow mounting method of the first embodiment, the stopper64is turned ON, and compressed air is supplied to the compressed air supply chamber66in the large cylinder61by the compressed-air supply and exhaust section69B.

First, a quantity of compressed air supplied to the compressed air supply chamber66is decreased stepwise by the compressed-air supply and exhaust section69B so that this supply of the compressed air is stopped, and thereafter supply of compressed air to the compressed air supply chamber65in the small cylinder58is started by the compressed-air supply and exhaust section69A. As a result of this, as shown inFIG. 14, the rod59of the small cylinder58is pushed up and moved upwardly within the guide60along the inner surface of the guide60, by which the upper end of the rod59is brought into contact with the lower surface of the load cell54. Further, the rod62in the large cylinder61is pushed up via the load cell54and moved upwardly within the guide63along the inner surface of the guide63.

Thereafter, the stopper64fitted within the recess portion62aof the rod62is withdrawn from the recess portion62aof the rod62by exhausting compressed air that has been supplied to the stopper driving cylinder67by the compressed-air supply and exhaust section69C, by which the stopper64that has been turned ON is turned OFF.

In the head tool50in such a state as described above, the electronic component1is sucked and held to the suction nozzle51, and positional alignment between the electronic component1and the circuit board4is performed. Thereafter, while the electronic component1is kept sucked and held by the suction nozzle51, the head tool50is moved down by the up/down moving unit21, and compressed air is supplied to the compressed air supply chamber66of the large cylinder61or the compressed air supply chamber65of the small cylinder58by the compressed-air supply and exhaust section69A or69B, by which the head-tool tip portion50ais pushed down, so that the solder bumps1bof the electronic component1are pressed against the solder portions2of the circuit board4. In this case, a load with which the suction nozzle51, sucking and holding the electronic component1, presses against the circuit board4is generated by an operation in which a pressing load detected by the load cell54via the rod62or rod59is transferred to the suction nozzle51via the shaft57by pressure of the compressed air that has been supplied to the compressed air supply chamber66in the large cylinder61or the compressed air supply chamber65in the small cylinder58by the compressed-air supply and exhaust section69A or69B. It is noted that, in this case, a product of the pressure of the compressed air and an upper-surface area of the rod62or rod59is a pressing load. The large cylinder61is used when a larger pressing load is required, and the small cylinder58is used when a smaller pressing load is required.

The above description has been made for a case where the head tool50has two large-and-small cylinders. However, when a required pressing load is limited to within a range of some extent, electronic component mounting can be fulfilled as in the above-described case by a head tool having only one cylinder.

According to the third embodiment as described above, the head tool3having pneumatic cylinders of a type used in the local reflow mounting apparatus has structure for fixing the pneumatic cylinders, for example, the recess portion62aof the rod62of the large cylinder61and the stopper64as described above, and the electronic component mounting apparatus includes such a head tool3; thus making it possible to mount the electronic component1onto the circuit board4both by the local reflow mounting method of the prior art and by the local reflow mounting method of the first embodiment.

Therefore, for example, in a case where the electronic component1is a general-purpose electronic component for which high bonding precision is not required and where this general-purpose electronic component is mounted onto the circuit board4, the stopper64in the rod62of the large cylinder61is turned OFF so that the rod62is made free to move up and down within the guide63. Thereafter, compressed air is supplied to the compressed air supply chamber66of the large cylinder61or the compressed air supply chamber65of the small cylinder58. Thus, by making use of pressure of the supplied compressed air, a pressing load detected by the load cell54via the rod62or rod59is transferred to the suction nozzle51via the shaft57, so that the suction nozzle51is pushed down, thus making it possible to mount the electronic component by the local reflow mounting method of the prior art at a high mounting speed.

Moreover, for example, in a case where the electronic component1is a high-end electronic component for which high bonding precision is required, and where the high-end electronic component is mounted onto the circuit board4, the stopper64inside the recess portion62aof the rod62in the large cylinder61is turned ON, and compressed air is supplied to the compressed air supply chamber66of the large cylinder61, by which the rod62is pushed down so that the inner upper surface of the recess portion62aof the pushed-down rod62is put into contact with the upper portion of the stopper64, thereby making the load cell54, the rod62, the guide63and the upper frame56aformed into an integral structure. Furthermore, the rod59of the small cylinder58is pushed down by the rod62of the large cylinder61via the load cell54, by which the lower end of the rod59is put into contact with an inner lower end of the guide60, thereby making the head-tool tip portion50ain its entirety into an integral state, and the rod59is further pushed down so that the head-tool tip portion50ain its entirety is pushed down via the self-weight balancing spring55; thus allowing the head tool50to be of a structural state similar to that of the head tool3of the first embodiment. In the head tool50of such a state, by performing a move-down operation of the head tool50by the up/down moving unit21, contact between an electronic component and a circuit board is detected by the load cell54, and the up/down moving unit21is controlled by the control part9so that this detected contact load becomes a preset contact load. Thus, it becomes possible to mount the electronic component by the local reflow mounting method of the first embodiment with high bonding precision. Consequently, it becomes possible to change a mounting method as required depending on bonding precision required for mounting an electronic component to a circuit board, thus allowing both productivity and quality to be satisfied at the same time.

Further, in the head tool50in which the stopper64has been turned ON so that the head tool50is ready for performing the local reflow mounting method of the first embodiment, a tip height of the suction nozzle51can be maintained constant by controlling a contraction height of the self-weight balancing spring55to a constant height, by which a stable contact load control can be achieved when electronic component1is put into contact with circuit board4, thus making it possible to stabilize a bonding quality of the electronic component.

Therefore, in the above third embodiment, in the head tool50, dimensional precision of the recess portion62aprovided at the rod62of the large cylinder61and the stopper64is enhanced besides dimensional precision of individual constituent parts constituting the large cylinder61; and moreover, a fitting position of the stopper64within the recess portion62aof the rod62is made adjustable exteriorly of the guide63of the large cylinder61, thus making it possible to control a contraction height of the self-weight balancing spring55to a constant height.

Fourth Embodiment

Further, the mounting apparatus to be used for the electronic component mounting method according to a fourth embodiment of the invention is an electronic component mounting apparatus202which further includes the head tool50of the third embodiment for sucking-and-holding and mounting of an electronic component onto a circuit board, and which is of a dual-stage specification in that the mounting apparatus has two stages7for setting thereon a circuit board onto which electronic components, in the electronic component mounting apparatus201of the first embodiment, are to be mounted, as shown inFIG. 16.

As shown inFIG. 16, in the electronic component mounting apparatus202, a plurality of IC chips73formed in a grid-like form on a wafer are fed and set to an IC chip feed section74, a plurality of high-end electronic components71is fed and set to a component tray5A, and a plurality of general-purpose electronic components72are fed and set to a component tray5B. Also, the component tray5A and the component tray5B are fixed on slide bases6A and6B on which a stage7A and a stage7B are fixed, respectively. It is noted that the high-end electronic components71and the general-purpose electronic components72are similar to the high-end electronic components41and the general-purpose electronic components31of the foregoing second embodiment, respectively, and the IC chips73are an example of electronic components to which high precision for a bonding position is required, as with the high-end electronic components71.

Further, a plurality of circuit boards4A onto which the IC chips73, the high-end electronic components71and the general-purpose electronic components72are to be mounted is fed to a circuit board feed section76, where a loader77, which performs moving operations by suction and holding of the circuit boards4A, makes it possible to remove the circuit boards4A from the circuit board feed section76and to feed the circuit boards4A to the stages7A and7B, and also makes it possible to remove the circuit boards4A with the electronic components mounted thereon from the stages7A and7B and to discharge the circuit boards4A to a circuit board discharge section78.

Further, as in the case of the electronic component mounting apparatus201of the first embodiment, the head tool50is movable by X-direction moving mechanism22and the up/down moving unit21, and the slide bases6A and6B are movable by their respective Y-direction moving mechanisms23, respectively.

Also, the IC chips73fed to the IC chip feed section74are so positioned that their face having electrodes is up, and the face having the electrodes is sucked and held by a suction-and-inversion section75, which is an example of an inversion device. Then, while IC chip73is sucked and held, the suction-and-inversion section75is rotated so that a rear face of the IC chip73having no electrodes is up, thus making it possible to suck and hold the rear face of the IC chip73by head tool50.

Next, a case is explained where the IC chip73, the high-end electronic components71and the general-purpose electronic components72are mounted onto the circuit boards4A in the electronic component mounting apparatus202having the above-described constitution.

First, from the circuit board feed section76, circuit boards4A are sucked and held and removed by the loader77, and the circuit boards4A are fed and fixed to the stages7A and7B, respectively. Then, the suction-and-inversion section75is moved and, after performance of positional alignment of the suction-and-inversion section75with one IC chip73set in the IC chip feed section74, so that the IC chip73becomes suckable and holdable by the suction-and-inversion section75, the suction-and-inversion section75is lowered, thereby sucking and holding the IC chip73, and elevated, thereby removing the IC chip73from the IC chip feed section74. Along with this, a high-end electronic component71is sucked and held, and removed, from the component tray5A by the head tool50, and the high-end electronic component71is mounted onto the circuit board4A fixed on the stage7A. When this is done, stopper64has been turned ON inside recess portion62aof rod62in large cylinder61of the head tool50so that head-tool body portion50band head-tool tip portion50aare each in an integrated-structure state, where the head tool50is in a state of the foregoing third embodiment ready for management with the local reflow mounting method of the first embodiment.

Thereafter, the IC chip73sucked and held by the suction-and-inversion section75is inverted by rotating the suction-and-inversion section75so that a rear face of the IC chip73faces upwardly. Along with this, a high-end electronic component71is sucked and held, and removed, from the component tray5A by the head tool50, and the high-end electronic component71is mounted onto the circuit board4A fixed on the stage7B. Thereafter, the head tool50is moved upwardly of the suction-and-inversion section75, and the rear face of the IC chip73sucked and held by the suction-and-inversion section75is sucked and held by the head tool50, and moreover, with the IC chip73released from the suction and holding by the suction-and-inversion section75, the IC chip73is delivered from the suction-and-inversion section75to the head tool50. After that, the IC chip is mounted by the head tool50onto the circuit board4A fixed on the stage7A.

Further after that, a general-purpose electronic component72is sucked and held, and removed, from the component tray5B by the head tool50, and the general-purpose electronic component72is mounted onto the circuit board4A fixed on the stage7A. Along with this, performed is sucking and holding of IC chip73by the suction-and-inversion section75, and removing the IC chip73from the IC chip feed section73. When this is done, the stopper64has been turned OFF inside the recess portion62aof the rod62in the large cylinder61of the head tool50so that the head tool50is in a state of the foregoing third embodiment ready for management with the local reflow mounting method of the prior art.

Thereafter, general-purpose electronic component72is sucked and held, and removed, from the component tray5B by the head tool50, and the general-purpose electronic component72is mounted onto the circuit board4A fixed on the stage7B. Along with this, the IC chip73sucked and held by the suction-and-inversion section75is inverted by rotating the suction-and-inversion section75so that a rear face of the IC chip73faces upwardly. Thereafter, same as described the above, the head tool50is moved upwardly of the suction-and-inversion section75, and a rear face of the IC chip73sucked and held by the suction-and-inversion section75is sucked and held by the head tool50, and moreover, with the IC chip73released from the suction and holding by the suction-and-inversion section75, the IC chip73is delivered from the suction-and-inversion section75to the head tool50. After that, this IC chip is mounted by the head tool50onto the circuit board4A fixed on the stage7B. When this is done, the stopper64has been turned ON inside the recess portion62aof the rod62in the large cylinder61of the head tool50again so that the head tool50is in a state of the foregoing third embodiment ready for management with the local reflow mounting method of the first embodiment.

Further after that, the circuit board104with the IC chip101and the electronic component111mounted thereon is removed from the stage7by the loader77, and discharged to the circuit board discharge section78.

These working steps as described above are iteratively performed for each circuit board4A of a plurality of circuit boards4A, by which the IC chips73, the high-end electronic components71and the general-purpose electronic components72are mounted.

According to the fourth embodiment as described above, even in cases where electronic components to be mounted onto circuit board4A are multiple types of electronic components such as the IC chips73, the high-end electronic components71and the general-purpose electronic components72, the electronic component mounting apparatus202, by virtue of its including the head tool50of the third embodiment, can be ready for management with both the local reflow mounting method of the prior art and the local reflow mounting method of the first embodiment, by this electronic component mounting apparatus202alone. Therefore, electronic components can be mounted onto the circuit boards4A with high bonding precision by performing the local reflow mounting method of the first embodiment for the high-end electronic components71and the IC chips73to which high bonding precision is required, and with high mounting speed by performing the local reflow mounting method of the prior art for the general-purpose electronic components72to which high bonding precision is not required. Consequently, it becomes possible to provide an electronic component mounting apparatus capable of satisfying both productivity and bonding quality at the same time by changing a mounting method for respective electronic components as required depending on required bonding precision of the respective electronic components.

Further, the electronic component mounting apparatus202, by virtue of its including a plurality of stages for fixing thereon the circuit boards4A, e.g. two stages7A and7B, is capable of mounting electronic components, for which an identical mounting method is required, onto the circuit boards4A, and thereafter mounting other electronic components, for which another mounting method is required, onto the circuit boards4A. As a result, it becomes possible to reduce a number of operations of turning ON and OFF the stopper64so as to insert the stopper into the recess portion62aof the rod62of the head tool50, which are operations necessary for changing the mounting method required for the respective electronic components. Thus, time loss during mounting work of electronic components by performing the turning-ON and -OFF operations of the stopper64can be reduced, so that time required for performing electronic-component mounting work can be shortened.

Fifth Embodiment

Next, a fifth embodiment of the invention is to perform mounting of various kinds of electronic components by compositely adopting the local reflow mounting method of the first embodiment and an ultrasonic mounting method, which is an electronic component mounting method of the prior art. It is noted here that the terms, ultrasonic mounting method, refer to an electronic component mounting method in which ultrasonic vibrations are applied to surfaces of bonding base materials, i.e., to surfaces of respective electrodes of electronic components or electrodes of a circuit board or the like, thereby causing friction to occur between contact surfaces of the electrodes of the electronic components and the electrodes of the circuit board, wherein resultant frictional heat serves for bonding. This fifth embodiment of the invention is explained by way of working examples as shown below.

First, a first working example of the fifth embodiment of the invention is to perform mounting of electronic components through steps of mounting high-end electronic components onto a circuit board by the local reflow mounting method of the first embodiment, and thereafter mounting electronic components onto the circuit board, on which the high-end electronic components have been mounted, by the ultrasonic mounting method.

An electronic component mounting apparatus203for performing the electronic component mounting method in the first working example is first described.

As shown inFIG. 17, the electronic component mounting apparatus203includes the head tool3of the first embodiment for sucking and holding a high-end electronic component and mounting it onto a circuit board, and an ultrasonic tool113for mounting electronic components by the ultrasonic mounting method, wherein a circuit board104is fixed on a stage7fixed on a slide base6. Also, a plurality of IC chips101formed in a grid-like form on a wafer, which are an example of the high-end electronic component, is fed to an IC chip feed section74, and a plurality of electronic components111to be mounted onto the circuit board104by the ultrasonic mounting method is fed and set to a component tray5.

Further, a plurality of circuit boards104onto which the IC chips101and the electronic components111are to be mounted is fed to a circuit board feed section76, where a loader77, which performs moving operations by suction and holding of circuit board104, makes it possible to remove the circuit board104from the circuit board feed section76and to feed the circuit board104to the stage7, and moreover, makes it possible to remove the circuit board104with the electronic components mounted thereon from the stage7and to discharge the circuit board104to a circuit board discharge section78.

Further, as in the case of the electronic component mounting apparatus201of the first embodiment, the head tool3is movable by the X-direction moving mechanism22and the up/down moving unit21, and the ultrasonic tool113is also movable by the X-direction moving mechanism22and an up/down moving unit21A, and furthermore, slide bases6are movable by the Y-direction moving mechanism23.

Also, the IC chips101fed to the IC chip feed section74are so positioned that their face having electrodes is positioned up, and the face having the electrodes is sucked and held by a suction-and-inversion section75. Then, while an IC chip101is sucked and held, the suction-and-inversion section75is rotated so that a rear face of the IC chip101having no electrodes is positioned up, thus making it possible to suck and hold the rear face of the IC chip101by the head tool3.

Next, the electronic component mounting method of the first working example in a case where the IC chips101and the electronic components111are mounted onto the circuit board104with the electronic component mounting apparatus203having the above-described constitution is explained in detail.

As shown inFIG. 18A, a quadrangular-plate shaped circuit board104has pads104aand104b, which are a plurality of electrodes, on its upper surface. The pads104aare bondable to a plurality of electrodes101aof IC chip101, and the pads104bare bondable to a plurality of electrodes111aof electronic component111.

Referring toFIG. 17, from the circuit board feed section76, to which a plurality of such circuit boards104has been fed, a circuit board104is sucked and held, removed, and fed and fixed to the stage7, by the loader77.

Then, referring toFIG. 17, the suction-and-inversion section75is moved and, after performance of positional alignment of the suction-and-inversion section75with one quadrangular-plate shaped IC chip101set in the IC chip feed section74so that the IC chip73becomes suckable and holdable by the suction-and-inversion section75, the suction-and-inversion section75is lowered, thereby sucking and holding the IC chip101, and elevated, thereby removing the IC chip101from the IC chip feed section. Thereafter, the IC chip101sucked and held by the suction-and-inversion section75is inverted by rotating the suction-and-inversion section75so that the rear face of the IC chip101is positioned up. Then, the head tool3is moved upwardly of the suction-and-inversion section75, and the rear face of the IC chip101sucked and held by the suction-and-inversion section75is sucked and held by a suction nozzle11of the head tool3, and moreover, with the IC chip101released from the suction and holding by the suction-and-inversion section75, the IC chip101is delivered from the suction-and-inversion section75to the head tool3.

Next, referring toFIG. 18B, as solder bumps101bare formed on individual electrodes101aof the IC chip101sucked and held by the suction nozzle11of the head tool3, the IC chip101is aligned with the circuit board104so that the solder bumps101bof the IC chip101become bondable to the pads104aof the circuit board104, respectively.

Thereafter, as shown inFIG. 18C, while the suction nozzle11of the head tool3sucking and holding the IC chip101is being moved down, the solder bumps101bof the IC chip101are brought into contact with the pads104aof the circuit board104, respectively. After this contact, the solder bumps101bof the IC chip101in contact with the pads104aof the circuit board104are heated and melted by the ceramic heater12of the head tool3. Thereafter, heating by the ceramic heater12is stopped, and then the molten solder is subjected to cooling by blows from the cooling blow nozzle19, thereby the molten solder bumps101bare solidified, so that the electrodes101aof the IC chip101and the pads104aof the circuit board104are bonded via the solder bumps101b. The solder may also be solidified by natural cooling of the molten solder instead of forced cooling of the molten solder by the cooling blow nozzle19.

Thereafter, as shown inFIG. 18D, sucking and holding of the IC chip101by the suction nozzle11of the head tool3is released, and the head tool3is moved up, thus the IC chip101is mounted onto the circuit board104.

At this point, for example, in a case where flux is fed onto surfaces of respective solder bumps101bof the IC chip101or onto respective pads104aof the circuit board104, flux cleaning for removing flux is performed. This flux cleaning in some cases may be unnecessary depending on the type of the flux that is fed.

Next, referring toFIG. 17, the ultrasonic tool113is moved, and after performance of positional alignment of the ultrasonic tool113with one quadrangular-plate shaped electronic component111set in the component tray5so that the electronic component111becomes suckable and holdable by the ultrasonic tool113, the ultrasonic tool113is lowered, thereby sucking and holding the electronic component111, and elevated, thereby removing the electronic component111from the component tray5.

Next, as shown inFIG. 19E, as solder bumps111bare formed on individual electrodes11aof the electronic component111sucked and held by the ultrasonic tool113, the electronic component111is aligned with the circuit board104so that the solder bumps111bof the electronic component111become bondable to pads104bof the circuit board104with the IC chip101mounted thereon.

Thereafter, as shown inFIG. 19F, while the ultrasonic tool113sucking and holding the electronic component111is moved down so that the solder bumps111bof the electronic component111are pressed against the pads104aof the circuit board104, ultrasonic vibrations are applied to surfaces of the individual solder bumps111bof the electronic component111and surfaces of the individual pads104bof the circuit board104, which are in contact with each other, by the ultrasonic tool113, thus causing friction to occur between these individual contact surfaces. By frictional heat resulting from this friction, the solder bumps111bof the electronic component111and the pads104bof the circuit board104are bonded together.

Thereafter, as shown inFIG. 19G, sucking and holding of the electronic component111by the ultrasonic tool113is released, and the ultrasonic tool113is moved up; thus the electronic component111is mounted onto the circuit board104.

Through the electronic component mounting method as described the above, the IC chip101and the electronic component111are mounted onto the circuit board104.

Further after that, the circuit board104on which the IC chip101and the electronic component111have been mounted is sucked and held by the loader77, and thereby removed from the stage7and discharged to the circuit board discharge section78.

These working steps as described above are iteratively performed for each circuit board104of a plurality of circuit boards104, by which the IC chips101and the electronic components111are mounted on individual circuit boards104.

According to the first working example of the fifth embodiment as described above, by virtue of an arrangement in which the electronic component mounting apparatus203includes the head tool3capable of performing the local reflow mounting method of the first embodiment and the ultrasonic tool113capable of performing the ultrasonic mounting method, it becomes possible to perform mounting of IC chip101onto circuit board104by the local reflow mounting method of the first embodiment and thereafter perform mounting of electronic component111by the ultrasonic mounting method. Therefore, for example, in a case where the electronic component111is an electronic component which requires prevention from any effects of heat, the electronic component111is kept from any effects of heat due to melting and heating of solder during mounting of IC chip101, thus allowing the electronic component111to be mounted onto the circuit board104without being affected by heat. Also, for example, in a case where flux is fed onto solder bumps101bof IC chip101or onto pads104aof circuit board104, and where flux needs to be removed after mounting of the IC chip101, the IC chip101can be mounted onto the circuit board104by the local reflow mounting method of the first embodiment, followed by removal of flux that has been fed by performance of flux cleaning, and thereafter, the electronic component111can be mounted by the ultrasonic mounting method, thus eliminating a need for taking into consideration any effects of a flux cleaning liquid on the electronic component111that is mounted by the ultrasonic mounting method during the flux cleaning, or any effects of re-deposition or the like of minute chips or the like, cleaned away during the flux cleaning, onto the electronic component111. Thus, it becomes possible to compositely mount onto a circuit board the electronic component111that requires consideration for such effects as described the above, e.g. electronic components to which a heatproof environment or waterproof environment is required during their mounting, by the ultrasonic mounting method, together with a high-end electronic component such as IC chips to which high precision for a bonding position is required.

Next, a second working example of the fifth embodiment of the invention is to first perform mounting of electronic component111onto circuit board104by the ultrasonic mounting method, and thereafter perform mounting of IC chip101, which is an example of high-end electronic components, onto the circuit board104, on which the electronic component111has been mounted, by the local reflow mounting method of the first embodiment. That is, the second working example is a result of reversing the order of the ultrasonic mounting method and the local reflow mounting method of the first embodiment with respect to the first working example of the fifth embodiment.

According to the second working example of the fifth embodiment as described above, mounting of the electronic component111onto the circuit board104is performed by the ultrasonic mounting method, and thereafter mounting of the IC chip101onto the circuit board104, on which the electronic component111has been mounted, is performed by the local reflow mounting method of the first embodiment. Therefore, it becomes possible to eliminate a need for taking into consideration any effects of ultrasonic vibrations, generated during the ultrasonic mounting, on the IC chip101. Thus, in a case where the high-end electronic component, such as IC chips to which high precision for a bonding position is required, is an electronic component that requires further consideration as to effects of vibrations, the electronic component can be mounted onto the circuit board mixedly and together with an electronic component that is mounted by the ultrasonic mounting method.

Further, a third working example of the fifth embodiment of the invention is to first perform by the ultrasonic mounting method mounting of an electronic component onto a circuit board via a sealing material for sealing a bonding portion between the electronic component and the circuit board, and thereafter perform by a collective reflow mounting method temporary bonding of a general-purpose electronic component onto the circuit board, on which the electronic component has been mounted, via solder, and thereafter perform primary bonding, and thereby mounting, by applying heat collectively to the electronic component, the general-purpose electronic component to the circuit board to make a seal of the bonding portion between the electronic component and the circuit board by the sealing material, and also to melt solder of the general-purpose electronic component that has been temporarily bonded via the solder. Subsequently, the third working example is further to perform, by the local reflow mounting method of the first embodiment, mounting of a high-end electronic component onto the circuit board on which the electronic component and the general-purpose electronic component have been mounted. Hereinbelow, the electronic component mounting method of this third working example is described in detail.

As shown inFIG. 20A, a quadrangular-plate shaped circuit board124has pads124a,124band124c, which are a plurality of electrodes, on its upper surface. The pads124aare bondable to a plurality of electrodes121aof electronic component121to be mounted onto the circuit board124by the ultrasonic mounting method, the pads124bare bondable to a plurality of electrodes131aof general-purpose electronic component131, and the pads124care bondable to a plurality of electrodes141aof high-end electronic component141. A sealing material122, which is a non-conductive resin material, is fed to portions on the circuit board124where the quadrangular-plate shaped electronic component121is to be mounted, including places on the pads124aand their vicinities of the circuit board124. Also, Au bumps121bare formed on the electrodes121aof the electronic component121. First, a rear face of the electronic component121, which is a face having no electrodes121a, is sucked and held by an ultrasonic tool123, and the electronic component121is aligned with the circuit board124so that the Au bumps121bof the electronic component121become bondable to the pads124aof the circuit board124, respectively.

Thereafter, as shown inFIG. 20B, while the ultrasonic tool123, sucking and holding the electronic component121, is being moved down, the Au bumps121bof the electronic component121are pressed against the pads124aof the circuit board124, respectively, via the sealing material122. As a result, the sealing material122between the Au bumps121bof the electronic component121and the pads124aof the circuit board124is pushed away, and the Au bumps121bof the electronic component121are pressed against the pads124aof the circuit board124, respectively, wherein ultrasonic vibrations are applied to surfaces of the individual Au bumps121bof the electronic component121and surfaces of the individual pads124aof the circuit board124, which are in contact with each other, by the ultrasonic tool123, thus causing friction to occur between these individual contact surfaces. By frictional heat resulting from this friction, the Au bumps121bof the electronic component121and the pads124aof the circuit board124are bonded together, wherein these bonding portions are covered with the sealing material122fed between the electronic component121and the circuit board124.

Thereafter, sucking and holding of the electronic component121by the ultrasonic tool123is released, and the ultrasonic tool123is moved up, thus the electronic component121is mounted onto the circuit board124.

Next, as shown inFIG. 20C, as solder bumps131bare formed on the electrodes131aof quadrangular-plate shaped general-purpose electronic component131, a rear face of the general-purpose electronic component131, which is a face having no electrodes131a, is sucked and held by a tool133, and the general-purpose electronic component131is aligned with the circuit board124so that the solder bumps131bof the general-purpose electronic component131become bondable to the pads124bof the circuit board124, respectively.

Thereafter, as shown inFIG. 20D, the tool133, sucking and holding the general-purpose electronic component131is moved down, so that the solder bumps131bof the general-purpose electronic component131are pressed against the pads124bof the circuit board124, thereby being temporarily bonded. In a case where a plurality of general-purpose electronic components131are mounted onto the circuit board124, the above working steps are iteratively performed for each general-purpose electronic component131, by which the general-purpose electronic components131are temporarily bonded to the circuit board124.

Next, as shown inFIG. 21E, in a state that the bonding portions are covered with the sealing material122, the electronic component121is mounted, and the circuit board124with the general-purpose electronic component131temporarily bonded thereto is conveyed to a reflow soldering working section. In the reflow soldering working section, the electronic component121, the general-purpose electronic component131and the circuit board124are heated by a heat source, by which the solder bumps131bof the general-purpose electronic component131are melted, and moreover, the sealing material122of the electronic component121is also heated. Thereafter, the heated electronic component121, general-purpose electronic component131and circuit board124are cooled. As a result, the solder bumps131bof the molten general-purpose electronic component131are solidified, so that the electrodes131aof the general-purpose electronic component131are finally bonded, and thereby mounted, to the pads124bof the circuit board124via the solder bumps131b. Moreover, the sealing material122of the heated electronic component121is solidified, so that the Au bumps121bof the electronic component121and the pads124aof the circuit board124, which are bonding portions between the electronic component121and the circuit board124, are sealed by the sealing material122.

Next, referring toFIG. 21F, as solder bumps141bare formed on the electrodes141aof quadrangular-plate shaped high-end electronic component141, a rear face of the high-end electronic component141, which is a face having no electrodes141a, is sucked and held by the suction nozzle11of the head tool3, and the high-end electronic component141is aligned with the circuit board124so that the solder bumps141bof the high-end electronic component141become bondable to the pads124c, respectively, of the circuit board124on which the electronic component121and the general-purpose electronic component131have been mounted.

Thereafter, as shown inFIG. 21G, while the suction nozzle11of the head tool3, sucking and holding the high-end electronic component141, is being moved down, the solder bumps141bof the high-end electronic component141are brought into contact with the pads124cof the circuit board124. After this contact, the solder bumps141bof the high-end electronic component141, which are in contact with the pads124cof the circuit board124, are heated and melted by the ceramic heater12of the head tool3. Then, after heating by the ceramic heater12is stopped, the molten solder bumps141bare subjected to cooling by blows from the cooling blow nozzle19, with the molten solder bumps141bbeing thereby solidified so that the electrodes141aof the high-end electronic component141and the pads124cof the circuit board124are bonded together, respectively, via the solder bumps141b. The molten solder bumps141bmay also be solidified by natural cooling of the molten solder instead of the forced cooling of the molten solder bumps141bby the cooling blow nozzle19.

Thereafter, as shown inFIG. 21H, sucking and holding of the high-end electronic component141by the suction nozzle11of the head tool3is released, and the head tool3is moved up, thus the high-end electronic component41is mounted onto the circuit board124.

Through the electronic component mounting method as described the above, the electronic component121, the general-purpose electronic component131and the high-end electronic component141are mounted onto the circuit board124.

According to the third working example of the fifth embodiment as described above, in addition to effects of the second working example, sealing by the sealing material122for the bonding portions of the electronic component121bonded to the circuit board124by the ultrasonic mounting method, as well as the primary bonding by the collective reflow for the general-purpose electronic component131temporarily bonded to the circuit board124, can further be performed simultaneously by collectively heating electronic components and a circuit board by a heat source. Therefore, in cases where electronic components to be mixedly placed on a circuit board are general-purpose electronic components, electronic components which are mounted by the ultrasonic mounting method and which need sealing of bonding portions, and high-end electronic components to which high precision for a bonding position is required, it becomes possible to reduce a mounting time of these electronic components onto a circuit board.

In addition, combining any arbitrary embodiments together appropriately from among the foregoing various embodiments allows their respective effects to be produced.

According to the first aspect or second aspect of the present invention, while electrodes of an electronic component sucked and held by the component holding member and electrodes of a circuit board are kept in contact with bonding members, the bonding members between these electrodes are melted by heating, and releasing of the electronic component from suction and holding by the component holding member is performed, not at a time during melting of the bonding members as in the conventional local reflow mounting method, but at a time after the bonding members are melted, cooled and solidified. That is, the electronic-component mounting is not performed based on obtainment of a self alignment effect by surface tension of the molten bonding members as in the conventional local reflow mounting method, but mounting of the electronic component onto the circuit board is performed at a contact position positioned by the component holding member. As a result of this, there can be eliminated any bonding position shifts of the electronic component due to a vacuum break blow occurring when the electronic component is released from the suction and holding by the component holding member. Consequently, it becomes possible to achieve mounting onto the circuit board of such electronic components as those of narrowed electrode pitches of electronic components in which bonding position shifts of the electronic components, due to the vacuum break blow at the component holding member, would matter rather than obtainment of the self alignment effect.

According to the third to sixth aspects of the invention, the bonding-material feeding method, the bonding-material constituent materials or the flux feeding method which have been used in the electronic component mounting method of the prior art can be applied, thus making it possible to provide a mounting method for electronic components of general-purpose use.

According to the seventh to ninth aspects of the invention, operations of causing electrodes of an electronic component, sucked and held by the component holding member, and electrodes of a circuit board to be brought into contact with respective bonding members, and melting the bonding members by heating, are performed not in the manner, as in the local reflow mounting method of the prior art, that the electrodes of the electronic component and the electrodes of the circuit board are merely pressed against the bonding members to make the bonding members melt, or that the electrodes of the electronic component and the electrodes of the circuit board are pressed against the bonding members after melting of the bonding members by heating, but in a manner that the electrodes of the electronic component and the electrodes of the circuit board are brought into contact with the bonding members and thereafter the bonding members are melted by heating. Therefore, since the bonding members are not yet in a molten state at a time of contact, it becomes possible to detect a load that actually occurs between the electrodes of the electronic component and the electrodes of the circuit board, and further to exert control so that, at this contact, a detected load actually occurring becomes beyond a contact load that is predicted to occur upon such contact. Therefore, in a process of performing mounting onto the circuit board iteratively for a plurality of electronic components, it is possible to exert precise control so that an actually occurring load constantly becomes beyond a contact load that is predicted to occur upon contact. Thus, a contact position upon contact of each electronic component with the circuit board can be made more uniform, an interval pitch between the electrodes of the electronic component can be made narrower, and mounting onto the circuit board can be achieved while a bonding position relative to the circuit board is kept more stable for electronic components for which high precision for the bonding position relative to the circuit board is required, such as high-end electronic components.

According to the tenth aspect of the invention, after detection of contact between either electrodes of an electronic component sucked and held by the component holding member or electrodes of a circuit board and bonding members, in this contact state, individual bonding members between the electrodes are heated and thereby melted, and releasing of the electronic component from the suction and holding by the component holding member is performed not at a time during melting of the bonding members as in the conventional local reflow mounting method, but at a time after the bonding members are melted, cooled and solidified. That is, the electronic-component mounting is not performed based on obtainment of a self alignment effect by surface tension of the molten bonding members as in the conventional local reflow mounting method, but mounting of the electronic component onto the circuit board is performed at a contact position positioned by the component holding member. As a result of this, there can be eliminated any bonding position shifts of the electronic component due to a vacuum break blow occurring when the electronic component is released from suction and holding by the component holding member. Consequently, it becomes possible to achieve mounting onto the circuit board of such electronic components as those of narrowed electrode pitches in which bonding position shifts of the electronic components due to a vacuum break blow at the component holding member would matter rather than obtainment of the self alignment effect.

According to the eleventh to fourteenth aspects of the invention, the bonding-material feeding method, bonding-material constituent materials or a flux feeding method which have been used in an electronic component mounting method of the prior art can be applied, thus making it possible to provide a mounting method for electronic components of general-purpose use.

According to the fifteenth aspect of the invention, in addition to effects of the foregoing aspects, after detection of contact between either electrodes of an electronic component or electrodes of a circuit board and bonding members, it is decided whether or not a correction of an elongation amount of the component holding member due to heating is executed, and further, after start of cooling of molten bonding members, it is decided whether or not a correction of shrinkage amount of the component holding member due to cooling is performed. Thus, it becomes possible to obtain a required bonding quality of an electronic component depending on whether both the elongation-amount correction and the shrinkage-amount correction of the component holding member are performed, or only either one of the elongation-amount correction or the shrinkage-amount correction is performed, or neither the elongation-amount correction nor the shrinkage-amount correction is performed, depending on a number of electrodes of the electronic component or a bonding precision required for the electronic component.

According to the sixteenth aspect or seventeenth aspect of the invention, only either one of the elongation-amount correction or the shrinkage-amount correction is performed. Thus, it becomes possible to obtain a required bonding quality of an electronic component, like effects of the fifteenth embodiment.

According to the eighteenth aspect or nineteenth aspect of the invention, after detection of contact between either electrodes of an electronic component or electrodes of a circuit board and bonding members, a load that actually occurs between these electrodes, due to this contact is maintained at a generally constant level, and thereafter, upon a decision that a detection of a decrease of the load is regarded as a start of melting of the bonding members, a control mode is switched from one control mode in which the load is maintained generally constant to another control mode in which a contact height position of the electronic component relative to the circuit board is maintained generally constant, by which even in a molten state of the bonding members, a contact height position of the electronic component can be maintained generally constant. As a result, during melting of the bonding members, molten bonding members can be prevented from crushing due to lowering of the contact height position of the electronic component. Thus, it becomes possible to reliably perform control of the contact height position of the electronic component even during a molten state of the bonding members.

Further, in the control mode in which the load is maintained generally constant, the load is set to a load not less than a contact load upon a contact detection, and this set load is, while maintained generally constant, applied to the electronic component and the circuit board. By so doing, even if some of the electrodes are not in contact with each other via the bonding members because of variations in a formation height of the bonding members upon detection of contact between either electrodes of the electronic component or the electrodes of the circuit board and the bonding members, it is possible to enhance contactability between the electrodes and the bonding members by applying a load that is maintained generally constant, and thus to enhance bonding reliability of the electronic component and the circuit board.

According to the twentieth aspect of the invention, before an electronic component is put into contact with a circuit board, a leveling operation is performed so that bonding members that have preliminarily been fed onto electrodes of the electronic component are made more uniform in their feed height. As a result, even if there are variations in feed height among the bonding members on the electrodes of the electronic component, it is possible to eliminate these variations and make the bonding members more uniform in feed height. Thus, upon contact of the bonding members and either the electrodes of the electronic component or the electrodes of the circuit board, there can be eliminated any effects on a contact load control due to variations in feed height of the bonding members, so that successful controllability for contact load can be obtained and that the contact load can be applied to individual bonding members more uniformly. Consequently, the electrodes of the electronic component and the electrodes of the circuit board can be brought into contact with the bonding members with a more uniform contact load and with reliability. Thus, it is possible to stabilize a bonding quality between the electronic component and the circuit board.

According to the twenty-first aspect of the invention, in the electronic component mounting method for mounting two types of electronic components, a first electronic component and a second electronic component, onto a circuit board, wherein higher bonding positional precision for mounting onto the circuit board is required of the second electronic component than of the first electronic component, the first electronic component is temporarily bonded to the circuit board by the conventional collective reflow mounting method, and this temporarily bonded first electronic component and the circuit board are heated so that the first electronic component is mounted, and thereafter the second electronic component is mounted onto the circuit board, on which the first electronic component has been mounted, by the electronic component mounting methods of the foregoing individual embodiments.

As a result of this, the first electronic component, after being separately temporarily bonded onto the circuit board, can be heated to melt bonding members, and then the first electronic component can be finally bonded and mounted onto the circuit board, thus allowing mounting work to be achieved efficiently. Therefore, mounting costs of the first electronic component onto the circuit board can be suppressed.

Moreover, the second electronic component is maintained sucked and held by the component holding member from contact with bonding members between electrodes of the second electronic component and electrodes of the circuit board until solidification of the bonding members after their melting. As a result of this, there occur no bonding position shifts between the second electronic component and the circuit board, so that the second electronic component can be mounted onto the circuit board with high precision for a bonding position.

Accordingly, in the electronic component mounting method in a case where a plurality of electronic components different in bonding positional precision from each other, like the first electronic component and the second electronic component, are mixed mounted onto a circuit board, it becomes possible to satisfy both productivity and bonding quality at the same time by changing a mounting method for respective electronic components as required depending on required bonding precision of the respective electronic components.

According to the twenty-second aspect or twenty-third aspect of the invention, while electrodes of an electronic component sucked and held on the component holding member by the suction-and-holding mechanism, and electrodes of a circuit board, are kept in contact with bonding members, the bonding members between these electrodes are heated and melted by the heating mechanism, and releasing of the electronic component from the suction and holding on the component holding member by the suction-and-holding mechanism is performed, not at a time during melting of the bonding members as in the conventional local reflow mounting method, but at a time after the bonding members are solidified by cooling by the cooling mechanism, after heating and melting of the bonding members by the heating mechanism. That is, the electronic-component mounting is not performed based on obtainment of a self alignment effect by surface tension of molten bonding members as in the conventional local reflow mounting method, but mounting of the electronic component onto the circuit board is performed at a contact position positioned by the component holding member. As a result of this, there can be eliminated any bonding position shifts of the electronic component due to a vacuum break blow occurring when the electronic component is released from the suction and holding on the component holding member by the suction-and-holding mechanism. Consequently, it becomes possible to achieve mounting onto the circuit board of such electronic components as those of narrowed electrode pitches in which bonding position shifts of the electronic components due to a vacuum break blow at the suction-and-holding mechanism would matter rather than obtainment of the self alignment effect.

According to the twenty-fourth to twenty-sixth aspects of the invention, it becomes possible to provide an electronic component mounting apparatus capable of obtaining the effects of the seventh to ninth embodiments.

According to the twenty-seventh aspect of the invention, it becomes possible to provide an electronic component mounting apparatus capable of obtaining the effects of the tenth embodiment.

According to the twenty-eighth aspect of the invention, after positional alignment is performed so that electrodes of an electronic component sucked and held by the suction-and-holding mechanism of the component holding member are bondable to electrodes of a circuit board, a pressing load with which the shaft at the component-holding-member tip portion is pressed against the load-detecting surface of the load-detecting section by the elastic member is detected by the load detecting section, and this detected pressing load is outputted to the control part. In the control part, this pressing load is set as a load-zero point in the load detecting section. Thus, even in a case where the pressing load by the component-holding-member tip portion changes in the load detecting section because of changes of elastic characteristics of the elastic member under influence of heat or the like, there are no differences between an actual contact load upon contact between either the electrodes of the electronic component or the electrodes of the circuit board and bonding members, and a detected value of the contact load detected by the load detecting section, thus allowing control of the actual contact load according with a preset contact load to be achieved. Thus, in a case where mounting to the circuit board is iteratively performed for a plurality of electronic components, individual electronic components can be put into association with the circuit board constantly with a preset contact load, so that a stable bonding quality of electronic components to the circuit board can be achieved.

According to the twenty-ninth aspect of the invention, the suction-and-holding mechanism in the component holding member, the shaft, and the load detecting section have their centers positioned coaxially on one axis that is positioned parallel to the axis of up/down operations of the component holding member performed by the up-and-down moving mechanism. Thus, the suction-and-holding mechanism, the shaft, and the load detecting section are moved up and down on the same axis. Further, in the component holding member, an end portion of the shaft in the component-holding-member tip portion is pressed against the load-detecting surface of the load detecting section by the elastic member, which is fitted to the support portion to support the shaft. Thus, it becomes possible for the load detecting section to detect a load that acts in the coaxial direction of the component-holding-member tip portion. Then, by a contact load occurring between electrodes of an electronic component sucked and held by the suction-and-holding mechanism of the component holding member and electrodes of a circuit board upon contact between these electrodes and bonding members, the end portion of the shaft in the component-holding-member tip portion is pressed against the load-detecting surface of the load detecting section, thus making it possible for the load detecting section to detect the contact load by the load detecting section with reliability.

Therefore, contact between the electrodes of the electronic component or the electrodes of the circuit board and the bonding members can be detected by detection of the contact load in the load detecting section, and moreover, the component holding member is moved down in small steps by the up/down moving mechanism so that the actual contact load can be more accurately controlled so as to become a preset contact load. Accordingly, in a case where mounting to a circuit board is iteratively performed for a plurality of electronic components, the actual contact load can be more accurately controlled so as to become a preset contact load constantly. Thus, a contact position upon contact of each electronic component with the circuit board can be made more uniform, an interval pitch between the electrodes of the electronic component can be made narrower, and mounting onto the circuit board can be achieved while a bonding position relative to the circuit board is kept more stable for electronic components to which high precision for the bonding position relative to the circuit board is required, such as high-end electronic components.

According to the thirtieth aspect of the invention, the component holding member further includes a pressing mechanism having two pneumatic cylinders different in inner diameter from each other. Therefore, for example, in a case where an electronic component is a general-purpose electronic component to which high bonding precision is not required, and where the general-purpose electronic component is mounted onto a circuit board, a pneumatic cylinder of an inner diameter suitable for a load of use is selected from the pneumatic cylinders, and compressed air is supplied to this selected pneumatic cylinder. By utilizing pressure of this supplied compressed air, the pneumatic cylinder is operated, causing the component-holding-member tip portion to be moved down, so that electrodes of the general-purpose electronic component sucked and held by the suction-and-holding mechanism can be pressed, along with electrodes of the circuit board, against bonding members therebetween. Thus, it becomes possible to operate the pneumatic cylinders by pressure of compressed air, so that the general-purpose electronic component can be mounted with a high mounting speed by the local reflow mounting method of the prior art.

In addition to this, at least one pneumatic cylinder, out of the two pneumatic cylinders of different inner diameters, includes a restricting mechanism for restricting operations of the one pneumatic cylinder. Therefore, for example, in a case where an electronic component is a high-end electronic component to which high bonding precision is required, and where the high-end electronic component is mounted onto a circuit board, compressed air is supplied to the pneumatic cylinder including the restricting mechanism out of the pneumatic cylinders, thereby activating the pneumatic cylinder, by which the other pneumatic cylinder is pressed and operation of the other pneumatic cylinder is restricted. Further, in this state, restricting operation of the pneumatic cylinder including the restricting mechanism by the restricting mechanism results in a state that operations of the two pneumatic cylinders are restricted, wherein the component-holding-member tip portion and the component-holding-member body portion in the component holding member can each be in an integrated-structure state. As a result, the component holding member can be made in a structural state similar to that of the component holding member of the twenty-first aspect, and therefore, like the effects of the twenty-first aspect, contact between either electrodes of a high-end electronic component or electrodes of a circuit board and bonding members can be detected by detection of a contact load in the load detecting section, and moreover, the component holding member is moved down in small steps by the up/down moving mechanism so that an actual contact load can be more accurately controlled so as to become a preset contact load. Accordingly, in a case where mounting to a circuit board is iteratively performed for a plurality of the high-end electronic components, an actual contact load can be more accurately controlled so as to become a preset contact load constantly. Thus, a contact position upon contact of each high-end electronic component with the circuit board can be made more uniform, an interval pitch between the electrodes of the electronic component can be made narrower, and mounting onto the circuit board can be achieved while a bonding position relative to the circuit board is kept more stable for electronic components for which high precision for the bonding position relative to the circuit board is required, such as high-end electronic components.

According to the thirty-first aspect of the invention, the restricting mechanism includes a recessed portion of a rod of a pneumatic cylinder having the restricting mechanism, a guide hole, and a bar member which extends through the hole and which is fittable into the recessed portion. Thus, by inserting the bar member through hole so that the bar member is fitted into the recessed portion, it becomes possible to mechanically restrict operations of the pneumatic cylinder having the restricting mechanism with a simpler mechanism.

According to the thirty-second aspect of the invention, a large cylinder is provided in the component-holding-member body portion, and a small cylinder is provided in the component-holding-member tip portion. By this arrangement, increase in weight due to placement of the pneumatic cylinders at the component-holding-member tip portion supported by the component-holding-member body portion via the elastic member can be suppressed. Thus, smaller contact loads can be detected, so that an actual contact load can be controlled with higher controllability so as to become a preset contact load.

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom. For example, even though the electrodes have been described as being distinct from solder that forms the bonding members, insofar as the appended claims are concerned an “electrode” is considered to be any electrically conductive member that functions as an electrode, including a combination of electrode4aand solder portion2, or a combination of electrode1aand other electrically conductive material thereon.