Paste transfer unit, electronic component mounting device, and transferred film thickness measuring method

To measure a film thickness of a coating film (25a) of a flux (25) serving as a bonding paste formed on a transfer stage (24) of a paste transfer unit (7), the film thickness of the coating film (25a) in a transfer area (26) is measured through a light-transmitting member (51) by a light interference method and by an optical type film thickness measuring sensor (53) which is arranged below the transfer stage (24). Thus, it is possible to automatically and accurately measure the film thickness of the flux (25) in the transfer area (26) without requiring any complicated measurement work.

TECHNICAL FIELD

The present invention relates to a paste transfer unit, an electronic component mounting device and a transferred film thickness measuring method, which are used for transferring a bonding paste to an electronic component in the electronic component mounting device.

BACKGROUND ART

In solder bonding for bonding electronic components to a substrate through solder bumps of a semiconductor package etc., the solder bumps are landed on electrodes of the substrate in the state in which a bonding paste (hereinafter simply referred to as “paste”) such as a flux or a soldering paste has been supplied to the solder bumps. In an electronic component mounting device for such electronic components to be mounted through solder bumps, a paste transfer unit for transferring a paste is disposed and the film thickness of a coating film formed on the paste transfer unit is required to be measured accurately in order to precisely adjust a transfer amount of the paste to each solder bump. Therefore, there has been disclosed a transfer unit using a system in which the film thickness can be measured automatically in place of a method which has been heretofore used to measure the film thickness by manual operation by means of a film thickness measuring jig (e.g. Patent Literature 1). In the conventional technique shown in the example of the Patent Literature, a film thickness measuring sensor is disposed above a peripheral position avoiding a transfer area to which a mounting head moves during transfer operation, so that the film thickness measuring sensor can be prevented from interfering with the mounting head which moves while holding electronic components in a space above the transfer unit.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, in the background-art technique described in the aforementioned Patent Literature, the film thickness to be practically transferred in the transfer area is not a target to be measured. Due to this fact, there is a disadvantage as follows. That is, recently, due to a growing demand for halogen-free also in the electronic device industry from the viewpoint of environment protection, the kinds of additive components contained in the paste used for solder bonding have been limited. As a result, the viscosity of the paste to be transferred is lower than before.

Therefore, the paste formed into a film to be transferred may get out of shape easily due to sagging as time elapses. Thus, a difference is generated in the film thickness of the paste between the transfer area and its periphery. As a result, when a measurement result obtained from the film thickness measured in the periphery of the transfer area is used, an accurate measurement value of the practically required film thickness in the transfer area cannot be obtained. Thus, the bonding quality is made unstable due to a variation in the transfer amount of the paste transferred to each of the solder bumps. In this manner, there is a problem that it is difficult to automatically and accurately measure the film thickness of the paste in the transfer area without requiring any complicated measurement work in order to transfer the paste for use in the electronic component mounting device according to the background art.

Therefore, an object of the present invention is to provide a paste transfer unit, an electronic component mounting device and a transferred film thickness measuring method, in which the film thickness of a paste in a transfer area can be measured automatically and accurately without requiring any complicated measurement work.

Solution to Problem

A paste transfer unit according to an aspect of the present invention is used for transferring a light-transmissible bonding paste to a solder bump in an electronic component mounting device which mounts, on a substrate, an electronic component having a lower surface on which the solder bump is formed, the paste transfer unit including: a transfer stage to which the bonding paste is supplied and in which at least a part of a transfer area is made of a light-transmitting member, the transfer area being configured to transfer the bonding paste as a result of the solder bump moving; a squeegee which is arranged above the transfer stage to have a predetermined film-formation-gap from a coating film formation surface on the transfer stage and which moves relatively and horizontally to the transfer stage to thereby form the supplied bonding paste into a coating film with a predetermined film thickness; and an optical type film thickness measuring sensor which is arranged below the transfer stage and which measures the film thickness of the coating film in the transfer area through the light-transmitting member.

An electronic component mounting device according to an aspect of the present invention causes a mounting head to pick up an electronic component from a component feeding portion and carry and mount the electronic component onto a substrate, the electronic component having a lower surface on which a solder bump is formed, the electronic component mounting device including: a paste transfer unit which is used for transferring a light-transmissible bonding paste to the solder bump on the electronic component held by the mounting head; and a head moving unit which moves the mounting head to make the mounting head move toward the substrate and the paste transfer unit; wherein the paste transfer unit is the aforementioned paste transfer unit.

A transferred film thickness measuring method according to an aspect of the present invention measures a film thickness of a coating film of a light-transmissible bonding paste formed on a transfer stage of a paste transfer unit used for transferring the bonding paste to a solder bump in an electronic component mounting device which mounts on a substrate, an electronic component having a lower surface on which the solder bump is formed, wherein the film thickness of the coating film in a transfer area is measured through a light-transmitting member by an optical type film thickness measuring sensor which is arranged below the transfer stage, the light-transmitting member being formed in at least a part of the transfer area, the transfer area being configured to transfer the bonding paste as a result of the solder bump moving.

Advantageous Effects of Invention

According to the present invention, to measure a film thickness of a coating film of a bonding paste formed on a transfer stage of a paste transfer unit, the film thickness of the coating film in the transfer area is measured through a light-transmitting member by an optical type film thickness measuring sensor arranged below the transfer stage. Thus, the thickness of the film of the paste in the transfer area can be measured automatically and accurately without requiring any complicated measurement work.

DESCRIPTION OF EMBODIMENT

An embodiment of the present invention will be described below with reference to the drawings. First, the structure of an electronic component mounting device will be described with reference toFIG. 1andFIG. 2. InFIG. 1, a substrate conveyance mechanism2is arranged in an X direction (substrate conveyance direction) on a base1aof an electronic component mounting device1. The substrate conveyance mechanism2conveys a substrate3as a target of a component mounting work. Component feeding portions which feed electronic components are arranged on both sides of the substrate conveyance mechanism2. A plurality of kinds of electronic components including electronic components which include solder bumps formed in their lower surfaces are received in the component feeding portions.

A plurality of tape feeders6feeding electronic components held on tapes and a paste transfer unit7having mounting compatibility with other component feeders including the tape feeders6are mounted detachably in the component feeding portion4A on one side so that the tape feeders6and the paste transfer unit7can be arranged in parallel with one another. A tray feeder5which feeds trays5areceiving electronic components is set in the component feeding portion4B on the other side.

The paste transfer unit7has a function of supplying a bonding paste such as a flux or a soldering paste in the state of a coating film to a coating film formation surface. The bonding paste is applied by transfer to electronic components held by a mounting head10which will be described later. Here, a light-transmissible flux to be applied by transfer to bumps for mounting the electronic components P (FIG. 2) including the bumps is a target to be transferred as the bonding paste.

A Y-axis table8is arranged in a Y direction in one X-direction end portion of the base1a. The Y direction is perpendicular to the substrate conveyance mechanism2. Two X-axis tables9A and9B are connected to the Y-axis table8so as to be movable in the Y direction. Mounting heads10are mounted on the X-axis table9A and9B respectively. When the X-axis table9B and the Y-axis table8are driven, the corresponding mounting head10picks up electronic components P from one of the trays5aheld by the tray feeder5of the component feeding portion4B, and carries and mounts the picked-up electronic components P onto the substrate3positioned and held by the substrate conveyance mechanism2.

In addition, when the X-axis table9A and the Y-axis table8are driven, the corresponding mounting head10picks up electronic components P from some of the tape feeders6of the component feeding portion4A by nozzles10a(seeFIG. 2) mounted on a lower portion of the mounting head10, and makes the picked-up electronic components P move to the paste transfer unit7for paste transfer. In addition, the corresponding mounting head10carries and mounts the electronic components P to which the paste has been transferred, onto the substrate3positioned and held by the substrate conveyance mechanism2. Accordingly, the X-axis table9A and the Y-axis table8constitute a head moving unit which moves the mounting head10to thereby make the mounting head10move toward the substrate3and the paste transfer unit7.

The X-axis tables9A and9B are equipped with substrate recognizing cameras11which move integrally with the mounting heads10respectively. When one of the mounting heads10moves above the substrate3, the corresponding substrate recognizing camera11also moves to capture an image of the substrate3. A component recognizing camera12and a nozzle stocker13are arranged between each component feeding portion4A,4B and the substrate conveyance mechanism2in the base1a.

The nozzle stocker13receives the nozzles10awhich can be mounted on the corresponding mounting head10for a plurality of component kinds. When the mounting head10is made to move to the nozzle stocker13and execute a predetermined nozzle exchange operation, the nozzles10ain the mounting head10can be exchanged in accordance with the component kinds. The mounting head10having held electronic components P is relatively moved in the X direction above the component recognizing camera12. In this manner, the component recognizing camera12can read an image of the electronic components P from below. As a result, the kind or shape of each of the electronic components P which are held by the mounting head10can be recognized. In the operation in which the electronic components P are mounted by the mounting head10, mounting positions in the substrate3are corrected in consideration of the substrate recognition result made by the substrate recognizing camera11and the component recognition result made by the component recognizing camera12.

Next, the structure of the paste transfer unit7will be described with reference toFIG. 2,FIG. 3,FIG. 4(a) andFIG. 4(b). As shown inFIG. 2, the paste transfer unit7has a configuration in which respective portions which will be described below are provided in a base portion20having a long shape. The base portion20is mounted detachably from an opposite side of a moving direction (arrow a) of the mounting head10while the longitudinal direction of the base portion20is aligned with a feeder base16(seeFIG. 3)in the Y direction. The feeder base16is provided in the component feeding portion4A. In the description, the moving side where the mounting head10is moved toward the paste transfer unit7is defined as front side and the opposite direction to the moving side where the mounting head10is moved the paste transfer unit7is defined as rear side.

An engagement portion20awhich is engaged with the feeder base16so as to fix the base portion20to the feeder base16in the same manner as the other tape feeders6is provided in the paste transfer unit7. Further, a handle21is provided to protrude rearward from the engagement portion20a. To attach the paste transfer unit7to the feeder base16, the handle21is pushed forward while being held in the state in which the lower surface side of the base portion20extends along the upper surface of the feeder base16. In this manner, the engagement portion20ais engaged with a rear end portion of the feeder base16. Thus, the base portion20is mounted in a predetermined position.

Guide rails22are arranged in the longitudinal direction on the upper surface of the base portion20. Sliders23fitted to the guide rails22so as to be slidable thereon are firmly fixed to the lower surface of a transfer stage24. A transfer area26is provided in the transfer stage24so that a flux25as a light-transmissible bonding paste can be supplied to the transfer area26while solder bumps of electronic components P can move to the transfer area26. Thus, the flux25can be transferred to the solder bumps of the electronic components P in the transfer area26. As shown inFIG. 3, a feed screw32is screwed to a nut34connected to the lower surface of the transfer stage24. The feed screw32is driven and rotated by a motor31disposed on a rear end portion side of the base portion20. Accordingly, when the motor31is driven, the transfer stage24moves back and forth in the longitudinal direction over the upper surface of the base portion20.

That is, the guide rails22, the sliders23, the nut34, the feed screw32, and the motor31serve as a stage driving unit which can move the transfer stage24back and forth in the longitudinal direction with respect to the base portion20. This stage driving unit is covered with a safety cover33in order to protect the safety of a worker. Here, the stage driving unit has a configuration in which the motor31as a drive source of the stage driving unit is disposed on the opposite side of the moving direction of the mounting head10. In this manner, move of the mounting head10to the paste transfer unit7in a component mounting operation performed by the mounting head10can be prevented from being disturbed.

The transfer stage24has the structure of a rectangular member in which a recess having a smooth bottom is formed on its upper surface side. The bottom of the recess serves as a coating film formation surface24afor forming a coating film of the flux25and transferring the coating film of the flux25to electronic components. The transfer area26where the coating film of the flux25is transferred to electronic components P held by the mounting head10is set in a front end portion of the coating film formation surface24a. Here, the size of the transfer area26is set in such a manner that the flux25can be collectively transferred to a plurality of electronic components P held by a plurality of (eight in this case) nozzles10aof the mounting head10. On this occasion, the transfer stage24is shaped like a rectangle. Accordingly, the transfer area26can be set to be as large as possible with respect to the width of the transfer stage24so that the whole width of the paste transfer unit7can be made as small as possible.

A film formation squeegee unit28and a scraping unit29are disposed above the transfer stage24, at the rear of the transfer area26and in positions not interfering with the mounting head10. Further, a needle30aof a paste supply cylinder30is inserted and disposed between the film formation squeegee unit28and the scraping unit29. The paste supply cylinder30and the needle30asupply the flux25to the transfer stage24. The film formation squeegee unit28is held by a bracket27provided erectly on the base portion20so that the horizontal position of the film formation squeegee unit28can be fixed with respect to the base portion20.

The detailed structure of the film formation squeegee unit28will be described with reference toFIG. 3,FIG. 4(a) andFIG. 4(b).FIG. 4(a) andFIG. 4(b) show a section taken along Line A and a section taken along Line B inFIG. 3respectively. InFIG. 3, the film formation squeegee unit28is provided with a squeegee28awhich extends downward to have its lower end portion arranged at a predetermined film-formation-gap g (seeFIG. 6(a)) from the coating film formation surface24a. Accordingly, the squeegee28ais connected to a connection member35. The connection member35is mounted on the bracket27through slide units37. The squeegee28acan move up and down relatively to the bracket27.

When the transfer stage24in the state in which the flux25has been supplied to the coating film formation surface24ais relatively moved in the Y direction by the aforementioned stage driving unit, the squeegee28aspreads the flux25which has been supplied to the coating film formation surface24a, so as to form a coating film25awith a predetermined film thickness corresponding to the film-formation-gap g. When the transfer stage24on which the film has been formed is moved to the side of the moving direction performed by the mounting head10, the transfer area26(FIG. 2) where the coating film25aof the flux25has been formed can be positioned in a position where a paste transfer operation will be performed by the mounting head10, as shown inFIG. 3.

A film thickness measuring unit50is arranged on the upper surface of a front end portion of the base portion20and located below the transfer area26in the state in which the transfer stage24has moved to the front. As shown inFIG. 4(b), the film thickness measuring unit50is located below a light-transmitting member51such as glass provided within the range of the transfer area26in the transfer stage24. The film thickness measuring unit50is connected to a measurement processing portion52. The film thickness measuring unit50has a function of optically measuring the film thickness of the coating film25awhich has been formed on the coating film formation surface24ain the transfer area26through the light-transmitting member51.

The configuration and function of the film thickness measuring unit50will be described with reference toFIG. 5(a) andFIG. 5(b). As shown inFIG. 5(a), the film thickness measuring unit50has a configuration in which an optical type film thickness measuring sensor53and an optical prism54are received inside a rectangular sensor block50adisposed horizontally. The optical type film thickness measuring sensor53serves as a spectral interference type displacement sensor which is inserted into a reception hole50bprovided longitudinally in the sensor block50a.

A measurement opening50cis formed in a front end portion of the sensor block50aand located below the light-transmitting member51mounted in a mounting hole24bof the transfer stage24. The optical prism54is mounted below the measurement opening50c. To measure the film thickness, inspection light (arrow b) of a broad wavelength band radiated from a sensor head of the optical type film thickness measuring sensor53is reflected upward by the optical prism54. The reflected light of the inspection light entering the flux25from below through the light-transmitting member51is received by the optical type film thickness measuring sensor53so that the film thickness of the flux25can be obtained.

That is, as shown inFIG. 5(b), inspection light (arrow c) radiated from the optical type film thickness measuring sensor53enters the light-transmitting member51through the optical prism54and is further reflected by a lower surface25cand an upper surface25bof a coating film25a(arrows d and e). These reflected lights are received by the optical type film thickness measuring sensor53through the optical prism54(arrow f). Signals of these received lights are transmitted to the measurement processing portion52(FIG. 4(b)) so that a film thickness t of the coating film25aon the light-transmitting member51can be obtained based on the intensity of coherent light of these reflected lights.

In order to obtain an accurate measurement result in the film thickness measurement based on the aforementioned spectral interference method, the material used for the light-transmitting member51is required to have an optical characteristic with a higher light refractive index than that of the light-transmissible flux25which is typically used. For example, it is desirable that a material having a refractive index not smaller than 1.7 is used as the light-transmitting member51.

The portion where the light-transmitting member51is formed in the transfer stage24can be set suitably as long as the film thickness within the transfer area26can be measured in the portion. For example, the light-transmitting member51may be mounted in a rectangular range set within the transfer area26in the coating film formation surface24aor the light-transmitting member51may be formed as spots in the transfer area26. In brief, it might be sufficient that the light-transmitting member51is formed in at least a part where film thickness measurement is required in the transfer area26.

In addition, an example in which the film thickness is measured through the optical prism54arranged below the light-transmitting member51has been shown as the method for arranging the optical type film thickness sensor53in the aforementioned embodiment. In some layout of components in the paste transfer unit7, however, the optical type film thickness measuring sensor53may be arranged without using the optical prism54. For example, the optical type film thickness measuring sensor53may be set in an upright posture so that inspection light can enter the light-transmitting member51directly. Further, an example in which the optical type film thickness measuring sensor53is arranged fixedly but separately from the transfer stage24which can move horizontally has been shown in the embodiment. However, the optical type film thickness measuring sensor53may have a configuration in which the optical type film thickness measuring sensor53is provided integrally with the lower surface of the transfer stage24to be always able to measure the film thickness.

InFIG. 3, the scraping unit29is provided with a scraper29aextending downward. The scraper29ais urged downward to be always brought into abutment against the coating film formation surface24ain spite of the height position of the transfer stage24. When the transfer stage24is moved back and forth in the Y direction by the stage driving unit, the scraper29ascrapes the flux25on the transfer stage24.

An elevating member36arranged in an up and down direction is connected to the connection member35. A cam follower38is connected to a lower end portion of the elevating member36which penetrates the inside of the base portion20. A motor40is arranged in a horizontal posture inside the base portion20. A circular plate cam39connected to a rotary shaft of the motor40abuts against the cam follower38. When the motor40is driven and rotated in this state, the elevating member36moves up and down in accordance with the cam characteristic of the circular plate cam39. Accordingly, the squeegee28amoves up and down relatively to the coating film formation surface24a.

That is, the elevating member36, the cam follower38, the circular plate cam39and the motor40serve as a squeegee position adjusting unit which adjusts the position of the squeegee28ain the up and down direction. In a film formation operation which will be described later, the position of the squeegee28acan be adjusted in the up and down direction so that the film-formation-gap g between the lower end portion of the squeegee28aand the coating film formation surface24acan be changed. Accordingly, the thickness of the coating film of the flux25in the coating film formation surface24acan be changed. Although a cam mechanism in which the cam follower38and the circular plate cam39are combined with each other is used as the squeegee position adjusting unit here, any other drive system than the cam mechanism may be used as long as the drive system is a linear motion mechanism which can move the elevating member36up and down desirably.

As shown inFIG. 3, an air coupler41aand an electric connector41bconstituting a unit side connection portion41are provided in the engagement portion20aprovided on the lower surface side of the base portion20. The air coupler41aand the electric connector41bare connected to a control and drive unit45built in the paste transfer unit7by air piping and electric wiring respectively. The control and drive unit45has a function of controlling and driving the motor31as the drive source of the stage driving unit or the motor40as the drive source of the film formation squeegee unit28, supplying or controlling compressed air for discharging the flux25from the paste supply cylinder30, further controlling the film thickness measuring unit50and the measurement processing portion52to measure the transferred film thickness of the flux25in the coating film formation surface24a, and controlling the squeegee position adjusting unit based on the measurement result to adjust the film-formation-gap g. Accordingly, the control and drive unit45serves as a gap adjusting portion which adjusts the film-formation-gap g based on the measurement result of the film thickness measured by the optical type film thickness measuring sensor53.

A base side connection portion42constituted by an air coupler42aand an electric connector42bis provided in the rear end portion of the feeder base16. The air coupler42aand the electric connector42bare connected to a control and power supply portion43and a compressed air supply source44by air piping and electric wiring respectively. When the paste transfer unit7is slid forward along the feeder base16and mounted, the unit side connection portion41is fitted to the base side connection portion42. In this manner, the control and power supply portion43is electrically connected to the control and drive unit45. Further, compressed air can be supplied from the compressed air supply source44to the control and drive unit45. When the paste transfer unit7is slid rearward, connection of the control and drive unit45with the control and power supply portion43and the compressed air supply source44is cut off.

That is, the paste transfer unit7configured thus is provided with the unit side connection portion41which is connected to the base side connection portion42provided in the feeder base16to transmit a control signal or to supply motive power. In this manner, by a simple operation of mounting the paste transfer unit7onto the feeder base16, transmission of the control signal and supply of drive electric power from the control and power supply portion43to the control and drive unit45can be performed without any separate connection work, and drive compressed air can be supplied from the compressed air supply source44to the control and drive unit45.

Next, a film formation operation and a scraping operation performed by the paste transfer unit7will be described with reference toFIG. 6(a) toFIG. 6(d). First,FIG. 6(a) shows a state in which the transfer stage24has been in a retreat position, and the squeegee28aand the scraper29ahave been located in a film formation start side end portion (right end portion in this example) in the coating film formation surface24aand the flux25has been supplied between the squeegee28aand the scraper29athrough the needle30abefore the start of the film formation operation. The film-formation-gap g between the lower end portion of the squeegee28aand the coating film formation surface24ais set at a predetermined film thickness which is proper for transferring the flux25to bumps of electronic components P when the film formation operation is started.

Then, a stage moving unit is driven to move the transfer stage24forward (arrow h), as shown inFIG. 6(b). In this manner, the flux25is spread on the coating film formation surface24aby the squeegee28aand a coating film25awith a predetermined film thickness is therefore formed on the coating film formation surface24a. Then, the film thickness in the transfer area26is measured. That is, as shown inFIG. 6(c), inspection light is made incident on the coating film25athrough the light-transmitting member51by the film thickness measuring unit50so that the film thickness t of the coating film25acan be measured by the measurement processing portion52(FIG. 4(b)).

Here, when the measurement result is within a specified range, the mounting head10having the nozzles10aholding electronic components P is moved above the transfer stage24and the nozzles10aare moved up and down (arrow i) here to perform a transfer operation, as shown inFIG. 6(d). In this manner, the flux25can be transferred to the bumps of the electronic components P so that the bumps of the electronic components P can be coated with the flux25. On the other hand, when the measurement result is out of the specified range, a process of adjusting the film-formation-gap g is performed based on the measurement result.

Then, the scraping operation of the flux25is performed. That is, in the state in which the squeegee28ahas been moved up, the transfer stage24is retreated. Thus, the flux25existing on the coating film formation surface24ais scraped to one side by the scraper29aso as to return to the state shown inFIG. 6(a). Then, the film formation operation and the scraping operation are performed repeatedly in the same manner. In this process, the film thickness of the coating film25ain the transfer area26is always measured so that proper film thickness management can be performed. Accordingly, a proper transfer amount for the flux25can be secured for mounting the electronic components P.

As described above, according to a transferred film thickness measuring method in the paste transfer unit7and the electronic component mounting device1shown in the embodiment, to measure the film thickness of a coating film of the flux25formed on the transfer stage24of the paste transfer unit7, the film thickness of the coating film25ain the transfer area26is measured through the light-transmitting member51by the optical type film thickness measuring sensor53arranged below the transfer stage24. In this manner, even when a light-transmissible material such as the light-transmissible flux25which has a viscosity characteristic easy to lose its shape and from which an accurate measurement result cannot be obtained easily by a typical film thickness measuring method is used as the bonding paste to be transferred, the film thickness in the transfer area where transfer is practically performed can be measured automatically and accurately without requiring any complicated measurement work.

The present application is based on Japanese Patent Application No. 2012-284186 filed on Dec. 27, 2012, the contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The paste transfer unit, the electronic component mounting device and the film thickness measuring method according to the present invention have an effect that the thickness of a film of a paste in the transfer area can be measured automatically and accurately without requiring any complicated measurement work. Accordingly, the paste transfer unit, the electronic component mounting device and the film thickness measuring method according to the present invention are useful in a field where electronic components to which a paste is necessarily supplied before mounting are mounted on a substrate.

REFERENCE SIGNS LIST

1electronic component mounting device

4A,4B component feeding portion

7paste transfer unit

24acoating film formation surface

50film thickness measuring unit

52measurement processing portion

53optical type film thickness measuring sensor

P electronic component