Abstract:
An electronic component mounting method is disclosed. The method includes the following steps: applying a paste remaining on a stamping pin to the bottom wall of at least one reservoir; forming the paste retained in the at least one reservoir to a predetermined film thickness by a clearance regulation section; causing the paste formed into a film to adhere to the stamping pin; stamping the paste to a substrate; and mounting the electronic components held by a mounting head to the substrate on which the paste has been stamped.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to an electronic component mounting apparatus that mounts electronic components on a substrate with a paste adhesive stamped thereto. 
     2. Description of the Related Art 
     In a field of electronic components being mounted on a substrate, stamping a paste adhesive affixed to a stamping pin provided on a stamping head to the substrate has hitherto been known as a method for supplying the substrate with the paste adhesive. The stamping pin has a stamp surface for letting the paste adhesive adhere and stamping the thus-adhering adhesive to a substrate. Projections appropriate for a shape desired to be stamped are formed on the stamp surface. Although the paste adhesive adhering to the projection is stamped to the substrate, the paste adhesive builds up in space between the projections with an increase in the number of times stamp is performed. The adhesive adheres to a substrate, which in turn becomes a cause for deteriorating stamp quality. A hitherto known apparatus has a cleaning unit disposed between a paste adhesive supply position and a stamp position. A stamp surface is brought into contact with a cleaning material, such as non-woven fabric, thereby cleaning the stamp surface and removing the built-up paste adhesive (see Patent Document 1). 
     Patent Document 1: JP-A-2001-7136 
     However, the cleaning unit is situated at a position where the cleaning unit occupies a location and does not interfere with another member. Therefore, the cleaning unit does not always situate at a position on a traffic line of the stamp head achieved during normal operation. For this reason, the stamp head is required to perform movement, which differs from movement performed during normal operation, for cleaning purpose. As a result, there arises a problem of movement of the stamp head involving consumption of time and deterioration of productivity. 
     SUMMARY OF THE INVENTION 
     The present invention aims at providing an electronic component mounting apparatus that can eliminate a paste adhesive from a stamp pin without deterioration of productivity. 
     A first aspect of the invention provides with an electronic component mounting apparatus, comprising: a paste retaining section retaining a paste that bonds an electronic component to a substrate; a stamp head causing the paste of the paste retaining section to attach to a stamp pin and stamping the paste to the substrate; and a mounting head mounting the electronic component to the substrate to which the paste has been stamped; wherein the paste retaining section has at least two annular reservoirs that are concentrically arranged, a reservoir rotation section rotating the reservoirs, a squeegee shielding cross sections of at least one of the reservoirs, and a clearance regulation section adjusting clearance between the squeegee and a bottom wall of the at least one of reservoirs; and wherein the paste remained on the stamp pin is test-stamped to at least the other one of the reservoirs. 
     According to the present invention, a paste reservoir is embodied as a plurality of concentrically-arranged annular reservoirs, and one of the reservoirs is used as a test-stamping field. A necessity for providing a test-stamping field is obviated, and a distance over which the stamping head moves for test-stamping purpose can be shortened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an oblique perspective view of an electronic component mounting apparatus of an embodiment of the present invention; 
         FIG. 2  is an oblique perspective view of a paste supply section movement mechanism of the embodiment of the present invention; 
         FIG. 3  is a plan view of the electronic component mounting apparatus of the embodiment of the present invention; 
         FIG. 4  is a flowchart of test-stamping operation of the electronic component mounting apparatus of the embodiment of the present invention; and 
         FIG. 5  is an oblique perspective view of a reservoir of the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention is now described by reference to the drawings.  FIG. 1  is an oblique perspective view of an electronic component mounting apparatus of an embodiment of the present invention;  FIG. 2  is an oblique perspective view of a paste supply section movement mechanism of the embodiment of the present invention;  FIG. 3  is a plan view of the electronic component mounting apparatus of the embodiment of the present invention;  FIG. 4  is a flowchart of test-stamping operation of the electronic component mounting apparatus of the embodiment of the present invention; and  FIG. 5  is an oblique perspective view of a reservoir of the embodiment of the present invention. 
     As shown in  FIG. 1 , an electronic component mounting apparatus  1  includes, as principal portions, three working heads; namely, a pickup head  2 , a bonding head  3 , and a stamping head  4 , and four working tables; namely, a component supply table  5 , a component relay table  6 , a mounting table  7 , and a paste supply table  8 . The working heads are arranged, in a depth-wise direction, in sequence of the pickup head  2 , the bonding head  3 , and the stamping head  4  from a front side to a rear side of the electronic component mounting apparatus  1 . Likewise, the working tables are arranged in sequence of the component supply table  5 , the component relay table  6 , the mounting table  7 , and the paste supply table  8 . In addition, the electronic component mounting apparatus  1  has a substrate conveyance mechanism  10  for conveying a substrate  9 , a rectilinearly movable mechanism  11  for moving the respective working heads, a rectilinearly movable mechanism  30  for moving the paste supply table  8  (see  FIG. 2 ), and four cameras  12 ,  13 ,  14 , and  15 . 
     The pickup head  2  moves in both a vertical direction and a depth-wise direction of the electronic component mounting apparatus  1  [designated by an arrow “a”: a direction orthogonal to a direction of conveyance of the substrate  9  (designated by an arrow “b”)], thereby convey chips  20 . The chips  20  are affixed onto a wafer sheet  21  held on the component supply table  5 . The pickup head  2  attracts each of the chips  20  with a nozzle  22  by suction, to thus peel the chip  20  away from the wafer sheet  21  and place the chip  20  on the component relay table  6 . 
     The first camera  12  ascertains positions and orientations of the chips  20  on the wafer sheet  21 . When a positional displacement is ascertained, a correction is made to the position of the chip  20  by moving the component supply table  5  within a horizontal plane and also to an angle of the nozzle  22  according to the orientation of the chip  20 . 
     The component relay table  6  is arranged on a movable table  23  along with a nozzle stocker  24  and the second camera  15 . The movable table  23  can move in the direction of conveyance of a substrate (designated by the arrow “b”) by means of a rectilinearly movable device  25 . A cleaning head  26  is disposed in a travel pathway of the movable table  23 . When the movable table  23  moves immediately below the cleaning head  26 , the cleaning head  26  cleans up an upper surface of the component relay table  6  (a chip mounting surface) or eliminates an unwanted chip. Nozzles and stamping pins for replacement purpose are stored in the nozzle stocker  24 . 
     The bonding head  3  moves in both the vertical direction and the depth-wise direction (designated by the arrow “a”) of the electronic component mounting apparatus  1  and mounts the chip  20  attracted through suction by a nozzle  27  onto the substrate  9 . In addition to attracting the chip  20  placed on the component relay table  6  by suction, the bonding head  3  can also directly attract, by suction, the chip  20  from the wafer sheet  21  and the chip  20  attracted through suction by the pickup head  2 . When the chip is received from the pickup head  2 , the chip  20  turned upside down is attracted by suction along with inversion of the pickup head  2 . The chip remaining turned upside down is mounted, as it is, whereby flip-chip bonding is performed. 
     The third camera  13  ascertains the position and orientation of the chip  20  on the component relay table  6 . When positional displacement of the chip is ascertained, a correction is made to a positional relationship between the nozzle  27  and the chip  20  by means of movement of the bonding head  3  (designated by the arrow “a”) and movement of the component relay table (designated by the arrow “b”). An angle of the nozzle  27  is corrected according to the orientation of the chip  20 . In the case of flip-chip bonding, the second camera  15  captures an image of the chip  20  attracted through suction by the nozzle  27  of the bonding head  3 , thereby ascertaining the position and orientation of the chip. 
     The stamping head  4  moves in both the vertical direction and the depth-wise direction (designated by the arrow “a”) of the electronic component mounting apparatus  1  and stamps the paste attached to a stamping pin  28  onto the substrate  9 . Paste is retained in the paste supply table  8 . The stamping head  4  immerses the stamping pin  28  into the paste, whereby a given amount of paste is affixed to the stamping pin  28 . The paste is stamped by pressing the stamping pin  28  against the substrate  9 . 
     A position and a shape of the paste stamped to the substrate  9  may also be ascertained by means of the fourth camera  14 . After the paste is ascertained to have been stamped to a correct position and into a correct shape, the chip  20  is mounted onto the paste. The fourth camera  14  is also used for ascertaining the position and orientation of the mounted chip  20 . 
     The substrate  9  conveyed into the electronic component mounting apparatus  1  from its side is conveyed onto the mount table  7  by the substrate conveyance mechanism  10 . The substrate conveyance mechanism  10  hooks a tip end of an arm  29  to a rear portion of the substrate  9  and conveys the substrate  9  in such a manner that the substrate  9  is synchronized with movement of the arm  29 . 
     The paste supply table  8  and the rectilinearly movable mechanism  30  are described by reference to  FIG. 2 . The paste supply table  8  has an L-shaped plate  31  as a principal element, and two annular paste reservoirs  32  and  33  are integrally formed with each other and concentrically arranged on a horizontal portion of the plate. The first reservoir  32  is placed inside the second reservoir  33 , and a paste-like adhesive is retained in the first reservoir  32 . The second reservoir  33  acts as a vacant reservoir where no paste is present and is used as a test-stamping field for eliminating the paste still remaining on the stamping pin  28 . The first reservoir  32  and the second reservoir  33  are rotated around the center axis of the concentric circles by a motor  34 . 
     Each of the reservoirs  32  and  33  has a squeegee  35  for shielding a cross section of the reservoir. The two squeegees  35  can independently ascend or descend by means of regulation mechanisms  36  and  37  using micrometer heads, and the like, to thus be able to adjust clearance between the squeegees  35  and bottom walls  38 ,  39  of the respective reservoirs  32 ,  33  according to elevated and lowered positions. The paste retained in the first reservoir  32  is made, at a position downstream of the squeegee  35 , to a uniform thickness commensurate with clearance between the squeegee  35  and the bottom wall  38 . Meanwhile, in the second reservoir  33 , the applied paste is scraped by the squeegee  35  held in close contact with the bottom wall  39 , so that no paste adheres to a downstream portion of the bottom wall  39  with respect to the squeegee  35 . Since there is no chance of paste again adhering to the stamping pin  28  at the downstream position with respect to the squeegee  35 , the paste can be applied again and again even in a small area diverted from the paste reservoir. Further, the application can always be performed at the same location. 
     As shown in  FIG. 3 , the electronic component mounting apparatus  1  is arranged such that the concentrically-arranged two annular reservoirs  32  and  33  are spaced apart from the substrate  9  in the direction of movement of the stamping head  4 , so that the stamping head  4  can linearly move between the reservoirs  32  and  33  and the substrate  9 . Paste is stored in the inner first reservoir  32 , and the outer second reservoir  33  serves as a paste application field. The stamping head  4  performs paste stamping operation while moving between a position P 1  set on the first reservoir  32  and the substrate  9 . A position P 2  where the application is performed is set on the second reservoir  33  along the traffic line of the stamping head  4 . 
     The stamping head  4  immerses the stamping pin  28  into the paste of the first reservoir  32  at the paste receive position P 1 , thereby causing the paste of a regulated thickness to adhere to the stamping pin  28 . The stamping head moves to a position above the substrate  9  and stamps the paste to the substrate  9  after being positioned. The test paste application position P 2  is situated in a direction “a” (the direction of movement of the stamping head  4 ) with respect to the paste receive position P 1  and along the traffic line of the stamping head  4  that moves between the first reservoir  32  and the substrate  9  for stamping operation. Therefore, the stamping head  4  can perform application operation without moving away from the traffic line during stamping operation. 
     A rotary shaft of the motor  34  and the paste reservoirs  32  and  33  are coupled together at a rear of the L-shaped plate  31  by an endless belt  40 . The pickup head  2 , the component relay table  6 , and the bonding head  3  are arranged along the traffic line of the stamping head  4 . Specifically, the pickup head  2 , the bonding head  3 , and the stamping head  4  are arranged so as to move along a single traffic line. By means of such an arrangement, exchange of a chip between the heads and positioning for taking over operation can readily be performed. 
     The rectilinearly movable mechanism  30  is made up of a horizontally-extending rail  41 , a rod-less cylinder  42 , and a slider  43  slidably attached to the rail  41 , A built-in magnet provided in the rod-less cylinder  42  is pneumatically actuated, whereby a slider  43  exhibiting a magnetic property moves so as to follow motion of the magnet. The slider  43  is provided with a rail  44  extending in the vertical direction, and another slider  45  attached to a vertical portion of the L-shaped plate  31  is slidably attached to the rail  44 . 
     The paste supply table  8  can move in the depth-wise direction (designated by the arrow “a”) of the electronic component mounting apparatus  1  while taking the entire length of the rail  41  as a travel. When paste is stamped to the substrate  9 , the paste supply table  8  is moved to the rear side of the electronic component mounting apparatus  1 , to thus approach the substrate  9 . A travel distance of the stamping head  4  is thus shortened, thereby attempting to enhance efficiency of stamping operation. On the contrary, the paste supply table  8  is reversely moved toward the front side during maintenance operation, such as cleaning of the reservoirs  32  and  33  and replenishment of the paste, so as to approach an operator situated at the front. Thus, operability of maintenance is enhanced. 
     Even when ascertaining a shape of paste applied to the second reservoir  33  by use of the third camera  13 , the paste supply table  8  performs movement. The fourth camera is for ascertaining the shape of the paste stamped to the substrate  9 , or the like. Since the position where paste is to be stamped and the position P 2  where paste is to be applied are arranged side by side along the direction of movement of the paste supply table  8 , the paste supply table  8  is moved, whereby the paste applied to an angular field of view of the fixed fourth camera  14  can be moved. 
     The rectilinearly movable mechanism  30  has a paste supply table elevation mechanism  46  for vertically moving the paste supply table  8 . The paste supply table elevation mechanism  46  is a cylinder mechanism having a recess  48  that is provided at a leading end of a piston rod so as to engage with a protrusion  47  formed on a side of the L-shaped plate  31 . The paste supply table elevation mechanism  46  causes the paste supply table  8  to ascend or descend by means of extraction and contraction of the piston rod. The paste supply table elevation mechanism  46  is disposed on the rear side of the electronic component mounting apparatus  1  and controls an elevated or lowered position of the paste supply table  8  in such a way that a difference of elevation between a liquid level of paste and an upper surface of the substrate  9  becomes smaller. In this case, the paste supply table  8  descends closer to the substrate  9 , which may interfere with the arm  29  in motion. For this reason, the paste supply table  8  is caused to ascend during a period of conveyance of a substrate to an elevated position where the table does not interfere with the arm  29  in motion. 
     Application operation of the electronic component mounting apparatus  1  is now described by reference to a flowchart shown in  FIG. 4 . When the electronic component mounting apparatus  1  starts operation (ST 1 ), a test-stamping counter is first reset to zero (ST 2 ). The applied counter is provided in a control system of the electronic component mounting apparatus  1  and counts the number of times test-stamping is performed. Since a count achieved as a result of count-up operation having been performed during previous operation is sometimes left in the test-stamping counter, the counter must be reset to zero on the occasion of initiation of new operation. 
     The electronic component mounting apparatus  1  started operation requires performance of test-stamping at predetermined timing (ST 3 ). Paste is pressed against the stamping pin  28  at the time of stamping operation and becomes affixed with elapse of time. Timing at which the request is issued is generally determined from a time elapsed since operation was started and the number of times paste stamping operation is performed. Therefore, a round of test-stamping operations are performed at the time of replacement of a substrate and a chip or replacement of each of the nozzles, so as not to interrupt production for test-stamping operation. 
     The round of test-stamping operation starts from cleaning (ST 4 ) of the second reservoir  33  that is a reservoir for test-stamping. Cleaning of the second reservoir  33  is performed by rotating the second reservoir  33  while the squeegees  35  remain in close contact with the bottom wall  39 . In relation to the first test-stamping operation performed after initiation of operation, since no paste is yet affixed to the bottom wall  39 , the cleaning operation may also be omitted. Subsequently, test-stamping operation for pressing the stamping pin  28  against the bottom wall  39  is performed (ST 5 ). By means of the test-stamping operation, at least a portion of the paste still remaining in contact with the bottom wall  39  of the paste still remaining on the stamping pin  28  adheres to the bottom wall  39 , to thus be eliminated from the stamping pin  28 . 
     Next, the third camera  13  photographs the shape of the paste applied on the bottom wall  39 , to thus ascertain the shape of the paste (ST 6 ). Since the shape of the paste changes according to an amount and a position of the paste still remaining on the stamping pin  28  as well as to a type of the stamping pin  28 , shape patterns of paste are previously created as electronic data, and image data pertaining to the paste applied on the bottom wall  39  are matched against the electronic data. When the shape of the paste is ascertained to be normal as a result of the match with the shape patterns (ST 7 ), the test-stamping operation ends (ST 8 ). The number of times test-stamping operation is performed is counted up (ST 9 ), and the electronic component mounting apparatus returns to normal mounting operation. 
     A normal shape of paste is a shape that makes it possible to eliminate majority of the paste still remaining on the stamping pin  28  by means of test-stamping operation, so that a resultant shape is considered to be or can be seen to be identical with a shape of the paste adhered to the bottom wall  39 . When the paste adhering to the bottom wall  39  assumes such a shape, the stamping pin  28  can be considered to be in a cleaned state where no paste remains on the stamping pin. 
     When the shape of the paste is ascertained to be anomaly as a result of matching (ST 7 ), the number of times test-stamping operation is performed is counted up (ST 9 ), and the round of test-stamping operations (ST 4  to ST 6 ) are again iterated. The round of test-stamping operation (ST 4  to ST 6 ) are iterated until the shape of paste is ascertained to be normal. When the number of test-stamping operations exceeds a preset allowable value, it is determined that the stamping pin  28  cannot be cleaned by test-stamping operation, and an error alarm is issued (ST 10 ). 
     Upon receipt of the error alarm, the operator temporarily suspends operation of the electronic component mounting apparatus  1  and visually checks the state of the stamping pin  28 . If the stamping pin can be cleaned by means of washing, or the like, the cleaned stamping pin  28  is used as it is, and operation of the electronic component mounting apparatus  1  is resumed. When it is determined that the stamping pin cannot readily be cleaned, the stamping pin is replaced with another stamping pin, and operation of the electronic component mounting apparatus  1  is subsequently resumed. 
     The stamping pin may also be automatically replaced in place of the error alarm (ST 10 ). In this case, the stamping head  4  is moved up to a nozzle stocker  24 , where the head is replaced with a stamping pin stored in the nozzle stocker  24 . Subsequently, stamping operation is continually performed by use of the thus-replaced new stamping pin. 
     Since the reservoirs  32  and  33  are formed from metal or resin in many cases, the bottom wall  39  itself has no capability of cleaning the stamping pin  28 . Accordingly, as shown in  FIG. 5 , a cleaning material  50 , such as felt impregnated with a chemical that dissolves paste, is placed on the bottom wall of the second reservoir  33 , whereby the stamping pin  28  can be cleaned. In this case, the cleaning material  50  keeps a portion of the bottom wall exposed rather than covering the entirety of the bottom wall, whereby the stamping pin  28  can be cleaned by combined use of test-stamping operation and cleaning operation. For instance, when the shape of paste is not normal even as a result of test-stamping operation being iterated several times, the stamping pin  28  can also be cleaned. 
     In the foregoing embodiment, paste is stored in the first reservoir  32  and test-stamped in the second reservoir  33 . However, the first reservoir  32  may also be used for test-stamping purpose, and paste may also be retained in the second reservoir  33 . In this case, the position P 2  shown in  FIG. 2  serves as a stamping position, and the position P 1  serves as a test-stamping position. Since a direct distance between the stamping position P 2  and the substrate  9  thereby becomes shorter, the time required to actuate the stamping head  4  can be shortened, so that productivity is enhanced. On the contrary, the amount of travel required during test-stamping operation is increased. However, the test-stamping operation is performed less frequently as compared with stamp operation. Therefore, productivity is not deteriorated. 
     A paste reservoir is provided as a plurality of concentrically-arranged annular reservoirs, and one of the reservoirs is used as a test-stamping field. As a result, a necessity for providing a specifically-designed test-stamping field is obviated. There is also yielded an advantage of the ability to shorten a distance over which the stamping head travels for test-stamping purpose. 
     The present invention is useful in a field where electronic components are mounted by stamping paste to a substrate.