Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a die bonder and a bonding method, and particularly to a die bonder and a bonding method with a high operation ratio. 
         [0003]    2. Description of the Related Art 
         [0004]    As a part of steps of mounting a die (semiconductor chip) (hereinafter, simply referred to as a die) on a substrate such as a printed circuit board or a lead frame to assemble a package, a step of dividing a semiconductor wafer (hereinafter, simply referred to as a wafer) into dies and a bonding step of mounting the divided dies on the substrate are provided. 
         [0005]    In the bonding step, the dies divided from the wafer are peeled off one-by-one from a dicing tape to be bonded on the substrate using an absorption jig that is referred to as a collet. 
         [0006]    In such a die bonder, it is necessary to replace the collet in accordance with the type (die size), or to increase the frequency of replacement of the collet in contact with the surface of the die to prevent damage or taint of the surface of the die. 
         [0007]    As conventional techniques of replacing the collet, for example, there are those described in Japanese Patent Application Laid-Open No. H4-321243 and Japanese Patent Application Laid-Open No. 2001-156083 are known. In Japanese Patent Application Laid-Open No. H4-321243, a collet clamper that holds a collet and a spring that operates the collet clamper are provided at the tip end of a bonding head to mechanically control the operation. Thus, the collet is replaced using a collet holder (a stock unit for collets for replacement, and corresponding to a supplying unit and a discarding unit of the application). On the other hand, in Japanese Patent Application Laid-Open No. 2001-156083, a collet attached to the tip end of a collet shank is inserted from the side to a port in a U-groove shape, and the collet is removed from the collet shank. Then, the collet shank is inserted into plural collets for replacement disposed on a plane, and is attached thereto. Further, Japanese Patent Application Laid-Open No. 2001-156083 discloses that the attachment of the collet is confirmed on the basis of the descent distance of the collet shank or optical means. 
         [0008]    However, in the technique disclosed in Japanese Patent Application Laid-Open No. H4-321243, the mechanism of the tip end of the collet clamper is disadvantageously complicated. On the other hand, in the technique disclosed in Japanese Patent Application Laid-Open No. 2001-156083, an inserting space and a replacement area for collets for replacement become disadvantageously wide. Further, a die package has recently become thinner and the following problems occur. First, since a collet holder to hold a collet that stably absorbs the thinner die is used, it is necessary to replace only the collet while leaving the collet holder. Second, when confirming the attachment of the collet, it is necessary to move the collet to another installation position such as an alignment stage in a method using the descent distance of the collet shank, and the attachment cannot be promptly confirmed at the time of replacement. In addition, new optical means needs to be provided, or it is necessary to move to an area where another optical means is provided. Third, variations in the height of the collet at the time of manufacturing in a unit of nm have an impact on the descent distance of the collet when mounting the die, and it is necessary to address this problem. 
         [0009]    Accordingly, an object of the present invention is to provide a bonding device and a bonding method with a high operation ratio by solving at least one of the above-described problems. 
       SUMMARY OF THE INVENTION 
       [0010]    In order to achieve the above-describe object, the present invention includes at least the following characteristics. 
         [0011]    The present invention provides a die bonder including: a collet holder that holds a collet; a bonding head that includes the collet holder at its tip end and absorbs a die with the collet to bond the die on a substrate; a collet replacing unit having a discarding unit that includes a first opening portion having plural first engagement portions engaged with the collet on the upper side and discards a used collet, a supplying unit that includes a second opening portion on the upper side, stacking plural unused collets, and a moving means that moves the unused collets to the second opening portion, and a protrusion prevention means to prevent the unused collets from protruding from the second opening portion; and a control device that inserts the collet holder from the first opening portion, controls the engagement of the engagement portions with the collet holder to discard the used collets to the discarding unit, inserts the collet holder from the second opening portion, and ejects the plural stacked unused collets to be attached to the collet holder. 
         [0012]    Further, the present invention provides a bonding method including the steps of: bonding a die to a substrate after absorbing the die with a collet of a bonding head having a collet holder holding the collet at its tip end; inserting the collet holder grasping a used collet from a first opening portion with the upper face open; engaging the used collet with first engagement portions provided at the first opening portion; discarding the used collet after removing the same from the collet holder by lifting the collet holder; inserting the collet holder from a second opening portion with the upper face open; grasping the uppermost unused collet among plural stacked unused collets; and attaching the uppermost unused collet ejected from the first opening portion to the collet holder. 
         [0013]    Further, in the present invention, the engagement portions are provided so as to be engaged with a part of the collet, and the part of the collet may include avoiding portions to avoid the engagement portions. 
         [0014]    Further, in the present invention, the second opening portion includes second engagement portions having the same structures as those of the first engagement portions, the protrusion prevention means is each of the second engagement portions, and the engagement of the second engagement portions with the collet holder may be controlled to attach the unused collets to the collet holder. 
         [0015]    Further, the first engagement portions or the second engagement portions are fixing claws or movable claws that are provided at the first opening portion and the second opening portion, respectively, so as to be engaged with the collets, and the engagement with the fixing claws or the movable claws may be controlled while rotating the collets in parallel with the first opening portion and the second opening portion. 
         [0016]    Further, in the present invention, the attachment of the collet may be confirmed. 
         [0017]    Further, in the present invention, the attachment of the collet may be confirmed on the basis of changes in the volume of flow flowing to an absorption hole of the bonding head including the collet holder or differential pressure. 
         [0018]    Further, in the present invention, the height of the collet held by the collet holder is measured, and the descent distance of the collet may be corrected on the basis of the measurement result. 
         [0019]    According to the present invention, it is possible to provide a bonding device and a bonding method with a high operation ratio by solving the problems of the conventional techniques. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a conceptual diagram of a die bonder viewed from the upper side according an embodiment of the present invention. 
           [0021]      FIG. 2  is a diagram for showing structures of a bonding head, a collet, and a collet holder, and a configuration of collet attachment confirmation means. 
           [0022]      FIG. 3  is a birds-eye view of a collet replacing unit shown in  FIG. 1 , and is a diagram for showing a state in which an unused collet is housed in a supplying unit. 
           [0023]      FIG. 4  is a birds-eye view of the collet replacing unit shown in  FIG. 1 , and is a diagram for showing a state in which the collet holder is grasped to attach the collet. 
           [0024]      FIG. 5  is a plan view of the collet replacing unit viewed from the upper side in the state of  FIG. 3 . 
           [0025]      FIG. 6  is a diagram of the inside of the supplying unit viewed from the direction of the arrow A in  FIG. 4 . 
           [0026]      FIG. 7  is a diagram for showing a state in which the collet is rotated by the bonding head in the counterclockwise direction by θ from the state of  FIG. 5  to be separated from fixing claws  51   t.    
           [0027]      FIG. 8  is a diagram for showing a state in which the collet is allowed to descend and is rotated in the counterclockwise direction by θ on the upper side of a discarding unit to discard a used collet. 
           [0028]      FIG. 9  is a diagram for showing a state in which the collet is allowed to descend with the bonding head to be inserted into an opening portion and is rotated in the clockwise direction by θ so as to interfere with the fixing claws. 
           [0029]      FIG. 10  is a diagram for showing a second embodiment of the collet replacing unit  50 . 
           [0030]      FIG. 11  is a diagram for showing a configuration of a collet descent distance correcting unit. 
           [0031]      FIG. 12  is a diagram for showing a bonding flow according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    Hereinafter, embodiments of the present invention will be described on the basis of the drawings. 
         [0033]      FIG. 1  is a conceptual diagram of a die bonder  10  viewed from the upper side according to an embodiment of the present invention. The die bonder roughly includes a wafer supplying unit  1 , a work supplying/feeding unit  2 , a die bonding unit  3 , and a control device  4  that controls the respective units and a bonding flow in each embodiment to be described later. 
         [0034]    The work supplying/feeding unit  2  includes a stack loader  21 , a frame feeder  22 , and an unloader  23 . A work (a substrate such as a lead frame or a die already laminated on a substrate) supplied to the frame feeder  22  by the stack loader  21  is fed to the unloader  23  via two processing positions on the frame feeder  22 . 
         [0035]    The wafer supplying unit  1  includes a wafer cassette lifter  11  and a pickup device  12 . The wafer cassette lifter  11  includes wafer cassettes (not shown) filled with wafer rings, and sequentially supplies the wafer rings to the pickup device  12 . Each wafer ring holds a wafer W having a die D, and the pickup device  12  holds the wafer rings. 
         [0036]    The die bonding unit  3  includes a preform unit  31  and a bonding head unit  32 . The preform unit  31  applies a die adhesive agent on the work fed by the frame feeder  22 . 
         [0037]    The bonding head unit  32  includes a bonding head  35 , an XZθ driving unit  36  that drives the bonding head in the X or Z direction or rotates the same by θ, a Y driving unit  37  that drives the XZe driving unit in the Y direction, a collet replacing unit  50 , and a collet descent distance correcting unit  60 . The bonding head  35  is lifted by the XZθ driving unit  36  while picking up the die D from the pickup device  12 , and translates the die D in the X direction to a bonding point on the frame feeder  22 . Then, the bonding head  35  allows the die D to descend to be bonded onto the work with the die adhesive agent applied. 
         [0038]    Hereinafter, as a feature of the embodiments, the collet attachment confirmation means  70  that confirms whether or not a collet is attached, the collet replacing unit  50 , and the collet descent distance correcting unit  60  that corrects a collet descent distance after collet replacement will be described. 
       First Embodiment 
       [0039]    In the first place, structures of the bonding head  35 , a collet  40  and a collet holder  41  and a configuration of the collet attachment confirmation means  70  will be described using  FIG. 2 . 
         [0040]    The bonding head  35  has, in the middle, an absorption hole  35   v  to which absorption air flows, and includes, on the tip end side, a collet shank  35   s  connected to the collet holder  41  and a collet fixing unit  35   k  that fixes the collet holder  41  to the collet shank  35   s.    
         [0041]    The collet holder  41  has, in the middle, an absorption hole  41   v  in communication with the absorption hole  35   v , a magnet  41   j  fixing the collet  40 , and the collet attachment confirmation means  70  provided in the absorption hole  41   v.    
         [0042]    As shown in  FIG. 4 , the four sides of the collet  40  are held by the collet holder  41 , and the collet  40  includes plural absorption holes  40   v  in communication with the absorption hole  41   v  to absorb the die D. 
         [0043]    The collet attachment confirmation means  70  includes an orifice  70   o , a confirmation bar  70   b  with one end fixed to the orifice, and a compression spring  70   c  that presses the orifice towards the collet holder  41 . In the case where the collet  40  is attached to the collet holder  41  as shown in  FIG. 2 , the confirmation bar  70   b  is pushed up by the collet  40  against the compression spring  70   c  in the collet attachment confirmation means  70 , and the orifice  70   o  is lifted to secure the volume of air flow. On the other hand, in the case where no collet  40  is attached, the compression spring  70   c  allows the orifice  70   o  to descend to decrease the volume of air flow. The attachment of the collet  40  is confirmed by the volume of air flow or differential pressure. 
         [0044]    According to the above-described collet attachment confirmation means  70 , the attachment of the collet can be reliably confirmed without providing optical means. 
       Second Embodiment 
       [0045]    Next, a first example of the collet replacing unit  50  as a second embodiment will be described using the drawings. In the first place, a configuration of the collet replacing unit  50  will be described using  FIG. 3  to  FIG. 6 . Each of  FIG. 3  and  FIG. 4  is a birds-eye view of the collet replacing unit  50  shown in  FIG. 1 .  FIG. 3  shows a state in which an unused collet  40  is housed in a supplying unit  51 .  FIG. 4  shows a state in which the collet holder  41  is grasped to attach the collet  40 .  FIG. 5  is a plan view of the collet replacing unit  50  viewed from the upper side in the state of  FIG. 3 .  FIG. 6  is a diagram of the inside of the supplying unit  51  viewed from the direction of the arrow A in  FIG. 4 . 
         [0046]    As shown in each of  FIG. 3  and  FIG. 5 , the collet replacing unit  50  includes the supplying unit  51  that supplies an unused collet  40 , and a discarding unit  56  that discards a used collet  40 . The supplying unit  51  and the discarding unit  56  include opening portions  51   k  and  56   k  on the upper side, respectively. The opening portions  51   k  and  56   k  have the same structure, and include fixing claws  51   t  and  56   t , respectively, of engagement portions at diagonal positions denoted by the circles. It should be noted that in consideration of a case in which the direction of mounting the die D is shifted by 90° as shown by the dotted line in the embodiment, two engagement portions are each provided at the positions where the fixing claws  51   t  and  56   t  are rotated by 90°. 
         [0047]    As shown in  FIG. 6 , the supplying unit  51  includes a collet housing unit  51   s  in which plural unused collets  40  are stacked, a compression spring  51   b  as pressing and moving means that presses and moves the unused collets  40  in the collet housing unit towards the opening portion  51   k , and a spring housing unit  51   r  in which the compression spring is housed. On the other hand, the discarding unit  56  includes a waste housing unit under the opening portion in which used collets  40  are housed. A cylinder or the like may be provided as the pressing and moving means. 
         [0048]    In the supplying unit  51 , the fixing claws  51   t  serve as protrusion prevention means to prevent the collet from protruding by being engaged with the collet  40 . In addition, the fixing claws  51   t  and  56   t  are highly important when the collet  40  is attached to the collet holder  41 , or when the collet  40  is detached from the collet holder  41 . 
         [0049]    As shown in  FIG. 4 , the areas of the collet holder  41  corresponding to the fixing claws  51   t  and  56   k  are cut in a triangle shape so as not to interfere with the fixing claws  51   t  and  56   k.    
         [0050]    A method of attaching the collet  40  to the collet holder in the collet replacing unit  50  with such a configuration will be described using  FIG. 3  to  FIG. 7 . 
         [0051]    Each of  FIG. 3  and  FIG. 5  shows a state in which the collet  40  is simply housed in the supplying unit  51 . In this case, the fixing claws  51   t  serve to prevent the collet  40  from protruding. Next, as shown in  FIG. 4 , the bonding head  35  is controlled to move the collet holder  41  to the upper side of the unused collet  40 . After discarding, the bonding head  35  is only moved from the discarding unit  56  to the supplying unit  51  in the lateral direction. Thereafter, the collet holder  41  is allowed to descend to grasp the unused collet  40  while covering the whole, and the unused collet  40  is held by the magnet  41   j . Since the four corners of the collet holder  41  are cut in a triangle shape, the collet can be held without interfering with the fixing claws  51   t . Next, as shown in  FIG. 7 , the collet  40  is rotated by the bonding head  35  in the counterclockwise direction by θ from the state of  FIG. 5  to be separated from the fixing claws  51   t . Then, the bonding head  35  is lifted, and the attachment of the collet  40  is confirmed by the method shown in the first embodiment. Thereafter, the process is moved to the following operation. 
         [0052]    Next, a method of discarding a used collet  40  to the discarding unit  56  will be described using  FIG. 8  and  FIG. 9 . In the case of discarding, procedures opposite to the case of supplying an unused collet are performed. Specifically, the bonding head  35  is first controlled to move the collet  40  to the upper side of the opening portion  56   k  of the discarding unit  56 . Thereafter, the collet  40  is rotated in the counterclockwise direction by θ so that the diagonal positions of the collet  40  do not interfere with the fixing claws  56   t , and the state shown in  FIG. 8  is realized. Next, the collet  40  is allowed to descend using the bonding head  35  to be inserted into the opening portion  56   k , and the collet  40  is rotated in the counterclockwise direction by θ. Then, the diagonal positions of the collet  40  are moved to the lower side of the fixing claws  56   k , and the state shown in  FIG. 9  is realized. Thereafter, by pressing the diagonal positions of the collet  40  with the fixing claws  56   t , the bonding head  35  is lifts the collet to overcome the holding force of the magnet  41   j  in order to detach the collet  40  from the collet holder  41 . The collet  40  falls into the waste housing unit under the opening portion. 
         [0053]    Then, the bonding head  35  is moved to the side of the supplying unit  51  to hold an unused collet  40 , and the above-described procedures are performed. 
         [0054]    In the above-described embodiment, the fixing claws are provided at the diagonal positions. Avoiding portions  41   c  cut in a triangle shape are provided at the diagonal positions of the collet holder  41  corresponding to the fixing claws in order to avoid the fixing claws. The positions of the fixing claws are not limited to the diagonal positions, but may be other positions. For example, the fixing claws are provided at the middle positions of the opposite two sides, and the shape of the avoiding portions  41   c  may be set in the middle portions of the collet holder  41  corresponding to the fixing claws so as not to interfere with the fixing claws by the rotation of the collet holder. To put it in an extreme way, a trapezoidal portion on the shorter side of the collet holder shown in  FIG. 4  may be cut. In this case, it is necessary to position in the longitudinal direction. For example, convex portions are provided in the longitudinal direction of the collet holder for positioning, and concave portions may be provided at the corresponding positions of the collet. Even in the above-described embodiment, the avoiding portions  41   c  may not be in a triangle shape. For example, the avoiding portions  41   c  may be in a rectangular shape or ¼ circular shape. 
         [0055]    In the above-described embodiment, the collet replacing unit  50  is provided at one position. However, the collet replacing unit  50  may be installed at any position in a movable range of the bonding head as long as a mounting process is not affected, and plural collet replacing units  50  may be installed. In this case, the collet replacing units  50  may be provided for different die sizes. Further, even if the die sizes are different, the outer shape of the collet may be standardized so as to be held by the common collet holder. 
         [0056]    According to the above-described second embodiment, plural unused collets  40  are orderly stacked and housed, so that a stock area can be narrowed. 
         [0057]    Further, according to the above-described second embodiment, the collet replacing unit  50  can be downsized by accessing the supplying unit  51  and the discarding unit  56  from the upper side, and a replacement area including the stock area can be narrowed. 
         [0058]    Further, according to the above-described second embodiment, the collet  40  can be attached or detached to/from the collet holder  41  (bonding head  35 ) with a simple structure in which the fixing claws  51   t  and  56   t  are provided at the opening portions  51   k  and  56   k  of the supplying unit  51  and the discarding unit  56 , respectively, and the magnet  41   j  is provided at the collet holder  41 . 
       Third Embodiment 
       [0059]    Next, a second example of the collet replacing unit  50  as a third embodiment of the collet replacing unit  50  will be described using  FIG. 10 . The third embodiment is different from the second embodiment in the following two points, and the other points are the same. First, the collet  40  is detached from the collet holder  41  by the rotation of the fixing claws  51   t  and  56   t  and the collet  40  in the second embodiment. In the third embodiment, movable claws  52   t  and  57   t  are provided at the positions where the fixing claws  51   t  and  56   t  exist. By moving the movable claws  52   t  and  57   t  with shape-memory alloy springs  52   b  and  57   b , respectively, the collet  40  is attached or detached to/from the collet holder  41 . The shape-memory alloy springs  52   b  and  57   b  release the holding of the collets  40  by shrinking the springs when current flows. Thus, it is not necessary to rotate the collet when the collet  40  is attached or discarded in the third embodiment. 
         [0060]    Second, as similar to the first embodiment, when the collet  40  is pushed up by the compression spring  51   b  in the supplying unit  51  in the third embodiment, the movement of the movable claw  52   t  causes a collet for replacement to protrude. In order to prevent this, when the collet  40  is replaced in the third embodiment, the stretch of the compression spring  51   b  is fixed by a pulse motor (not shown), and the fixing by the pulse motor is released when the movable claw  52   t  holds the collet. Specifically, the pulse motor that fixes the stretch of the compression spring  51   b  configures protrusion prevention means. 
         [0061]    In this case, using a pulse motor or a servo motor as moving means of the stacked unused collets, the collet is moved by the pulse motor or the servo motor by the height of the collet to serve as protrusion means, so that the movable claws  52   t  can be eliminated. This point can be applied to the second embodiment, and the fixing claws  51   t  can be eliminated. 
         [0062]    It should be noted that there are various driving methods of the movable claws  52   t  and  57   t . For example, the movable claws  52   t  and  57   t  may be driven by a cylinder or a motor. 
       Fourth Embodiment 
       [0063]    Next, an embodiment of the collet descent distance correcting unit  60  and a collet descent distance correcting method will be described using  FIG. 11 . The collet descent distance correcting unit  60  includes a collet height measuring unit  61  that measures changes of the height of the collet, and a control device  4  that corrects the descent distance of the collet, namely, the bonding head  35  on the basis of the measurement result by the collet height measuring unit. The collet height measuring unit  61  is a commercial sensor configured using a light emitting unit  61   h  and a light receiving sensor  61   j . The collet height measuring unit  61  is fixed to the die bonder structure unit while being adjacent to the collet replacing unit  50  or the collet replacing unit  50 . The light emitting unit  61   h  emits light  61   b  with a certain bandwidth to the light receiving sensor  61   j , and the light receiving sensor  61   j  can measure the length H of a light receiving unit or the length of a light-blocking unit in a unit of nm. 
         [0064]    A collet descent distance correcting method by such a collet descent distance correcting unit  60  will be described. The collet  40  is allowed to descend to a certain position of the collet descent distance correcting unit  60 . When the length of the light receiving unit of the collet  40  before collet replacement is Hb and the length of the light receiving unit of the collet  40  after collet replacement is Ha, the height change ΔH of the collet  40  is represented as the following formula (1). 
         [0000]      Δ H=Hb−Ha   (1)
 
         [0065]    The descent distance BH of the bonding head  35  when the die D is picked up or is attached to the substrate is corrected only by the height change ΔH of the collet  40 . The correction may be done by using previous descent distance BHb or a standard descent distance BH. 
         [0066]    According to the above-described fourth embodiment, variations in the height of the collet at the time of manufacturing can be corrected in a unit of nm, and the die can be picked up and mounted to the substrate or the like without an adverse effect on the die such as destruction in the worst case. 
       Fifth Embodiment 
       [0067]    Next, a bonding flow in the embodiment will be described using  FIG. 12 . 
         [0068]    In the first place, a collet  40  is attached to the bonding head on the basis of the collet attachment method shown in the second or third embodiment (S 1 ). The attachment of the collet  40  is confirmed on the basis of the first embodiment (S 2 ). If the attachment of the collet cannot be confirmed, S 1  is performed again. Next, the descent distance of the collet is corrected on the basis of the fourth embodiment (S 3 ). Thereafter, the die D is mounted (S 4 ). During the mounting, time of replacing the collet  40  is determined (S 5 ). If replacement is necessary, the flow is moved to S 1  to replace the collet  40 , and the processes after S 2  are continued. Finally, it is determined whether or not a predetermined mounting process is completed, and the process is completed (S 6 ). 
         [0069]    As a method of confirming the attachment in the flow, optical means provided at the die bonder to confirm the posture of the die may be used without using the method of the first embodiment. 
         [0070]    According to the above-described fifth embodiment, a bonding method with a high operation ratio can be realized. 
         [0071]    According to the above-described first to fourth embodiments, a die bonder and a bonding method with a high operation ratio can be provided. 
         [0072]    The embodiments of the present invention have been described above, and various alternative, modified, or converted examples are available for those skilled in the art on the basis of the above description. The present invention includes various alternative, modified, or converted examples without departing from the gist of the present invention.

Technology Category: y