Abstract:
In lead forming of a packaged semiconductor device having sides and leads extending outwardly from the sides of a package, separation between first and second bottom dies is adjusted to receive the package. The first and second bottom dies have top surfaces that include oblique portions. The package is placed between the first and second bottom dies with the leads proximate the top surfaces of the first and second bottom dies. At least one of (i) the first and second bottom dies and (ii) first and second top dies having respective bottom surfaces with oblique portions complementary to the top surfaces of the first and second bottom dies are moved toward each other. The leads are clamped between the top and bottom dies and are formed. Simultaneously, lateral forces, produced through contact of the complementary top and bottom surfaces and the leads, move the first and second top dies laterally, changing separation between the first and second top dies.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to lead forming of a semiconductor device.  
         [0003]     2. Description of Prior Art  
         [0004]     A semiconductor device has leads extending through two sides of a package thereof. In a fabrication process of semiconductor device, the leads are formed on a semiconductor device after it is covered with a resin. For example, when gull-wing type leads are formed in a prior art process, a semiconductor device after covered with a resin is put between top and bottom dies for preliminary bending, so that lead parts extended from the two sides of the semiconductor device are bent with press working. Next, the semiconductor device is put between top and bottom dies for bending, so that distal portions of the lead parts are bent in the reverse direction by press working. Then, the semiconductor device having the gull-wing leads is put between top and bottom dies for adjustment, so as to have a final form.  
         [0005]     In the above-mentioned lead forming, when the type of semiconductor device is changed or even if the type is not changed, but the shape of the leads is changed, all of the three die assemblies have to be replaced. That is, the dies are needed for each lead shape of semiconductor device. Therefore, much capital investment, labor and time are needed.  
         [0006]     In the above-mentioned lead forming, exclusive die assemblies each consisting of top and bottom dies are necessary according to a size of a work to be formed. Therefore, it is proposed to use a general die. For example, in the die disclosed in Japanese Utility Model laid open Publication 60-99033/1985 for bending a work such as a wire or a plate with press work, the position of a top die in a die assembly can be changed vertically. Furthermore, one of die assemblies provided at right and left sides can be moved horizontally with a screw. It is to be noted that lead forming of a semiconductor device is not described. Further, in an apparatus for bending disclosed in Japanese Patent laid open Publication 6-47445/1994, a die consists of a plurality of components, and one of them is movable. The shape of the die can be changed by moving the movable component. It is to be noted that the publication also does not describe lead forming of a semiconductor device. An apparatus for lead bending, disclosed in Japanese Patent laid open Publication 10-163396/1998, has a holder for holding the leads at bases thereof and another holder for holding them at edges thereof. When the bending form of lead is changed, the positions at the base and/or at the edge have to be changed. Then, the positions of the holders are adjusted, and the edges of the leads are moved like an arc so as to form the leads.  
         [0007]     Furthermore, in the apparatuses disclosed in Japanese Utility Model laid open Publication 60-99033/1985 and Japanese Patent laid open Publications 6-99033/1994 and 10-163396/1998, the position or the like of a die can be changed according to a work to be processed. However, they cannot realize high precision of the order of for example one micrometer. For example, in the apparatuses shown in Japanese Utility Model laid open Publication 60-99033/1985 and Japanese Patent laid open Publications 6-99033/1994 do not form leads, and they do not take high precision into account, for example, by adjusting the die position with a screw. Furthermore, in the apparatus for lead bending shown in Japanese Patent laid open Publication 10-163396/1998, the die assembly for lead bending does not have a punch and a die. In the apparatus the lead portions are clamped at a base position and at a forming position, to enforce an arc trajectory so as to form the lead parts. However, such forming has low precision consequently. Further, these apparatuses only bent the lead portions, and they cannot deal with a complicated form of leads.  
       SUMMARY OF THE INVENTION  
       [0008]     An object of the invention is to form lead parts of a semiconductor device at high precision even when the shape or the like of dies is changed according to the size of the semiconductor device.  
         [0009]     In a lead forming apparatus for a semiconductor device according to the invention, a holder holds a semiconductor device to be formed, the semiconductor device having leads extending from a package thereof. Two die assemblies (for bending, for cutting or the like) are set in parallel, each comprising a pair of top and bottom dies matched with each other. A mover changes a relative distance between the two die assemblies. The top and bottom dies in the two die assemblies are positioned to interpose the leads of the semiconductor device held on said holder and form the leads between them. Preferably, a size of a semiconductor device is measured before lead forming thereof, and the positions of components in the lead forming apparatus is adjusted according to a difference between the measured size and a normal value. Then, the semiconductor device is formed with the adjusted apparatus. Alternatively, after lead forming of a semiconductor device, a size thereof is measured, and the lead forming apparatus is adjusted for lead forming for a next semiconductor device.  
         [0010]     An advantage of the present invention is that a plurality of types of semiconductor devices can be formed by the above-mentioned lead forming apparatus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, and in which:  
         [0012]      FIG. 1  is a front view of an apparatus for forming leads of a semiconductor device according to a first embodiment of the invention;  
         [0013]      FIG. 2  is a diagram of a controller therefor;  
         [0014]      FIG. 3  is a part of a side view of the apparatus shown in  FIG. 1 ;  
         [0015]      FIG. 4  is a diagram of an example of device holder;  
         [0016]      FIG. 5  is a part of a front view of the apparatus shown in  FIG. 1 ;  
         [0017]      FIG. 6  is a front view of a process in the apparatus shown in  FIG. 5 ;  
         [0018]      FIG. 7  is a diagram for explaining fabrication of semiconductor device of different sizes;  
         [0019]      FIG. 8  is a front view of a process in the apparatus shown in  FIG. 7 ;  
         [0020]      FIG. 9  is a front view of a die according to a second embodiment of the invention;  
         [0021]      FIG. 10  is a front view of a die according to a third embodiment of the invention;  
         [0022]      FIG. 11  is a front view of a die according to a fourth embodiment of the invention;  
         [0023]      FIG. 12  is a front view of an apparatus for lead forming with cutting according to a fifth embodiment of the invention;  
         [0024]      FIG. 13  is a side view of a part of the apparatus shown in  FIG. 1 ;  
         [0025]      FIG. 14  is a front view of an apparatus for lead forming with bending according to a sixth embodiment of the invention;  
         [0026]      FIG. 15  is a flowchart of lead forming according to a seventh embodiment of the invention;  
         [0027]      FIG. 16  is a diagram for explaining a size of a semiconductor device;  
         [0028]      FIG. 17 s  a flowchart of lead forming according to an eighth embodiment of the invention; and  
         [0029]      FIG. 18  is a diagram for explaining a size of a semiconductor device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, embodiments of the invention are explained below. A lead forming apparatus for semiconductor devices has two sets of die assembly including a punch and a die for forming leads at a side of the device in parallel to each other. In order to form the leads at two sides of a semiconductor device, die assemblies of a punch and a die are positioned for bending, cutting or the like at two sides of the device. In the lead forming apparatus, the relative distance between the two sets of die assemblies can be changed by a mover or the like. Then, leads of a plurality of types of semiconductor devices can be formed by using the same die assemblies provided for the lead forming apparatus. Furthermore, the type of the semiconductor device can be changed automatically, and the capital investment for the dies can be reduced.  
       First Embodiment  
       [0031]      FIG. 1  shows a lead forming apparatus according to the first embodiment of the invention. The affixes, “L” and “R”, for the names of the components in the apparatus mean positions when viewed from a front side. A semiconductor device as a work to be processes by the lead forming apparatus has lead parts extended from two sides of a resin package thereof, and they are formed as a gull-wing type leads. When the lead shapes are the same and only the size of the resin package is different, the lead forming apparatus can bend the lead parts without changing the die assemblies, but by changing the relative distances of the two sets of die assemblies.  
         [0032]     In the lead forming apparatus, a ball screw  12  provided above a base plate  10  and supported by bearings  14 L and  14 R is screwed in the reverse directions at the left and right sides when viewed from the front in  FIG. 1 . The ball screw  12  is connected at an end thereof with a coupling  16  connected further to a motor  18 . Thus, the ball screw  12  is rotated by driving the motor  18 . Left and right screws provided for the ball screw  12  at the left and right sides thereof are engaged with nuts  10 L and  20 R, and tables  22 L and  22 R are fixed to the nuts  10 L and  20 R. A left bottom die  24 L is mounted on the table  22 L, while a right bottom die  24 R is mounted on the table  22 R. Top dies  28 L and  28 R supported by a top platen  26  oppose the bottom dies  24 L and  24 R. The top platen  26  is pressed down by a pressing machine  30 . The top and bottom dies  28 L and  24 L at the left side and those  28 R and  24 R at the right side have shapes in correspondence with a pair of punch and die engaging with each other, respectively. Thus, the lead forming apparatus includes two pairs of die assemblies each consisting of the top and bottom dies  28 L and  24 L,  28 R and  24 R. Furthermore, a sensor  32  is fixed on opposing sides of the tables  22 L and  22 R so as to measure the relative distance between the bottom dies. The sensor  32  shown in  FIG. 1  is an optical sensor, and an arrow shows schematically an optical path. Still further, device holders  34 L and  34 R are also fixed to the tables  22 L and  22 R. The device holders  34 L and  34 R holds a semiconductor device  80  at a predetermined position. In the lead forming apparatus, each of the left and right dies forms lead parts extending from a side of the semiconductor device  80 , or the lead parts at the two sides of the semiconductor device are formed at the same time.  
         [0033]     As shown in  FIG. 2 , a central processing unit (CPU)  62  in the controller  60  controls the lead forming apparatus. On operation, the controller  62  acquires signals from the signals  32  and receives setting of a desired position from an input device  64  instructed by an operator. Then, it drives the motor  18  according to a difference of the current and desired positions to rotate the ball screw  12 . Therefore, the relative distance between the dies can be adjusted according to the setting of the desired position. In other embodiments, a suitable measuring device may be provided at different positions of the dies. The dies can be moved automatically according to the difference of the measurement data with a desired position by using a driver for moving the dies.  
         [0034]     In the lead forming apparatus, when the motor  18  rotates the ball screw  12  to move the nuts  20 L and  20 R, the nut  20 L and the table  22 L are moved towards or away from the nut  20 R and the table  22 R. That is, the relative distance between the two pairs of dies is changed by rotating the ball screw  12 . Therefore, the relative distance is set by controlling the ball screw  12 . Alternatively, by providing ball screws at the left and right sides, the dies at the left and right sides can be moved independently.  
         [0035]     The top dies  28 L and  28 R make contact closely to the platen  26 , but they are not fixed thereto. This makes top dies  28 L and  28 R follow the shift of bottom dies  24 L and  24 R by the ball screw  12 .  FIG. 3  shows a side view of the platen  26  and one of the top dies  28 R. In the example shown in  FIG. 3 , a pair of guide rollers  38 R holding the top die  28 R is supported by a pair of plates  40 R fixed to two sides of the platen  26 . Thus, the top die  28 R is supported by the pair of guide rollers  38 R fixed to the platen  26 , while it is moved freely to the left and right directions in  FIG. 1 . The other top die  28 L is supported similarly.  
         [0036]     A semiconductor device  80  with lead parts extended to the right and left directions from a resin package thereof are put by a carrier (not shown) on the device holders  34 L and  34 R provided at the right and left sides. The device holders  34 L and  34 R hold a shoulder of the resin package, so that the semiconductor device  80  is put at a predetermined position between the top and bottom dies. At the position, lead parts at one of sides of the resin package of the semiconductor device  80  are positioned between the left top and bottom dies  28 L and  24 L, while lead parts at the opposite side thereof are positioned between the right top and bottom dies  28 R and  24 R. In the lead forming, the lead parts held on the device holders are formed by pressing the platen  26  downward by the pressing machine  30 .  
         [0037]     In another example shown in  FIG. 4 , device holders  134 L and  134 R are provided instead of the device holders  34 L and  34 R shown in  FIG. 1 . The device holders  134 L,  134 R are engaged with a drive axis (ball screw)  70 , and the distance between them is adjusted by a servo motor  74  connected via a coupling  72  to the drive axis  70 . Furthermore, similarly to the dies shown in  FIG. 1 , a sensor (not shown) is provided to measure the relative distance between them. The drive shaft  70  is positioned for example at the depth side of the ball screw  12  shown in  FIG. 1 . In this example, the controller  60  also controls the servo motor  74 . Therefore, the holding position can be adjusted according the package size of the semiconductor device independently of the relative distance between the left and right dies. Alternatively, the device holder is integrated with a different component.  
         [0038]      FIG. 5  shows the top dies  28 L,  28 R and the bottom dies  22 L,  22 R in detail. At the left top die  28 L, a top holder  44 L supports a punch  48 L at a fulcrum  46 L. Still further, the punch  48 L has a roller SOL at the bottom thereof. At the right bottom die  24 L, a cam plate  54 L and a die  56 L are fixed on a bottom holder  52 L. Similarly, at the right top die  28 R, a top holder  44 R supports the punch  48 R at a fulcrum  46 R. Still further, the punch  48 R has a roller  50 R at the bottom thereof. At the right bottom die  24 R, a cam plate  54 R and a die  56 R are fixed on a bottom holder  52 R. The punch  48 L,  48 R pivots around the fulcrum  46 L,  46 R, and the roller  50 L,  50 R makes contact rotatably with a shoulder or taper formed obliquely to lead the roller  50 L,  50 R towards the inside on the top of the cam plate  54 L,  54 R. The shapes of the bottom of the punches  48 L,  48 R and of the top of the dies  56 L,  56 R are designed to form gull-wing leads of the semiconductor device  80  between them. Though not shown, the device holders  34 L,  34 R for holding the device  80  are fixed to the dies  56 L,  56 R.  
         [0039]     The operation of the above-mentioned apparatus is explained. First, in order to set the relative distance between two pairs of die assemblies, the left and right bottom and bottom dies  24 L,  28 L,  24 R,  28 R are moved by the ball screw  12  according to the desired size for the semiconductor device  80 . Next, the semiconductor device  80  is set by a carrier (not shown) on the device holders  34 L,  34 R at the predetermined position. Next, the platen  26  driven by the pressing machine  30  moves the top dies  28 L,  28 R downward (as shown with arrows in  FIG. 5 ). When the platen  26  is moved further downward while the rollers  50 L,  5 OR make contact with the shoulders of the cam plates  56 L,  56 R, and the top holders  44 L,  44 R held by the guide roller  38 L,  38 R are moved to the inside.  
         [0040]     The top dies  28 L,  28 R in contact with the leads of the semiconductor device  80  are moved to a bottom dead center by the platen  26  driven by the pressing machine  30 . At this time, the punches  48 L,  48 R are moved around the fulcrum  46 L,  46 R to the predetermined position by the contact and rotation of the roller  50 L,  5 OR and the cam plate  54 L,  54 R. Thus, the semiconductor device  80  has the desired shape at the position of bottom dead center according to the engagement of the punch  48 L,  48 R with the die  56 L,  56 R (refer to  FIG. 6 ). The semiconductor device at the bottom dead center is called as as-formed semiconductor device  81 .  
         [0041]     As shown in  FIG. 7 , when a semiconductor device having the same shape of the lead parts as the above-mentioned one  80 , but having a different size thereof (for example a semiconductor device  82  shown in  FIG. 7 ) is formed in the lead forming apparatus, the ball screw  12  is driven by the motor  18  according to a size of the semiconductor device  82  to move the left and right top and bottom dies  28 L,  24 L,  28 R,  24 R while confirming the position of the dies  24 L,  24 R with the sensor  32 . The change of the positions of the dies  28 L,  24 L,  28 R and  24 R is performed just before the engagement thereof by the pressing machine  30  because they form an apparent single die at this position such that the left top die  28 L engages with the left bottom die  24 L and that the right top die  28 R engages with the right bottom die  24 R. Then, the semiconductor device  82  is set by a carrier (not shown) at the desired position. Next, the top dies  28 L,  28 R and the bottom dies  24 L,  24 R are moved downward by the platen  26  pressed by the pressing machine  30 . As shown in  FIG. 7 , the top dies  28 L and  28 R in contact with the semiconductor device  82  are moved further to the bottom dead center by the platen  26  pressed by the pressing machine  30 . At this time, the left punch  48 L is moved around the fulcrum  46 L to the predetermined position according to the contact and rotation of the roller  50 L with the cam plate  54 L, so that the lead parts of the semiconductor device  82  are formed to have the desired sizes at the bottom dead center by the punch  48 L and the die  56 L. At the same time, the right punch  48 R is moved around the fulcrum  46 R to the predetermined position according to the contact and rotation of the roller  5 OR with the cam plate  54 R, so that the lead parts of the semiconductor device  82  are formed to have the desired sizes at the bottom dead center by the punch  48 R and the die  56 RL. The semiconductor device at the bottom dead center is an as-formed semiconductor device  83 .  
       Second Embodiment  
       [0042]     Next, a lead forming apparatus according to the second embodiment of the invention is explained. The lead forming apparatus is similar to that of the first embodiment except the internal structure of the dies. It can adjust the height of the cam at the bottom die.  
         [0043]      FIG. 9  shows a pair of the dies  128 R,  124 R at the right side in the lead forming apparatus. The dies  128 L,  124 L at the left side have symmetrical structures with the counterparts  128 R,  124 R, so the dies  128 L,  124 L are not shown. The top die  128 R consists of a top holder  144 R, a fulcrum  146 R, a punch  148 R and a roller  150 R. This structure is similar to the counterpart in the first embodiment. On the other hand, the bottom die  124 R consists of a bottom holder  152 R, a die  156 R, a cam  154 R, a taper block  155  to be integrated with the cam  154 R, a bottom plate  158 R, an elastic member  162 R and a screw  160 R. The die  156 R is fixed on the bottom holder  152 R. The taper block  155 R is mounted on the bottom holder  152 R, so that it can be moved in the left direction in  FIG. 9  by the screw  160 R engaged with the bottom plate  158 R fixed to an end of the bottom holder  152 R. The cam  154 R is mounted on the taper block  155 R so as to be integrated therewith. The shapes at the tops of the die  156 R and the cam  154 R are similar to the die  56 R and the cam plate  54 R in the first embodiment. The elastic member  162 R provided between the die  156 R and the taper block  155 R pushes the taper block  155 R to the right direction. The shapes at the top plane of the taper block  155 R and the bottom plane of the cam  154 R are not in parallel to the top plane of the bottom holder  152 R. Therefore, when the taper block  155 R is moved by the screw  160 R to the left or right, the position and height of the cam  154 R are changed. Though not shown, the device holders  34 L,  34 R are fixed to the tables  22 L,  22 R on which the bottom dies  124 L,  124 R are mounted.  
         [0044]     The operation of the above-mentioned apparatus is explained. A semiconductor device  84  is set at a predetermined position. Next, the platen  26  driven by the pressing machine  30  moves the top die  128 L,  128 R in contact with the semiconductor device  84  to the bottom dead center. At this time, in the right die assembly, the punch  148 R is set at the desired position by the die  156 R according to the relative operation of the fulcrum  146 R, the punch  148 R, the roller  15 OR and the cam  154 R. Similarly in the left die assembly, the punch  148 R is set at the desired position. Thus, the lead parts of the semiconductor device  84  are formed to have the desired forms.  
         [0045]     If the lead parts do not have the desired forms, they can be adjusted without changing the components in the lead forming apparatus by changing the positions of the cam  156 R and the tape block  155 R with the screw  158 R. For example, by adjusting the screw  160  to move towards the plate  156 R at the top dead center, the taper block  155 R is pushed towards the plate  156 R so that the height of the cam  154 R is decreased. Thus, the relative distance of the roller  15 OR to the cam  154 R is changed, so as to bend the lead parts of the semiconductor device  64  at a shallower position. On the other hand, by adjusting the screw  160  to the outside at the top dead center, the taper block  155 R is pushed back by the elastic member  162 R so that the height of the cam  154 R is increased. Thus, the relative distance of the roller  15 OR to the cam  154 R is changed, so as to bend the lead parts of the semiconductor device  64  at a deeper position.  
       Third Embodiment  
       [0046]     Next, a lead forming apparatus according to the third embodiment of the invention is explained.  FIG. 10  is a front view of a die assembly at the right side of the lead forming apparatus. A die assembly at the left side is not shown because it has a symmetrical structure. The lead forming apparatus can adjust the die height of the bottom die.  
         [0047]     As shown in  FIG. 10 , the top die  228 R consists of a top holder  244 R, a fulcrum  246 R, a punch  248 R and a roller  250 R. This structure is similar to the right top die  28 R in the first embodiment. On the other hand, the bottom die  224 R consists of a bottom holder  252 R, a cam  254 R, a die  256 R, a taper block  257 R to be integrated with the die  256 R, a plate  258 R, a screw  260 R and an elastic member  262 R. This die  224 R has a different structure from the bottom die  28 R in the first embodiment. The cam  254 R is fixed on the bottom holder  252 R. The taper block  257 R is mounted on the bottom holder  252 R, so that it can be moved on the holder  252 R in the left direction in  FIG. 9  by the screw  260 R engaged with the plate  258 R fixed to an end of the bottom holder  252 R. The die  256 R is mounted on the taper block  257 R so as to be integrated therewith. The shapes at the tops of the die  256 R and the cam  254 R are similar to the die  56 R and the cam plate  54 R in the first embodiment. The elastic member  262 R is provided between the cam  254 R and the taper block  257 R. The elastic member  262 R acts to push the taper block  257 R in the backward direction. The shapes at the top plane of the taper block  257 R and the bottom plane of the die  256 R are not in parallel to the top plane of the bottom holder  252 R. When the taper block  257 R is moved by the screw  260 R to the left or right, the position of the die  256 R is changed. Though not shown, the device holders  34 L,  34 R are mounted to the tables  22 L,  22 R.  
         [0048]     The operation of the above-mentioned apparatus is explained. A semiconductor device  86  is set at a predetermined position. Next, the platen  26  driven by the pressing machine  30  moves the top die  10 L,  14 R downward to the bottom dead center. At this time, in the right die assembly, according to the relative movement of the fulcrum  246 R, the punch  248 R, the roller  250 R and the cam  254 R, the punch  248 R is set at the desired position by the die  256 R. Thus, the lead parts of the semiconductor device  86  are formed to have the desired shapes. Similarly in the left die assembly, the punch  248 R is set at the desired position. Thus, the lead parts of the semiconductor device  86  are formed to have the desired forms.  
         [0049]     If the lead parts of the semiconductor device  86  do not have the desired forms, they can be adjusted without changing the components in the lead forming apparatus, by changing the position of the die  256 R and the tape block  257 R with the screw  260 R. For example, by adjusting the screw  260  relative to the plate  258 R at the top dead center, the taper block  257 R is pushed towards the plate  258 R so that the height of the die  256 R is decreased. Thus, the relative distance of the punch  248 R to the die  256 R is changed, so as to bend the lead parts of the semiconductor device  86  at a deeper position. On the other hand, by adjusting the screw  260  toward the outside at the top dead center, the taper block  257 R is pushed back by the elastic member  262 R so that the height of the die  256 R is increased. Thus, the relative distance of the punch  248 R to the die  256 R is changed, so as to bend the lead parts of the semiconductor device  64  at a shallower position.  
       Fourth Embodiment  
       [0050]     Next, a lead forming apparatus according to the fourth embodiment of the invention is explained.  FIG. 11  is a front view of a right die assembly of the lead forming apparatus. A die assembly at the left side is not shown because it has a symmetrical structure. The lead forming apparatus can adjust the height of the semiconductor device and the bending angle of the lead parts thereof.  
         [0051]     As shown in  FIG. 11 , in a top die  328 R, a top holder  344 R supports a punch  348 R at a fulcrum  346 R. Furthermore, the punch  348 R has a roller  350 R at the bottom thereof. The structure of the top die  328 R is similar to the top die  28 R in the first embodiment. In the bottom die  324 R, a cam  354 R is fixed on a bottom holder  352 R. Furthermore, a holder  359 R is provided near the cam  354 R to hold a die  358 R for changing the angle. A die  356 R is fixed on the bottom holder  352 R, and a screw  357 R is provided to engaged with a screw hole provided in the die  356 R in the left and right direction. On the other hand, a taper block  37  is mounted on the bottom holder  352 R, so that it can be moved on the holder  352 R in the left and right direction in  FIG. 11  by a screw  361 R engaged with a plate  360 R fixed to an end of the bottom holder  352 R. The shapes at the tops of the die  356 R and the die  358 R are formed according to the shape of the leads to be formed. Furthermore, a base  36  for holding a semiconductor device  88  is placed on the tape block  37 . The shapes at the top of the taper block  37  and the bottom of the base  36  are not in parallel to the top plane of the bottom holder  352 R. When the taper block  37  is moved by the screw  357 R to the left or right, the position (or height) of the base  36  is changed. Though not shown, the device holders  34 L,  34 R are mounted to the tables  22 L,  22 R on which the bottom die  324  is supported. The device holders  34 L,  34 R hold shoulders of a resin package of the semiconductor device  88 .  
         [0052]     The operation of the above-mentioned apparatus is explained. A semiconductor device  88  is set at a predetermined position on the base  36 , and the pressing machine  30  presses it to the bottom dead center. At this time, according to the relative movement of the fulcrum  346 R, the punch  348 R, the roller  350 R and the cam  354 R, the punch  348 R is set at the desired position by the die  356 R. Similarly in the left die assembly, the punch  348 R is set at the desired position. Thus, the lead parts of the semiconductor device  88  are formed to have the desired forms.  
         [0053]     If the lead parts of the semiconductor device  88  do not have the desired forms, they can be adjusted without changing the components in the lead forming apparatus, by adjusting the screw  357 R at the top dead center to move the die  357 R for changing the relative angle of the lead parts to the resin package of the semiconductor device  88 . For example, by moving the screw  357 R towards the inside of the die  356 R, the angle at the edge of lead parts is changed towards a flat position. Similarly, by moving the screw  357 R towards the outside of the die  356 R, the angle at the edge of a lead part is changed to have a larger angle relative to the flat position. Thus, the relative position of the die  358 R is changed by the screw  357 R, so as to change the angle of the die  358 R.  
         [0054]     Furthermore, by adjusting the screw  361 R at the top dead center to move the taper block  35  in the left direction in  FIG. 11 , the taper block  35  is moved to the left so that the height of the base  34  is set higher. Similarly, by moving the screw  361 R in the right direction in  FIG. 11  at the top dead center, the taper block  35  is moved to the right so that the height of the base  34  is set lower. Thus, if the tolerance of the lead position of the semiconductor device  88  is small, the above-mentioned operation can control the lead shapes within the tolerance. Therefore, the height of the semiconductor device  88  can be adjusted by changing the height of the base  34  with the screw  361 R, without changing the components in the lead forming apparatus.  
       Fifth Embodiment  
       [0055]      FIG. 12  shows a lead forming apparatus for cutting according to the fifth embodiment of the invention. The lead forming apparatus shown in  FIG. 12  is similar to the counterpart in the first embodiment shown in  FIG. 1 , except the dies  424 R,  428 R,  424 L and  428 L. A lead frame has comb-like lead parts connected partially to each other. The lead parts are separated with dies for cutting in the lead forming apparatus. The dies  424 R,  428 R,  424 L and  428 L having shapes similar to dents of a comb engage with each other, when viewed from a side thereof.  FIG. 13  is a side view of the platen  26  and the right top die  428 R. This structure is similar to the platen  26  and the right top die  428 R of the first embodiment shown in  FIG. 3 . Though not shown, device holders  34 L,  34 R are fixed to the tables  22 L,  22 R. Alternatively, the device holders shown in  FIG. 3  are used. In the example shown in  FIG. 13 , a pair of guide rollers  438 R holding the top die  428 R are supported by a pair of plates  440  fixed to both sides of the platen. Therefore, the die  428 R can be moved to the left or to the right while supported by the guide rollers  438 . The left top die  428  not shown is supported similarly. The controller shown in  FIG. 2  is used. In the above-mentioned lead forming apparatus having dies  424 R,  428 R,  424 L and  428 L for cutting, lead cutting can be performed, without changing the dies, for semiconductor devices having the same lead forms, but having a different size of a resin package thereof.  
       Sixth Embodiment  
       [0056]     Next, a lead forming apparatus according to the sixth embodiment of the invention is explained. It can perform lead forming for a semiconductor device having leads at all the four sides thereof. As shown in  FIG. 14 , the lead forming apparatus has two units shown in  FIG. 1  set on a common base plane  510 , and a carrier  560  is provided between them. The carrier  560  rotates by  90  degrees a semiconductor device  92  which have been formed by one of the units and carries the rotated device to the other unit. Thus, the leads of the semiconductor device at all the four sides thereof are formed.  
         [0057]     In the lead forming, first, in the unit shown at the left in  FIG. 14 , the died  28 L,  24 L,  28 R and  24 R are moved by the ball screw  12  driven by the motor  18  by an amount in correspondence to a semiconductor device  92 . By operating the motor, the left nut  20 L and the left table  22 L are moved toward or away from the right nut  20 R and the right table  22 R, to match the size of the semiconductor device  92 . Then, the semiconductor device  92  is set on a predetermined position by a carrier (not shown). Next, the pressing machine  30  is operated to move the top dies  28 L,  28 R by the platen  26  downward. The top dies  28 L,  28 R are moved to the bottom dead center, and the semiconductor device  92  is formed to have the desired shape.  
         [0058]     As mentioned above, the semiconductor device  92  has leads at the four sides thereof. After the leads at two sides are formed by the above-mentioned operation, the carrier  560  takes and carries the device  92  for the next step, while rotating it by  90  degrees in the horizontal plane.  
         [0059]     In the unit shown at the right in  FIG. 14 , by operating the motor  18 , the left nut  20 L and the left table  22 L are moved toward or away from the right nut  20 R and the right table  22 R, to match the size of the semiconductor device  92 . Then, the semiconductor device  92  is set on a predetermined position on the device holders by the carrier  560 . Next, the pressing machine  30  is operated to move the top dies  28 L,  28 R by the platen  26  downward. The top dies  28 L,  28 R are moved to the bottom dead center, and the semiconductor device  92  is formed to have the desired shape of the leads at the other two sides.  
         [0060]     Thus, the leads at the four sides of the semiconductor device  92  are formed. The lead forming can be performed, without changing the components in the lead forming apparatus, for a semiconductor device having a different size of resin package.  
         [0061]     As will be understood by a person skilled in the art, the components provided in the lead forming apparatuses of the above-mentioned embodiments can be incorporated in various way.  
         [0062]     In a prior art lead forming apparatus, the shape of the as-formed semiconductor device is not checked at the time of lead forming. The devices are checked after production of a lot thereof is completed. Then, based on the quality control data, the dies are adjusted manually if necessary. In the embodiments explained below, each semiconductor device is measured to adjust the positions of the components in the lead forming apparatus, so that semiconductor devices of high quality can be produced.  
       Seventh Embodiment  
       [0063]     Next, a lead forming method according to the seventh embodiment of the invention is explained.  FIG. 15  is a flowchart of lead forming by the controller  60  in the lead forming apparatus according to one of the above-mentioned embodiments. In the lead forming apparatus, the relative distance between the left and right dies can be controlled by the ball screw  12  driven by the motor  18 . Furthermore, the screw  160 R,  260 R,  357 R,  361 R can be operated by drivers not shown. In lead forming, the size of a semiconductor device before lead forming is measured by a measuring device  66 , and the dies and the device holders are adjusted according to the measured data. Then, the lead forming is performed.  
         [0064]     The measured sizes of the semiconductor device are, for example, size A on a resin package and size B of lead thickness as shown in  FIG. 16 . The sizes A and B scatter among the semiconductor devices due to shrinkage of the resin or the like, so that optimization due to measured data is effective. Among the various sizes of the semiconductor device before lead forming, as to the size A on the resin package, as shown in the flow of  FIG. 15 , the size A is measured, and the measured data is received (S 10 ). Next, the positions of the device holders  34 L,  34 R are optimized by operating the motor  18  in the lead forming apparatus by an amount based on the measured data (S 12 ). After confirming with the sensor  32  that the device holders  34 L,  34 R are adjusted, the pressing machine  30  is operated for lead forming of the semiconductor device (S 14 ). These steps are repeated. Thus, before carrying a semiconductor device, the size A of the resin package thereof is measured, and the apparatus is optimized according to the measured size. Then, lead forming is performed. Then, a semiconductor device of high precision can be produced.  
         [0065]     Similarly, as to size B of lead thickness, in the flow shown in  FIG. 15 , the size B of a semiconductor device is measured before lead forming (S 10 ). Then, based on the measured data, the position of the bottom dead center, explained with reference to  FIGS. 5 and 6 , is optimized (S 12 ). Then, lead forming of the semiconductor device is performed (S 14 ). These steps are repeated. Thus, a semiconductor device of high precision can be produced.  
         [0066]     In the above-mentioned example, the sizes A and B shown in  FIG. 16  are controlled. However, needless to say, a size to be adjusted is not limited to the sizes A and B. For example, sizes shown in  FIG. 18  referred to later may be used.  
         [0067]     In the flow shown in  FIG. 15 , the lead forming apparatus is controlled for each semiconductor device. However, the control may be performed for one among a predetermined amount of semiconductor devices or once per lot.  
       Eighth Embodiment  
       [0068]     Next, a lead forming method according to the eighth embodiment of the invention is explained with reference to a flowchart of the controller  60  shown in  FIG. 17 . In the lead forming method, after leads of a semiconductor device are formed by a lead forming apparatus, sizes of the as-formed device are measured by a measurement device  66 . Then the lead forming apparatus is adjusted according to the measured data for following lead forming. In an example, as shown in  FIG. 18 , sizes to be measured are size C of distance between two ends of the leads, size D of a distance between the bottom of a resin package and an end of the lead in the vertical direction, and angle E of the lead edge relative to the bottom plane of the resin package.  
         [0069]     In the flow shown in  FIG. 17 , after the pressing machine  30  is operated to form leads of a semiconductor device (S 20 ), the sizes of the as-formed semiconductor device are measured to receive the measured data (S 22 ). The measured data may be an average of the measured data of a plurality of semiconductor devices. Then, a difference between the measured data and a normal value is calculated (S 24 ), and the apparatus is adjusted according to the difference, for example, on the position of the screw  160 R,  260 R,  357 R,  361 R (S 24 ), for the feedback for the lead forming of a next semiconductor device.  
         [0070]     For example, size E of a semiconductor device is measured after the semiconductor device is formed by the lead forming apparatus, and a difference between the measured data and the normal value is calculated by the controller  60 , and the positions of the dies in the apparatus are adjusted according to the difference. Then, a next semiconductor device is formed by the adjusted apparatus. For example, if the measured size E is smaller than the normal value, the die  358 R for changing the angle in the lead forming apparatus shown in  FIG. 11  is adjusted to have an optimum position. Similarly, as to sizes C and D, if they are different from the normal values, the punch  248 R in the lead forming apparatus shown in  FIG. 11  or the die  256 R in the lead forming apparatus shown in  FIG. 10  is adjusted. Then, a next semiconductor device is formed with the adjusted apparatus. Thus, a semiconductor device of high quality can be produced. In the above-mentioned example, the sizes C, D and E shown in  FIG. 18  are controlled, but needless to say, a size to be measured is not limited to the sizes C-E.  
         [0071]     As explained above, a plurality of types of semiconductor devices can be formed by the above-mentioned lead forming apparatus. Thus, the lead forming apparatus can be adjusted automatically according to the type of semiconductor device. Further, investment cost therefor can be reduced.  
         [0072]     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.