JP4074426B2 - Semiconductor module manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to wedge wire bonds in the manufacture of semiconductor modules.
[0002]
[Prior art]
In the manufacture of a semiconductor module, a conductive wire (eg, an aluminum wire) is generally used to electrically connect a case electrode of a semiconductor module case and a bonding pad of a semiconductor chip placed on a substrate in the case. Bonding by ultrasonic bonding or the like has been performed. FIG. 7 shows a semiconductor module 100 in which a semiconductor chip 82 and a case electrode 84 are electrically connected by a wire 86. Bonding is performed by the wire guide 74 of the bonding unit 70 supplying the wire 86 and the wedge bond tool 76 fixing the wire 86 by ultrasonic bonding or the like at a desired position. The electrical connection between the semiconductor chip 82 and the case electrode shown in FIG. 7 is obtained as follows. First, the wedge bond tool 76 bonds the wire 86 to the position E of the bonding pad on the semiconductor chip 82 (first bonding). Subsequently, the bonding unit 70 moves onto the case electrode 84 while supplying the wire 86 from the wire guide 74, and the wedge bond tool 76 bonds the wire 86 at the position F of the case electrode 84 (second bonding). Thereafter, the bonding unit 70 moves in the wire supply direction (right direction in the drawing) in order to cut unnecessary wires (remaining wires). This is because the cutter 78 is positioned on the left side of the wedge bond tool 76, so that the cutter 78 cannot cut the remaining wire as it is. This operation is called “shift back”. As a result of the movement of the bonding 70, the remaining wire is cut by the cutter 78, and one bonding operation is completed.
[0003]
The bonding portion 70 has a predetermined width in the horizontal direction parallel to the substrate due to its structure. Therefore, in order for the bonding part 70 to shift back, the distance L (shift back space L) from the second bonding position F to the case inner wall 88 needs to be at least as large as the width of the bonding part 70. The shift back space L was about 10 mm, for example. Thus, conventionally, when first bonding is performed on the bonding pad on the semiconductor chip 82 and then second bonding is performed on the case electrode 84, a relatively large shift back space is required, which hinders miniaturization of the semiconductor module case. It was.
[0004]
In order to reduce the shift back space L, there is a method in which the first bonding is performed at the position F on the case electrode 84 and the second bonding is performed at the position E on the semiconductor chip 82. The bonding part used in this method is configured symmetrically with the bonding part 70 of FIG. That is, since the wire 86 needs to be supplied from the case electrode 84 in the direction of the semiconductor chip 82 (left direction in the drawing), the wire guide 74 and the clamper 72 are located on the left side of the wedge bond tool 76 and the cutter 78 is located on the right side. To do. Considering that shift back is unnecessary in the first bonding, according to such a bonding portion, the distance L is secured to a length (for example, about 3 mm) corresponding to the width of the wedge bond tool 76 and the cutter 78. Therefore, the semiconductor module can be downsized.
[0005]
[Problems to be solved by the invention]
In the method in which the first bonding is performed at the position F on the case electrode 84 and the second bonding is performed at the position E on the semiconductor chip 82, it is necessary to cut the wire after the second bonding. Since this wire cutting is performed on the semiconductor chip 82, the semiconductor chip 82 receives an impact from the cutter 78 immediately after the wire cutting, and as a result, scratches such as cutter scratches and wire pressing scratches remain on the surface. Such a flaw has a large possibility of adversely affecting the characteristics of the semiconductor chip 82, and also affects the performance of a device in which the semiconductor module is incorporated, for example, a power module.
[0006]
An object of the present invention is to provide a semiconductor module manufacturing method that realizes wire bonding without giving impact, scratches, etc. to a semiconductor chip when first bonding is performed on a case electrode and second bonding is performed on a semiconductor chip. is there.
[0007]
[Means for Solving the Problems]
The semiconductor module manufacturing method of the present invention is a method of manufacturing a semiconductor module in which a semiconductor chip and a case electrode of a case are electrically connected by a bonded wire, the step of first bonding the wire to the case electrode; Subsequently to the first bonding step, the step of second bonding the wire to the semiconductor chip, and the remaining wire other than the wire between the case electrode and the semiconductor chip are half- cut in the air near the semiconductor chip by a cutter. A semiconductor module manufacturing method including a step of cutting, and a step of fixing the half-cut wire with a clamper and then tearing the wire, whereby the above object is achieved.
[0008]
The step of tearing the wire may be performed by tearing the half-cut wire horizontally or diagonally upward.
[0009]
The step of tearing the wire may be performed by pulling the remaining wire in the direction of the position where the next first bonding step is performed when the next first bonding is newly performed after the second bonding.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0013]
FIG. 1 shows a semiconductor module 10 manufactured by a semiconductor module manufacturing process according to the present invention. In the semiconductor module 10, the semiconductor chip 12 and the case electrode 14 of the case are electrically connected by a bonded wire 16. It is assumed that the semiconductor module 10 is already provided with a substrate on which the semiconductor chip 12 is placed, and the semiconductor chip 12 is provided thereon. The wire 16 is bonded to a bonding pad (not shown) provided on the semiconductor chip 12. The semiconductor module 10 performs the first bonding (first bonding) at the position A on the case electrode 14 and performs the second bonding (second bonding) with the semiconductor chip 12. As a result, the distance d from the position A to the case inner wall (or terminal) 18 can be set to about 3 mm, for example. Therefore, the semiconductor module 10 can be significantly reduced in size compared to the distance d when the first bonding is performed on the semiconductor chip 12 and the second bonding is performed on the case electrode 14, for example, about 10 mm.
[0014]
The main feature of the present invention is that the wire cutting after the second bonding is not performed in contact with the semiconductor chip 12 but in the air in the vicinity thereof. Specifically, in the wire cutting, first, almost half of the remaining wire other than the wire 16 between the semiconductor chip 12 and the case electrode 14 is cut by a cutter (cutter 28 in FIG. 5) (the remaining wire is half-cut). Thereafter, the wire is fixed by a clamper (clamper 22 in FIG. 6) and then pulled by moving the bonding part (bonding part 20 in FIG. 6) horizontally or obliquely upward in the wire supply direction side, and the remaining part is left in the half-cut portion. Tear the wire. In another example of wire cutting, the remaining wires are cut with scissors provided in the bonding portion in the air near the semiconductor chip 12. By cutting the remaining wire in this way, the remaining wire can be cut without giving an impact and a scratch to the semiconductor chip 12.
[0015]
FIG. 2 shows the bonding unit 20 that performs first bonding. The bonding unit 20 includes a clamper 22, a wire guide 24, a wedge bond tool 26, and a cutter 28. The wire guide 24 supplies a conductive wire 16 such as an aluminum wire. The clamper 22 fixes the conductive wire 16 supplied by the wire guide 24 as necessary. The wedge bond tool 26 fixes the wire 16 supplied by the wire guide 24 to a desired site by ultrasonic bonding or the like. The cutter 28 is used when cutting the wire 16 in a portion that is no longer needed. FIG. 2 shows an example in which the wedge bond tool 26 first bonds the wire 16 supplied from the wire guide 24 at the position A on the case electrode 14.
[0016]
In the present embodiment, the first bonding is performed at the position A on the case electrode 14 and the second bonding is performed on the semiconductor chip 12 (FIG. 1) on the left side of the case electrode 14 in the drawing. Therefore, the clamper 22 and the wire guide 24 are located on the left side of the wedge bond tool 26 and the cutter 28 is located on the right side in order to provide the wire 16 in the left direction of the drawing. Since the first bonding is performed by such a bonding portion 20, the distance from the position A on the case electrode 14 to the case inner wall 18 is substantially a length corresponding to the width of the wedge bond tool 26 and the cutter 28 (for example, about 3 mm). ) As long as it is secured.
[0017]
FIG. 3 shows the bonding portion 20 after the wire 16 is bonded to the case electrode 14. After bonding the wire 16 to the case electrode 14, the bonding unit 20 moves, for example, upward while supplying the wire 16 from the wire guide 24. The distance d from the bonding position A of the case electrode 14 to the case inner wall 18 is simply the distance d (FIG. 2) ensured at the time of bonding because the movement is simply upward (vertical in the drawing) perpendicular to the substrate. Note that this movement is not limited to the upward direction in the drawing, and may be from the upper left direction to the left direction in the drawing, for example.
[0018]
FIG. 4 shows the bonding unit 20 that performs second bonding. The bonding unit 20 moves from the position shown in FIG. 3 to a desired position B on the semiconductor chip 12 (for example, a desired bonding pad position on the semiconductor chip 12) while supplying the wire 16 from the wire guide 24, The wedge bond tool 26 second bonds the wire 16 at the position B. Similar to the first bonding, the second bonding is performed by fixing the wire 16 by ultrasonic bonding or the like. As described above, the processes up to the first bonding and the second bonding are completed.
[0019]
FIG. 5 shows the bonding part 20 that performs wire half-cut after the second bonding. After the second bonding is completed, it is necessary to cut the wire 16 in order to leave only the wire between the case electrode 14 (FIG. 4) and the semiconductor chip 12. However, since the cutter 78 is located on the right side of the wedge bond tool 76 in the bonding unit 20, the cutter 28 cannot cut the wire 16 as it is. Accordingly, the bonding unit 20 moves horizontally or obliquely upward (left or upper left in the drawing) on the wire supply direction side while supplying the wire 56 from the wire guide 24 again. The wire 56 is an unnecessary wire other than the wire between the case electrode 14 (FIG. 4) and the semiconductor chip 12, and is referred to as “residual wire” in this specification. The bonding unit 20 moves until there is an interval that allows the cutter 28 to operate between the wire supply port of the wire guide 24 and the position B. As apparent from FIG. 5, since the wire supply port does not exist on the semiconductor chip 12, the remaining wire 56 from the position B to the wire supply port crosses the air in the vicinity of the semiconductor chip 12. After the bonding unit 20 is moved, the supply of the remaining wire 56 is stopped, and the cutter 28 moves downward to half-cut the remaining wire 56 at a position C in the air near the semiconductor chip 12. This “half cut” does not completely cut (full cut) the wire but cuts the remaining wire 56 to the middle of the remaining wire 56, for example. As will be described with reference to FIG. 6, the half cut has a significance of making a cut in order to make the residual wire 56 easy to tear at the position C and thinning a portion to be torn. By performing half-cutting in the air near the semiconductor chip 12, the semiconductor chip 12 is not damaged at all, and the length of the extra wire from the bonding position B can be sufficiently shortened.
[0020]
FIG. 6 shows a state in which the remaining wire 56 is torn after the wire half cut. After the half cut is completed, the wire guide 24 stops supplying the wire, and the clamper 22 fixes the wire. Thereafter, the bonding unit 20 moves in the left direction of the drawing, that is, in a direction parallel to the chip, or in a diagonally upward (upper left side of the drawing) direction. Since there is no supply of wire and the remaining wire 56 (FIG. 5) is bonded at the position B (FIG. 5), the remaining wire 56 (FIG. 5) is pulled, and the remaining wire 56− at the half-cut position C−. 1 and 56-2. The remaining wire 56-2 is connected to the position B and is preferably sufficiently short. Due to the movement of the bonding part 20 described above, the tip of the wedge bond tool 26 close to the wire and the remaining wire 56 (FIG. 5) may come into contact with each other at the position D. Also in this case, the bonding part 20 may be moved in a horizontal direction parallel to the semiconductor chip 12 (FIG. 5) or in an obliquely upward direction (upper left direction in the drawing). By further moving in the horizontal direction (left direction in the drawing), the remaining wire 56 (FIG. 5) is pulled between the position B (FIG. 5) and the position D and broken at the position C.
[0021]
The moving direction of the bonding unit 20 is not limited to the direction parallel to the above-described chip or the obliquely upward direction, and may be any direction. For example, in order to connect a plurality of case electrodes 14 (FIG. 4) and one or more semiconductor chips 12 with wires as often seen in a manufacturing process, first bonding, second bonding, half-cutting, and tearing operations are performed. Consider the case of repeating multiple times. In such a case, after the half cut, if the bonding unit 20 is moved to the position of the first bonding to be performed next, the next first bonding can be performed immediately at the same time as the tearing operation, and the series of processes can be performed smoothly. Can progress. Therefore, a semiconductor module can be manufactured efficiently.
[0022]
In the description so far, the half-cut operation and the tearing operation in the air have been adopted so as not to damage the semiconductor chip 12. However, it is possible to prevent the semiconductor chip 12 from being damaged by other operations. For example, in FIG. 5, scissors (not shown) are provided in place of the cutter 28, and the remaining wire 56 is cut in the air near the semiconductor chip. If the scissors are used, the semiconductor chip 12 can be manufactured at high speed and easily because the semiconductor chip 12 is not damaged and the two steps of the half-cut operation and the tearing operation are not required. The scissors may have any shape as long as the wire is cut between two blades.
[0023]
【The invention's effect】
According to the method comprising the steps described above, when first bonding is performed at the position on the case electrode and second bonding is performed at the position on the semiconductor chip, the remaining wire is half-cut in the air near the semiconductor chip by a cutter , After fixing the remaining wire with a clamper, tear it off. As a result, it is possible to manufacture a semiconductor module that is small and has no wire-cut scratches on the surface of the semiconductor chip, with the shift back space removed.
[0024]
Further, since the half cut is performed in the air in the vicinity of the semiconductor chip, the length of the wire from the bonding position on the semiconductor chip to the tearing position can be sufficiently shortened.
[0025]
If the direction tearing away the wires in the direction of the position where the step of the next first bonding, tear operation at the same time can do the following first bonding immediately can proceed a series of steps smoothly. Therefore, a semiconductor module can be manufactured efficiently.
[Brief description of the drawings]
FIG. 1 shows a semiconductor module manufactured by a semiconductor module manufacturing process according to the present invention.
FIG. 2 shows a bonding part that performs first bonding.
FIG. 3 shows a bonding portion after a wire is bonded to a case electrode.
FIG. 4 shows a bonding part for performing second bonding.
FIG. 5 shows a bonding part that performs wire half-cut after second bonding.
FIG. 6 shows a state where the remaining wire 56 is torn after the wire half cut.
FIG. 7 shows a semiconductor module in which a semiconductor chip and a case electrode are electrically connected by a wire.
[Explanation of symbols]
12 Semiconductor chip, 16 wires, 20 Bonding part, 24 Wire guide, 26 Wedge bond tool, 28 Cutter, 56 Residual wire

Claims (3)

A semiconductor module manufacturing method in which a semiconductor chip and a case electrode of a case are electrically connected by a bonded wire,
First bonding a wire to the case electrode;
Following the first bonding step, second bonding the wire to the semiconductor chip;
The remaining wire other than the wire between the case electrode and the semiconductor chip is half-cut in the air near the semiconductor chip by a cutter , and
A method of manufacturing a semiconductor module , comprising: fixing the half-cut wire by a clamper and then tearing the wire. The method of manufacturing a semiconductor module according to claim 1, wherein the step of tearing the wire is a step of tearing the half-cut wire in a horizontal direction or obliquely upward. Wherein the step of tearing off the wire, when performing new next first bonding after said second bonding is performed by subtracting the residual wire in the direction of the position where the step of the next first bonding claim 1 A method for producing a semiconductor module according to claim 1.

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