JPH05226532A - Manufacture of lead frame for power transistor - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the production of resin flash on the heat sink and to eliminate the process of removing the resin flash to improve work efficiency. [Structure] Knockout 6 on one surface of heat sink 2
By pressing the side edges of the heat sink 2 with the ear punches 7 arranged on both sides of the knockout 6 to form a step on the side edge of the heat sink and to remove the step from the side edge. In a method of manufacturing a lead frame for a power transistor, which is manufactured by subjecting the ear portion 5 to one side, a clearance A between the outer surface of the knockout 6 and the side surface of the earing punch 7 facing the outer surface is provided. It is characterized in that it is set to a large size, and the projecting edge portion 10 which acts as a dam for preventing the resin flow at the time of resin molding is formed at the edge portion of the step portion by press working with the ear punch 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame for a power transistor.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a lead frame used for manufacturing a power transistor. In the figure, 2 is a heat sink, 3 is a lead, and 4 is a resin molded portion. The heat sink 2 is for improving the heat dissipation of the power transistor. However, in the case of resin molding, the heat sink 2 may be molded by exposing the outer surface of the heat sink 2 to the outer surface of the resin molding portion 4 as shown in FIG. is there. When the heat sink 2 is exposed and molded as described above, if the side edge portion of the heat sink 2 is cut off, the mold resin and the heat sink 2 may not be sufficiently joined and the mold resin may be peeled off. Therefore, as shown in FIG. 5, the side edge portion of the heat sink 2 may be pressed to form a step on the side edge portion to perform earing processing for protruding the ear portions 5 and 5 outward. FIG. 7 shows a state in which the ears 5 are sealed in a molding resin and resin-molded.
By forming the above, it is possible to improve the bondability with the molding resin at the side edge portion of the heat sink 2.

[0003]

FIG. 3 shows a schematic structure of an apparatus generally used in the earing process. In the figure, 6 is a knockout, 7 is an ear punch, and 8 is a die. Knockout 6 holds down the heatsink 2 in the earing process,
The side edge portion of the heat sink 2 is pressed by the earing punch 7 and is eared. By the way, the surface of the heat sink 2 with which the knockout 6 abuts in this earing process is an exposed surface that is exposed to the outside after resin molding, but when the lead frame subjected to the earing process by the conventional processing method is resin molded, There is a problem that flash of molding resin occurs on the back surface of the heat sink 2. The heat sink 2 with which the knockout 6 comes into contact during resin molding
The surface of is contacted with the surface of the mold and is filled with resin. At this time, the mold resin wraps around the back surface of the heat sink 2 and becomes a resin burr.

When the resin burrs as described above occur, the resin burrs are conventionally removed by a deburring process such as sandblasting after the resin molding. Therefore, in the conventional manufacturing of power transistors, there is a problem that the work for removing the resin burr becomes complicated. Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to enable resin molding without producing resin burrs on an exposed surface of a heat sink when manufacturing a power transistor, and to remove resin burrs. It is an object of the present invention to provide a method for manufacturing a lead frame for a power transistor, which can simplify the work by eliminating the step of performing.

[0005]

The present invention has the following constitution in order to achieve the above object. That is, the knockout is brought into contact with one surface of the heatsink, and the side edges of the heatsink are pressed by the edge punches arranged on both sides of the knockout to form a stepped portion on the side edge of the heatsink. In a method of manufacturing a lead frame for a power transistor, which is manufactured by performing an earing process of extending an ear portion outward from the side edge portion,
A protruding edge portion that acts as a dam that prevents resin flow during resin molding by a large clearance between the outer surface of the knockout and the side surface of the ear punch that faces the knockout, and is pressed by the ear punch. Is formed at the edge of the stepped portion.

[0006]

[Function] When the side edge of the heat sink is pressed with the ear punch to form the ear extending outward from the side edge of the heat sink, the clearance between the ear punch and the knockout holding the heat sink is provided. By making it large, the material has a raised shape on the outer surface portion of the knockout, and a protruding edge portion having a minute height is formed at the edge portion of the step portion.
During the resin molding, the projecting edge portion acts as a dam that blocks the resin flow, and effectively prevents the resin burr from being formed on the back surface of the heat sink.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an enlarged view showing a heat sink 2 portion of a lead frame for a power transistor manufactured by a manufacturing method according to the present invention. Figure 1
1A is a plan view of the heat sink 2, and FIG. 1B is a sectional view. Also in the method of the present invention, it is the same as the conventional method that the edge portions 5 on both sides of the heat sink 2 are outwardly extended to extend the edge portions 5 outward. A step portion 5a is formed at the base of the ear portion 5 by the earing process. In the method of the present invention, the clearance between the knockout 6 and the earing punch 7 is larger than that in the conventional processing device during the earing process. It is characterized in that it is set wide and a small projecting edge portion 10 is formed at the edge portion of the step portion 5a.

FIG. 2 shows a heat sink 2 according to the method of the present invention.
The configuration of a processing device that performs earing processing is shown in FIG. The basic configurations of the knockout 6 and the ear punch 7 are the same as those of the conventional apparatus, but as shown in the figure, the knockout 6 and the ear punch 7 are provided.
It is characterized in that the clearance A between the two is set to about 20 μm and the earing process is performed by pressing. In the conventional apparatus, the clearance between the knockout 6 and the ear punch 7 is set to a normal knockout and punch setting level, and the clearance is not specially set.

In this embodiment, the knockout 6 is performed as described above.
As shown in FIG. 2, when the heat sink 2 is pressed to form the ears 5, the material has a raised shape at the edge of the step 5a by setting a wide clearance between the ears and the ears punch 7 as shown in FIG. The protruding edge portion 10 is formed. The height of the ridge 10 is 2 to 4 μm. Edge 10
1B, the cross-sectional shape of the surface of the heat sink 2 exposed on the outer surface of the resin mold portion is such that the projecting edge portions 10 are formed on both edges and the intermediate portion becomes a flat surface.

Resin molding was performed on the exposed surface of the heat sink 2 on which the protruding edge portion 10 was formed by the above-described processing method, and as a result of observing the occurrence of resin flash, the contact surface of the knockout 6 of the heat sink 2 was positively pressed. On the edge 1
It was confirmed that in the case where 0 was formed, the wraparound of the mold resin was effectively suppressed and the generation of resin burrs could be effectively prevented. This is the flange 10 when resin molding.
Is considered to act as a dam for the mold resin, which can prevent the resin flow. In the lead frame obtained by the conventional processing method, the edge portion of the heat sink 2 does not act to prevent the resin from flowing, which tends to cause resin burrs. By positively forming the protruding edge portion 10 on the edge portion of No. 2, it is possible to suppress the resin flow, and it is possible to effectively prevent the occurrence of resin flash.

According to the method of the present invention, the clearance between the knockout and the ear punch is provided on the heat sink 2 by the flange portion 1.
By setting it to a size large enough to form 0, it is possible to prevent the occurrence of resin burrs, so the effect can be exhibited simply by adjusting the settings of the conventional device, and the manufacturing process is extremely easy. is there. In the actual manufacture of the lead frame, the lead frame product is managed by inspecting the flatness of the exposed surface of the heat sink and checking the dimension of the projecting edge and the flatness of the flat surface of the heat sink as needed. Although the present invention has been variously described with reference to the preferred embodiments, the present invention is not limited to the above embodiments and can be similarly applied to various patterns of lead frames for power transistors.

[0012]

As described above, when the lead frame manufactured by the method for manufacturing a power transistor lead frame according to the present invention is used for resin molding, it is possible to effectively prevent the occurrence of resin burrs in the heat sink portion as described above. It is possible to omit the step of removing the resin burrs and to improve the efficiency of the manufacturing work.

[Brief description of drawings]

1A is a plan view of a heat sink portion of a lead frame manufactured by the method of the present invention, and FIG. 1B is a sectional view.

FIG. 2 is an explanatory diagram showing a method for processing a lead frame to expose.

FIG. 3 is an explanatory diagram showing a conventional processing device used for processing the lead frame to the edge.

FIG. 4 is an explanatory diagram showing a conventional example of a lead frame.

FIG. 5 is an explanatory diagram showing an example in which a heat sink is subjected to earing processing.

FIG. 6 is a cross-sectional view of a lead frame resin-molded.

FIG. 7 is a cross-sectional view showing a state in which a lead frame is resin-molded.

[Explanation of symbols]

 2 heat sink 3 lead 4 resin mold part 5 ear part 6 knockout 7 ear stick punch 8 die 10 projecting edge part

Claims (1)

[Claims] 1. A stepped portion is formed on a side edge portion of the heat sink by abutting the knockout on one surface of the heat sink and pressing the side edge portion of the heat sink with ear punches arranged on both sides of the knockout. A method of manufacturing a lead frame for a power transistor, which is formed by performing an earing process for forming an ear portion outward from the side edge portion, the outer surface of the knockout and the earring punch facing the outer surface. A large clearance with respect to the side surface is formed, and a projecting edge portion that acts as a dam that prevents a resin flow at the time of resin molding is formed at the edge portion of the step portion by press working with the ear punch. Manufacturing method of lead frame for power transistor.