JPH05275588A - Ni-plated lead frame - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the occurrence of whiskers during coining. [Construction] A lead frame manufactured by punching by a press after applying Ni plating 17, and coining is performed in a mold area in order to improve adhesion and water resistance in a mold. At this time, the step 14 provided in the round hole 12 of the base plate 16 having the surface plated with Ni 17
Are sequentially processed from the edge portion 13 to form a taper shape.
As a means for this, the tip end surface of the coining punch 18 is made into a conical taper surface whose central portion is high and which is lowered as it approaches the peripheral edge.
Mold 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-plated lead frame, and more particularly to improvement of a coining portion to improve adhesion and water resistance in a mold.

[0002]

2. Description of the Related Art A Ni-plated lead frame may be molded with a heat sink portion 1 as shown in FIGS. Further, when the heat sink portion 1 is resin-molded, a round hole 2 is provided in the heat sink portion 1 in order to improve adhesion and water resistance in the mold, and a step 3 is formed on the periphery of the round hole 2 by coining. May be given.

The step 3 of the round hole 2 is formed by coining with a coining punch (not shown) having a flat tip.

[0004]

By the way, in the Ni-plated lead frame having the above-mentioned structure, copper or copper alloy is used as the base material, and the base material is plastically deformed by the coining process to form the step of the round hole 2. Mold 3. However, in this case, since nickel and copper have different hardness, ductility, etc., the Ni plating may be peeled off from the edge portion 4 which is the Ni plating boundary portion of the punched cross-sectional portion to cause a beard. The burrs of the Ni plating are likely to fall off, and if they fall off, they will become conductive foreign matter in the resin mold, and the insulating property of the resin mold will deteriorate.

Conventionally, in order to eliminate the beard burr, a method of adjusting the clearance of the punch / die during the punching process to expose the burr and enclosing the edge portion 4 with the burr to prevent the occurrence of the beard burr. Is generally done.

However, in this case, the clearance of the punch die changes depending on the wear condition of the punch die, and the difference in the clearance changes the occurrence of punching burrs necessary for enclosing the Ni plating boundary. For this reason, there is a problem that it is not possible to reliably prevent the occurrence of whiskers.

Further, in order to keep the size of the punching burr constant, the clearance of the punch die is adjusted according to the wear condition of the punch die, but this clearance frequently changes and in order to keep it constant. However, it requires frequent maintenance of the mold, which shortens the life of the mold.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a Ni-plated lead frame capable of preventing the occurrence of a beard of Ni plating due to coining and extending the life of a die. It is in.

[0009]

In order to solve the above-mentioned problems, the present invention provides a lead frame manufactured by punching by press after applying Ni plating to a base plate, which has good adhesion and water resistance in a mold. When the coining process is performed in the mold area for improvement, the Ni-plated surface of the base plate is sequentially processed from its edge portion.

[0010]

[Effect] Whiskers are apt to occur at the edge portion due to the difference in ductility between the base plate and the Ni plating. However, since the base plate first coins this edge portion and sequentially moves the processing area to other portions, The occurrence of whiskers disappears.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 is a partial plan view showing a main part of the transistor lead frame, and FIG. 5 is a sectional view taken along the line VV of the transistor lead frame of FIG.

This lead frame is molded with the heat sink portion 11 as in the prior art. The heat sink portion 11 has a round hole 1 for improving the adhesiveness and water resistance of the mold when resin-molding this portion.
2 is provided, and the edge portion 13 of the round hole 12 is provided with a step 14 by coining. In addition, the edge portion 13 refers to a boundary portion (see FIG. 1) between the base plate 16 and the Ni plating 17 in the punching cross-section portion, in the peripheral edge of the round hole 12.

Then, the round hole 12 of the heat sink portion 11
Is a side surface of the base plate 16 as shown in FIG.
The surface plated with i-plating 17 is pressed with a coining punch 18, and the other surface is pressed with a die (not shown) to form a round hole 12.
Steps 14 (see FIG. 5) are formed.

The tip end surface of the coining punch 18 is a conical taper surface having a high central part and a lower part as it approaches the peripheral edge.

When the step 14 is formed in the round hole 12 by coining using the coining punch 18, the steps are as follows.

The coining punch 18 is positioned at the center of the round hole 12 and is pressed against it. At this time, coining punch 18
The taper surface of the tip first contacts the edge portion 13 of the round hole 12, and presses this portion. By this pressure contact, the edge portion 13 is first retroactively deformed, and the Ni plating 17 is strongly pressed against the copper or copper alloy base plate 16. Then, the circumference of the round hole 12 is sequentially retroactively deformed to form the step 14.

As described above, since the tapered surface of the tip of the coining punch 18 is retroactively deformed from the edge portion 13 to the periphery of the round hole 12 to form the step 14, the base plate 1 is formed.
It is possible to reliably prevent the occurrence of whiskers due to the difference in hardness, ductility, etc. between the No. 6 and the Ni plating 17, and it is possible to surely prevent the problems due to the occurrence of whiskers.

As described above, since the occurrence of whiskers can be surely prevented, it is not necessary to take out punching burrs and envelop the burrs, and in order to keep the size of the punching burrs constant, maintenance of the mold is frequently performed. There is no need to perform this, the life of the mold can be significantly extended, and the manufacturing cost can be reduced.

Further, even if the punch burr becomes large and the punch burr becomes large due to the change of the clearance due to the wear of the cutting edge of the punch / die, the burr does not occur, so that the life of the die can be extended.

Although the coining process around the round hole 12 has been described in the above embodiment, the same process is also performed for a portion having the edge portion 13 such as the periphery of the heat sink portion 11 where the beard may be generated. can do.

[0022]

As described above in detail, according to the Ni-plated lead frame of the present invention, the base plate portion to be coined to improve the adhesion and water resistance in the mold is sequentially processed from the edge portion. Since processing is performed, it is possible to reliably prevent the occurrence of burrs due to differences in hardness, ductility, etc. of the base plate and Ni plating.

Further, even if the punch burrs become large due to the change in the clearance due to the wear of the cutting edge of the punch / die, the burrs do not occur, so that the life of the die can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a round hole of a Ni-plated lead frame according to the present invention.

FIG. 2 is a plan view of relevant parts showing a conventional Ni-plated lead frame.

FIG. 3 is a sectional view taken along the line II-II of FIG.

FIG. 4 is a plan view of an essential part showing a Ni-plated lead frame of the present invention.

5 is a cross-sectional view taken along the line VV of FIG.

[Explanation of symbols]

 11 heat sink part 12 round hole 13 edge part 14 step, 16 base plate 17 Ni plating 18 coining punch

Claims (1)

[Claims] 1. A lead frame manufactured by punching by press after Ni plating on a base plate, when coining the mold area to improve adhesion and water resistance in the mold, A Ni-plated lead frame, wherein the Ni-plated base plate is sequentially processed from its edge portion.