JPS63304650A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the wettability of solder, and prevent the spread of solder from reaching unnecessary parts, by making the particle of Ni-plating on the mounting part on a heat sink for a power transistor and the like large, and making the particle of Ni-plating on the other parts small. CONSTITUTION:The surface of a heat sink 1 is plated with Ni 4 of small particle. The mounting part 2 thereon where power transistor and the like are arranged is plated with Ni 5 of large particle. Thereby, the bounding failure of a case and the like, the deterioration of wettability of solder, and the connection failure of a power transistor chip and the like can be prevented in the case where solder spreads outside necessary parts and attatches to the sticking part of a case and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device such as a power transistor chip attached to a heat sink using an i+ field.

[Conventional technology]

Conventionally, this type of heat sink was made by applying nickel (N) plating to the surface of copper, aluminum, iron, etc. This N
A power transistor tip was soldered onto the i-plating.

[Problem that the invention seeks to solve]

The conventional heat sink mentioned above has the following problems because the Ni plating is uniform over the entire surface. 1) When trying to improve the wettability of solder to the Ni plating, the Ni plating particles It is possible to increase the size, but when the amount of solder is large, the solder spreads to areas other than the necessary areas, and when attaching a case, etc., if solder adheres to a part, etc., it causes poor adhesion of the case, etc.

2) Contrary to 1) above, if you try to reduce the spread of the solder by using a particle wheel of N1 plating, the wettability of the solder will be poor.
A connection failure occurred in the bass transistor chip, etc.

In order to solve the above-mentioned problems, it has conventionally been done to partially plate the tag with Ag, etc., but this has the disadvantage that the heat sink becomes expensive.

[A precautionary measure to resolve the problem]

According to the present invention, N□ plating is applied on the heat sink,
The particles of the Ni plating are made larger in a predetermined part than in other parts, and a transistor chip is soldered to this predetermined part to obtain a semiconductor device.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing a heat sink used in an embodiment of the invention. The surface of the heat sink l is covered with small particles of Ni.
The plating 4 is provided with Ni plating 4, and the mounting part 2 of the power transistor etc. on the Ni plating 4 is coated with large particles of N.
I-plating 5 is applied.

FIG. 2 is a sectional view taken along line A-A' in FIG.

Ni plating with small particles 4 on the entire base material of heat sink 1
The Ni plating 5 with large particles is hidden only on the mounting part 2 of the power transistor etc. The process of creating this heat sink 1 is to first apply Ni to the heat sink base material 3.
Plating 4 is applied to the entire surface, and then the areas other than the parts 2 where power transistors and the like are attached are masked with photoresist, etc., Ni plating 5 is applied, and finally the photoresist is peeled off.

[Effects of the Invention] As explained above, the present invention is effective for attaching power transistor chips, etc. with solder because the Ni plating on the mounting part of the heat sink for power transistors, etc. has large particles, and the Ni plating on other parts has small particles. The wettability of the solder is good and the spread of solder 9 is less likely to reach unnecessary areas.

Also, it is cheaper than partial plating of Au, Ag, etc.

[Brief explanation of drawings]

FIG. 1 is a plan view of a heat sink used in an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA'. 1...Heat sink, 2...Mounting part for power transistors, etc., 3...Heat sink base material, 4...N-plating, 5... Ni plated. Agent: Susumu Uchihara, patent attorney...
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Claims (1)

[Claims] 1. A semiconductor device characterized in that a heat sink surface is metal plated, particles of the metal plating are larger in a predetermined part than in other parts, and a transistor chip is attached to the predetermined part.