JPH01260844A - Plating of lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To form a plated film characterized by a low cost, less dispersion in thickness and uniform plated crystal, by forming a first plated film comprising a first metal on the entire surface of a lead frame, removing a specified part of said plated film, and forming a second plated film comprising a second metal at the removed part. CONSTITUTION:For example, tin is plated as a first metal on the entire surface of a lead frame for a resin sealed type semiconductor device, and a tin plated film 2 having a thickness of 8-10mum is formed. Then, a part other than an element mounting region 3 and a wire bonding region 4 is masked by using a jig. The tin plated film 2 that is the first metal is separated by using the solution of nitric acid. The surface is washed with water. Then a jig having the same configuration and size as those of the mask jig that is used for the separation and washing with water for the tin plated film 2 is used. For example, silver is plated as a second metal on the element mounting region 3 and the wire bonding region 4, and a silver plated film 5 having a thickness of 6-8mum is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for plating lead frames for semiconductor devices.

[Conventional technology]

Conventionally, in the plating method for this type of lead frame, when plating the first metal, the area to be plated with the second metal is masked with a jig, masking agent, tape, etc. Plating is applied, and then the jig, masking agent, tape, etc. are peeled off and removed. Then the first
The general method is to mask the metal-plated area with a jig, masking agent, tape, etc., apply a second metal plating to the other areas, and then peel off and remove the jig, masking agent, or tape. It was used.

[Problem to be solved by the invention]

The conventional method for plating lead frames for semiconductor devices described above requires a large amount of man-hours for applying and curing the masking agent, pasting the tape, etc. by masking with a masking agent or tape, and has the disadvantage that the masking accuracy is poor. be. When carried out using a masking jig, semiconductor devices may be formed due to retention of plating solution in the jig, uneven current distribution, and especially variations in the thickness of the plating film made of the first metal and crystal abnormalities in the plating film. When this happens, it has drawbacks such as causing poor solderability and impairing the reliability of the semiconductor device.

[Means to solve the problem]

The method for plating lead frames for semiconductor devices of the present invention includes:
A step of forming a first plating film made of a first metal on the entire surface of the lead frame, a step of removing a predetermined portion of the first plating film, and a step of forming a first plating film on the portion where the first plating film was removed. and forming a second plating film made of two metals.

〔Example〕

Next, the present invention will be explained using the drawings.

FIGS. 1A to 1C are cross-sectional views of a lead frame shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1(a), the entire surface of a lead frame 1 for a resin-sealed semiconductor device is plated with tin as a first metal to form a tin plating film 2 having a thickness of 8 to 10 μm.

Next, as shown in FIG. 1(b), areas other than the element mounting area 3 and the wire bonding area 4 are masked using a jig, and the first metal is masked using a nitric acid solution (15 to 20%). The tin plating film 2 is peeled off and washed with water.

Next, as shown in FIG. 1(C), the tin plating film 2 is peeled off,
Using a jig with the same shape and dimensions as the water-washed mask jig, the element mounting area 3 and wire bonding area 4 are plated with silver as a second metal, resulting in a silver plating film 5 with a thickness of 6 to 8 μm. form.

As described above, according to this embodiment, since a plating film made of the first metal is first formed on the entire surface without using a jig for a mask, the plating film is free from crystal abnormalities and has a uniform thickness. A film can be formed.

In the above embodiment, tin is used as the first metal, and tin is used as the second metal.
Although the case where silver is used as the metal has been described, the invention is not limited to this, and a tin-lead alloy can be used as the first metal, gold, etc. can be used as the second metal.

〔Effect of the invention〕

As explained above, the present invention involves plating the entire surface of a lead frame for a semiconductor device with a first metal, and then plating a plating film made of the first metal in an element mounting area and a wire bonding area where a second metal is to be plated. After chemically exfoliating the
By performing water cleaning and plating the element mounting area and wire bonding area with a second metal, a lead frame for semiconductor devices can be produced that is inexpensive, has little variation in plating thickness, and has a plating film with uniform plating crystals. There are effects that can be easily obtained.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are sectional views of a lead frame for explaining one embodiment of the present invention. 1...Lead frame, 2...Tin plating film, 3...
・Element mounting area, 4...Wire bonding area, 5
...Silver-plated film.

Claims (1)

[Claims] A step of forming a first plating film made of a first metal on the entire surface of the lead frame, a step of removing a predetermined portion of the first plating film, and a step of forming a first plating film on the portion where the first plating film was removed. 1. A method for plating a lead frame for a semiconductor device, the method comprising the step of forming a second plating film made of a second metal.