JPH0832004A - Method of plating lead frame for semiconductor device - Google Patents

Abstract

(57) [Abstract] [Objective] Excessive silver plating on the sides of the leads and islands in the lead frame is removed to prevent migration of the silver plating and to prevent deterioration of lead insulation. [Structure] After forming a lead frame 1 having outer leads, inner leads 3 and islands 4 by pressing, etc., one surface is sealed and silver plating 5 is applied to the ends of the inner leads 3 on the other surface and the islands 4. Give. After that, the elastic seal member 8 is pressed against the plated surface, the mask 7 is applied to the opposite surface to expose a required portion, and the stripping solution S is sprayed on the exposed portion, so that the side surfaces 4b and 3b of the island 4 and the inner lead 3 are exposed. The silver plating 5 adhered to is removed. Even if a polyimide tape having high hygroscopicity is adhered to the anti-plating surface of the island 4 and the lead 3, the silver plating 5 does not come into contact with the tape, so that silver migration does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of silver-plating islands and inner leads of a semiconductor device lead frame.

[0002]

2. Description of the Related Art Generally, the surface of a part of an island and inner leads of a lead frame is plated with silver. Conventionally, this plating process is performed by forming an island, an inner lead and an outer lead on a lead frame, and then spraying a plating solution with a resilient rubber mask on the surface excluding the portion to be plated.

[0003]

In the above conventional method,
The surface can be sealed with a rubber mask, but because of the thickness of the lead frame, silver plating adheres to the side and back surfaces and the plating area expands more than necessary. in this case,
For example, in a semiconductor device of a type in which an electrically insulating tape made of polyimide or the like is attached to the surface opposite to the plating and the leads and the island are supported in the manufacturing process, the plating on the side surface may come into contact with the tape. The tape is highly hygroscopic, so
The silver plating on the side surface may cause migration on the tape, leading to a short circuit between leads. On the other hand, in order to prevent the silver plating from adhering to the side surface of the lead,
There is also a method in which the lead frame material is press-molded after silver plating corresponding to the inner lead end and island pattern, but it is necessary to align the plating pattern with the lead frame outer shape with high accuracy. However, there is a problem in that it requires large-scale equipment and is not easy to manufacture. Therefore, the present invention is a semiconductor that can be implemented relatively easily by removing excess silver plating on the side surface of the lead frame, eliminating migration of silver plating, preventing deterioration of lead insulation, and requiring no large-scale equipment. An object is to provide a method for plating a lead frame for a device.

[0004]

According to the present invention, in order to solve the above problems, silver plating 5 is applied to a predetermined portion of the surface of the island 4 and / or the inner lead 3 in the lead frame 1.
Then, the plated surface is sealed with the sealing member 8, and the stripping solution S is sprayed from the side opposite to the plated surface to remove the silver plating 5 adhering to the side surfaces of the island 4 and the inner leads 3. Adopted the plating method.

[0005]

In the method of the present invention, the silver 4 is applied to the island 4 of the lead frame 1 and the predetermined portions of the surfaces 4a, 3a of the inner leads 3 by a jet method or the like. Next, the plated surface is sealed with, for example, a seal member 8 and the stripping solution S is sprayed from the back surface side of the plated surface to remove the silver plating 5 attached to the surfaces other than the surfaces 4a and 3a. Therefore, the silver plating 5 remains only on the necessary portions of the surfaces 4a, 3a of the sealed island 4 and the inner leads 3, and the silver plating 5 remains on the side surfaces 4b, 3b.
No migration of silver plating occurs even when a polyimide tape or the like is attached.

[0006]

An embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, an outer lead 2, an inner lead 3 and an island 4 are formed on a lead frame 1. The surface 3a near the tip of the inner lead 3 and the surface 4a of the island 4 are plated with silver.

The outer lead 2, the inner lead 3 and the island 4 of the lead frame 1 are formed by press working or the like. Then, as shown in FIG. 2, the elastic seal member 6 is brought into close contact with one surface of the lead frame 1, the mask 7 for limiting the plating range is applied to the opposite surface, the plating solution P is jetted, and the silver plating 5 is partially covered. Give it.
At this time, as shown in FIG. 3, the silver plating 5 adheres not only to the surfaces 3a and 4a of the inner lead 3 and the island 4 but also to the side surfaces 3b and 4b.

Next, the lead frame 1 is turned upside down and, as shown in FIG. 5, the elastic seal member 8 is applied to the plated surface.
Press against. Also, on the opposite side of the lead frame 1,
The mask 9 is applied, and only the required portion of the back surface of the plated surface is exposed. Then, the stripping solution S is sprayed on this exposed portion. Side surfaces 4b and 3 of the island 4 and the inner lead 3
As shown in FIG. 4, the silver plating 5 attached to b is removed by the stripping solution S, and the silver plating 5 remains only on the surfaces 4a and 3a of the sealed island 4 and the inner leads 3. The means for stripping the silver plating 5 with the stripping solution S may be an electrolytic method or a chemical method. Further, the present invention is not limited to the illustrated embodiment, but can be applied to a lead frame having no island, for example.

[0009]

As described above, according to the present invention, after silver plating 5 is applied to a predetermined portion of the surface of the island 4 and / or the inner lead 3 in the lead frame 1, the plated surface is sealed with the seal member 8 and plated. Stripping solution S from the opposite side
Is used to remove the silver plating 5 attached to the side surfaces of the island 4 and the inner leads 3, and thus the excess silver plating 5 on the side surfaces of the island 4 and the inner leads 3 is removed. It is possible to prevent migration of silver plating and prevent short circuit between leads. Has the effect.

[Brief description of drawings]

FIG. 1 is a plan view of a lead frame.

FIG. 2 is a schematic view of a plating process.

FIG. 3 is an enlarged cross-sectional view of a part of the lead frame after plating.

FIG. 4 is an enlarged cross-sectional view of a part of the lead frame after the peeling process.

FIG. 5 is a schematic view of a peeling process.

[Explanation of symbols] 1 lead frame 2 outer lead 3 inner lead 4 island 5 silver plating 8 elastic seal member 9 mask P plating solution S stripping solution

Claims (1)

[Claims] 1. A surface of an island and / or an inner lead of a lead frame is plated with silver, the plated surface is sealed with a sealing member, and a stripping solution is sprayed from the side opposite to the plated surface to release the island and the inner. A method for plating a lead frame for a semiconductor device, characterized in that the silver plating attached to the side surfaces of the leads is removed.