JPS61236147A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To suppress waste of the noble metal plating to be performed on lead frame element matters for IC to the minimum by a method wherein the noble metal plated layers to be adhered on the side surfaces of the lead frame element matters are peeled off and the plated layers are reproduced. CONSTITUTION:Lead frame element matters 3, whereon a noble metal plating is performed, are set between a top plate 1, which is attached with a silicon resin material having a chemicals resistance and an elastic force or is attached with an elastic material 2 to be represented by a neoprene rubber, and a bottom plate 6, wherein protruded substances 7 and small holes 8 are provided. At this time, the noble metal surfaces of the element matters 3 are brought into contact with the elastic material 2 and the places equivalent to the plated areas of the element matters 3 are pressed to the elastic material 2 by the protruded matters 7 from the back surfaces of the element matters 3. It is better for the areas of the protruded substances 7 to correctly coincide with those of the plated areas. Each noble metal plated surface 4 to be provided on part of the surface of each lead frame element matter 2 is completely pressed to the elastic material 2 and noble metal surfaces 5 to be adhered on the side surfaces of each lead frame element matter 3 are not brought into contact with the elastic material 2 whatever. In such a state, when removers 9 are made to pass through from the small holes 8 to be provided in the bottom plate 6, the noble metal surfaces 5 only to be adhered on the side surfaces of each lead frame element matter 3 can be removed. As a result, the noble metal surfaces 5 are recovered and can be recycled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a lead frame for a semiconductor integrated circuit (hereinafter referred to as IC), which minimizes the amount of precious metal plated.

The IC lead frame is made of 42 alloy (Ni42% by weight, F
e remainder), Kovar (Ni 29% by weight, C0 17% by weight,
Materials that have a coefficient of thermal expansion close to that of silicon IC chips, and have high strength and high thermal conductivity, such as iron-based alloys such as iron (Fe residue), phosphor bronze, and copper-based alloys such as tin-containing copper, are used. There is.

<Prior art> IC lead frames are made by forming a predetermined pattern by press punching or etching a metal material as shown above, and then forming an island part (the part on which the IC chip is mounted) and an inner lead tip part. Generally, the areas where wire bonding is performed are partially plated with precious metals such as gold, silver, and palladium alloys for the purpose of improving contact with IC chips and wires, imparting anti-corrosion properties, and preventing diffusion. It is true.

<Problems to be Solved by the Invention> In the conventional method, precious metal plating was applied not only to the above-described necessary surfaces of the island part and the inner lead tip, but also to the side surfaces thereof. The amount of precious metal (5) adhering to this side surface accounts for 20 to 50% of the total, wasting expensive precious metal.

The purpose of the present invention is to create an IC lead frame that can be recycled by peeling off the precious metal plating layer (5) attached to the side surface in order to minimize waste of precious metal plating on the IC lead frame body (3). The purpose is to provide a manufacturing method.

[Means to Solve the Problem] First, the surface of the island portion and the surface of the tip of the inner lead are plated with a precious metal by the same method as in the conventional method. At this time, the noble metal (5) is simultaneously electrodeposited on the side surfaces thereof.

Next, the process moves to a peeling step which is a feature of the present invention. FIG. 2 is an enlarged explanatory diagram illustrating an embodiment of the peeling process shown in FIG. 1; Lead frame body with precious metal plating (3)
A top plate (1) is attached with an elastic body (2) typically made of chemical-resistant and elastic silicone resin or neoprene rubber, and is provided with a protrusion (7) and a small hole (8). Set between the bottom plates (6). At this time, the noble metal surface is brought into contact with the elastic body (2), and the portion corresponding to the plating area is pressed with the protrusion (7) from the back side. Convex objects (it is preferable that the force and area exactly match the plating area.

In this way, the noble metal plating surface (4) applied to a portion of the surface of the lead frame body is completely pressed against the elastic body (2), so that it is possible to completely prevent liquid from entering.

Further, the noble metal surface (5) attached to the side surface remains without contacting anything. In this state, when the stripping liquid (9) is passed through the small hole (8) provided in the bottom plate (6), only the noble metal surface (5) attached to the side surface can be removed.

Costs can be reduced by recovering and reusing molten precious metals.

At this time, the upper plate (1) used may be of any type as long as it is corrosion resistant and has a smooth surface, and is selected from metal, plastic, and ceramic. Particularly in the case where the lead frame body is highly magnetic such as 42 alloy, it is preferable to use a magnet for the upper plate (1) from the viewpoint of handling.

Since the material of the bottom plate (6) and the protrusions (7) will come into contact with the stripping liquid (9), it is preferable to use corrosion-resistant plastics, such as vinyl chloride, acrylic, polyester, polypropylene, polyethylene, and glass fiber-containing epoxy resin plates. Can be mentioned.

The size of the small hole (8) is several Weiho to several IQ? A circular shape of IIB is desirable, but there is no particular restriction on the shape or number of pieces. , Gold plating was partially applied to a thickness of 2μ using a conventional method.

After this, the upper plate (1) made of vinyl chloride on which the elastic body (2) made of Q.31 thick silicone resin (KB112 manufactured by Shin-Etsu Chemical Co., Ltd.) is pasted is placed at the same position and with the same size convexity as the predetermined plating area. A large number of small holes T81 (10 m
Glass fiber-filled epoxy resin bottom plate (6
) and tightened the lead frame body completely between the elastic body (2) and the WJ (4), and then let the stripping liquid (9) pass through the small hole (8) to the side surface. The electrodeposited gold plating layer (5) was removed. The conditions are as follows.

Temperature: 30° C. Time: 1.5 minutes As a result, it was possible to manufacture an IC lead frame in which the amount of gold used was kept to a minimum.

The gold dissolved in the stripping solution can be recovered and recycled.

<Example 2> 0.25 mm thick copper alloy (MF202 manufactured by Mitsubishi Electric, Sn2
．． 0%, Ni 2 O, 2%, Cu remaining) was formed into a predetermined pattern by press punching, and then silver plating was partially applied to a thickness of 5μ using a conventional method.

After this, 0.2 mm thick silicone resin (K made by Shin-Etsu Chemical Co., Ltd.
An upper plate (1) of glass fiber-containing epoxy resin on which an elastic body (2) made of B12) is pasted is placed at the same position as the predetermined plating area, and a protrusion (7) of the same size (height: 5 mw,
) and the bottom plate (6) (same material as the top plate (1)) having a large number of small holes (8) (5rnaψ), and completely flatten the plating surface to the elastic body (2). (
4) was tightened until it adhered, and then a stripping solution (9) was passed through the small hole (8) to remove the silver plating layer (5) electrodeposited on the side surface. The conditions are as follows.

Temperature: 50°C Time: 2 minutes As a result, it was possible to manufacture an IC lead frame in which the amount of silver used was kept to a minimum. Note that the silver dissolved in the stripping solution can be recovered and recycled.

<Effects of the Invention> Using this manufacturing method, it has become possible to save about 20 to 50% of the amount of precious metal used.

This effect becomes extremely large when gold is used as the precious metal in the lead frame, or when the lead frame has a large number of pins and a narrow tip. Further, according to the present invention, since the surface on which the plating layer is to be left is reliably covered by the upper plate since it is pressed by the protrusions, there is no risk that a necessary portion of the plating layer will be removed. Furthermore, since the stripping liquid is supplied from a location close to the plating layer to be removed, the plating layer can be removed reliably in a short time.

Furthermore, the manufacturing method of the present invention has the advantage of being able to cope with the recent trend toward higher precision in lead frames, such as increased number of lead frames and increasingly complex shapes.

[Brief explanation of drawings]

FIG. 1 is an enlarged explanatory view showing the main steps of an example of the method for manufacturing a semiconductor lead frame according to the present invention, and FIG. 2 is an enlarged explanatory view showing an example of the bottom plate used in the peeling process. (1)...Top plate (2)...Elastic body (3
)...Lead frame body (4)...Precious metal plating (5)...Precious metal plating attached to the side (6)
・・Bottom plate (7)・Protrusion (8)・・・
Small hole (9)...Removal liquid agent Aio Suzuki

Claims (1)

[Claims] After precious metal plating is applied to the bonding area of the semiconductor lead frame body (3), the plating surface (4) is attached to the upper plate (
A convex object (2) having an area corresponding to the bonding area is placed in contact with the elastic body (2) attached to the
7), and remove the precious metal (5) adhering to the side surface by passing the stripping liquid (9) through the small hole (8) provided in the bottom plate (6) having the protrusion (7). A method for manufacturing a lead frame characterized by: