JPS6254945A - Lead frame for ic - Google Patents

Abstract

PURPOSE:To obtain a preferable bonding work by forming a ringlike coined portion which is shallower than the depth of a lead end coining portion and deeper than the partial plating thickness between the lead end coined portion and a lead base. CONSTITUTION:The depth DELTA2 of a ringlike coining is designed to be larger than a partial plating thickness (d), and the end of a bonding retainer jig 5 is designed to be disposed at a ringlike coining region. Accordingly, the jig 5 is not contacted with a partial silver or gold plating 4 at wire bonding time of a lead frame for an IC, and the plating materials are not bonded to the jig. The depth DELTA2 of the coining 8 is formed to be shallower than the depth DELTA1 of an inner lead coining 7 to reduce the deformation amount of the material synthetic rubber of a partial plating mask 3, thereby eliminating a gap in the coining steps.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to improvements in lead frames for ICs.

<Prior Art> A lead frame for an IC is formed by punching or etching as shown in the plan view of FIG. In Fig. 5, 1 is a lead frame, 1a is an inner lead, 1
b is the outer lead. In the case of punching IC lead frames, there is an avalanche 2 on the punching surface as shown in Figure 6(a).
occurs. With such a droop 2 still in place, the inner lead tip portion 1a of the IC lead frame 1 is plated with gold, silver, etc., and then wire bonded. In such a case, due to the sag 2, the bonding area required for bonding is small, resulting in insufficient bonding and an accident in which the bonded portion breaks. For this reason, generally the inner lead tip 1
There is a mangled syllable called coining in a. As shown in FIG. 6), the adhesion of wire bonding is improved by performing a coining process with a flattening amount Δ.

<Problems to be solved by the invention> FIG. 7(a) is a side view of the coined inner lead tip, and FIG. 7(b) is a sectional view taken along the line a-a shown in FIG. 7(a). be. In FIG. 7 (~, (b), la is the inner lead, and Δ is the amount of crushing due to coining. After the inner lead tip of such a lead frame is coined, as shown in FIG. 8, A partial plating mask 3 made of silicone rubber or the like is covered except for the tip of the inner lead, and partial plating 4 is applied to the portion of the tip of the inner lead left covered by the partial plating mask 3, followed by wire bonding. In order to ensure the stability of the mending work, the lead frame 1 is held down from above by a holding jig 5 during each mending process, as shown in Fig. 9. Fig. 10 shows the partially plated inner lead tip 1a and the lead frame 1. Presser jig 5
FIG. As shown in FIG. 10, when the holding jig 5 presses the lead portion of the lead frame each time during the handing process, the holding jig 5 presses the inner lead 1a portion through the plating portion 4. For this reason, the lower surface of the presser jig 5 comes into contact with the plating portion 4 each time 9. The plating material gradually adhered to the lower surface of the holding jig 5, and then suddenly peeled off, causing damage to the IC chip. This is to avoid such contact between the presser jig 5 and the partial plating 4.

The plating mask 3 is applied so that the partial plating 4 is stopped halfway to the coining part of the inner lead 1a as shown in FIG.
One idea was to extend the periphery of the coining part to the middle of the coining part and plate the exposed tip of the inner lead. However, in this case, a gap 6 was formed between the corner of the coining part and the mask 3, and the plating solution entered the gap 6, causing the side surface of the inner lead to be plated, which was not preferable.

The present invention was made in view of the deficiencies of the prior art, and by improving the coining shape, the problem of plating solution leakage does not occur during the partial plating process, and the lower surface of the holding jig is partially removed. The object of the present invention is to provide an IC lead frame that does not come into contact with plating and can be easily mended.

<Means for Solving the Problems> The structure of an IC lead frame according to the present invention that achieves the above object is an IC lead frame manufactured by punching.

A coining part is provided at the lead tip, and a ring-shaped coining part is provided between the lead tip coining part and the lead base, which is shallower than the depth of the lead tip coining part and deeper than the partial plating thickness. It is characterized by this.

<Example> An IC lead frame according to the present invention will be described with reference to the drawings of an example.

FIG. 1 is a plan view of an IC lead frame according to the present invention. In FIG. 1, c and d indicate the coining range of the lead tip 1a in the X and Y directions. According to the present invention, when coining the inner lead tip fat, the range c of the lead tip coining in the x + Y direction as shown in FIG.
A ring-shaped coining part 8 having a groove width t is provided on the outside of the lead tip coining part 7 shown by d. In this case, the depth Δ of the ring-shaped coining portion 8 is shallower than the depth Δ of the lead tip coining portion 7, and also deeper than the partial plating thickness d. Coining width 1.
As shown in FIGS. 3 and 4, the width 4 of the bank portion 9 left between the lead tip coining portion 7 and the ring-shaped coining portion 8 corresponds to the edge and den of the partial plating mask 3 during plating. The tip of the presser jig 5 at the time of loading is in the area 1 of the ring-shaped coining part 8. It is designed in advance to fit inside.

Experimental Example An IC lead frame according to the present invention was manufactured under the following conditions.

IC lead frame material is 42 alloy, partial plating material is silver, plating thickness d = 6μ, inner lead coining depth △, = 20μ"s') "ri-shaped coining depth Δ
, 310 μm, ring-shaped coining groove width 1. = Q
, 8M, 4 in the bank between the ring-shaped coining and the lead tip coining part = 0.2 error, According to the IC lead frame of the present invention manufactured under such conditions, the drawbacks of the conventional ones can be eliminated. An excellent product was obtained.

<Effects of the Invention> According to the IC lead frame according to the present invention, the depth Δ of the ring-shaped coining is larger than the partial plating thickness d, and the tip of the pounding presser jig 5 is designed to be in the ring-shaped coining area. As a result, the pressing jig 5 does not come into contact with the silver or gold partial plating 4 during the wire bonding work of the IC lead frame, and these plating materials do not adhere to the holding jig. do not have.

Further, according to the present invention, the depth Δ2 of the ring-shaped coining portion 8 is smaller than the depth Δ□ of the inner lead coining portion 7, thereby reducing the risk of deformation of the composite material comb of the partial plating mask 3. The plating solution does not form the gap 6 as shown in Fig. 11 at the coining step, and the plating solution flows into the gap 6.
A product of excellent quality was obtained with no seepage and unnecessary plating on the tip of the lead.

[Brief explanation of drawings]

FIG. 1 is a plan view of an IC lead frame according to the present invention;
Figure 2 is a side view of the lead tip showing the coining part and ring-shaped coining part of the lead tip shown in Figure 1, and Figure 3 is the lead tip when a partial plating mask is used for the item shown in Figure 1. FIG. 4 is a side view showing the relationship between the holding jig and the lead tip when wire-bottoming the wire bolt shown in FIG. 1, and FIG. 5 is a conventional IC lead frame. A plan view of FIG. 6 (IL) is a diagram showing sagging caused by punching. Figure 6(b) is a diagram explaining the coining process to correct the sagging shown in Figure 6(al), Figure 7(al is a side view of the lead tip of the lead shown in Figure 5, Figure 7(b) is shown in Figure 7 (
8 is a diagram showing the relationship between the lead tip 1a and the mask for partial plating, and FIG. 9 is a holding jig and IC lead frame used during wire bonding. 10 is a partial view of FIG. 9, and FIG. 11 is a diagram illustrating the state of the tip of the partial plating mask when partial plating is applied to the coining portion of the lead tip. Inside the drawing. 1 is a lead frame for IC, 3 is a mask for partial plating. 4 is the partial plating layer, 5 is the holding jig, 6 is the gap,
7 is a lead tip coining part, and 8 is a ring-shaped coining part.

Claims (2)

[Claims] (1) In an IC lead frame manufactured by punching, a coining part is provided at the lead tip, and a depth shallower than the coining part at the lead tip is provided between the lead tip coining part and the lead base. , an IC lead frame characterized by having a ring-shaped coining part deeper than the partial plating thickness. (2) The IC according to claim 1, wherein the rear end portion of the partial plating applied to the lead tip portion is located within the range of the ring-shaped coining processing portion.
lead frame.