JPS5999750A - Manufactue of lead frame for ic - Google Patents

Abstract

PURPOSE:To reduce the number of unsatisfactroy products by a method wherein a positioning hole is provided on both sides of a metal stripe, and a plating position discriminating hole is formed in the center part, thereby enabling to discriminate the positional deviation of plating after the plating has been performed. CONSTITUTION:A positioning pin hole 8 is provided on both sides of a metal stripe 7 and channel-like through holes 10 and 11 are formed in the center part 9. The holes 10 and 11 are coincided with the gap located between a lead 2 and an island 3. When a precisous metal plating is performed at the center part 9, the tip of the lead 2 and the island 3 are also plated. If the plated metal stripe is checked, the relations between the holes 10 and 11 and the plated position can be find out immediately, and the production of unsatisfactory articles due to positional deviation can be reduced to minimum. When the partially plated metal stripe 7 is punched out using the hole 8, the lead frame with a plated layer on the upper surface and the end face of the lead 2 and having no plated layer at all on both side faces can be obtained.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing an IC lead frame.

As a packaging material for semiconductor integrated circuit (IC) elements,
For example, a lead frame 1 as shown in FIG. 1 is used. This lead frame 1 is Kizuki mold type DI
This is for P (abbreviation for Dual In1ine Pack/@ge), and includes a group of many leads 2 and an IC element mounting part (
Three sets (hereinafter referred to as "islands") are continuously formed. As shown in FIG. 2, the lead frame 1 is usually plated with a noble metal such as gold or silver on the island 3 and the inner leading edge of the leads 2 to provide a package for an IC element. Generally, a precious metal is plated on the %PJr4J portion where the series leads 2 and islands 3) are formed by photo-etching or press punching a metal plate or metal strip. For example, a partial plating device that plated only the required area was developed by the Japanese government in 1973.
As described in Japanese Patent No. 72.47751, a material to be plated is held between a mask plate and a suppressing plate, which have holes that are completely transparent in the part to be plated, and a plating solution is injected into the holes, and at the same time, the material to be plated (cathode) is Electricity is passed between the electrode and the anode.

However, when such partial plating is applied to lead frame 1, the lead frame usually has a thickness of 0.25 mm.
Due to the thickness of the pressing plate and the massaging plate, it is unavoidable that some gap will be generated near the sides of the small lead 2 being held, and as a result, the plating solution will enter this gap, as shown in Figure 3. As a result, plating leakage portions 5 protruding from the normal plating boundary line 4 are formed on both sides of the lead 2. When a resin mold having an outer shape indicated by the broken line 6 in FIG. 2 is applied to a lead frame having this plating leakage portion 5, the plating leakage portion 5 will reach the vicinity of the boundary between the resin and the outside world, and will be affected by the humidity of the outside world. Electromigration occurs between the leads, resulting in a short circuit. This migration is particularly noticeable in the case of silver. If the distance between the plating boundary line 4 and the resin mold outline line 6 is optically separated, the presence of some plating wet area 5 will not be much of a problem, but as the degree of integration of IC elements increases, the island 3 If an attempt is made to suppress the thick CI and the outer shape of the resin mold to a certain limit, this distance will become smaller, and the presence of the plating leakage portion 5 will no longer be tolerated. For example, if the lengthwise dimension of the broken line 6 in Figure 2 is 6.35 mm, and the lengthwise dimension of the precious metal plating area is 6, the gap on both sides will be as narrow as 9.175m. .

In order to eliminate such plating leakage portions 5, it is considered that partial plating should be performed before forming the boards 2 and islands 3. That is, as shown in FIG. 4, positioning holes 8 are provided at both edges of the metal strip 7.
The central part 9 of the metal plate is partially plated with precious metal, and then the gold carrying strip 7 is plated.
The lead 2 and the island 3 are formed by performing press punching while positioning using the pin hole 8.

However, this method has the disadvantage that it is not easy to determine whether the plating position is accurate after the lead frame is finally formed. The plating position can be made as accurate as possible by using the bottle hole 8, but it is difficult to accurately set the press mold of the partial plating device, so the clearance between the plating positioning pin and the bottle hole 8 has to be increased. Therefore, it is virtually impossible to ensure accuracy using only this bottle hole 8. For this reason, conventional partial plating apparatuses allow the plating position to be adjusted by other means. For example, in an apparatus for continuous partial plating while feeding a metal strip intermittently, adjustment in the width direction is performed by guide rollers, and adjustment in the longitudinal direction is performed by fine adjustment of a driving device for the metal strip. However, this adjustment cannot be used effectively unless positional deviations are confirmed immediately after plating. If a plating position shift is detected only after press punching after plating and then feedback is provided, a large number of defective products will be produced.

The present invention eliminates the above-mentioned drawbacks and provides a method for manufacturing an IC lead frame in which misalignment in plating position can be determined immediately after plating. In order to achieve this object, the present invention forms positioning pin holes at both ends of the metal strip and a through hole for determining the plating position at the center of the metal strip, and after partially plating the center with precious metal, It is characterized in that the series lead frame is formed by press punching the metal strips while aligning them using the bin holes.

FIG. 5 is a diagram for explaining one embodiment of the present invention.

In FIG. 5, the metal strip 7 is provided with positioning holes 8 at both ends and a channel-shaped through hole 10.11 at the center. These through holes io and it are arranged to match the gap between the lead 2 and the island 3 in FIG. If the central portion 9 of such a metal strip 7 is plated with a precious metal in the same manner as shown in FIG. 4, the tip of the lead 2 and the island 3 in FIG. 2 will be plated. The positioning hole 8 and the through hole 10.11 can be formed by photo-etching or press punching. The precious metal plating on the central part 9 is carried out using a batch type partial plating apparatus as described in Japanese Patent Publication No. 49-24775 if the metal strip 7 is short, or using a batch-type partial plating apparatus as described in Japanese Patent Publication No. 49-24775 when the metal strip 7 is long;
It can be carried out in a continuous partial plating apparatus such as that described in US Pat. No. 788,963. In any case, if you look at the metal strip 7 after plating, you can immediately determine the relationship between the through holes io, i1 and the plating position, so if there is a positional deviation, you can immediately correct the position of the metal strip 7, and The occurrence of defective products due to misalignment can be minimized. The partially plated metal strip 7 is subjected to a press punching process, and if a lead frame is formed by positioning it using the bottle hole 8, the first group of lead frames will look like the one 9 shown in FIG. As shown in FIG. 6, the tip of the lead 2 has a plating layer on the upper surface and the end surface, and a lead frame having no precious metal plating layer on both side surfaces can be obtained.

The position and shape of the through hole for determining the plating position are not limited to the example shown in FIG. No problem. However, if the position of the through hole is too far from the center plating position, it will be difficult to align the misalignment.
Therefore, it must be placed in an appropriate position. For example, the position may be line symmetrical with respect to the center line in the width direction and/or length direction, or the position may be point symmetrical with respect to the center of the area to be plated.

Although the above explanation has been made regarding a lead frame with an island 3, the method of the present invention can also be applied to manufacturing a lead frame without an island. In this case, if the island 30 portion is opened along with the bottle hole 8, the through hole can be used for determining the plating position shift. 1, island 3
In some lead frames, the island 30 portion may not be plated with precious metal, and it goes without saying that such a case is also included in the method of the present invention.

According to the present invention, the plating position of an IC lead frame that does not have a noble metal plating layer on the side surface of the lead can be manufactured with high precision, and the material yield can be increased and the reliability of the IC device can be significantly improved. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a general I'C lead frame. FIG. 2 is an enlarged plan view of the lead frame shown in FIG. 1 with precious metal plating applied thereto. FIG. 3 is a perspective view showing a plating leakage portion at the tip of a lead according to the prior art. FIGS. 4 and 5 are explanatory diagrams showing specific examples of the relationship between the via hole provided in the metal strip and the plating position, and the positional relationship of the through hole for determining the plating position according to the present invention, respectively. No. '6. The figure is a perspective view of a lead tip having a plating layer formed according to the present invention. 1... Linidoff □, frame; 2... Lead; 3 land: 7... Metal strip; 8... Positioning bottle hole;
9... Central part: 10, 11... Through hole. Patent applicant: Sumitomo Metal Mining Co., Ltd. Agent: Yasushi Kaizu, patent attorney: Yasuyuki Hirayama, patent attorney

Claims (1)

[Claims] A pin hole for positioning is formed on both edges of the metal strip, and a through hole for determining the plating position is formed in the center of the metal strip, and a metal strip partially plated with precious metal is formed in the center using the pin hole. A method for manufacturing an IC lead frame, which comprises forming lead frames into clusters by performing press punching while aligning the lead frames.