JPH0821663B2 - Lead frame manufacturing method - Google Patents

Description

The present invention relates to a lead frame manufacturing method, and more particularly to a positioning method for partial plating of a lead frame.

(Prior Art) For example, in a normal IC, a semiconductor element 3 is fixed to a die pad 2 of a lead frame 1 and a bonding pad of the semiconductor element 3 and an inner lead 4 of the lead frame are attached as shown in FIG. It is manufactured by connecting with a bonding wire 5 of a gold wire or an aluminum wire and further sealing them with a resin 6.

The lead frame used here is a die pad 2 for mounting a semiconductor element, as shown in FIG. 4 as an example.
A number of inner leads 4 whose tips extend to surround the die pad, a tie bar 7 extending in a direction substantially orthogonal to the inner leads and integrally supporting the inner leads, and an outer side of the tie bar. The outer lead 8 and the support bar 9 supporting the die pad 2 are arranged so as to be connected to the inner leads.

By the way, the tips of the inner leads are plated with a noble metal in order to improve the bonding property.

In general, such a lead frame is generally one in which a lead and an element mounting portion are formed by photoetching or press punching a metal plate or metal conditions, and then a predetermined region is plated with a noble metal.

When such partial plating is performed, the plating solution may penetrate into a slight gap between the leads, resulting in plating leakage on both sides of the leads. When this reaches the vicinity of the boundary between the resin and the outside world, there is a problem in that electromigration occurs between the leads under the influence of moisture in the outside world and a short circuit occurs.

In particular, as the degree of integration of semiconductor devices has recently increased, the size of the device mounting area has also increased, and the distance between the edge of the resin sealing area and the plating area at the lead tip and the distance between the inner leads have also become narrow, causing short circuits due to plating leakage. Has become an unavoidable problem.

In order to solve such a problem, before forming the lead and the element mounting part, the required part on the metal strip is partially plated with a noble metal, and then the lead frame is formed by press working. A method of doing so has been proposed.

(Problems to be Solved by the Invention) However, this method has a drawback in that it is not possible to easily determine whether or not the plating position is appropriate unless the lead frame is finally shaped.

For this reason, after the lead frame has been shaped, it is necessary to determine whether or not there is a positional deviation, perform feedback based on that determination, and readjust the position of the plating head. There was a problem that plating defects frequently occurred.

The present invention has been made in view of the above circumstances, and it is possible to immediately determine whether or not the plating position is appropriate,
An object of the present invention is to provide a method for manufacturing a lead frame using partial plating of the lead frame, which enables quick position adjustment.

[Structure of Invention]

(Means for Solving the Problems) Therefore, in the present invention, in the method for manufacturing a lead frame in which partial plating is performed prior to shape processing, a metal strip surrounds the reference pin hole for reference positioning and the entire periphery of the plating permissible region. Forming a display part consisting of a concave groove formed as
The plating position is determined based on the display portion and the reference pin hole, and the plating is selectively performed.

(Operation) According to the method of the present invention, since the display portion composed of the concave groove is formed corresponding to the plating position, it is easy to confirm the position, and the displacement of the plating position immediately after plating is performed. It can be determined whether or not there is, for example, whether or not the display unit is in contact. Therefore, when there is a deviation, it is possible to immediately detect the occurrence of the deviation and adjust the position of the plating head.

In addition, the concave groove serves as a plating reservoir, and it is possible to reduce excess defects in the plating region.

Furthermore, it is possible to prevent the molding resin from being hardened in the groove and causing the lead to come off.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 (a) to 1 (d) are reference explanatory views for explaining the manufacturing process of the lead frame of the embodiment of the present invention.

First, as shown in FIG. 1A, reference pin holes 11 for positioning are narrowed at predetermined intervals along the longitudinal direction of a strip-shaped material made of a copper-iron alloy by a stamping method.

Next, as shown in Fig. 1 (b), the plating allowable area
A plating position display portion 14 including a concave portion showing 13 is formed.

Thereafter, as shown in FIG. 1 (c), plating is performed based on the plating position display portion and the reference pin hole. Here, the spot plating is performed by using a partial plating method of a batch method for a strip-shaped lead frame or a continuous method of a continuous body lead frame, and using a silver plating solution (silver jet 220 manufactured by Janan Roll) as a plating solution. A silver plating layer 12 having a film thickness of about 3 μm is formed on the tips of the die pad and the inner leads. At this time, after plating, it is visually determined whether or not the plating position is within the plating allowable area. Then, when the plating position is in contact with the plating position display portion, the plating head is adjusted immediately.

Then, as shown in FIG. 1D, a die pad 2 for mounting a semiconductor element is formed by a stamping method,
A large number of inner leads 4 having their tips extending so as to surround the die pad, a tie bar 7 extending in a direction substantially orthogonal to the inner leads and integrally supporting the inner leads, and an outer side of the tie bar. A lead frame including an outer lead 8 arranged so as to be connected to each inner lead and a support bar 9 supporting the die pad 2 is molded.

As described above, according to the method of the present invention, the plating position display portion showing the plating permissible region is provided, and immediately after plating, it is possible to visually determine whether or not the plating position is inside. Then, when the plating position is in contact with the plating position display portion, the defect due to the displacement of the plating position can be minimized by adjusting the plating head immediately.

In this way, a lead frame having a silver plating layer with good film quality and good bondability is formed without forming a plating layer on the side surfaces of the inner leads.

According to the lead frame formed in this way,
It is possible to obtain a highly reliable semiconductor device which is positioned with high accuracy, has a high manufacturing yield, and is highly reliable.

Next, an embodiment of the present invention will be described based on the reference example described in FIG.

FIG. 2 is a diagram showing a manufacturing process of the lead frame of the embodiment of the present invention.

In this step, in the reference example, while the recesses are scattered as the plating position display portion 14 showing the plating permissible area 13,
The method according to the embodiment of the present invention is characterized in that the continuously formed concave groove is provided so as to surround the entire plating permissible region 13.

First, a band-shaped material made of 42% nickel steel, which is called alloy 42, is processed and processed by the stamping method in the same manner as shown in FIGS. 1 (a) and 1 (b) in the first embodiment. , Shape processing. Here, as shown in FIG. 2 (a) and FIG. 2 (b) (FIG. 2 (b))
Is a sectional view taken along the line AA in FIG. 2A), and the entire plating permissible area 23 is surrounded by a groove-shaped display portion 24, and the plating layer 22 is formed based on the position of the display portion 24. The other parts are formed in exactly the same manner as in the reference example.

Then, a lead frame is completed through a stamping process in exactly the same manner as the reference example.

According to the method of the present invention, the plating position display portion showing the plating permissible region is provided, and immediately after plating, it is possible to visually determine whether or not the plating position is inside. Then, when the plating position is in contact with the plating position display portion, the defect due to the displacement of the plating position can be minimized by adjusting the plating head immediately.

In this way, a lead frame having a silver plating layer with good film quality and good bonding properties is formed without forming a plating layer on the side surfaces of the inner leads.

According to the lead frame formed in this way,
It is possible to obtain a highly reliable semiconductor device which is positioned with high accuracy, has a high manufacturing yield, and is highly reliable.

Further, in addition to the above effects, since the recessed groove is continuously formed so as to surround the entire plating permissible region, the recessed groove serves as a plating reservoir and may reduce excess defects in the plating region. it can.

Furthermore, since the groove formed in the tip of the inner lead locks the encapsulation resin and strengthens the bond with the encapsulation resin, the position of the inner lead tip is displaced due to pulling due to bending of the outer lead. It has the effect of preventing it. Therefore, even if the element mounting portion becomes large and the distance between the end of the sealing resin and the plating area at the tip of the lead becomes narrow, the pulling due to bending of the outer lead does not affect the bonding area.

In addition, although the case where silver plating is used as the noble metal plating is described in the above-mentioned embodiment, it is needless to say that the present invention can be applied to the case where gold plating is used.

Further, the shape of the lead frame is not limited to the lead frame having the die pad, and can be appropriately modified.

〔The invention's effect〕

As described above, according to the method of the present invention, when the lead frame is manufactured using the partial plating method in which the partial plating is performed prior to the shape processing, the display area formed of the concave groove is formed corresponding to the plating allowable position. Since it is easy to confirm the position, it is possible to correct the misalignment immediately after plating and to significantly reduce the occurrence of misalignment, thus significantly improving the yield. be able to.

Furthermore, since the concave groove is continuously formed so as to surround the entire plating allowable area, the concave groove serves as a plating reservoir, and it is possible to reduce excess defects in the plating area. The groove formed on the tip of the lead locks the sealing resin and strengthens the bond with the sealing resin, so it is possible to prevent the position of the inner lead tip from being displaced due to pulling due to bending of the outer lead. it can.

[Brief description of drawings]

1 (a) to 1 (d) are reference diagrams for explaining the manufacturing process of the lead frame of the embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are the present invention. FIG. 3 is a diagram showing a manufacturing process of the lead frame of the embodiment, FIG. 3 is a diagram showing a normal semiconductor device, and FIG. 4 is a diagram showing a lead frame of the semiconductor device of FIG. 1 ... Lead frame, 2 ... Die pad, 3 ... Semiconductor element, 4 ... Inner lead, 5 ... Bonding wire, 6 ... Resin, 7 ... Tie bar, 8 ... Outer lead, 9 ... Support bar , 12 …… Silver plating layer, 13 ……
Plating position permissible area, 14 …… Display section, 22 …… Plating layer,
23: Plating position allowable area, 24: Display section.

Claims (1)

[Claims] 1. A display part forming step of forming, on a metal strip, a display part consisting of a reference pin hole for reference positioning and a groove continuously formed so as to surround the entire periphery of a plating permissible region, It is characterized by including a partial plating step of determining a plating position based on the display section and the reference pin hole and selectively plating, and a shaping step of shaping the lead frame into a desired shape. Lead frame manufacturing method.