JPH03116771A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the generation of needle-shaped shaving of plating resulting from the protrusion of plating so as to prevent accidents such as short, etc., and improve productivity and quality by putting it in such structure that the width of the outer lead inside a tie bar part is wider than the width of the outer lead outside the tie bar part. CONSTITUTION:In the outer lead 3 of a lead frame, the width of the outer lead 3a inside a tie bar part 4 is made wider than that of the outer lead 3b outside the tie bar part. For this reason, the plating applied on the outer lead 3 is crushed at the time of sealing with resin, and juts out to its side and the protrusion 5 of plating is formed, but since the jutted plating does not contact with a tie bar punch at the time of tie bar cutting in a post-charge process, the protrusion of the plating is not shaved off, and it has an effect of preventing the shortage between leads by needle-shaped shaving.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-sealed lead frame for a semiconductor device, and particularly to the structure of its external leads.

[Conventional technology]

Conventionally, lead frames for semiconductor devices of this type have been plated with tin or a tin-lead alloy before being sealed with resin, and have a structure in which the width of the external leads is the same on the inside and outside of the tie bar portion.

The sealed lead frame had a structure in which the tie bars described above were cut and removed in a subsequent tie bar cutting process, and then external leads were formed.

[Problem to be solved by the invention]

The above-mentioned conventional lead frame that is plated with tin or tin-lead alloy before resin sealing has a structure in which the width of the external lead is the same on the inside and outside of the tie bar part.
If the plating is crushed by being clamped by the resin sealing mold during mold encapsulation, the plating will be scraped into needle-like shapes during the tie bar cutting or lead bending process in the subsequent process, causing a short circuit between the leads. .

The purpose of the present invention is to prevent the occurrence of needle-shaped plating scraping due to the plating protruding during tie bar cutting in the post-process in lead frames that have been previously plated with tin or tin-lead before resin sealing. It is an object of the present invention to provide a lead frame for a semiconductor device that can prevent accidents such as sills, and improve productivity and quality.

[Means to solve the problem]

The lead frame for a semiconductor device of the present invention has a lead frame that is plated with tin or tin-lead before resin sealing, and the width of the external lead inside the tie bar portion is the same as that of the external lead outside the tie bar portion. It has a structure that is wider than its width.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a schematic plan view of an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a schematic plan view showing the tie bar cutting state in the tie bar cutting process after resin sealing. It is.

In FIGS. 1 to 3, external leads 3 are parts that perform electrical conduction outside the resin-sealed package 1 of the semiconductor device, and external leads 3a are located inside the tie bar portion 4 and external leads 3a are located outside the tie bar portion. In 3-b, plating with tin or tin-lead alloy is applied in advance before resin sealing. The tie bar portion 4 blocks the resin leaking between the molds when the lead frame is clamped by the resin sealing mold during resin sealing, and forms the dam portion 2.

In this embodiment, in the external lead 3 of the lead frame, the external lead 3a on the inside of the tie bar part 4 is wider than the external lead 3b on the outside of the tie bar part, so the resin was applied onto the external lead 3b during sealing. The plating is crushed and protrudes from the sides, forming a plating protrusion 5 as shown in Figure 5. However, when cutting the tie bar in the post-encapsulation process, the protruding plating does not come into contact with the tie bar punch as shown in Figure 3. The protruding plating is not scraped off and becomes as shown in Figure 6, which has the effect of preventing short circuits between the leads due to needle-like scratches.

FIG. 4 is a partially enlarged view of another embodiment of the present invention. The external lead 3C outside the tie bar part 4 has a tapered structure, and when cutting the tie bar, the tie bar punch does not come into contact with the protruding plating that occurs in this part during resin sealing, so this plating does not collapse. is not scraped off, resulting in needle-like scratches, and has the effect of preventing short-circuits between the leads as in the first embodiment.

〔Effect of the invention〕

As explained above, in the present invention, tin, tin-
In a lead frame with lead plating, the external leads on the inside of the tie bar are wider than the external leads on the outside of the tie bar, which may cause the plating to stick out when cutting the tie bar in the later process. This has the effect of preventing the occurrence of needle-like plating scrapes, preventing accidents such as short circuits, and improving productivity and quality.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. FIG. 4 is a partially enlarged view of another embodiment of the present invention, FIG.
The figure is a perspective view showing the collapsed state of solder that occurs during resin sealing, FIG. 6 is a partial perspective view for explaining the effect of the first embodiment of the present invention, and FIG. 7 is a conventional semiconductor device. FIG. 3 is a schematic plan view of external leads of the lead frame. DESCRIPTION OF SYMBOLS 1... Semiconductor device, 2... Dam part, 3... External lead, 3a... External lead (portion inside from the tie bar part>, 3b, 3c... External lead (portion outside from the tie bar part) , 4... Tie bar part, 5... Extrusion of plating, 6... Tie bar punch.

Claims (1)

[Claims] In a resin-sealed lead frame for semiconductor devices, the structure of the external leads is such that the width of the external leads inside the tie bar is wider than the width of the external leads outside the tie bar, and the external leads are coated with tin before resin encapsulation. A lead frame for a semiconductor device characterized by being plated with an alloy containing tin.