JPH03212963A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To improve reliability by a method wherein a stamped-out part is formed inside a cavity region in such a way that one part of the tip part of a narrowly formed inner lead is left. CONSTITUTION:Regions 21 whose end parts are widely round in such a way that the end parts become wide and which have been punched through out by using a punch are formed. Inner-lead regions 22 are patterned. The, a second stamped-out region 24 as a cavity region at remaining inner lead end parts is stamped out. In a state that regions formed so as to narrow the width by the widely stamped-out parts are left as inner lead tip parts, a die pad part 25 is separated from the inner lead tip parts and a shape working operation is finished. Protrusions 23 are formed at crossed parts of the two stamped-out regions, i.e. crossed parts of edges 28 formed by the stamped-out regions 24 and side edges 241 formed by the regions 21. Since the distance between inner leads can be maintained sufficiently, it is possible to prevent a short circuit. Thereby, reliability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a lead frame, and particularly to shaping the tips of inner leads of the lead frame.

(Conventional technology) As semiconductor devices have become smaller, thinner, and more highly integrated in recent years,
The lead width of the lead frame used for this,
Both lead spacing and board thickness are becoming smaller and smaller, and extremely advanced technology is required for design and manufacturing, and research is ongoing.

Recently, it has become possible to mold products with more than 100 leads by stamping.

Typically, such a lead frame is formed by forming a band-shaped metal material (strip material) of iron or copper into a desired pattern by stamping or etching, and then performing a plating process or the like.

In particular, for lead frames formed by stamping, it is difficult to mold all of the inner leads in one punching process, so a so-called progressive die is used to divide the inner leads into multiple stages and punch them out. Designed.

For example, as shown in FIG. 4(a) and FIG. 4(b), a belt-like abrasive material containing copper as a main component is coated with a desired shape of inner lead (excluding the ends) 1, diver 2, and outer lead. The first punching region 11 is formed by attaching it to a mold equipped with a punching die such as No. 3 and performing press working,
Butter ninx the inner lead part 1, leaving the end of the inner lead. Here, the punch for punching between inner leads has a radius of 0.05 m, which is the same size as the lead interval (0, 1 or Ill), at the end of the punched part in the cavity area.
It is configured to form a circular shape of m.

Next, as shown in FIGS. 5(a) and 5(b), the second punching area 14 (cavity area) of the inner lead end left in the molding process is punched out, and the die pad 15 and the inner lead are punched out. The tip is separated and the lead frame shape processing is completed. FIG. 6 shows an overall view of the lead frame formed in this manner. 4 is a support bar.

However, in recent lead frames, the lead spacing tends to be narrower than the plate thickness at the tip of the inner lead.
It may be necessary to punch out a width of 121 mm.

When such a fine lead frame is divided into a plurality of stations and punched out using a stamping method, the pad size and cavity size are determined by the chip size, and extremely fine processing is required.

When punching is performed using the method described above, the first punching region 11 is formed as shown in FIG. As shown in FIG. 5(b), a second punched region 14 that becomes a cavity region is formed, but a minute protrusion 13 may be formed at this intersection.

This protrusion narrows the gap between the tips of the inner leads,
In addition, when plating is applied after the tips are formed, there is a problem that the plating concentrates on the protrusions, further narrowing the gap between the tips.

In particular, as the density of semiconductor devices has increased recently, the number of lead frame bins has also increased, and the gap between the tips of the inner leads has narrowed further. This had the disadvantage of lowering performance and yield.

(Problem to be Solved by the Invention) As described above, with the miniaturization of lead frames, when the second punching is performed to punch out the region corresponding to the cavity region near the pad at the tip of the inner lead, the formation of the first punched region There is a problem in that fine protrusions are generated at the intersections with the side portions of the resulting inner leads, narrowing the gap between the tips of the inner leads.

In particular, when plating is applied after forming the tips, the plating will concentrate on the protrusions, further narrowing the gap between the tips.
This causes a short circuit, which causes a decrease in the reliability and yield of semiconductor devices.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to improve the reliability of the lead frame by preventing the influence of minute protrusions that occur at the tips of the inner leads when punching the cavity region in the punching of the lead frame. With the goal.

(Means for Solving the Problems) Therefore, in the lead frame manufacturing method of the present invention, in the molding step of molding a lead frame from a strip, first,
Punching the strip material to form a wide punched part wider than the inner lead spacing at least in the vicinity of the pad of the inner lead, and shaping a lead frame including a part of the inner lead, the outer lead, and the diver, After that, the peripheral edge of the pad at the tip of the inner lead left in this molding process is punched out so as to leave a part of the tip of the inner lead whose width is narrowed by the wide punched part. and the tip of the inner lead are separated from each other.

(Function) By forming the punched portion in the cavity region so as to leave a part of the tip of the inner lead formed so that the width is narrowed by the wide punched portion, the intersection of the two punched regions has a narrow width. Even if a protrusion is formed because the inner lead has a narrow tip, a sufficient distance between the inner leads can be maintained.

(Example) Hereinafter, a method for manufacturing a lead frame according to an example of the present invention will be described in detail with reference to the drawings.

First, as shown in FIG. 1(a) and FIG. 1(b),
A strip-shaped material containing copper as a main component is formed into a desired shape of an inner lead (excluding the end face) 1, a diver 2, and an outer lead 3.
By attaching it to a mold equipped with a cutting die such as the above, and performing press processing, the first
A punched area 21 is formed, and an inner lead area 22 is formed.
pattern. Here, as shown in FIG. 3, the punch for punching between the inner leads is shaped into a circular shape with a radius of 0.075 mm wider than the lead spacing (0, 1 am) so that the ends are wide. It is configured to do the following. Therefore, the tip of this first punched area 31 constitutes a wide area 240. Here, 3A is the outer edge of the punch.

Next, as shown in FIGS. 2(a) and 2(b), the second punching area 24, which is the cavity area of the inner lead end left in the molding process, is punched out, and a wide punching part is used to The die pad 25 and the inner lead tips are separated, leaving the region formed so as to have a narrow width as the inner lead tips, and the shaping of the lead frame is completed. FIG. 2(a) is an overall view, and FIG. 2(b) is a diagram showing a main part. Here the first
And at the intersection of the two punched areas, which are the second punched areas, that is, the intersection of the end 28 formed by the second punched area and the side edge 241 formed by the first punched area, there is a protrusion. 23 is formed, but since the tip end of the inner lead is narrow in this region, the protrusion 23 does not penetrate into the region between the inner leads.

After this, the lead frame is completed through a process such as plating the tips of the inner leads.

By forming the lead frame in this way,
Since the second punching part is formed so as to leave the tip of the inner lead formed so that the width is narrowed by the wide punching part, the intersection of the two punching areas is the narrow tip of the inner lead. Even if a protrusion is formed, a sufficient distance between the inner leads can be maintained, and short circuits can be prevented.

In addition, the punch for punching between inner lids used during punching has a wide tip, which improves buckling strength, making it possible to lengthen the straight part of the punch and significantly increasing the strength of the punch. This greatly improves productivity, making it possible to form high-quality lead frames with high precision.

Here, when the surface pressure at the end of the punch was measured in the first punching process shown in FIG. 1, it was found that it was reduced by more than 30% compared to when a conventional punch was used.

Further, in the above embodiment, copper was used as the lead frame material, but it goes without saying that the lead frame material is not limited to copper and other materials may also be used.

Further, in the embodiment described above, the plating process was performed after the shaping of the lead frame was completed, but it may be performed during the shaping.

Furthermore, the molding area in each step can be changed as appropriate.

〔Effect of the invention〕

As explained above, according to the lead frame manufacturing method of the present invention, when shaping a strip material into the shape of a lead frame, the tip of the punch for punching between inner leads is formed wide, and Since the cavity area is punched out leaving a slightly wide punched part, the intersection of the punched areas becomes a narrow tip, so even if a protrusion is formed, the distance between the inner leads can be maintained sufficiently. can be maintained, and reliability can be significantly improved.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing the manufacturing process of a lead frame according to an embodiment of the present invention, FIG. 3 is a diagram showing the main parts of a punch used in the same manufacturing process, and FIGS. 4 and 5 are ,
FIG. 6 is an explanatory diagram showing a part of the manufacturing process of a conventional lead frame, and FIG. 6 is a diagram showing an overall view of a conventional lead frame. 1... Inner lead, 2... Diver 3...
Outer lead, 4...Support par 11.21・
...First punching area, 13.23...Protrusion, 14
．． 24...Second punching area, 15.25...Die pad. 1 B) Nare lead (a) (b) Figure 4 5 Figure 5 1 Ishina lead (Q) 1st 2 ＼ Diagram (b) 2ω flight 11 group (b)

Claims (1)

[Scope of Claims] In a method for manufacturing a lead frame including a plurality of inner leads and an outer lead extending from the inner leads, a molding step of molding a lead frame from a strip material includes forming at least one of the inner leads from the strip material. a first molding step of punching to form a wide punched part wider than the inner lead interval at the tip of the lead frame, and shaping a lead frame including a part of the inner lead, the outer lead and the diver; Punching out the peripheral edge of the pad at the tip of the inner lead left in the first molding process so as to leave a part of the tip of the inner lead whose width was narrowed by the wide punching part in the first molding process. A method for manufacturing a lead frame, comprising a second molding step of separating the pad portion and the inner lead tip portion.