JPS5824020B2 - semiconductor equipment - Google Patents

Abstract

PURPOSE:To increase a bonding efficiency without contact of a wire to an adjacent lead by a method wherein shapes of top ends of inner-leads which form a lead frame are made broader in width for surfaces where wire-bondings are applied and narrower in width for the reverse. CONSTITUTION:A sectional shape of the inner-lead 11 forming the lead frame should be made as follows. That is, the width of one main surface 12 applied a wire bonding is made a predetermined one necessary for the bonding and the other main surface 13 facing thereto is made narrower in width that the former. Thus, the broadest width W comes at the position near the main surface 12 and the cutout width is also made narrower than the half of a thickness (t) of the lead on the main surface 12 side. This is accomplished by the application of an ordinary etching. Whereby the distance between the leads 11 adjacent to each other becomes broader, the bonding efficiency is improved and if necessary, the frame can be made small corresponding to making pellets small-size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin-sealed semiconductor device, and more particularly to an improvement in a lead frame to which a semiconductor chip is attached.

Side fat-sealed semiconductor devices are made by etching or pressing a long thin metal plate to form an island, which is a support area for attaching a semiconductor chip, and an inner lead, which is an input/output path for electrical signals to the semiconductor nap. It is usually formed using a lead frame provided with outer leads.

On the other hand, the dimensions of semiconductor chips themselves tend to be reduced in order to improve the yield from semiconductor wafers.

In accordance with this trend, lead frames to which semiconductor chips are mounted are required to have multiple leads and appropriate tip position stones and a predetermined surface width for wire bonding of inner leads.

However, when manufacturing a lead frame from a thin metal plate by etching, the shape of the tip of the inner lead requires a removal width that is approximately the same as the thickness of the thin metal plate. The distance from the tip of the inner lead is limited by the conditions at the time of manufacturing the lead frame described above, and it has not been possible to shorten the distance to a distance that allows proper wire bonding.

Therefore, when performing wire bonding, the length of the wire must be increased, which often causes short circuit failures due to contact between bonding wires, bonding wires and islands of lead frames, and bonding wires and inner leads during sealing. Ta.

The present invention has been made to eliminate such defects, and is to provide a resin-sealed semiconductor device having good characteristics by improving a lead frame to which a semiconductor chip is bonded.

In other words, the shape of the tip of the inner lead is improved, thereby making it possible to reduce the inner lead pitch, and even when the semiconductor chip becomes smaller, wire bonding can be performed efficiently and characteristics can be improved. .

Embodiments of the present invention will be described below with reference to the drawings.

Conventionally, the shape of the inner lead was a tip portion as shown in FIGS. 1 and 2.

That is, FIG. 1 is a cross-sectional view in the width direction, and FIG. 2 is a cross-sectional view in the longitudinal direction.

In FIG. 1, the main surface 2 of the inner lead 1 to which wire bonding is applied and the main surface 3 on the opposite side have the same width, and the width of the lead, that is, the width indicated by A in the figure, is the thickness of the lead. It is formed by etching in half of the length.

In addition, in FIG. 2, the main surface 2 of the inner lead 1 and the other main surface 3 have the same distance from their tips to the island (not shown), and the removal width B is also half of the lead thickness t. It is formed by etching.

In contrast, in the present invention, the lead tips are etched to form the shapes shown in FIGS. 3 and 4.

That is, as shown in FIG. 3, in the cross section in the width direction, the main surface 12 of the inner lead 11 to be wire bonded
has a predetermined width necessary for bonding, and the other main surface 13 of the inner lead 11 is etched to have a narrower width than the main surface 12.

Therefore, the maximum width portion W is closer to the main surface to which wire bonding is performed, and the dropout width C is also smaller than half of the lead thickness t on the main surface 12 side.

In addition, as shown in FIG. 4, in the longitudinal cross section, the removal width on the main surface 12 side to which wire bonding is performed is smaller than half of the lead thickness t, and the tip 15 of the main surface 12 is It is formed closer to an island (not shown) than the tip 16 of the main surface 13.

For etching in this way, for example, as shown in FIG.
oy) Apply a photoresist 22 to both sides of the resist film 21, stack negative masters 23 and 24 having a pattern for forming a predetermined lead on each resist film 22, and further place a presser plate 25 made of a glass plate on top of the negative masters 23 and 24. Later exposed.

The widths of the light-blocking portions of the masks 23 and 24 are different, and are provided so that when etched, they have the width of the main surfaces 12 and 13 of the leads.

Then, it is developed and the unexposed portions, which correspond to the inner lead portions, are developed.

This part is left and baked to harden.

Next, etching is performed from both sides. Corrosion progresses from both sides of the alloy plate exposed through the mask. The parts of the alloy plate are removed, and the hardened photoresist is removed to form the lead frame. It is something that will be done.

According to this invention, as shown in FIG. 6 (cross-sectional view in the width direction of the lead tip according to the present invention) and FIG. In the case of the present invention, the width of removal is small (C<A), so the pitch between the leads can be made small.

For example, the lead effective width a is 0.2 myrt, the IJ-do gap d is 0.1 mrn, and the lead thickness t is 0.2 rI.
LrIL, the removal width C of this invention is 115
t = 0.215 h, and the width A of the conventional one is 1/2t = 0.2/21rL11L, so the pitch P of the one of the present invention is 0.2.Therefore, as shown in Fig. 8, the inner lead 20 Although the tip of the inner lead 21 conventionally had a width of 6.0, the tip of the inner lead 21 can be narrowed down to a width of 4.8 as shown in FIG.

Therefore, the length of the bonding wire can be shortened,
For example, compared to the conventional one, which was 1.8 to 2.6,
According to this invention, the length can be reduced to 1.2 to 2.0 mm, which is an improvement.

Further, as shown in FIGS. 10 and 11, when bonding the electrodes of the semiconductor chip 32 mounted on the island 31 of the lead frame and the inner leads 33,
Since the bonding position on the lead is fixed, if the length of the bonding wire 36 is long, loop-down (as shown by the dotted line) is likely to occur. Since the length can be shortened, such a problem will not occur.

In addition, when the length of the bonding wire is the same, the distance 11 from the bonding point to the tip on the main surface to be bonded when the conventional lead tip shape (35 in Fig. 11) is used, the tip of the present invention is Shape (36 in Figure 10)
When the distance is 12, it becomes a dog, and is more effective in preventing loop down.

In this way, the invention can prevent problems such as short circuits that occur during wire bonding.
This can contribute to improving the characteristics.

The shape of the lead end is not limited to the one described above.

In accordance with the gist of the invention, various deformed structures, such as those shown in cross-sectional shapes in FIGS. 12 and 13 (A represents the cross section in the width direction and B represents the cross section in the longitudinal direction), are etched. It goes without saying that products formed using the same method can also be obtained.

The semiconductor device of the present invention is an extremely industrially useful semiconductor device that reduces the occurrence of defects due to wire bonding and can respond well to miniaturization of semiconductor pellets.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of the tips of the leads of a conventional lead frame. Figure 1 is a cross-sectional view in the width direction, Figure 2 is a cross-sectional view in the longitudinal direction, and Figures 3 and 4 are FIG. 3 is a cross-sectional view in the width direction, FIG. 4 is a cross-sectional view in the longitudinal direction, and FIG. 5 is a cross-sectional view showing the state in which a metal plate is etched. , FIG. 6 is a cross-sectional view in the width direction of the tips of multiple leads of the present invention, FIG. 7 is a cross-sectional view in the width direction of the tips of multiple leads of the conventional lead, and FIG. 8 is a cross-sectional view of the tips of multiple leads of the conventional lead frame. FIG. 9 is a plan view of a portion of the central portion of the lead frame of the present invention shown with the island removed; FIG. 10 is a plan view of a portion of the central portion of the lead frame of the present invention with the island removed. , 1st
FIG. 1 is a side view showing a wire-bonded state, and FIG. 12A is a side view showing a state in which wire bonding is performed. B FIGS. 13A and 13B are cross-sectional views of other embodiments of the lead of the present invention. 11...Lead of lead frame, 12, 13
... Lead main surface, 15, 16 ... Tip of lead main surface, 3 ... Predetermined width of lead main surface necessary for wire bonding, t ... ...Lead thickness, P...Lead pitch, 20, 21...
...Lead (tip). 31...Lead frame island, 32.
・Four semiconductor pellets, 33...lead frame leads, 36...bonding wires.

Claims (1)

[Claims] 1. In a resin-sealed semiconductor device in which a semiconductor chip is bonded to an island of a lead frame, the shape of the tip of the inner lead of the lead frame is such that the largest width part in the cross section in the width direction is the main surface to which wire bonding is to be performed. What is claimed is: 1. A semiconductor device, characterized in that a leading end of a main surface that is formed closer to each other and wire-bonded in a longitudinal cross section is formed closer to an island than a leading end of the other main surface, and that the lead pitch is reduced.