JPH0661397A - Lead frame and resin sealing method of semiconductor device provided therewith - Google Patents

Abstract

PURPOSE:To prevent the die pad of a lead frame from being deformed and voids from being generated in the lead frame and to accelerate the standardization of the lead frame. CONSTITUTION:A die pad 12 is composed of a peripheral frame 12A and semiconductor chip supporting leads 12B, and through-holes 13 large enough in diameter to enable molten resin to pass through them are provided to the die pad 12. A semiconductor chip 8a is fixed to the die pad 12, and molten resin 9a injected into a molding die is made to flow from the upside of the die pad 12 to the underside of the pad and vice versa through the through-holes 13 at molding to seal off a semiconductor chip 8a with resin. By this setup, the upside and underside of a die pad can be uniform in the flowing top line of molten resin 9a independent of the size of a semiconductor chip, and the standardization of a lead frame can be accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a resin-encapsulated semiconductor device in which a semiconductor chip is encapsulated with a resin by a transfer molding method and a resin encapsulation method for a semiconductor chip using the same. Is.

[0002]

2. Description of the Related Art A conventional lead frame and a resin sealing method for a resin-sealed semiconductor device using the same will be described with reference to FIGS. FIG. 3 is a general SO of the prior art.
FIG. 4 is a perspective view showing an existing lead frame used in a P-type semiconductor device, and FIG. 4 is a resin-sealed semiconductor of the related art in which a semiconductor chip mounted on the lead frame shown in FIG. 3 is resin-sealed. FIG. 5 is a cross-sectional view for explaining an example of the apparatus, and FIG. 5 is a partial cross-sectional view of the upper and lower molding dies in which the lead frame shown in FIG. FIG. 6 is a cross-sectional view for explaining a phenomenon that occurs when the semiconductor chip in the state shown in FIG. 5 is resin-sealed by the transfer molding method of the prior art.

First, FIG. 3 shows a current lead frame 1 used in a general SOP type semiconductor device in only one unit. The lead frame 1 is composed of one flat quadrilateral die pad 2, a plurality of inner leads 3 arranged at a predetermined pitch along each side of the die pad 2, and corresponding to these inner leads 3. Outer leads 5 arranged and a tie bar 4 connecting the both leads 3, 5
And a suspension lead 6 for connecting two opposing sides of the die pad 2 to the frame 7. Since each suspension lead 6 is bent downward at the bent portion 6a, the die pad 2 is in a depressed state.

The lead frame 1 configured as described above
The semiconductor chip 8 (FIG. 4) is adhered and fixed to the die pad 2 using silver paste or the like.
After wire-bonding the respective electrodes to the inner ends of the inner leads 3 (not shown), the semiconductor chip 8 is sealed with a resin 9 by a transfer molding method. A type semiconductor device (hereinafter, simply referred to as “semiconductor device”) 10 is obtained.

In this case, for example, JP-A-2-27164
8, the thickness Ta from the upper surface of the semiconductor chip 8 to the upper surface of the sealing resin 9 and the thickness Tb from the lower surface of the die pad 2 to the lower surface of the sealing resin 9 are made equal, and the suspension lead 6 is sealed from the upper surface. If the thickness Tc to the upper surface of the stop resin 9 and the thickness Td from the lower surface of the suspension lead 6 to the lower surface of the sealing resin 9 are made equal, the fluidity of the molten resin can be improved.

[0006]

However, as shown in FIG. 5, when a semiconductor chip 8a having a small area is placed on the die pad 2 having a large area and resin sealing is performed, the die pad having a considerable area is formed. The molten resin will flow through the second portion. Therefore, the depth Te from the upper surface of the die pad 2 to the inner surface of the upper die 20 of the molding die is larger than the depth Tf from the lower surface of the die pad 2 to the inner surface of the lower die 30.

Due to this difference in depth, as shown in FIG. 6, the flow of the molten resin 9a supplied from the injection port 31 of the lower mold 30 is different in the upper and lower passages of the die pad 12. The speed of the molten resin 9a generated and flowing thereabove is higher than the speed of the molten resin 9a flowing below the die pad 2. That is, the molten resin 9a flowing below the die pad 2
Of the molten resin 9a is impeded, and its speed becomes slower than the speed of the molten resin 9a flowing above the semiconductor chip 8a. as a result,
The wide surface die pad 2 is pushed down and deformed, and the molten resin 9a on the upper side wraps around downward, trapping the gas in the molding die and generating voids.

Therefore, if a lead frame having a die pad having an area corresponding to the size of the semiconductor chip is used, the above-mentioned inconvenience can be prevented, but the size of the semiconductor chip is numerous and suitable for each size. Preparing a lead frame complicates the management of the lead frame, and there are many problems in standardization. The present invention aims to eliminate such inconvenience.

[0009]

Therefore, according to the present invention,
The die pad is composed of a peripheral frame and a supporting lead, and a plurality of through holes having large openings through which molten resin can flow are formed between the two, and the molten resin is passed through the through holes from the front surface to the back surface of the die pad, and On the contrary, by making it flow,
The semiconductor chip was resin-sealed.

[0010]

Therefore, regardless of the size of the semiconductor chip, the flow front line of the molten resin at the time of molding can be easily aligned above and below the die pad, and the standardization of the lead frame can be further promoted.

[0011]

Embodiments of the present invention will be described with reference to FIGS. 1 is a perspective view showing a lead frame of one unit in an embodiment of a lead frame of the present invention, and FIG. 2 shows a semiconductor chip placed on the lead frame of FIG. 1 and transfer molded. FIG. 1 is a sectional view taken along line AA of FIG. The same parts as those in FIGS. 3 to 6 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the die pad 12 of the lead frame 11 of the present invention has a quadrangular peripheral frame 1
2A and a pair of diagonally-supporting leads 12B for supporting a semiconductor chip in a cross shape.
That is, the present invention has a structure in which the through hole 13 through which the molten resin can flow is formed over most of the area of the die pad 2 of the conventional lead frame 1 shown in FIG. In addition to the function of reinforcing the die pad 12, the supporting lead 12B has a function of supporting a semiconductor chip 8a having such a small area near the intersection 12C even if the area of the semiconductor chip 8a is small. ing.

Like the lead frame 1 of the prior art, such a lead frame 11 is manufactured by punching or etching a metal plate, for example, a 42% Ni / Fe alloy having a thickness of 0.1 to 0.3 mm. be able to.

On the die pad 12 of the lead frame 11 having such a structure, for example, a semiconductor chip 8 having a small area is provided.
After fixing a and electrically connecting the electrodes of the semiconductor chip 8a to the inner ends of the inner leads 3 (not shown), as shown in FIG.
1, the semiconductor chip 8a has an upper die 20 and a lower die 3
It is fastened with a molding die so that it fits in the cavity of 0, and the injection port 31 of the lower die 30 is formed by the transfer molding method.
Then, the molten resin 9a is injected.

In the die pad 12 on which the semiconductor chip 8a having such a small area is mounted, the distance Te from the upper and lower surfaces of the die pad 12 to the inner surfaces of the upper die 20 and the lower die 30 is the same as in the prior art. Although Tf is in the state of Te> Tf, the injected molten resin 9a can flow from the front surface to the back surface of the die pad 12 and vice versa through the through hole 13 of the die pad 12. The flow front line of the molten resin 9a can be easily aligned.

In the case of encapsulating a large area semiconductor chip 8 with resin, the semiconductor chip 8 can be supported not only by the supporting leads 12B of the die pad 12 but also by the peripheral frame 12A, and Te> Tf. Almost disappeared,
That is, Ta = Tb (FIG. 4) is achieved, and good resin sealing can be performed as in the conventional technique.

Further, by preliminarily widening the area of the depressed die pad 12, one type of lead frame can be used for semiconductor chips having several types of areas.

In the above-mentioned embodiment, the supporting lead 12B, which is one component of the die pad 12, is constituted by a braided lead, but it is constituted by a net having a very coarse mesh. Good. In the above embodiment, the SOP
Although the lead frame used for the type semiconductor device has been described as an example, it is needless to say that the present invention is not limited to the SOP type and can be applied to a lead frame used for a QFP type semiconductor device or the like.

[0019]

As is apparent from the above description, according to the lead frame of the present invention and the resin sealing method for a semiconductor device using the lead frame, the tip line of the molten resin can be easily formed at the time of molding the semiconductor chip. Can be aligned,
Therefore, it is possible to obtain a high-quality semiconductor device in which voids and deformation of the die pad do not occur. Further, the standardization of the lead frame can be further promoted, which can contribute to the improvement of productivity.

[Brief description of drawings]

FIG. 1 is a perspective view showing one unit of a lead frame in an embodiment of the lead frame of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, showing a state where a semiconductor chip is placed on the lead frame of FIG. 1 and transfer molding is performed.

FIG. 3 is a perspective view showing a conventional lead frame used in a general SOP type semiconductor device of the related art.

FIG. 4 is a cross-sectional view for explaining an example of a conventional resin-sealed semiconductor device in which the semiconductor chip mounted on the lead frame shown in FIG. 3 is resin-sealed.

5 is a partial cross-sectional view of the upper and lower molding dies in which a small-area semiconductor chip is mounted on the lead frame shown in FIG. 3 and the lead frame is housed.

FIG. 6 is a cross-sectional view for explaining a phenomenon that occurs when the semiconductor chip in the state shown in FIG. 5 is resin-sealed by a transfer molding method of a conventional technique.

[Explanation of symbols]

 3 Inner Lead 4 Tie Bar 5 Outer Lead 6 Suspension Lead 6a Bending Part 7 Connection Frame 8 Semiconductor Chip 8a Small Area Semiconductor Chip 9 Encapsulating Resin 9a Molten Resin 10 Resin Encapsulating Semiconductor Device 11 Lead Frame 12 Die Pad 12A Peripheral Frame 12B Support Lead 12C Cross section 13 Through hole 20 Upper mold 30 Lower mold 31 Injection port

Claims (2)

[Claims] 1. A lead frame composed of a die pad, an inner lead, an outer lead, etc., wherein the die pad is composed of a peripheral frame and a supporting lead, and a plurality of large through-holes through which a molten resin can flow are formed between them. A lead frame characterized by being formed. 2. A semiconductor chip is fixed to the die pad of the lead frame according to claim 1, and each electrode of the semiconductor chip is electrically connected to an inner end portion of the inner lead. Using a molding die, at the time of resin sealing by the transfer molding method, through the through hole of the die pad, from the front surface of the die pad to the back surface, and vice versa, by flowing.
A resin encapsulation method for a resin-encapsulated semiconductor device, which comprises encapsulating the semiconductor chip with a resin.