JPH0774193A - Method for sealing semiconductor device - Google Patents

Abstract

PURPOSE:To provide a sealing method by which a good moldability and a long life of a die can be achieved by making a thermal resistance between a semiconductor element and the rear face of a mold small and by reducing the content of a filler which causes the abrasion of a die. CONSTITUTION:Flow channels between dies 1, 2 and a lead frame 3 in a mold space are roughly divided into two. Out of the two channels, a first channel having a larger cross sectional area is provided with a flow pressure adjusting member 11 which can move up and down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of encapsulating a full-mold type semiconductor device, and more particularly, to an improvement of a method of encapsulating a semiconductor device which can prevent void defects occurring in the mold resin on the heat dissipation surface side. It is about.

[0002]

2. Description of the Related Art A conventional method for manufacturing a full-mold type semiconductor device will be described with reference to FIGS. Here, FIG. 3 is a plan view of the finished lead frame, FIG.
Is a sectional view of the mold when the sealing resin is in an uncured state, FIG.
(B) shows the case where the sealing resin is in a semi-cured state. In FIG. 3, the semiconductor element 7 is die-bonded onto the lead frame 3, and further electrically connected to the lead terminal of the lead frame 3 by the bonding wire 8. The lead frame 3 includes an upper surface molding die 1 and a lower surface molding die 2.
And is molded by the transfer molding method.

The movable pins 4 and 5 support the lead frame 3 as shown in FIG. 4A when the liquid thermosetting resin 9 flows from the resin injection port 6 and is filled in the mold space. In the semi-cured state, as shown in FIG. 4 (b), it moves to the upper or lower mold dies 1 and 2 surface, and in the resin cured state, it acts as an eject pin to take out the molded product when the molded product is separated from the mold. .

[0004]

In the full-mold type semiconductor device, the resin thickness d1 under the heat radiation surface must be made as thin as possible in order to quickly radiate the heat generated by the semiconductor element 7 to the outside. If the resin thickness is reduced,
The ratio of d1 / d2 shown in (a) becomes very small, and a large fluid pressure difference occurs between the resin a flowing through the flow path above the lead frame and the resin b flowing through the flow path below the lead frame 3, As a result, void defects 10 were generated in the mold resin, and the product had a poor appearance.

In order to prevent the occurrence of the void defect 10, it is conceivable to thicken the thin resin portion d1. However, this increases the thermal resistance between the semiconductor element 7 and the back surface of the mold resin in contact with the heat radiating plate, so that the heat radiation is prevented. The effect decreases and is not appropriate.

Further, in order to reduce the thermal resistance, it is sufficient to increase the thermal conductivity of the resin itself, and in order to increase the thermal conductivity, it is necessary to increase the content of the filler in the resin. But,
When the content of the filler is increased, the die wear becomes severe, resulting in a shortened die renewal period and an increase in die cost.

[0007]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a fluid pressure adjusting member that can move up and down in a first flow path having a wide flow path area with a lead frame 3 in a mold space as a boundary. 11 is provided to make the flow pressures of the first flow passage and the second flow passage substantially equal.

[0008]

As a result of providing the flow pressure adjusting member and making the flow pressures of the first flow path and the second flow path substantially equal, the liquid insulating resin flows at substantially the same speed in the first flow path and the second flow path. It is possible to provide a good method for sealing a semiconductor device without the occurrence of void defects.

[0009]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 (a) is a mold cross-sectional view of a full mold type of the present invention in which an encapsulating resin is uncured, and FIG. 1 (b) is a mold cross section of the same full mold type in which an encapsulating resin is semi-cured. Figure, Figure 2
[Fig. 3] shows a plan view of a molded product obtained by the sealing method of the present invention.

In FIG. 1A, the semiconductor element 7 is die-bonded to the lead frame 3, and the lead frame 3 and the semiconductor element 7 are electrically connected by a bonding wire 8 to form a circuit. The lead frame 3 is set on the lower surface molding die 2, and then the upper surface molding die 1 is lowered by a pressing machine to inject a liquid thermosetting resin 9 from a resin injection port 6 to form by a transfer molding method. During molding, the movable pins 4 and 5 perform the same function as in the prior art.

The flow pressure adjusting member 11 which is the point of the present invention
Is set at the position of d1 = d3 at the time of resin injection so that the flow path cross-sectional area of the upper part of the lead frame is equal to the flow path cross-sectional area of the lower part of the lead frame. Can be made almost even. Therefore, it is possible to prevent a void defect in the lower portion of the lead frame which occurs in the conventional method.

Further, by further reducing the resin thickness d1 under the heat sink, the filler content can be reduced while maintaining the same thermal resistance as the conventional one, and the life of the mold can be extended.

As shown in FIG. 1B, the fluid pressure adjusting member 11
Is lifted to the surface of the molded product when the injection of the liquid thermosetting resin 9 is completed, and the space of the flow pressure adjusting member 11 is further filled with the resin, and when the resin is completely cured, the molded product is molded. And the lead frame 3 is completely resin-sealed except for the lead terminals to complete a semiconductor device.

Further, the method for discriminating the flow pressure adjusting member 11 on the molded product is that the position of the flow pressure adjusting member 11 is above the surface of the molded product when the fluid pressure adjusting member 11 rises to the surface of the molded product at the end of the resin injection. Since it stops at a position lowered by several tens of microns, the shape of the molded product can be identified from the fact that a recess 12 of several tens of microns is formed on the surface of the molded product as shown in FIG.

The reason for forming the concave portion is that when the molded product is mounted on the heat dissipation plate with screws and washers when the molded product is mounted, a convex portion causes floating of the washer, which causes a problem.

[0016]

As described above, according to the present invention, the mold and the lead frame in the mold space are roughly divided into two parts.
By providing a vertically movable fluid pressure adjusting member in the first flow passage having a large flow passage cross-sectional area among the two flow passages, the thermal resistance between the semiconductor element and the back surface of the mold resin is reduced, and the cause of die wear is considered. It is possible to reduce the content of the filler, and it is possible to provide a molding method with good moldability and long mold life.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a full-mold type mold of the present invention,
FIG. 7A is a diagram at the time of resin injection, and FIG. 9B is a diagram from the resin injection to the cured state.

FIG. 2 is a plan view of a molded product of the present invention.

FIG. 3 is a diagram showing a conventional lead frame finished product.

FIG. 4 is a cross-sectional view of a conventional full-mold type mold, in which FIG. 4A is a diagram in which the resin is in an uncured state, and FIG.
Is a diagram of the resin in a semi-cured state.

[Explanation of symbols]

 1 Upper surface mold die 2 Lower surface mold die 3 Lead frame 4,5 Movable pin 6 Resin injection port 7 Semiconductor element 8 Bonding wire 9 Thermosetting resin 10 Void defect 11 Flow pressure adjusting member 12 Recessed part of molded product surface

Claims (1)

[Claims] 1. A semiconductor element, a lead frame on which the semiconductor element is mounted, and a bonding wire portion for electrically connecting the semiconductor element and the semiconductor element and the lead frame are arranged in a mold space. In a method of sealing a semiconductor device, in which a fluid insulating resin is injected and cured into a mold, a first flow channel having a wide flow channel area is provided above a lead frame in a mold space which is a flow channel of the fluid insulating resin when the fluid insulating resin is injected. A second flow passage having a narrow flow passage area is formed in the lower portion, and a vertically movable fluid pressure adjusting member is provided in the first fluid passage so that the fluid pressure of the first fluid passage and the fluid pressure of the second fluid passage are substantially equalized. A method of encapsulating a semiconductor device, wherein the method is the same.