JPH0432254A - Semiconductor package - Google Patents

Abstract

PURPOSE:To improve heat dissipating characteristic while performing alleviation of a stress due to thermal expansion by forming release of resin adhesive at the connecting part of a semiconductor chip at a heat diffusing plate. CONSTITUTION:A base 4 is connected to a heat diffusing plate 1, and the protrusion 1a of the plate 1 is coated with suitable amount of adhesive 7. Thereafter, a semiconductor chip 3 is placed on the protrusion 1a, and dried while applying a suitable load to the chip 3. Excessive part of the coated adhesive 7 flows to a through hole 2, and only necessary amount remains on the surface to be connected. Accordingly, only the thickness of the adhesive 7 can be reduced, for example, to about 10mum. In this case, since the diameter of the hole 2 is previously so set that the adhesive 7 does not overflow to drop, the adhesive is stopped on the way of the hole 2, and does not flow to the bottom of the plate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technology related to heat dissipation of a semiconductor chip, and particularly to a technology for efficiently dissipating heat from a large-sized semiconductor device that generates a large amount of heat.

[Conventional technology]

For example, one type of semiconductor device has a semiconductor chip mounted on a heat diffusion plate that functions as a heat sink, and a base with pins set up on the heat diffusion plate with the semiconductor chip exposed in the center. Some use a package structure.

By the way, the present inventor has studied the problem of bonding between a semiconductor chip and other members.

The following are the techniques studied by the present inventor, and the outline thereof is as follows.

In other words, if the packaging density of semiconductor chips is high (the amount of heat generated will increase and some kind of heat dissipation measure will be required).For this reason, a heat diffusion plate is used to dissipate heat from the semiconductor chip, but the heat diffusion plate and the semiconductor chip Since the coefficient of thermal expansion is different between the two, it is not possible to make a solder connection.

Therefore, bonding is performed using a flexible adhesive such as silicone rubber. As a result, even if the thermal expansion coefficients of the thermal diffusion plate and the semiconductor chip are different, the bonding area can be fixed! MIIi can be prevented from occurring.

[Problem to be solved by the invention]

However, as mentioned above, in the case of semiconductor device package structures that are bonded using adhesive, the thermal conductivity deteriorates when the adhesive becomes thicker, so it is necessary to make it as thin as possible, but currently the thickness is 20 to 30 μm. is the limit.

The inventors have discovered that although it has been attempted to apply a load to thin the adhesive layer, it is difficult to ensure an appropriate thickness, and that applying too much load may cause damage to the semiconductor chip. Ta.

Therefore, an object of the present invention is to provide a technique that can achieve sufficient thermal conductivity and stress relaxation while using an adhesive for bonding.

The above objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in a semiconductor package in which a semiconductor chip is bonded to a heat diffusion plate using a resin adhesive, an escape portion for the resin adhesive is formed in the heat diffusion plate at a joint portion of the semiconductor chip. .

[Effect]

According to the above-mentioned method, when the semiconductor chip is pressed, excess adhesive applied to the surface to be bonded to the semiconductor chip enters the relief part, leaving only the necessary amount on the bonding surface. . Therefore, it is possible to make the adhesive layer on the joint surface extremely thin, and the thermal resistance of the joint can be reduced, so that it is possible to improve heat dissipation characteristics while achieving relaxation of stress caused by thermal expansion.

[Embodiment 1] FIG. 1 is a sectional view showing an embodiment of a semiconductor package according to the present invention.

A trapezoidal convex portion 1a is formed in the center of a heat diffusion plate 1 made of a metal material with excellent thermal conductivity such as copper, and a plurality of through holes 2 are provided in this convex portion 1a at regular intervals. The diameter of the through hole 2 is set to a size that allows the adhesive to enter and not overflow. The semiconductor chip 3 is covered with a fixed film on the convex portion 1a using an adhesive. Further, a paste 4 made of bismaleid riazine (BT resin) or the like is similarly fixed on the heat diffusion plate 1 except for the convex portions 1a using an adhesive.

As shown on the right, the reason why the convex portion 1a is provided like this is that the thickness of the semiconductor chip 3 and the thickness of the paste 4 are different, so the surface height is made to be the same so as not to interfere with wire bonding. It's for a reason.

A plurality of lead pins 5 are erected around the pad 40, and a wiring pattern electrically connected to the lead pins 5 is formed on the base 4, the end of which is exposed near the semiconductor chip 3. The ends of this wiring pattern and the electrode portions of the semiconductor chip 3 are connected by bonding wires 6.

Next, the assembly process of the embodiment with the above configuration will be explained.

First, the base 4 on which the lead pins 5 have been set up in advance is joined to the heat diffusion plate 1, and then an appropriate amount of adhesive 7 (silicone rubber, silver paste, etc.) is applied onto the convex portions la of the heat diffusion plate 1. Thereafter, the semiconductor chip 3 is mounted on the convex portion la, and is dried while applying an appropriate load to the semiconductor chip 3. Due to this suppression, the excess of the applied adhesive 7 flows into the through hole 2, leaving only the necessary amount on the bonding surface.

Therefore, the thickness of the adhesive 7 on the joint surface should be set to 10 μm, for example.
It can be made as thin as about m.

At this time, the diameter of the through-hole 2 is set in advance to prevent the adhesive 7 from spilling out, so it stops midway through the through-hole 2 and does not come out on the bottom surface of the heat diffusion plate l. In addition to adjusting the diameter of the through holes 2, the same effect can be obtained by taking measures such as placing a patch plate on the back surface of the heat diffusion plate 1 in advance.

Moreover, the effect can be further improved by chamfering the upper end of the through hole 2 so that the excess adhesive 7 can easily flow in.

As described above, even if deformation or thermal stress occurs in the package, the adhesive 7 absorbs this, so that no unreasonable force is applied to the semiconductor chip 3.

[Embodiment 2] FIG. 2 is a perspective view showing the main parts of a second embodiment of the present invention.

This embodiment is characterized in that grooves 8 are formed radially from the center of the protrusion 1a, whereas in the previous embodiment, the through hole 2 was provided in the protrusion 1a to form an escape part for the adhesive 7. There is.

With this configuration, the surplus of the adhesive 7 permeates into the groove 8 in the horizontal direction (width direction of the convex portion 1a) during bonding, and does not accumulate on the bonding surface. It can be made thin as well.

[Embodiment 3] FIG. 3 is a perspective view showing the main parts of a third embodiment of the present invention.

In contrast to the embodiment shown in FIG. 2 in which trapezoidal projections 1a are formed on the heat diffusion plate 1'', this embodiment has a plurality of cylindrical small-diameter projections 9 arranged in a row.

The protrusions 9 are formed using a mold press or by placing individually manufactured cylindrical bodies on the heat diffusion plate 1 in close contact and joining them (soldering or welding). In this case, the cylindrical bodies are not brought into close contact with each other, but a gap is formed between the bodies so that the excess adhesive 70 can easily flow in during joining. Although we have shown an example of a cylindrical body,
It is not limited to this, but may be a hexagonal prism, for example.

The effects of this embodiment are the same as those of the embodiment shown in FIG. 2, so redundant explanation will be omitted.

Above, the invention made by the present inventor has been specifically explained based on Examples, but it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. stomach.

For example, in the embodiment shown in FIG. 2, the grooves 8 are provided radially in the convex portion 1a, but they may be provided in the shape of a base plate as shown in FIG. 4, or vertically as shown in FIG. Alternatively, it may have a shape in which a plurality of grooves are provided at regular intervals in the lateral direction.

In addition, in the embodiment shown in FIG. 1, the through holes 2 are provided vertically, but as shown in FIG. Stress caused by directional thermal expansion differences can be alleviated.

Furthermore, although it was assumed that the relief part of the joint part is formed uniformly regardless of the location, by providing the through holes 2 (or grooves) so that the number of relief parts is larger around the joint part than in the center,
It is possible to alleviate the large stress around the periphery that tends to occur with large semiconductor chips.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical ones are as follows.

That is, in a semiconductor package in which a semiconductor chip is bonded to a heat diffusion plate using a resin adhesive, an escape portion for the resin adhesive is formed in the heat diffusion plate at the bonding portion of the semiconductor chip. As a result of being able to make the adhesive layer on the joint surface extremely thin, the thermal resistance of the joint can be reduced.
Heat dissipation characteristics can be improved while achieving relaxation of stress due to thermal expansion.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a semiconductor package according to the present invention, FIG. 2 is a perspective view showing main parts of a second embodiment of the invention, and FIG. 3 is a main part of a third embodiment of the invention. FIG. 4 is a plan view showing another example of grooves provided in the convex portion of the heat diffusion plate; FIG. 5 is a plan view showing still another example of grooves provided in the convex portion; FIG. 6 2 is a sectional view showing another state of formation of the through hole in FIG. 1. FIG. DESCRIPTION OF SYMBOLS 1... Heat diffusion plate, 1a... Convex part, 2... Through hole,
3...Semiconductor chip, 4...Pace, 5...Lead pin, 6...φ bonding wire, 7...Adhesive, 8...Groove, 9...Protrusion. Agent Patent Attorney Daiwa Tsutsui Figure 9: Protrusion Figure 5

Claims (1)

[Scope of Claims] 1. A semiconductor package in which a semiconductor chip is bonded to a heat diffusion plate using a resin adhesive, wherein a relief part of the resin adhesive is provided to the heat diffusion plate at a bonded portion of the semiconductor chip. A semiconductor package characterized by forming. 2. The semiconductor package according to claim 1, wherein the relief portion is a plurality of through holes provided at regular intervals. 3. The semiconductor package according to claim 1, wherein the relief portion is a plurality of grooves. 4. The semiconductor package according to claim 1, wherein the relief portion is a collection of a plurality of columnar bodies arranged at the joint portion with gaps between them.