JPH09199647A - Semiconductor device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To attach a heat radiation fin to a package mounted on a printed circuit board, conventionally, fastening with a bolt welded to the package or bonding the package and the heat radiation fin with an adhesive is used. However, there was concern about the bonding strength, and reliability was low. Further, when the cooling effect is enhanced, the height of the heat radiation fin is increased, which causes a problem that the area occupied by the entire semiconductor device is increased. SOLUTION: A horizontal dimension of a heat radiation fin 40 is set to be larger than an outer dimension of a package 20, the heat radiation fin 40 is mounted on the package, and a portion where the heat radiation fin projects from the package is fastened to the printed board with a bolt or the like. The heat radiation fins are closely attached to the package sandwiched between them. The horizontal extension enhances the cooling effect without increasing the occupied volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for mounting a semiconductor chip and a method and structure for mounting a radiation fin attached to the package for air cooling on a printed circuit board.

[0002]

2. Description of the Related Art In order to meet the demand for higher speed, smaller size and higher density of electronic equipment, semiconductor chips are becoming faster and more highly integrated,
As a result of the increased power consumption of the semiconductor chip, the amount of heat generated from the semiconductor chip has also increased. Therefore, a fin-shaped radiator is often attached in order to cool the package on which the semiconductor chip is mounted. Conventionally, the mounting means is such that the bolt is joined upward to the package lid, it is passed through the mounting hole provided on the bottom surface of the radiation fin, and it is fastened with a nut, or the radiation fin and the package are bonded with an adhesive. Has been done. If the heat radiation from the fins is insufficient, the fin height is increased to increase the heat radiation area per fin.

[0003]

In the case of fastening with the above-mentioned bolts, a process such as brazing the bolts to the package side in advance is required, which affects work efficiency and cost, and the brazing portion is destroyed to radiate heat. The fins may come off. Also, in the case of joining with an adhesive, the adhesive may deteriorate due to a thermal fatigue test such as a thermal shock test or a temperature cycle test that is performed after mounting the radiation fin, and the radiation fin bonding part may be broken. Often had problems with product reliability.

Further, even if the height of the fins is increased for heat dissipation, the amount of heat dissipation converges to a certain value, and if the fins are made higher than that, the heat dissipation is not improved. On the other hand, as the height of the fin is increased, the size of the entire semiconductor device (occupied volume when the device is installed in a device) increases in the vertical direction, which violates the demand for miniaturization.

[0005]

Generally, a package is used by mounting it on a substrate such as a printed circuit board having a larger area than itself. Therefore, instead of attaching the heat radiation fin to the package, set the horizontal dimension of the heat radiation fin larger than the external dimensions of the package and place it on the package.
The heat radiation fin was improved by closely fixing the heat radiation fin to the package sandwiched by fastening the heat radiation fin to the printed circuit board at the protruding portion of the package.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In FIG. 1, 20 is a package, 21 is its lid, and the semiconductor chip 10 is enclosed in the inside. This package is mounted on the printed circuit board 30, and the contact material 22 connects the respective electrodes. In the illustrated example, the socket 32 and the back attachment 31 for preventing bending are provided, but they may be omitted depending on the design.

In the cavity-up structure as shown in the figure, the heat from the semiconductor chip 10 is transferred from the package 20 to the radiation fin 40 through the lid 21, so that the thermal conductivity of the package and the lid greatly affects the radiation performance. Therefore, it is desirable to use aluminum nitride having high thermal conductivity as these materials.

The radiating fins 40 are extended in the horizontal direction, and the extended portions project from both ends of the package like eaves. At this portion, the heat radiation fin 40 is fastened to the printed circuit board 30 with bolts 50 and nuts 51.
At this time, it is necessary to avoid over-tightening and uneven tightening, but if, for example, a collar 52 of a predetermined length is covered on the bolt or a spacer is sandwiched as shown in the drawing, uniform fastening without excess or deficiency can be easily performed. be able to. It is also effective to interpose an elastic body such as a spring washer. In the case of this embodiment, instead of the nut 51, the back attach 31 may be provided with a female screw.

According to this structure, the heat radiation fin extends in the horizontal direction to increase the heat radiation area. As a result, the heat radiation performance can be improved without changing the height of the entire semiconductor device. Further, if a thermal grease or the like for improving the thermal conductivity is interposed on the contact surface between the radiation fin 40 and the lid 21, the effect of the thermal conductivity becomes large. Various electronic components 11, 12, ... Are mounted on the printed circuit board around the package. However, since these components are lower in height than the package, even if the heat radiation fins are extended in the horizontal direction. There is no hindrance.

(Embodiment 2) FIG. 2 shows an example of a semiconductor device configured in a so-called cavity down system.
Illustration of wiring circuits and the like is omitted. In this method, the heat from the semiconductor chip 10 is directly transferred from the package 20 to the radiation fins 40, so that the package
It is desirable to use aluminum nitride, which has a high thermal conductivity, as the material. Aluminum and its alloy are generally used for the material of the radiation fin. The procedure for fastening by bolting is the same as in the first embodiment.

[0011]

As described above in detail, according to the present invention, the radiation fin can be attached to the semiconductor device more reliably and easily than the conventional soldering or the joining by the adhesive.
Moreover, since the cooling performance can be improved without increasing the volume occupied in the height direction, it is possible to obtain a small-sized and highly reliable semiconductor device.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the invention.

FIG. 2 is a sectional view of a semiconductor device according to a second embodiment of the invention.

[Explanation of symbols]

 10 Semiconductor Chip 20 Package, 21 Lid, 22 Contact Material 30 Printed Circuit Board 40 Radiating Fin 50 Bolt, 51 Nut, 52 Color

Claims (4)

[Claims] 1. A package on which a semiconductor chip is mounted,
In a semiconductor device having a board on which this package is mounted and a heat radiator mounted on the upper surface of the package, the horizontal dimension of the heat radiator is set to be larger than the outer dimensions of the package, and the board overhangs from both ends of the package. A semiconductor device characterized in that a heat radiator is coupled to the package and the heat sink is brought into close contact by sandwiching the package between the substrate and the heat radiator. 2. The semiconductor device according to claim 1, wherein the substrate and the heat radiator are coupled by mechanical coupling means. 3. The semiconductor device according to claim 1, wherein the substrate and the radiator are coupled with each other by bolts and nuts. 4. The semiconductor device according to claim 1, wherein the package is made of aluminum nitride having a high thermal conductivity.