JPS6373651A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device, to which ceramics can be fixed by soldering without causing hair cracks in the ceramics, by a method wherein, as a heat- radiating fin, a copper-tungsten alloy layer is used for the upper surface for fixing the ceramics, a copper layer is fixed to its lower surface with a brazing metal and so on, and the heat-radiating fin is formed into a two-layer structure. CONSTITUTION:The upper surface, which is used for fixing ceramics 4, of a heat- radiating fin 1 is constituted of a copper-tungsten alloy layer 2 having a thermal expansion coefficient approximate to that of the ceramics 4 for preventing hair cracks from occurring due to the heat at the time of soldering, a mechanical strength necessary when the fin is mounted on a heat sink and so on is ensured by the lower surface, and two layers of the alloy layer 2 and a copper layer 3 having a specific gravity smaller than that of the copper-tungsten alloy layer 2 and a thermal conductivity larger than that of the alloy layer 2 are combined together by soldering and so on. As the upper surface of the heat-radiating fin 1 is constituted of the copper-tungsten alloy layer 2 having a thermal expansion coefficient approximate to that of the ceramics 4 in such a way, even such the comparatively large ceramics 4 as 10 mm deg. or layer can be soldered without causing hair cracks due to the thermal strain at the time of soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor device, and particularly to a heat dissipation fin structure for dissipating heat generated from a semiconductor chip to a heat sink.

[Conventional technology]

FIG. 3 is a perspective view showing a semiconductor package in which a conventional single steel material is used for the heat dissipation fin, and ceramics having an arbitrary pattern is fixed thereon by brazing in order to fix a semiconductor chip thereon. In FIG. 3, 1 is a heat dissipation fin made of a single steel material, 4 is a ceramic to which a semiconductor chip (not shown) is fixed, and 5 is a brazing material for fixing the heat dissipation fin 1 and the ceramic 4. ing.

As mentioned above, in order to dissipate the heat of the ceramic 4 generated by the heat generated by the semiconductor element to the heat sink, the heat dissipation fin 1 made of a single material consisting of copper or a copper-tungsten alloy layer and the ceramic 4 are connected to the brazing material 5. It was stuck after being used.

[Problem that the invention seeks to solve].

However, when the radiation fin 1 is manufactured from a single steel material as described above, and the ceramics 4 are fixed thereon using the brazing material 5, hairs may form on the ceramics 4 due to the distortion caused by the difference in the thermal expansion coefficients of the two. Cracks occur.

Further, when the radiation fin 1 is made of a copper-tungsten alloy having a coefficient of thermal expansion similar to that of the ceramic 4 and is fixed using the brazing material 5, there is a problem that the weight of the product increases.

This invention was made to solve the above-mentioned problems, and aims to provide a semiconductor device that can be fixed by brazing without causing hair cracks in ceramics.

[Means for solving problems]

The semiconductor device according to the present invention uses a copper-tungsten alloy layer, which has a coefficient of thermal expansion close to that of the ceramic, on the upper surface to which the ceramic is fixed as a heat dissipation fin, and has mechanical strength on the lower surface, so that it has thermal conductivity. Copper, which has a high density and has a specific gravity lower than that of the copper-tungsten alloy layer, is fixed with a brazing material or the like to form a two-layer structure.

[Effect]

In this invention, by combining copper and a copper-tungsten alloy layer, hair cracks that occur in ceramics when only copper is used, and product weight, which is a problem when only a copper-tungsten alloy layer is used, can be reduced. Increase can be prevented.

〔Example〕

An embodiment of this invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 denotes a radiation fin, which is formed by fixing a copper layer 3 with a copper-tungsten alloy layer 2 as an upper layer. 4 is a ceramic with a pattern drawn thereon for attaching a semiconductor chip; 5 is a brazing material for fixing the radiation fin 1 and the ceramic 4;

In Fig. 1, the upper surface of the radiation fin 1 for fixing the ceramic 4 has a coefficient of thermal expansion of the ceramic 4 to prevent hair cracks from occurring due to the heat of brazing.
The lower surface has a specific gravity smaller than that of the copper-tungsten alloy layer 2, ensuring the necessary mechanical strength when attaching to a heat sink, etc.
The two layers, including the copper layer 3 having high thermal conductivity, are bonded together by brazing or the like.

In this way, since the upper surface of the radiation fin 1 is composed of the copper-tungsten alloy layer 2 having a coefficient of thermal expansion close to that of the ceramic 4, it is difficult to braze a relatively large ceramic 4 with a diameter of 10 mm or more due to thermal distortion. Can be brazed without causing hair cracks.

In addition, only the necessary thickness can be made from copper, which has a relatively high specific gravity.
By using the tungsten alloy layer 2 and using the copper layer 3 with high thermal conductivity as the other layer, it is possible to suppress an increase in the weight of the heat dissipation fin 1 without impairing the heat dissipation effect.

In addition, in the above embodiment, the copper-tungsten alloy layer 2 has a larger area than the ceramic 4, but
As shown in FIG. 2, a similar effect can be expected even if a ceramic material having the same size as the ceramic material 4 is fixed on the copper layer 3.

〔Effect of the invention〕

As explained above, the present invention provides a heat dissipation fin that is made of copper having a coefficient of thermal expansion close to that of the ceramic, on the top surface of which is brazed to the ceramic to which the semiconductor chip is fixed.
Since a tungsten alloy layer is used and a copper layer with high thermal conductivity is brazed on the bottom surface, large ceramics can be brazed to the heat dissipation fin without hair cracks, and the product weight is also reduced. There are other effects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a semiconductor device showing one embodiment of the invention, FIG. 2 is a perspective view of another embodiment of the invention, and FIG. 3 is a perspective view of a conventional semiconductor device. In the figure, 1 is a radiation fin, 2 is a copper-tungsten alloy layer, 3 is a copper layer, 4 is a ceramic, and 5 is a brazing material. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a semiconductor device in which a ceramic to which a semiconductor chip is fixed is brazed to a radiation fin, the radiation fin is
A semiconductor device characterized in that a copper-tungsten alloy layer having a coefficient of thermal expansion close to that of the ceramic is used on the upper surface to which the ceramic is fixed, and a copper layer having high thermal conductivity is used on the lower surface.