JPH1022425A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration due to heat cycle and improve heat dissipation characteristics by permitting a support body to contain nickel steel which has a small linear expansion coefficient in a shape of particles and providing a copper which has a high heat conductivity between the nickel steel particles. SOLUTION: A support board 1a, which is a mixed mold of copper particles 11 and Invar particles, is provided by rolling a mixed material of copper particles and Invar particles by a weight ratio of 1:1 into disc shape. Therefore, the linear expansion coefficient of the support body 1a becomes 10×10<-6> K<-1> , approximately at the middle of those of copper and Invar, which is a value close to that of silicon which constitutes a diode chip 2. Therefore, a semiconductor device which is less deteriorated clue to brazing material 3 and the heat cycle of a diode chip 2 is obtained. A heat conduction path due to the copper particles 11 is formed at the part under the diode chip 2 of the support body 1a, and heat generated by the diode chip 2 is efficiently discharged to the bottom side of the support board 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a rectifier diode having a structure in which a semiconductor element is fixed to a metal support plate.

[0002]

2. Description of the Related Art A rectifier diode is sometimes constructed as shown in FIG. In FIG. 1, a silicon diode chip 2 is provided on one main surface of a dish-shaped metal support plate 1 made of copper.
A bar-shaped lead member 5 having a header portion 4 is fixed to the upper surface of the diode chip 2 with a brazing material (solder) 6. On one main surface of the support plate 1, a protective resin coating 7 made of silicon rubber is provided so as to include the diode chip 2 and the header 4.

[0003]

By the way, a heat cycle (repetition of high temperature and low temperature) is applied to the semiconductor device of FIG.
Is added many times, the electrical characteristics of the diode chip 2 may be degraded. It is considered that this is because the mechanical stress generated due to the difference in expansion coefficient between the diode chip 2 and the support plate 1 is applied to the diode chip 2 or the brazing material 3 by repeatedly applying the heat cycle. To solve this problem, it is conceivable to make the expansion coefficient of the support plate 1 close to that of the diode chip 2. Specifically, the support plate 1 is made of copper, invar,
A three-layer structure of copper is considered. Invar is a type of nickel steel and has 63.4% Fe and 36 Ni
%, Mn 0.4% and C 0.2%. The linear expansion coefficient of Invar is 1.2 × 10 ⁻⁶ K ⁻¹ , which is smaller than the linear expansion coefficient of copper, 16.2 × 10 ⁻⁶ K ⁻¹ , and the linear expansion coefficient of silicon is 4.1 × 10 ^−6. It has a value close to K ^-1 . Therefore, when Invar is used, mechanical stress can be reduced. However, since the thermal conductivity of Invar is lower than that of copper, the heat radiation effect of the support plate 1 is impaired.

Accordingly, an object of the present invention is to provide a semiconductor device which is less deteriorated by a heat cycle and has excellent heat radiation characteristics.

[0005]

According to the present invention, there is provided a semiconductor device having a metal support and a silicon semiconductor element fixed to the support with a brazing material. The body is made by rolling copper particles and nickel steel particles, and the nickel steel has a linear expansion coefficient closer to silicon than copper, and has a lower thermal conductivity than copper. The present invention relates to a semiconductor device characterized by the above.

[0006]

In the present invention, nickel steel having a small coefficient of linear expansion is contained in the form of particles in the support, and copper having high thermal conductivity is interposed between the particles of the nickel steel. Therefore, heat generated in the semiconductor element is satisfactorily released from one main surface of the support to the other main surface through the copper. Further, since the support contains nickel steel having a linear expansion coefficient close to that of silicon, it is possible to prevent the brazing material and the semiconductor element from deteriorating due to stress due to a heat cycle.

[0007]

Next, a semiconductor device (rectifier diode) according to an embodiment of the present invention will be described with reference to FIG. The semiconductor device of FIG. 2 has a dish-shaped metal support plate 1a as a support and a semiconductor element fixed to the center of one main surface of the support plate 1a with a brazing material 3 made of solder, similarly to FIG. , A bar-shaped lead 5 having a header portion 4 fixed to an electrode (not shown) on the upper surface of the diode chip 2 with a brazing material 6, and a protective resin coating 7. The diode chip 2 includes a silicon semiconductor substrate having a pn junction and a pair of electrodes formed on upper and lower main surfaces of the substrate.

The semiconductor device shown in FIG. 2 is a conventional support plate 1 shown in FIG.
The configuration is substantially the same as that of FIG. The support plate 1a in FIG. 2 is made of a mixture of copper particles and invar particles mixed at a weight ratio of 1: 1 and rolled into a dish shape. As shown in FIG. And invar particles 12. The average particle size (measurement size) of the copper particles 11 and the invar particles 12 is such that the planar shape is quadrangular in order to satisfactorily release the heat of the diode chip 2 from one main surface of the support plate 1a to the other main surface. The length of one side (longest side) of the diode chip 2 is 1/4 or less (preferably 1/6 or less).

Since the support plate 1a is a 1: 1 mixture of the copper particles 11 and the invar (nickel steel) particles 12, its linear expansion coefficient is approximately 10 × 10 ^−6, which is approximately intermediate between copper and invar.
K ^−1, which is close to the value of silicon constituting the diode chip 2. Therefore, it is possible to provide a semiconductor device in which the brazing material 3 and the diode chip 2 are less deteriorated by the heat cycle. Further, since the copper particles 11 are arranged between one main surface and the other main surface of the support plate 1a so as to be in contact with or close to each other, the copper particles 11 are provided on a portion of the support plate 1a below the diode chip 2. Is formed, and the heat generated in the diode chip 2 is satisfactorily released to the lower surface side of the support plate 1a. Further, by forming the support plate 1a by rolling, the invar particles 1 are contained in the copper.
2 can be easily obtained in a uniformly dispersed form,
Features of copper (high thermal conductivity) and features of invar (low expansion coefficient)
Can be utilized in a well-balanced manner. Therefore, it is possible to provide a semiconductor device with good heat dissipation despite little deterioration due to a heat cycle.

[0010]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The weight ratio of copper to Invar can be changed, for example, in the range of 30 to 80% by weight of copper and 20 to 70% by weight of Invar. (2) The support plate 1a can be heated in a range that does not melt during rolling. (3) Invar of the example is Fe 63.4 in weight ratio.
%, Ni 36%, Mn 0.4%, and C 0.2%, but the composition is not limited to this, and the composition can be changed within a range where a linear expansion coefficient closer to that of silicon can be obtained than that of copper. (5) The side surface of the diode chip 2 can be an inclined surface to increase the breakdown voltage. (6) The present invention can be applied not only to the rectifier diode but also to another semiconductor device such as a thyristor. (7) A flat copper-nickel steel rolled product (support) according to the present invention is disposed on a relatively large-area ceramic substrate or copper substrate (metal substrate), and a semiconductor chip is fixed thereon. It can be configured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a conventional semiconductor device.

FIG. 2 is a sectional view showing a semiconductor device according to an embodiment of the present invention.

[Explanation of symbols]

 1a support plate 2 diode chip 12 invar particles

Claims (1)

[Claims] 1. A semiconductor device comprising: a metal support; and a silicon semiconductor element fixed to the support with a brazing material, wherein the support is formed by rolling copper particles and nickel steel particles. Wherein the nickel steel has a linear expansion coefficient closer to that of silicon than copper and has a lower thermal conductivity than copper.