JPS5832443A - Semiconductor device - Google Patents

Abstract

PURPOSE:To effectively emanate the heat generated at the semiconductor element of the titled device by a method wherein said element is placed in the concavity of a concaved electrode, the electrode on the other side is contacted to the above, and when the semiconductor device is formed by filling the insulator to be used for airtight sealing into the concavity, these electrodes are constituted by a compound material in which carbon fibers were buried in a copper matrix. CONSTITUTION:On surface of the semiconductor is adhered to the inner part of the concavity of the concaved electrode 1 using solder material 4, and the electrode 3 located on the other side is adhered to the othr surface of the element 2 using solder material 4 in the same manner as above. Subsequently, the semiconductor device is formed by filling silicon rubber 6, which is the insulator to be used for airtight sealing, into the concavity. According to this constitution, the electrodes 1 and 3 are composed of the compound material in which carbon fibers were buried in a copper matrix. Accordingly, the heat generated at the element 2 can be emanated effectively, and the thermal stress of the solder material 4 generated due to the difference in the thermal expansion coefficient between component materials can be lessened, thereby enabling to greatly increase the life of the device for thermal fatigue and breakdown.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a composite material in which carbon fibers are embedded in a copper matrix (
This relates to a semiconductor device using a composite material (hereinafter abbreviated as composite material) as an electrode, which can effectively dissipate heat generated in a semiconductor element, and reduce thermal stress on the solder material caused by the difference in thermal expansion coefficient between the semiconductor element and the electrode. The present invention relates to semiconductor devices that can be used.

As shown in FIG. 1, a conventional semiconductor device has a concave electrode 1 made of steel and a semiconductor element 2. A structure in which the other side electrode 3 is fixed with a solder material 4, or a concave electrode 1 made of steel as shown in FIG.
Semiconductor element 2. The other side electrode had a structure in which a thermal stress relieving material 5 such as tungsten or molybdenum was fixed with a solder material 4. However, in the former, the heat dissipation to the electrode 1 side is good, but the heat dissipation to the other electrode 3 is poor, and the thermal stress on the solder material 4 is large; in the latter, the stress is alleviated by the thermal stress relaxation material 5. However, there were drawbacks such as a decrease in heat dissipation and an increase in product cost. Furthermore, in both figures,
6 is silicone rubber.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device that can effectively dissipate heat generated in a semiconductor element and alleviate thermal stress generated in a solder material due to differences in thermal expansion coefficients of constituent members.

During operation of a semiconductor device, the thermal stress generated in the solder metal portion is determined by the difference in thermal expansion coefficients of the constituent members, the solder metal ring, the temperature rise of the device, etc., and it is desirable that the difference in thermal expansion coefficients and the temperature rise be as small as possible. On the other hand, the temperature rise is determined by the thermal resistance of the device itself and the loss generated during operation, and is preferably as small as possible.

Conventionally, materials such as tungsten and molybdenum, which have thermal expansion coefficients similar to those of semiconductor elements, have been used as thermal stress relaxation materials, but they are expensive.

There was a problem in terms of thermal resistance, and on the other hand, copper, iron, aluminum, etc. were generally used as materials to improve heat dissipation, but there were problems in terms of differences in thermal expansion coefficients. In this respect, composite materials can solve the above-mentioned problems at the same time because their coefficient of thermal expansion is close to that of semiconductor elements and their thermal conductivity is close to that of copper. Therefore, in the present invention, the composite material is used as an electrode, and the electrode structure is arranged so that the heat generated at the joint of the semiconductor element is spread equally to both sides of the semiconductor element, thereby reducing the thermal resistance of the device. The focus is on minimizing.

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

Concave electrode 1. Semiconductor element 2. The other side electrode 3 is fixed with a solder material 4, and the inside of the concave electrode 2 is filled with silicone rubber 6 as an insulator for airtight sealing. In the present invention, the concave electrode τ□ and the other side electrode 3 are particularly made of a composite material and have excellent thermal conductivity, so that the heat generated in the semiconductor element 2 is quickly dissipated. At this time, the heat flow diffused from the concave electrode side spreads as shown by the broken line, so it is important to make the shape of the other side electrode 3, especially the electrode diameter and electrode ring, equal to or larger than the broken line, that is, to give almost equal spread of the heat flow. b The thermal resistance of the semiconductor device is defined as the series thermal resistance from the semiconductor element 2 junction to the concave electrode 1 as r, the series thermal resistance from the semiconductor element 2 junction to the other side electrode 3 as r2, and this composite thermal resistance. R8, and because of this relationship, there was a drawback that the combined thermal resistance R8 of the device was large, but the present invention
By reducing t, the composite thermal resistance R0 of the device can be reduced.

In the present invention, as a result of carrying out a so-called thermal fatigue resistance test of the solder material in which a current is intermittently applied to the device and a temperature cycle is applied, it was found that the temperature rise on the concave electrode side is mainly T1. On the other hand, the relationship between T2 on the electrode side is T and <T2 when rl<12 in the conventional device, and thermal fatigue failure of the solder material occurs on the semiconductor element 2.
Although only the other side electrode 3 side was destroyed, the present invention was introduced into the other side electrode structure r1ζr! By doing so, the thermal fatigue fracture life could be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, FIG. 2 is a sectional view of the conventional device through a thermal stress relaxation material, and FIG. 3 is a sectional view of a semiconductor device showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Concave electrode, 2...Semiconductor element, 3...Other side electrode, Figure 1, Figure 3

Claims (1)

[Claims] 1. In a semiconductor device in which the recessed electrode, the semiconductor element, and the other electrode are sequentially fixed with a soldering material, and the recessed electrode is filled with an insulator for airtight sealing, the recessed electrode and the other electrode are made of carbon fiber in a copper matrix. Comprised of a composite material made by burying
A semiconductor device characterized in that the other side electrode has a shape that provides a heat flow spread approximately equal to the heat flow spread in the concave electrode.