JPH0358535B2 - - Google Patents

Abstract

PURPOSE:To enhance the reliability of the device, in a semiconductor device having an auxiliary electrode in a thyristor, a power transistor and the like, by bonding a conductor wire, which is attached to the auxiliary electrode that is held between main electrodes, on at least two parts, coating the wire with an insulator, and exposing the conductor wire at the intermediate part. CONSTITUTION:An auxiliary electrode 5 is held between main electrodes 2 and 3 in the structure of a thyristor, a power transistor and the like. The following procedure is used when a conductor wire 6 made of Al and the like is bonded to the auxiliary electrode 5. At least two parts 6a or more are used as bonding parts. The entire surface including these parts is coated with an insulator 7 such as silicone rubber. A part of the conducting wire 6, which is connected between the bonding parts, is not embedded. Said part 6b is floated and exposed on the insulator 7. Therefore, the exposed part serves the role of cushion, and the bonding parts 6a are not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor device, and particularly to a power semiconductor device having an auxiliary electrode such as a thyristor or a power transistor.

[Technical Background of the Invention] FIG. 2 shows a known thyristor with a flat envelope structure in half longitudinal section. In the figure, 1 is a semiconductor pellet, 2 and 3 are main electrodes, and 4 is a semiconductor pellet.
5 is a thermal buffer plate; 5 is an auxiliary electrode; 6 is a conductive wire connected to the auxiliary electrode 5; 7 is an insulator covering the bonding portion of the conductive wire 6 to the auxiliary electrode 5;
Reference numeral 8 denotes a cylindrical envelope surrounding the semiconductor pellet and the outer periphery of the main electrodes 2 and 3, and 9 an insulator fitted between the thermal buffer plate 4 and the envelope 8 to insulate them. The body 10 is a protective tube that protects the conductive wire 6 at a position outside the envelope 8.

In the known thyristor, the conductive wire 6 has
An Al wire is used, and one end of the conductive wire 6 is fixed to the protective tube 10 at the outer end of the protective tube 10 by crushing and caulking the outside of the protective tube 10. The other end of the conductive wire 6 is connected to an auxiliary electrode, and its extraction method is generally to press the conductive wire 6 to the auxiliary electrode or by bonding, and the bonding is usually performed by an ultrasonic method. . The insulator 7 covering the bonding portion of the conductive wire 6 is silicone rubber, and the insulator 7 is applied onto the bonding portion at the same time as it is applied to the beveled surface of the semiconductor pellet 1.

In the conventional thyristor as described above, in order to improve reliability, the conductive wire 6 of the auxiliary electrode is usually bonded to form two or more bonding portions 6a, as shown in FIG. The bonding portion 6a and the conductive wires therebetween were all covered with an insulator 7 to prevent the bonding portion 6a from peeling off or being damaged during the envelope assembly process or the like.

[Problems with the Background Art] In the conventional thyristor having the above structure, the bonding portion 6a of the conductive wire 6 and the conductive wire therebetween are all covered with the insulator 7, so the bonding portion 6a and the vicinity thereof are covered with the insulator. On the other hand, since there is a large difference in the coefficient of thermal expansion between the insulator 7 and the conductive wire 6, thermal stress repeatedly occurs in the conductive wire inside the insulator 7 when the thyristor is in use. There was a risk that the conductive wire portion would become fatigued and the bonding portion would deteriorate.

That is, in the case of a conductive wire made of Al, its coefficient of thermal expansion is 2.3×10 ^-5 cm/deg., but if the insulator 7 is made of silicone rubber, its coefficient of thermal expansion is 3.0×
10 ⁻⁴ cm/deg., and the coefficient of thermal expansion of the conductive wire is 1/10 or less of that of the insulator 7. Therefore, when the thyristor is used in the operating temperature range of -40°C to +125°C, the conductive wire and the insulator 7 between the bonding portions 6a expand or contract together, but the amount of expansion and contraction of the conductive wire 6 is Since is smaller than the insulator 7, thermal stress is generated in the bonding portion 6a,
Since this thermal stress is repeated every time the temperature rises and falls as the thyristor turns on and off, there is a possibility that the bonding portion 6a may become fatigued and eventually peel off. In particular, Al has a tendency to creep when subjected to a constant load for a long time at a temperature of 100°C or higher, so it becomes brittle when the above-mentioned repeated stress state is applied at high temperatures. The risk of becoming
Therefore, conventional power semiconductor devices such as thyristors have had reliability problems.

[Object of the Invention] An object of the present invention is to provide an improved semiconductor device having higher reliability than the conventional semiconductor device as described above, and more specifically, to provide an improved semiconductor device having higher reliability than the conventional semiconductor device as described above. An object of the present invention is to provide an improved semiconductor device that is less likely to cause peeling or breakage.

[Summary of the Invention] The improved semiconductor device according to the present invention is characterized in that, for example, two or more bonding portions of a conductive wire connected to an auxiliary electrode of a thyristor are coated with an insulating material, and the conductive wire between the bonding portions is coated with an insulating material. The reason is that it is not covered with an insulating material. According to such a structure, the contact area between the conductive wire and the insulator can be reduced, so the external force applied from the insulator to the conductive wire during the temperature rising and cooling process associated with the on/off operation of the thyristor is reduced. As a result, stress in the bonding portion is reduced, and a semiconductor device can be obtained in which there is less risk of breakage of the conductive wire or peeling of the bonding portion.

[Embodiments of the Invention] An embodiment in which the present invention is applied to a thyristor will be described below with reference to FIG. In addition, the first
The figure shows an enlarged cross-sectional view of the conductive wire bonding part on the auxiliary electrode 5 of the thyristor as in Figure 3, and in the figure, the parts labeled with the same symbols as in Figures 2 and 3 are the same as in the conventional thyristor. It is a part.

As shown in FIG. 1, in the thyristor constructed by applying the present invention, a semiconductor pellet 1
An Al conductive wire 6 is bonded to the auxiliary electrode 5 at two points separated from each other to form two bonding portions 6a, and these bonding portions 6a are made of an insulating material 7 such as silicone rubber. Although covered, the bonding portion 6a
The conductive wire portion 6b between the two is exposed on the insulator 7. Therefore, even if the temperature of the semiconductor pellet 1 and the auxiliary electrode rises and falls during use of the thyristor and the insulator 7 expands and contracts, no external force is applied to the portion 6b due to the expansion and contraction of the insulator 7. Therefore, the thermal stress on the bonding portion 6a of the conductive wire 6 is significantly smaller than that of conventional thyristors, and as a result, the risk of peeling of the bonding portion, disconnection, and deterioration of the conductive wire is also extremely reduced. Moreover, the stress applied to the conductive wire portion covered with the insulator 7 is
Since it is consumed as a force to deform the bonding portion 6a, it does not lead to deterioration of the bonding portion 6a.

[Effects of the Invention] As described above, in the semiconductor device of the present invention, since the conductive wire between the two bonding parts is not covered with an insulating material, there is a risk of deterioration of the conductive wire and the bonding part compared to the conventional semiconductor device. Therefore, the present invention provides a semiconductor device that is more reliable than conventional semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a part of a semiconductor device improved by the present invention, FIG. 2 is a longitudinal sectional view of a half of a conventional semiconductor device, and FIG. 3 is an enlarged part of FIG. 2. FIG. 1... Semiconductor pellet, 2, 3... Main electrode, 4
... Thermal buffer plate, 5 ... Auxiliary electrode, 6 ... Conductive wire,
6a... Bonding portion, 6b... Exposed portion of the conductive wire, 7... Insulator, 8... Envelope, 9... Insulator, 10... Protection tube (of the conductive wire 6).

Claims (1)

[Claims] 1. In a semiconductor device that has two main electrodes and at least one auxiliary electrode, and in which a conductive wire connected to the auxiliary electrode is bonded to the auxiliary electrode at two or more places, the bonding portion of the conductive wire is made of an insulator. A semiconductor device characterized in that at least a portion of the conductive wire between the bonding portions is not covered with the insulator.