JPH0778907A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability of breakdown voltage of a device, by soldering one main surface of a semiconductor element on the top surface of a base which is formed on one surface of a metal retaining plate and smaller than the size of the main surface of the semiconductor element CONSTITUTION:Rectangular semiconductor chips 1 are fixed on a metal retaining plate 2 composed of molybdenum by using brazing material 3 like solder, so as to keep intervals. A guard ring which ensures specified breakdown voltage when a voltage is applied to both surface of a chip is formed in the outer peripheral part of the semiconductor chip 1. Trenches 5 are formed so as to surround the chips 1 while leaving bases 6 whose size is smaller than the chip 1. Each semiconductor chip 1 is soldered on the flat top surface of the base 6 surrounded by the trench. The trench 5 which is formed in the metal retaining plate 2 and surrounds the chip 1 is filled with insulator of silicon rubber, which covers the guard ring in the outer peripheral part 4 of the chip 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which one or more semiconductor chips such as transistors, diodes, and thyristors are fixedly attached to one metal supporting plate.

[0002]

2. Description of the Related Art A large-capacity semiconductor device is constructed by forming one element on a large-area semiconductor substrate and mounting a plurality of small-area semiconductor chips on one metal supporting plate. There is something I did. In the latter case, a large-area silicon wafer is divided into a plurality of small-area semiconductor chips after the wafer process is completed, and only the semiconductor chips with good characteristics are used, so the manufacturing yield is good. Besides, there is an advantage that it is possible to form a circuit composed of two or more kinds of semiconductor chips, for example, a thyristor and a flywheel diode on one support plate.

FIG. 2 shows an example of such a semiconductor device.
On the flat metal support plate 2, a transistor, a diode,
A state in which a plurality of semiconductor chips 1 such as thyristors are fixed using solder 3 is shown. When a chip is required to have a high breakdown voltage, a guard ring or the like is formed on the outer periphery of the chip to control the spread of the depletion layer when a voltage is applied between both sides of the chip to secure the breakdown voltage. .

[0004]

In the semiconductor device as shown in FIG. 2, excessive solder 3 may protrude and rise to the side surface of the chip 1 as shown in A part of the figure. Since the solder 3 has the same electric potential as the electrodes on the lower surface of the chip and the insulation distance between the double-sided electrodes of about several hundred μm, which is determined by the chip thickness of about several hundred μm, is reduced by the solder 3, the required withstand voltage cannot be obtained. There was a problem. Even if a plurality of chips satisfying the withstand voltage characteristics are used, the reliability of the withstand voltage becomes low in the entire semiconductor device when such a defect occurs.

An object of the present invention is to solve such a problem and improve the reliability of the breakdown voltage of a semiconductor device composed of a plurality of semiconductor elements fixed to one metal supporting plate.

[0006]

In order to achieve the above object, the present invention provides a plurality of semiconductor elements having electrodes on both main surfaces, each of which has one main surface on which electrodes are provided. In a semiconductor device brazed to a single metal support plate, the one main surface of the semiconductor element body is a top surface of a pedestal having a size smaller than the main surface of the semiconductor element body formed on one surface of the metal support plate. Be attached. The recess surrounding the base of the metal support plate is preferably filled with an insulating material that also covers the side surface of the semiconductor element body, and it is effective that the insulating material is silicone rubber.

[0007]

Operation: By brazing the main surface of the semiconductor element body having a size larger than the top surface of the base portion on the top surface of the base portion formed on one surface of the metal supporting plate, the side surface of the semiconductor element body of the brazing material can be changed. Since there is no rising of the semiconductor element body, an insulation distance corresponding to the sum of the semiconductor element body thickness and the substrate protrusion height can be obtained between the outer periphery of the semiconductor element body and the bottom surface of the recess surrounding the base of the metal supporting plate. There is no risk of lowering the breakdown voltage. Further, by filling the concave portion of the metal supporting plate with an insulating material and covering the side surface of the semiconductor element body, the reliability of the breakdown voltage is further improved.

[0008]

1 (a) and 1 (b) show an embodiment of the present invention. Each has characteristics of transistors, diodes, or thyristors with a withstand voltage of 2000 V or more. For example, twelve 20 mm square semiconductor chips 1 each having a thickness of 3 mm made of molybdenum and a brazing material 3 such as solder is used. It is fixed at intervals of about 3 mm. The outer peripheral portion 4 of the semiconductor chip 1 is provided with a guard ring for ensuring a predetermined breakdown voltage when a voltage is applied to both surfaces of the chip.

A groove 5 having a depth of 1.5 μm is formed in the metal supporting plate 2 so as to surround the chip 1, leaving a base 6 having a size smaller than the size of the chip 1, and a base surrounded by the groove. Each semiconductor chip 1 is brazed to the flat top surface 7 of the portion 6. As a result, the insulation distance between the outer peripheral guard ring portion 4 and the surface of the metal supporting plate 2 of the substrate is four times or more as compared with the case where it is fixed to the conventional flat metal supporting plate as shown in FIG. Therefore, the structure is stable against application of a high voltage of 2000 V or more.

FIG. 3 shows another embodiment of the present invention. The groove 5 dug in the metal supporting plate 2 surrounding the chip 1 is filled with an insulating material such as silicone rubber 8 so as to cover the guard ring of the outer peripheral portion 4 of the chip 1. 2000V by this
The reliability of the breakdown voltage of the high breakdown voltage chip 1 is improved.

[0011]

According to the present invention, a plurality of semiconductor elements are brazed so that their peripheral edges are projected onto a base portion projecting from one surface of a metal supporting plate, so that the upper surface of the element body and the bottom surface of the concave portion of the supporting plate. The insulating distance between and is significantly increased as compared with the case of brazing on a flat support plate, and the withstand voltage can be secured when a high voltage of 2000 V or more is applied between the double-sided electrodes of each semiconductor element. As a result, the semiconductor device as a whole does not become defective due to the breakdown voltage of some of the semiconductor elements. Furthermore, by filling the recess surrounding the metal support plate base with an insulating material and covering the side surface of the semiconductor element body, the reliability of the breakdown voltage is further improved. Also, since the peripheral edge of the semiconductor element body is protruded from the metal substrate base and brazed, the thermal stress at the time of brazing is relieved at the peripheral edge of the semiconductor element body, and mechanical reliability is improved. To improve.

[Brief description of drawings]

1A and 1B show a semiconductor device according to an embodiment of the present invention, in which FIG. 1A is a sectional view of a main part, and FIG.

FIG. 2 is a cross-sectional view of a main part of a conventional semiconductor device according to an embodiment.

FIG. 3 is a cross-sectional view of essential parts of a semiconductor device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Chip 2 Metal Support Plate 3 Solder 5 Groove 6 Stand 7 Stand Top 8 Silicone Rubber

Claims (3)

[Claims] 1. A semiconductor element body having a plurality of semiconductor elements having electrodes on both main surfaces, which are brazed to a single metal supporting plate on one main surface having electrodes on the entire surfaces, respectively. A semiconductor device, wherein the one main surface is brazed to a top surface of a pedestal having a size smaller than a main surface of a semiconductor element body formed on one surface of a metal supporting plate. 2. The semiconductor device according to claim 1, wherein the recess surrounding the pedestal of the metal supporting portion is filled with an insulating material that also covers the side surface of the semiconductor element body. 3. The semiconductor device according to claim 2, wherein the insulating material is silicone rubber.