JPH08186188A - Stud-type semiconductor device - Google Patents

Abstract

PURPOSE: To prevent insulation from deteriorating in the interior of a case in a stud-type semiconductor device with a press contact structure. CONSTITUTION: The flange part of an insulation tube 11 made from resin is held by insulation plates 7 made from inorganic substance with a large dielectric constant. An unbalanced electric field on the surface of the insulation plate 12 near the corner of a connection conductor 5 when applying a high voltage is relaxed, thus preventing corona discharge from occurring easily. Even if corona discharge occurs, insulation does not deteriorate due to inorganic substance, thus creating a reliable semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stud type semiconductor device having a pressure contact structure, and more particularly to a structure for preventing insulation deterioration.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view of a conventional stud type semiconductor device having a pressure contact structure. In the figure, a connecting conductor 5 having a disk at the tip of a cylinder is attached to an electrode on the upper surface of a diode element 4 placed on a stud 1, a washer 6, an insulating plate 7 made of mica, and a tetrafluoroethylene resin. Pressure contact is made by the disc spring 8 via the flange portion of the cylindrical insulating tube 11 made of aluminum. The upper end of the disc spring 8 is pressed by the ceramic insulator 3 brazed to the metal cylinder 2. Further, the terminal 9 is brazed to the insulator 3, and the connecting conductor 5 is flexibly coupled to the terminal 9. The disc spring 8 is at the same potential as the stud 1 and the welded metal cylinder 2, and the insulation between the connecting conductor 5 and the disc spring 8 and the washer 6 is a cylindrical insulating tube 11 having a flange portion and an insulating plate. Secured at 7.

[0003]

In the conventional device, when a voltage is applied between the stud 1 and the terminal 9, the disc spring 8 and the washer 6 which are equipotential to the stud 1 are connected to the terminal 9. A voltage is applied between the connecting conductor 5 and its withstand voltage, and the withstand voltage is determined by the respective materials and thicknesses of the tubular insulating tube 11 and the insulating plate 7, and the connection of the insulating tube 11 on the creeping surface of the flange portion. It is determined by the creepage distance between the conductor 5 and the metal cylinder 2. However, when a high voltage of, for example, 4000 V is applied, the electric field on the creeping surface of the flange portion of the insulating tube 11 in the vicinity of the corner of the connecting conductor 5 becomes strong, which may cause an unequal electric field to cause corona discharge. It was

When corona discharge occurs, insulation deterioration occurs at the flange portion of the resin insulating tube 11. In particular, insulation tube 1
No. 1 uses tetrafluoroethylene resin in consideration of heat resistance, withstand voltage, and processed shape. However, it has been found that the tetrafluoroethylene resin is apt to cause insulation deterioration with respect to corona discharge, the dielectric strength is rapidly lowered with discharge time, and the dielectric strength is easily lowered as the frequency is increased. Therefore, if the voltage application that causes corona discharge is repeated, the breakdown voltage of the semiconductor device gradually deteriorates.

In view of the above problems, it is an object of the present invention to provide a stud type semiconductor device in which insulation deterioration does not occur even when a high voltage is applied.

[0006]

[Means for Solving the Problems] In order to solve the above problems,
According to the present invention, a cylinder having a resin-made flange portion is brought into pressure contact with the electrode on the upper surface of the semiconductor element located on the stud by the force of a spring whose equipotential is the end surface of the disc portion of the connection conductor and the stud. In a stud-type semiconductor device in which the insulation between the spring and the connection conductor is ensured by the insulating tube and the insulating plate made of an inorganic material, the resinous flange portion is sandwiched by the insulating plates made of an inorganic material.

In particular, it is preferable that the insulating plate made of an inorganic material is a material having a relative dielectric constant larger than that of tetrafluoroethylene resin, for example, mica.

[0008]

By taking the above-mentioned means and sandwiching the flange portion of the cylindrical insulating tube made of resin between the insulating plates made of an inorganic material, the electric field on the creeping surface of the insulating plate 12 near the corners of the connecting conductor 5 becomes uneven. Therefore, even if corona discharge occurs, insulation deterioration is unlikely to occur because the insulating plate 12 is an inorganic substance.

In particular, if the insulating plate made of an inorganic material is a substance having a large relative dielectric constant, such as mica, the electric field strength on the creeping surface of the insulating plate 12 near the corners of the connecting conductor 5 is relaxed, and corona discharge occurs. Hateful.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a semiconductor device according to an embodiment of the present invention, and portions common to FIG. 2 are designated by the same reference numerals. In FIG. 1, a connecting conductor 5 in the form of a circular cylinder with a disk attached to the electrode on the upper surface of the diode element 4 placed on the stud 1, a washer 6, an insulating plate 7 made of mica, ethylene tetrafluoride The disc spring 8 makes pressure contact with the flange portion of the resin-made tubular insulating tube 11 and the insulating plate 12 made of mica. Insulation plates 7 and 1
The thickness of 2 was 0.5 mm. The upper end of the disc spring 8 is pressed by the ceramic insulator 3 brazed to the metal cylinder 2. The terminal 9 is also brazed to the insulator 3, and the connecting conductor 5 is flexibly connected to the terminal 9. The disc spring 8 is at the same potential as the stud 1 and the welded metal cylinder 2, and the insulation between the connection conductor 5 and the disc spring 8 and the washer 6 is a conventional tubular insulating tube 1 having a flange portion.
It is ensured by the insulating plate 12 in addition to the insulating plate 7 which sandwiches 1 between them. As described above, by adding the mica insulating plate 12 having a thickness of 0.5 mm, the insulation deterioration does not occur even when a high voltage of 4000 V is applied.

That is, the flange portion of the insulating pipe 11 made of tetrafluoroethylene resin is replaced with the insulating plates 7 and 12 made of an inorganic substance.
Therefore, even if corona discharge occurs due to an uneven electric field on the creeping surface of the insulating plate 12 near the corner of the connecting conductor 5, the insulating plate 12 is an inorganic substance, and therefore insulation deterioration is unlikely to occur. Furthermore, when the electric field strength near the corners of the connection conductor 5 was simulated, the flange portion of the insulating tube 11 made of tetrafluoroethylene resin was sandwiched between the insulating plates 7 and 12 having a large relative permittivity. It was found that the electric field strength on the creeping surface was alleviated, and the corona discharge did not occur at the applied voltage where discharge had occurred in the past. here,
The dielectric constant of tetrafluoroethylene resin is about 2, while that of mica is as large as about 7. Therefore, it is considered that the same effect can be obtained by similarly using an insulating plate made of an inorganic material, which has a large relative dielectric constant, even for materials other than mica.

Although the above example describes a diode,
It goes without saying that the present invention can also be applied to other high breakdown voltage stud type semiconductor devices such as thyristors.

[0013]

As described above, according to the present invention, since the flange portion of the insulating tube is sandwiched by the insulating plates made of an inorganic material having a large relative dielectric constant, insulation deterioration due to partial discharge is caused even when a high voltage is applied. A stud-type semiconductor device that does not occur and has high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional semiconductor device.

[Explanation of symbols]

 1 Stud 2 Metal cylinder 3 Insulator 4 Diode element 5 Connection conductor 6 Washer 7 Insulation plate 8 Disc spring 9 Terminal 11 Insulation tube 12 Insulation plate

Claims (3)

[Claims] 1. An electrode on the upper surface of the semiconductor element located on the stud is in pressure contact with the end surface of the disk portion of the connecting conductor under the force of a spring having the same electric potential as the stud, and has a resin flange portion. A cylindrical insulating pipe and an insulating plate made of an inorganic material that ensure insulation between a spring and a connecting conductor, characterized in that a flange portion of a resin insulating pipe is sandwiched by insulating plates made of an inorganic material. Stud type semiconductor device. 2. The stud type semiconductor device according to claim 1, wherein the insulating plate made of an inorganic material is made of a material having a relative dielectric constant larger than that of tetrafluoroethylene resin. 3. The stud-type semiconductor device according to claim 2, wherein the insulating plate made of an inorganic material is mica.