JPH07176657A - Pressing unit for planar semiconductor element - Google Patents

Abstract

PURPOSE:To prevent the pressing force, produced by tightening a bolt constantly, from decreasing or the fluctuation in the distribution of pressing force from increasing. CONSTITUTION:Adjacent coned disc springs 51A, 52A have different diametral dimensions at the large diameter contacting parts thereof. Consequently, the protruding part of coned disc spring having smaller diameter comes into line contact with the conical face on the inside of coned disc spring having larger diameter. The contact is sustained even if pressing force is applied to deform the coned disc springs 51A, 52A. Since a small circle does not protrude from a large circle even if the relative position of the springs 51A, 52A is shifted slightly in the radial direction so long as the shift is within the difference of diameter, the springs 51A, 52A do not come into point contact but come into line contact at all times. Consequently, the pressing force produced by tightening a bolt is not consumed for abrasive deformation at the mating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element such as a diode or a thyristor used in a power converter such as a rectifier or an inverter, especially when a flat semiconductor element used as a large-capacity element is incorporated in the apparatus. Further, the present invention relates to a pressurizing device for pressing a flat semiconductor element and a member such as a disc spring arranged coaxially with the flat semiconductor element together with a predetermined pressing force and maintaining the state for a long period of time.

[0002]

2. Description of the Related Art A large number of semiconductor elements such as diodes and thyristors are used in large capacity rectifiers and inverters. The larger the number of semiconductor elements used, the more disadvantageous it is in terms of cost and reliability. Therefore, in order to reduce the number of semiconductor elements used, a semiconductor element having a large capacity is used. Such large-capacity semiconductor elements are often dish-shaped so-called flat semiconductor elements. Since the flat semiconductor device itself does not have a cooling structure or a terminal drawing structure, a structure is adopted in which it is held with a predetermined pressure contact force sandwiched between a cooling body and a terminal conductor that have both a cooling function and a terminal drawing structure. To be done.

FIG. 6 is an elevational view including a cross-sectional view of a flat semiconductor device, members in the vicinity thereof, and a conventional pressing device that exerts a pressure contact force on them, and FIG. 7 is a plan view of the pressing device of FIG. These are collectively called a semiconductor stack. In these drawings, the flat semiconductor device 1 is stacked with the cooling body 2, the upper lead 3, the washer 4 and the two disc springs 5 and is arranged between the shaft support 7 and the pressing plate 8 to tighten the tightening bolts 6. Tightened by.

The tightening bolt 6 is inserted into a bolt hole provided in the pressing plate 8, and a screw corresponding to the thread of the thread portion 62 of the tightening bolt 6 is cut into this bolt hole. The shaft support 7 and the pressing plate 8 are fixed to each other by a predetermined distance with two connecting bolts 9. The connecting bolt 9 is electrically connected to the shaft support 7, and is covered with an insulating pipe not denoted by a reference numeral to ensure insulation between the pressing plate 8 and other metal members.

When the tightening bolt 6 is rotated, it moves in the vertical direction in the figure according to the thread of the screw portion 62. Therefore, when it is rotated so as to move downward, the head 61 of the tightening bolt 6 presses the disc spring 5. Torque is controlled by rotating the tightening bolt 6 with a torque wrench, and the pressure contact force of the flat semiconductor element 1 is managed through the tightening torque.

The cooling body 2 is for cooling the flat semiconductor element 1, and cooling water is passed inside to cool it strongly. Since the flat semiconductor element 1 is in contact with the cooling body 2 by the pressure contact force, the thermal resistance of the contact portion is small.
The cooling body 2 can efficiently absorb the heat generated by the flat semiconductor element 1. As is well known, flat semiconductor device 1
Both end faces are electrodes, and one is a cathode and the other is an anode. The upper electrode in the figure is a good heat conductor such as copper and is electrically connected to the upper lead 3 via the cooling body 2 made of a good conductor, and the shaft support 7 also serves as the lower lead, The electrodes are in contact with and electrically connected to the shaft support 7. As described above, the contacting portions of the cooling body 2, the upper lead 3 and the shaft support 7 which are electrically connected to the flat semiconductor element 1 are subjected to the same pressure contact force by the tightening bolts 6, so that the contact resistance is stable. A small value is retained.

As described above, the pressure contact force with respect to the flat semiconductor element 1 is important with respect to the cooling characteristic and the conductive characteristic. As far as only these characteristics are concerned, the value should be as large as possible, but the pressure contact force of each member should be as large as possible. There is a limit to the allowable value for and cannot be exceeded, so
As described above, it is managed so as to have a constant value. The member to which the above-mentioned pressure contact force is applied undergoes thermal expansion or contraction according to these temperatures. Therefore, even if the pressure contact force is set to a predetermined value by torque control of the tightening force of the tightening bolt 6 at the beginning of assembly, the pressure contact force may change according to the temperature change and may become excessive or insufficient. is there. The disc spring 5 is provided in order to suppress the change of the pressure contact force due to such temperature change within an allowable range. Although two disc springs are shown in this figure, the number is not limited to this number.

[0008]

By the way, when several semiconductor stacks were manufactured and the tightening torque and the actual pressure contact force were measured and their correlations were investigated, the distribution of the pressure contact force for a certain tightening torque was found. Occurs that shows a large deviation from the center value. The inventor has found that when the pressure contact force is different from that of other semiconductor stacks in such an actual measurement, a slip often occurs on the mutual contact surfaces of a plurality of disc springs, and the pressure contact force is relatively uniform. I noticed. And it turns out that this can be explained for the following reasons.

FIG. 8 is a sectional view of the disc spring 5 of FIG. In this figure, two disc springs 51, 52 that constitute the disc spring 5 are provided.
Has a V-shaped cross-section, and the open sides of the V-shape are opposed to each other so that the convex portions corresponding to the vertices of the rectangular cross section of the large-diameter portions are in contact with each other. However, in reality, the radial positions of the two disc springs 51 and 52, which are the left and right directions in the figure, are slightly deviated, so that the circles of the convex portions of the disc springs 51 and 52 are deviated, and the contact portions are formed by these two circles. Point contact is made at two points, which are the intersections of. Since all of the pressure contact force is concentrated at these two points, the contact pressure becomes extremely large, and when the contact parts mesh with each other and the tightening force is increased to increase the pressure contact force, this contact part wears and deforms. Moreover, most of the tightening force is consumed by this deformation, and it does not work effectively on the pressure contact force.

Such a phenomenon generally occurs at the contact portions of many disc springs 5, which causes the distribution of the pressure contact force with respect to a constant tightening force to shift to a smaller one, and causes a large variation. There is a problem that An object of the present invention is to solve such a problem and to provide a pressing device for a flat semiconductor element, which does not reduce the pressure contact force with respect to a constant tightening force or increase variation.

[0011]

In order to solve the above-mentioned problems, according to the present invention, a flat semiconductor element and a plurality of disc springs provided coaxially with the flat semiconductor element are predetermined by a tightening force of a tightening bolt. In a pressurizing device for a flat semiconductor element to which a pressure contact force is applied and which is held, the diameters of adjacent disc springs in contact with each other are different from each other. Alternatively, in this pressurizing device, the diameters of the contacting portions of the adjacent disc springs are different from each other, but the contacting portions are processed into a flat surface.
Further, a flat semiconductor element and a plurality of disc springs provided coaxially with the flat semiconductor element are adjacent to each other in a flat semiconductor element pressing device in which a predetermined pressure contact force is applied by the tightening force of the tightening bolt and this is held. It is assumed that washers having a predetermined diameter are inserted into portions of the disc springs that are close to each other.

[0012]

In the structure of the present invention, the diameters of the contacting portions of the plurality of disc springs are different from each other.
In the contact portion, one convex portion and the other conical surface are in contact with each other. Therefore, when the disc spring is deformed due to the pressure contact force, the contact position hardly changes, and even when the relative position slightly shifts,
As long as the deviation does not exceed the difference in diameter, the smaller circle does not protrude from the larger circle, so in any case, the contact portion is always a line contact and does not make point contact with each other. .

Alternatively, instead of having different diameters, the flat portions are formed by cutting the portions that come into contact with each other into flat surfaces, so that the convex portions disappear at the mutual contact portions and the flat portions come into contact with each other. Even if they are deformed by force or are displaced in the radial direction, their contact portions become line contacts. Also, without changing the shape and size of the disc springs, by inserting washers of a predetermined size in the portions where the adjacent disc springs come close to each other, the convex portion of each disc spring comes into contact with the flat portion of the washer. Even if the disc spring is deformed or displaced in the radial direction due to the pressure contact force, the convex portion of the disc spring and the flat portion of the washer are always in contact with each other.

[0014]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a sectional view of two disc springs showing a first embodiment of the present invention, which is similar to FIG. 8 but the tightening bolt 6 and washer 4 of FIG. 8 are omitted. In this figure, 2
The size of the large diameter portion of the disc spring 51A on the upper side of the disc springs 51A and 52A is smaller than that of the disc spring 52A. Therefore, the contact portions of the disc springs 51A and 52A are in line contact with each other such that the convex portion of the disc spring 51A is in contact with the inner conical surface of the disc spring 52A. Even if the disc springs 51A and 52A are deformed by the pressure contact force, the contact position hardly changes. Also, if the relative positions of the disc springs 51A and 52A are displaced in the radial direction, as long as the displacement dimension does not exceed the size difference of the large diameter portion of the disc springs 51A and 52A, the protrusion of the disc spring 51A is The spring 52A moves along the inner conical surface of the spring 52A, but the convex portions of the spring 52A do not make point contact with each other. Since the contact portion is always in line contact, the pressure contact force is not dispersed and concentrated, so that the tightening force is not spent on the wear deformation of the disc springs 51A and 52A, and is effectively converted into the pressure contact force. Therefore, the variation in the distribution of the pressure contact force with respect to the constant tightening force is reduced.

2 and 3 are sectional views of a disc spring showing a second embodiment of the present invention. The difference from FIG. 1 of FIG. 2 is that a flat portion 55B is provided at the contact portion of the disc springs 51B and 52B. That is.
Further, FIG. 2 shows an arrangement in which the large diameter portions of the two disc springs 51B and 52B are in contact with each other, while FIG. 3 is an arrangement in which the small diameter portions of the disc springs 53B and 54B are in contact with each other. Is different. Generally, when a plurality of disc springs are used, it is usual to arrange FIGS. 2 and 3 alternately. Therefore, for example, when four disc springs are used, two sets of the two disc springs having the arrangement shown in FIG. 2 are stacked, and the disc spring under the upper set and the disc spring over the lower set are combined. The contacting parts are as shown in FIG. When there are two sheets as shown in FIG. 6, the arrangement shown in FIG. 2 is common.

In FIG. 2, a flat portion 55B is provided on the large-diameter portions of the disc springs 51B, 52B which come into contact with each other. The flat surface portion 55B is in surface contact with the flat spring portion 51B when the two disc springs 51B and 52B are not pressed against each other. Belleville springs 51B, 52B
When the two are deformed under the pressure contact force, the flat portions 55B are not parallel to each other and are in line contact with each other. Further, even if the relative position is slightly deviated, the contact portion is displaced between the flat surface portions 55B, and the acute-angled convex portions do not engage with each other.

In FIG. 3, a flat portion 56B is provided on the small-diameter portions of the disc springs 53B, 54B which come into contact with each other. Even if the disc springs 53B, 54B are deformed or slightly displaced due to the pressure contact force, the contact parts of the disc springs 53B, 54B are not the same as in FIG. There is no point contact. 4 and 5 are cross-sectional views of a disc spring showing a third embodiment of the present invention. The difference from FIG. 2 and FIG.
2,53,54 are the same as the conventional disc spring shown in FIG. 8, and instead, washers 57C, 58C are provided at the portions where they approach each other. That is, in the case of FIG. 4, the convex portion of the disc spring 51 is in line contact with the plane portion above the washer 57C, and the disc spring 52 is in line contact with the plane portion below the washer 57C. When the disc springs 51, 52 are deformed by the pressure contact force and the size of the large diameter portion is increased, the contact portion only shifts from the flat portion of the washer 57C. Also, disc springs
When the relative positions of 51 and 52 are displaced in the radial direction, line contact is maintained and does not become point contact unless the movement of the contact part due to the displacement exceeds the range of the inner and outer diameters of the washer 57C. Since the same applies to the case of FIG. 5, detailed description will be omitted.

In FIG. 1, the two disc springs 51A and 52A are in contact with each other at their large diameter portions. However, as shown in FIGS. 3 and 5, the small diameter portions are also in contact with each other. By making the diameters different, it is possible to obtain the same operation and effect as in FIG.

[0019]

According to the present invention, the diameters of the portions of adjacent disc springs that come into contact with each other are made different, so that
In the contact portion, one convex portion and the other conical surface are in contact with each other. Therefore, even if the relative position of the disc spring slightly shifts in the radial direction, as long as the displacement dimension does not exceed the difference in diameter, the smaller circle does not protrude from the larger circle, so the contact portion is always Since line contact does not occur and point contact that meshes with each other does not occur, the pressure contact force generated when the tightening force is applied to the tightening bolt is not consumed by wear deformation of the meshing part, and an appropriate pressure contact force according to the tightening force is obtained. Further, it is possible to obtain the effect that the distribution of the actual pressure contact force with respect to a constant tightening force is reduced and the pressure device for a flat semiconductor element has high reliability.

Further, the same effect can be obtained by forming flat portions by cutting the portions in contact with each other into flat surfaces instead of making the diameters different. Further, the same effect can be obtained by inserting a washer of a predetermined size into the approaching portion of the adjacent disc spring instead of changing the size and shape of the disc spring.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of two disc springs showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a disc spring showing a second embodiment of the present invention.

FIG. 3 is a sectional view of a disc spring different from FIG. 2 showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a disc spring showing a third embodiment of the present invention.

5 is a sectional view of a disc spring different from FIG. 4 showing a third embodiment of the present invention.

FIG. 6 is an elevation view including a cross-sectional view of a flat semiconductor device and a conventional pressing device.

7 is a plan view of the pressure device of FIG.

FIG. 8 is a partially enlarged sectional view of FIG.

[Explanation of symbols]

1 Flat type semiconductor device 51,52,53,54,51A, 52A, 53A, 54A, 51B, 52B, 53B, 54B Disc spring 55B, 56B Flat part 57C, 58C Washer 6 Tightening bolt

Claims (3)

[Claims] 1. A pressing device for a flat semiconductor element, wherein a flat semiconductor element and a plurality of disc springs provided coaxially with the flat semiconductor element are applied with a predetermined pressure contact force by the tightening force of a tightening bolt and held by the flat spring. A device for pressing a flat semiconductor element, wherein the diameters of portions of adjacent disc springs that contact each other are different from each other. 2. The pressing device for a flat semiconductor device according to claim 1, wherein adjacent disc springs have mutually different diameters, but the mutually contacting portions are processed into a flat surface. Pressing device for flat semiconductor devices. 3. A flat semiconductor device pressing device in which a flat semiconductor device and a plurality of disc springs provided coaxially with the flat semiconductor device are provided with a predetermined pressure contact force by the tightening force of a tightening bolt and are held thereby. A flat-type semiconductor device pressing device, wherein washers each having a predetermined diameter are inserted into portions of adjacent disc springs that are close to each other.