RU2591744C2 - Thyristor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: present invention relates to power semiconductor devices, particularly to tablet thyristors with pressure control output. Thyristor contains rectifying element with central control electrode, placed in sealed housing, having first base as anode, second base as cathode, circular insulator, metal disc with central through hole, bushing, movable plunger of insulating material, compression spring and control output from flexible wire with contact element at one end. Metal disc is arranged between second base and rectifier element, bushing is inserted into central hole of metal disc, movable plunger is arranged inside bushing. One end of control output is located in central hole of movable plunger and fixed by contact element in lower end of plunger. Middle part of control output is electrically isolated and located in radial groove in upper part of metal disc, other end of control output is arranged in wall of annular insulator and extends outwards. Contact element of control output is made in form of two coaxial parts, upper of which is fixed at end of control output, and lower part of contact element is made in form of cup, diameter of which is greater than height and equal to inner diameter of bushing. Cup is arranged on central gate electrode of rectifying element and faces it with thin annular flange, and rear side is facing upper part of contact element. Second base in lower part is made with central recess to accommodate part of bushing, projecting above metal disc, and part of movable plunger projecting above bushing. At upper central part of movable plunger recess there is compression spring.

EFFECT: stability of parameters and characteristics, stable operation, higher reliability of thyristor.

2 cl, 5 dwg

Description

The present invention relates to power semiconductor devices, in particular to tablet thyristors with a clamping control unit.

There is a wide variety of designs for the internal nodes of the thyristors for creating pressure contacts between the control terminal and the central control electrode of the rectifier element of the thyristor.

The main elastic element for creating constant pressure between the control terminal and the central control electrode is a spring. In the designs of thyristors with a clamping control terminal, various types of springs are used: bending springs made of round wire, compression coil springs made of round wire, plate-shaped compression springs and others.

Belleville compression springs, Belleville springs, are used primarily for large workloads when it is necessary to create reliable physical contact between large surfaces. As applied to semiconductor technology, such springs are most effective in lockable thyristors with large pulsed control currents, which are comparable in order of magnitude with switched currents. For powerful lockable thyristors, pulsed blocking control currents amount to hundreds and thousands of amperes.

Most other types of thyristors are characterized by relatively small pulsed control currents of the order of (5 ÷ 10) A. In such devices, internal nodes based on compression springs of the first two types are used to create pressure contacts between the control terminal and the central control electrode. This provides simpler technical solutions for the construction of assemblies with fewer parts and easier to manufacture.

Known design of a tablet thyristor (Patent GB 1379017 A, IPC: H01L 21/52; H01L 21/60; H01L 23/04; H01L 23/05; H01L 23/16; H01L 23/488, published 02.01.1975) [1] comprising a rectifier element with a central control electrode, placed in a sealed enclosure consisting of a first base serving as an anode, a second base serving as a cathode, an annular insulator connected to the first and second bases with annular cuffs, a metal disk with a recess in the center and a radial groove, located between the rectifier element and the second base, a control terminal made of phosphor bronze, which is fixed on one side in a metal tube in the wall of an annular insulator, placed in the middle part in an insulating tube and laid in a radial groove in a metal disk, on the other hand curved in the form of a compression screw spring, placed in the recess of the metal disk using an insulating sleeve and a thrust bearing and brought into contact with the Central control electrode of the rectifier element.

The disadvantage of the design is that the compression spring creates a point pressure contact of a small area with the surface of the central control electrode.

The consequence of this is:

- increased current density in the area of the pressure contact;

- increased heating of the area of the pressure contact during the flow of control current and the release of Joule heat as a result;

- the risk of burning out a thin, a few micrometers, a metal layer of the central control electrode and a semiconductor pnpn structure of the rectifier element under it in the area of the pressure contact, an increase in the ohmic resistance of the contact, loss of controllability of the thyristor;

- increased specific pressure in the area of the pressure contact;

- the risk of abrasion of a thin metal layer of the central control electrode during vibration and shock;

- the risk of mechanical destruction of a thin metal layer of the central control electrode and the semiconductor pnpn structure of the rectifier element under it, loss of controllability and blocking ability of the thyristor.

All this negatively affects the stability of parameters and characteristics, the functioning and reliability of the thyristor.

Closest to the proposed technical solution is a thyristor (Patent US 5436472 A, IPC: H01L 23/051; H01L 23/48; H01L 29/74, published July 25, 1995.) [2] containing a rectifier element with a central control electrode placed in a sealed housing having a first base as an anode, a second base as a cathode, an annular insulator, a metal disk with a central through hole, a sleeve, a movable plunger of insulating material, a compression spring and a control lead from a flexible wire with a contact element on one the end. A metal disk is placed between the second base and the rectifier element, the sleeve is inserted into the central hole of the metal disk, a movable plunger is placed inside the sleeve. One end of the control terminal is placed in the central hole of the movable plunger and fixed by a contact element in the lower end of the plunger, the middle part of the control terminal is electrically isolated and placed in a radial groove in the upper part of the metal disk, the other end of the control terminal is placed in the wall of the ring-shaped insulator and brought out.

The disadvantage of this thyristor design with a clamping control terminal is that, due to geometrical restrictions on the case elements of tablet devices, the movable plungers used in them do not satisfy one crucial requirement: the length of the movable plunger must significantly exceed the diameter. In real devices, these parameters practically coincide.

The consequence of this is:

- skew of the movable plunger in the sleeve, skew of the contact disk of the control output relative to the plane of the central control electrode;

- reducing the area of physical contact of the control terminal to the central control electrode;

- an increase in the specific pressure and control current density in the area of the pressure contact with a significant increase in the skew of the contact disk and a decrease in the area of physical contact;

- instability of control circuit parameters: increase in control voltage and control signal power required to turn on the thyristor;

- the risk of mechanical destruction of a thin metal layer of the central control electrode and the semiconductor pnpn structure of the rectifier element under it, loss of controllability and blocking ability of the thyristor.

In addition, as the analysis shows, even in the absence of skewing of the movable plunger, the physical contact area in the “contact disk - central control electrode” system is (60 ÷ 80)% of the design. This effect is due to two factors: the skew of the contact disk relative to the movable plunger, non-flatness of the working surface of the contact disk.

These shortcomings adversely affect the quality and reliability of thyristors.

Measures to tighten the requirements for structural elements of the internal pressure control unit provide only a partial solution to the problem and lead to an increase in the cost of devices, but do not remove most of the problems discussed above.

The technical task of the proposed solution is to create a thyristor design with a clamping control terminal, which provides equalization of the clamping force between the contact element of the control terminal and the central control electrode.

The technical effect of the proposed technical solution is the stability of parameters and characteristics, stable operation, increasing the reliability of the thyristor.

The technical result of the proposed solution is the design of a thyristor with a clamping control terminal, the working surface of the contact element of which is automatically installed in the plane of the central control electrode during the assembly of the device under various adverse conditions, such as skewing of the movable plunger, etc.

The problem is solved due to the fact that:

1. A thyristor containing a rectifier element with a central control electrode, placed in a sealed housing having a first base as an anode, a second base as a cathode, an annular insulator, a metal disk with a central through hole, a sleeve, a movable plunger of insulating material, a compression spring and a control terminal from a flexible wire with a contact element at one end, the metal disk being located between the second base and the rectifying element, the sleeve is inserted in the center the hole of the metal disk, the movable plunger is placed inside the sleeve, in addition, one end of the control terminal is located in the Central hole of the movable plunger and fixed by a contact element in the lower end of the plunger, while the middle part of the control output is electrically isolated and placed in a radial groove in the upper part of the metal disk, and the other end of the control terminal is placed in the wall of the annular insulator and brought out, characterized in that the contact element of the control terminal you it is made in the form of two coaxial parts, the upper of which is fixed at the end of the control terminal, and the lower part of the contact element is made in the form of a cup whose diameter is greater than its height and equal to the inner diameter of the sleeve, while the cup is placed on the central control electrode of the rectifier element and faces a thin annular side, and the back side facing the upper part of the contact element, and the second base in the lower part is made with a Central recess in which the part of the sleeve is placed, high upayuschey above the metal disk and the movable plunger portion protruding above the bushing and the recess in the top center of the movable plunger arranged compression spring.

2. The upper part of the contact element is made in the form of a hemisphere, with a spherical surface facing the lower part of the contact element, made in the form of a cup.

The clamping control unit includes: a sleeve, a movable plunger, a contact element and a compression spring.

The features that distinguish the proposed technical solution include:

- the implementation of the contact element in the form of two coaxial parts: the upper part in the form of a hemisphere, the lower part in the form of a cup;

- coordination of the diameter of the cup with the inner diameter of the sleeve;

- placement of the sleeve of the pressure control unit simultaneously in two structural elements of the thyristor: in the hole of the metal disk and partially in the recess of the second base, the diameters of which are equal to the outer diameter of the sleeve;

- the implementation of the movable plunger in the form of two stages with different diameters of the steps, the diameter of the upper stage of which is equal to the diameter of the Central recess in the lower part of the second base, and the diameter of the lower stage is equal to the inner diameter of the sleeve;

- placement of the compression spring in the Central recess in the upper part of the movable plunger with an increased diameter.

A positive effect is achieved due to:

- eliminating the skew of the lower part of the contact element of the control terminal, cup, relative to the plane of the Central control electrode of the rectifying element;

- alignment of the clamping force and, as a result, the control current density between the control terminal and the central control electrode in the region of the annular surface of the lower part of the contact element, the cup;

- an additional function of the sleeve of the clamping control unit as an element for combining a metal disk with a second base and a metal cup with a central control electrode;

- reducing the risk of skewing and jamming of the movable plunger in the sleeve by increasing the "effective" length of the movable plunger while maintaining the dimensions of the pressure control unit;

- improving the conditions of the technological operation of the assembly of the thyristor due to the location of the compression spring in the upper Central part of the movable plunger of the clamping control unit and eliminating the consequent displacement of the movable plunger from the sleeve and its jamming;

- expanding the areas of use of the proposed design of the clamping control unit, for example, for lockable thyristors with medium control currents and for a new class of “smart” devices with integrated elements of self-protection against breakdown in the semiconductor p-n-p-n-structure of the rectifier element.

Known technical solutions with such a combination of features were not found in the patent and scientific and technical literature, which allows us to conclude that the proposed technical solution meets the criterion of "novelty."

The claimed technical solution is characterized by a combination of features exhibiting new qualities: the exclusion of skewing the working surface of the contact element of the control terminal relative to the plane of the central control electrode and the combination of the main and additional functions of the thyristor design elements, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

The claimed technical solution is illustrated by drawings.

In FIG. 1 shows a main sectional view of a thyristor.

In FIG. 2 shows a pressure control unit, a fragment of FIG. one.

In FIG. Figure 3 shows the contact element of the control output, consisting of two parts: the upper part is the hemisphere and the lower part is the cup facing the central control electrode with a thin annular side. The semiconductor pnpn structure of the rectifier element is partially shown.

In FIG. 4 illustrates the possibility of using the proposed technical solution for the thyristor design option, equipped with integrated elements of self-protection against breakdown in the semiconductor pnpn structure of the rectifier element in unauthorized operation modes, in particular when switching over the anode due to overvoltage.

in FIG. Figure 5 shows the direct branch of the current-voltage characteristic (CVC) of the thyristor control circuit at different stages of pressure contact degradation between the control terminal and the central control electrode during operation of the device, where CVC 1 is the initial CVC of the control circuit; CVC 2 - CVC after removing the metal coating of the central control electrode; CVC 3 - CVC after removing part of the doped p ⁺ layer of the control p-base region of the semiconductor pnpn structure of the rectifier element; A, B, C - points on the CVC 1, CVC 2 and CVC 3 - corresponding to the transition of the thyristor to the open state with the unlocking direct current control I _GT equal to 0.25 A.

The thyristor includes:

1 - rectifier element;

2 - central control electrode;

3 - the first base;

4 - second base;

5 - ring-shaped insulator;

6 - the first cuff;

7 - the second cuff;

8 - the third cuff;

9 - a metal disk;

10 - sleeve;

11 - a movable plunger;

12 - compression spring;

13 - control output;

14 - the outer part of the control output;

15 - a hemisphere;

16 - a cup;

17 is a compound for protecting the exit region of the pn junctions of the rectifier element to the surface;

18 - a ring of insulating material for fixing the rectifier element;

19 - cathodic metallization of the n - emitter of the semiconductor pnpn structure of the rectifier element;

20 - integrated elements of self-protection against breakdown in the semiconductor pnpn structure of the rectifier element.

In the proposed thyristor, the second base 4 as a cathode in the lower plane is in contact with the upper plane of the metal disk 9, in the radial groove of which is located the middle part of the electrically isolated control terminal 13 from the flexible wire. One end of the control terminal 13 is placed in the wall of the annular insulator 5 connected to the first base 3 of the first ring-shaped cuff 6 and the second base 4 of the ring-shaped cuffs, the second cuff 7 and the third cuff 8, and brought out the outer part of the control terminal 14. The other end of the control terminal 13 is placed in the Central hole of the movable plunger 11 and is fixed by the upper part of the contact element, a hemisphere 15, at the end of the movable plunger 11 installed in the sleeve 10. The contact element is made of metal in the form of two coaxial parts: the upper part in the form of a hemisphere 15 and the lower part in the form of a cup 16 placed on the central control electrode 2 of the rectifier element 1. A compression spring 12 is installed in the recess of the upper central part of the movable plunger 11. The rectifier element 1 with the central control electrode 2 is located between the metal disk 9 and the first base 3.

In the proposed thyristor design (Fig. 1), the alignment of the clamping force between the control terminal 13 and the central control electrode 2 in the area of the annular contact occurs automatically due to the axial clamp with the participation of a contact element consisting of two parts - a hemisphere 15 and a cup 16. In this case, based on the formulated requirement for automatic alignment of the clamping force in the area of the clamping contact, the height of the cup should be less than its diameter. From the point of view of the reliability of the ohmic contact between the hemisphere 15 and the cup 16, its area is not critical, since in this case the control current flows through the contact to the monolithic massive cup 16, and not to the thin metal coating of the central control electrode 2 and the semiconductor pnpn structure rectifier element underneath.

In the considered construction, a disk can be used as the upper part of the contact element. According to the same requirement of equalizing the clamping force, the diameter of the cup should be 4 times or more greater than the diameter of the disk. In this case, the ratio of 4 to 1 diameters is conditionally selected as the maximum allowable. This means that at the maximum skew of the disk, when the pressing force is localized at a point shifted from the center of the cup by one radius of the disk, the spread of the pressing force along the perimeter of the ring contact is plus or minus 25% of the average value. Given the range of weak dependence of the ohmic resistance of the contact on the clamping force, it is possible to obtain an acceptable heterogeneity in the distribution of the control current density along the perimeter of the ring contact. When the ratio of the diameters of the cup and the disc is 10 to 1, the maximum variation in the clamping force does not exceed plus or minus 11%, which is close to ideal conditions.

In FIG. 4, the ring-shaped control electrode 2 is located outside area 20 with elements of self-protection of the thyristor from breakdown. The configuration of the metal cup with a hollow inner part provides electrical control of the thyristor, without disrupting the functioning of the integrated self-defense.

In FIG. 5 I – V characteristics 1, I – V characteristics 2, and I – V characteristics 3 of the control circuit of a thyristor with a clamped point contact of the central control electrode were obtained in experiments on modeling the abrasion of the metal coating of the central control electrode. I – V characteristic 1 was measured with the initial metal coating. The thyristor was switched on in the open state with an unlocking direct current control I _GT equal to 0.25 A and an unlocking constant direct current control U _GT equal to 1.25 V, as indicated by point A on I – V characteristic 1. I – V characteristic 2 was measured after mechanical removal of the central metallization layer control electrode. The thyristor turned on at the same I _GT , but the U _GT increased to 5 V. This state corresponds to point B on the I – V characteristic 2. I – V characteristic 3 was obtained after removing part of the doped p ⁺ layer of the control p base region of the semiconductor p npn structure of the rectifier element . The value of I _GT remained at the same level, which is shown by point C on the I – V characteristic 3. U _GT increased to 10.5 V. Moreover, the direct dissipated control power of the thyristor P _FG increased by 8.4 times compared to the same parameter in the initial state of the metal coating thyristor central control electrode. Therefore, the instability of the control circuit parameters: an increase in the control voltage and the power of the control signal required to turn on the thyristor, leads to a decrease in the reliability of the thyristor.

The movable plunger is an essential part of the pressure control unit. Part of the movable plunger with a large diameter is guided by the cylindrical surface of the recess in the second base, increasing the “effective” length of the movable plunger and thereby reducing the risk of it being skewed and stuck in the sleeve. The movable plunger is made of durable non-deformable insulating material.

The sleeve, which performs additional centering functions, is also made of durable non-deformable insulating material.

The proposed thyristor design was used to develop a high-voltage powerful thyristor with self-protection against breakdown on silicon with a diameter of 100 mm. The outer diameter of the cup was 8 mm, the height was 2.5 mm, and the thickness of the rim was chosen to be 0.5 mm.

The inventive design of the thyristor can be used in the design and manufacture of powerful tablet thyristors, triacs, and other power electronics devices designed for use in modern converting devices for various purposes.

It was experimentally confirmed that in the claimed technical solution:

1) Performing a two-stage movable plunger with different step diameters, when the upper diameter of the movable plunger is equal to the diameter of the recess in the lower plane, and the lower diameter of the movable plunger is equal to the inner diameter of the sleeve, reduces the risk of skewing and jamming of the movable plunger in the sleeve;

2) The execution of the contact element in the form of two metal coaxial parts, the upper part in the form of a hemisphere, and the lower part in the form of a cup, the diameter of which is greater than its height and equal to the diameter of the sleeve, eliminates the skewness of the lower part of the contact element of the control terminal, the cup, relative to the upper the plane of the rectifier element;

3) Placing a compression spring in the recess of the central upper part of the movable plunger with an enlarged diameter eliminates the effect of the displacement of the movable plunger from the sleeve and its jamming during the thyristor assembly. The result is the stability of the parameters and characteristics of the device;

4) Placing the sleeve simultaneously in two structural elements of the thyristor: in the hole of the metal disk and partially in the recess of the second base leads to stable operation, increasing the reliability of the thyristor.

These technical results give the right to conclude that the proposed thyristor design with a clamping control terminal provides reliable ohmic contact between the control terminal and the central control electrode. Thus, the task is solved.

Information sources

[one]. (Patent GB 1379017 A, IPC: H01L 21/52: H01L 21/60; H01L 23/04; H01L 23/05; H01L 23/16; H01L 23/488, published 02/01/1975);

[2]. Patent US 5436472 A IPC: H01L 23/051; H01L 23/48; H01L 29/74, published July 25, 1995.

Claims (2)

1. A thyristor containing a rectifier element with a central control electrode, placed in a sealed housing having a first base as an anode, a second base as a cathode, an annular insulator, a metal disk with a central through hole, a sleeve, a movable plunger of insulating material, a compression spring and a control terminal from a flexible wire with a contact element at one end, the metal disk being located between the second base and the rectifying element, the sleeve is inserted in the center the hole of the metal disk, the movable plunger is placed inside the sleeve, in addition, one end of the control terminal is located in the Central hole of the movable plunger and is fixed by a contact element in the lower end of the plunger, while the middle part of the control terminal is electrically isolated and placed in a radial groove in the upper part metal disk, the other end of the control terminal is placed in the wall of the annular insulator and brought out, characterized in that the contact element of the control terminal in is complete in the form of two coaxial parts, the upper of which is fixed at the end of the control terminal, and the lower part of the contact element is made in the form of a cup, the diameter of which is greater than its height and equal to the inner diameter of the sleeve, while the cup is placed on the central control electrode of the rectifier element and faces a thin annular side, and the back side facing the upper part of the contact element, and the second base in the lower part is made with a Central recess in which the part of the sleeve, blunt over a metal disc and a portion of the movable plunger, projecting over the sleeve and the recess in the top center of the movable plunger arranged compression spring. 2. The thyristor according to claim 1, characterized in that the upper part of the contact element is made in the form of a hemisphere, with a spherical surface facing the lower part of the contact element, made in the form of a cup.

Images