KR100638759B1 - Bonding structure of metallic member and ceramic, and vacuum switch using the same - Google Patents

Abstract

An object of the present invention is to reliably reduce the residual stress of a joint in a joint structure between a ceramic and a metal used in a vacuum switch, thereby increasing the strength of the joint structure.

Specifying each outer diameter dimension at the joint surface of the metal member 4 and 7 and the ceramic member 12 so that a large residual stress may not generate | occur | produce in the ceramic member which contact | connects a metal member, Specifically, a metal is a joint end part. The outer diameter of the rod side is made to be 0.2 mm or more smaller than the outer diameter of the ceramic cylindrical body, and the ceramic cylindrical body is joined to each other, and the abutting part is joined through a brazing material, or the stress relief composite member 13 is interposed therebetween, specifically, In this case, a disk-shaped composite material formed by fitting a center member having a low thermal expansion rate into an inner hole of an outer ring member having a high thermal expansion rate as a stress relaxation material is interposed between the metal member 10 and the ceramic member 9 and joined. In order to prevent damage such as cracks in the ceramic member,

Description

Bonding structure of metal member and ceramic and vacuum switch using same {BONDING STRUCTURE OF METALLIC MEMBER AND CERAMIC, AND VACUUM SWITCH USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum switch, and more particularly, to a joining structure between a ceramic insulator and a metal member for insulating a current-carrying contactor stored in a vacuum container.

Fig. 6 shows a cross section of a general internal structure of a vacuum switch in the prior art, Fig. 7 shows a bonding cross section of a ceramic and a metal of the vacuum switch in the prior art, and Fig. 8 shows a ceramic cross section of the prior art. The stress distribution in the junction structure with metal is shown.

As shown in Fig. 6, in the vacuum switch, a plurality of pairs of main circuit opening and closing portions in which the fixed electrode 2 and the movable electrode 3 are arranged opposite to each other are accommodated in the vacuum container 1, and the movable electrode 3 is flexible. It is connected to each other by the conductor 6, and the fixed electrode 2 is connected to the load side conductor 11 through the fixed electrode rod 5 and the fixed electrode base 10. As shown in FIG. Moreover, the movable electrode 3 of copper or copper alloy is moved through the driving rod 7, the ceramic insulator 8, and the movable electrode rod 4 by the driving force of the operation mechanism provided out of the vacuum container 1. It moves up and down to realize contact separation with the fixed electrode 2 of copper or copper alloy in an insulating atmosphere.

In the above-mentioned vacuum switch, the ceramic (between the electrical contact such as the movable electrode 3 and the fixed electrode 2, and the other metal such as the driving rod 7 and the vacuum container 1 (for example, SUS) For example, an insulator 8 and an insulator 9 of alumina A1 ₂ O ₃ are provided. The joint structure of ceramic and metal is employ | adopted generally at the connection part of a ceramic and an electrical contactor, or a ceramic and a metal container.

Since the difference in thermal expansion is large in metals and ceramics, a high residual stress occurs at the bonding interface when the bonding temperature in the bonding structure is returned to room temperature. Conventionally, in the method of joining butt-bonding members having different thermal expansion rates, a method is known in which an intermediate layer having a lower thermal expansion rate is provided at both interfaces to be bonded (see Patent Document 1, for example). In this Patent Document 1, a method of joining a W material or a Mo material through an interface between them as a bonding structure between a ceramic and a metal is disclosed.

By the way, in the method according to the reference document 1, the residual stress at the center of the interface can be alleviated to a considerable extent, but the metal shrinks together with cooling to the junction interface end, in particular, high tensile stress is applied to the ceramic side, and external load is also applied to the interface. There exists a problem that a crack may generate | occur | produce in the ceramic near a negative part or an interface part.

Therefore, as a means of solving such a problem, the joint structure of the ceramic and metal which can alleviate the residual stress as shown in FIG. 7 is proposed (for example, refer patent document 2). According to the cited reference 2, in the joining structure of the ceramic and the metal in which the ceramic member A and the metal member B are joined to each other through the intermediate member C, the intermediate member C has a yield stress of ceramic and Disclosed is a structure having a taper which is smaller than the yield stress of the metal member and whose outer diameter increases on the outer peripheral surface of the intermediate member toward the ceramic material side. According to this, even if the tensile stress caused by the thermal expansion difference is applied to the end of the bonded interface, the residual stress between the interfaces can be alleviated by the plastic deformation of the intermediate member, and the bonding strength of the interface can be improved.

[Patent Document 1]

Japanese Utility Model Publication No. 59-160533

[Patent Document 2]

Japanese Patent Laid-Open No. 6-48853

However, in the method of alleviating the residual stress by using the plastic deformation of the intermediate member described in Patent Document 2, since the plastic deformation amount of the thin intermediate member is limited, the residual stress in the large-diameter joining member having a high residual stress There is a problem that the relaxation effect of is weakened and the original strength possessed by the joined body cannot be sufficiently exhibited.

As a cause of the stress specificity at the dissimilar material interface, the residual stress caused by the shrinkage of the metal with cooling exhibits the maximum residual stress at the joint fixed end. For example, as shown in Fig. 8, the maximum principal stress on the surface of the joined body is generated on the ceramic side near the joint fixed end, and the range of high stress is widened (the maximum stress value does not change that much even if the diameter is increased). In Fig. 8, a cross-sectional circular bonded structure in which copper and alumina are joined by silver lead is shown, and the maximum principal stress at the outer edge of the circular joint surface (called a fixed end) is shown on the vertical axis. Also from the viewpoint of reducing residual stress, the joining surface between the metal and the ceramic has a circular shape (the structure is also applied in the present invention).

In general, the destruction of ceramics is based on defects latent on the surface and inside of the member. The wider the range of high stress, the more the potential defects included in the range, the higher the probability of failure. Therefore, in order to enhance the reliability of the joined body between the ceramic and the metal, it can be said that it is most effective to reduce the residual stress at the fixed joint end (outer edge of the joined surface).

An object of the present invention is to reliably retain residual stress in a joint by employing an intermediate member that performs a concrete improvement of the joint structure or a stress relaxation effect in a joint structure between a ceramic and a metal used in a vacuum switch of a power device. The present invention provides a vacuum switch with high strength and reliability, by reducing the strength of the bonded structure.

In order to solve the said subject, this invention mainly employ | adopts the following structures.

A plurality of electrode pairs in which a vacuum container, a plurality of movable electrodes and a fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and In a vacuum switch comprising a flexible conductor for connecting a plurality of movable electrode rods to each other, and a drive rod for driving the movable electrode rod,

A first ceramic member interposed between the drive rod and the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod,

The bonding structure between the first ceramic member and the metal rod made of the driving rod and the movable electrode rod has an outer diameter of the metal rod 0.2 mm or more smaller than the outer diameter of the ceramic member, and solders the metal rod and the ceramic member. It is set as the structure which joins by ash.

In addition, a vacuum container, a plurality of electrode pairs in which the plurality of movable electrodes and the fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and In the vacuum switch comprising a flexible conductor connecting the plurality of movable electrode rods to each other, and a driving rod for driving the movable electrode rod,

A first ceramic member interposed between the drive rod and the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod,

Between the second ceramic member and the fixed electrode rod is a stress relief composite member in which the bonding structure between the second ceramic member and the fixed electrode rod relaxes the stress of the second ceramic member due to the reduction of the fixed electrode rod. It is set as the structure connected to interpose.

Further, in the vacuum switch, the stress relief composite member is composed of a disk-shaped center member having an outer diameter larger than the outer diameter of the second ceramic member, and an outer ring member fitted to the outer peripheral side of the center member.

The inner diameter of the outer ring member is smaller than the outer diameter of the fixed electrode rod.

In addition, a vacuum container, a plurality of electrode pairs in which the plurality of movable electrodes and the fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and And a flexible conductor connecting the plurality of movable electrode rods to each other, a driving rod for driving the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod. It is a composite member for stress relaxation to relax the stress of the second ceramic member,

The stress relief composite member is composed of a disk-shaped center member having an outer diameter larger than the outer diameter of the second ceramic member, and an outer ring member fitted to the outer circumferential side of the center member,

The inner diameter of the outer ring member is smaller than the outer diameter of the fixed electrode rod.

By adopting such a configuration, in the joint structure between the ceramic and the metal used in the vacuum switch, the residual stress of the joint portion can be reliably reduced to increase the strength of the joint structure.

EMBODIMENT OF THE INVENTION The vacuum switch which concerns on embodiment of this invention is demonstrated in detail below, referring FIGS. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the 1st and 2nd structural example regarding the joining structure of the vacuum switch which concerns on embodiment of this invention. Fig. 2 is a detailed cross sectional view showing a first structural example, which relates to the junction structure of the vacuum switch according to the present embodiment, and Fig. 3 is a related example of the junction structure of the vacuum switch according to the present embodiment. Detailed cross section. Fig. 4 is a diagram showing the bonded structure according to the present embodiment and the maximum principal stress characteristic in the bonded structure compared with the prior art. FIG. 5 is a view for explaining a method for producing a composite member for stress relaxation, which is a second structural example of the present embodiment. FIG.

In the drawings, reference numeral 1 denotes a vacuum vessel, 2 fixed electrode, 3 movable electrode, 4 and 14 movable electrode rod, 5 fixed electrode rod, 6 flexible conductor, 7 switch actuator rod, 8, 9, 12 and 21 are ceramic members, 10 are fixed electrode bases, 11 are load-side conductors, 13 and 19 are stress relief composite members, 15 are grooves, 16 are joint surfaces, 17, 20 and 30 are solder materials, 18 are protrusions, 21 and 26 are center members of the stress relief composite member, 22 and 25 are outer ring members of the stress relief composite member, 23 is a vacuum furnace, 24 is a sample stage, 27 is a guide, 28 is a carbon sheet, and 29 is a corner portion. Represent each.

First, the first structural example regarding the joining structure of the vacuum switchgear which concerns on embodiment of this invention is demonstrated, referring FIG. The detailed structure of the ceramic insulator 12 which couples the movable electrode rod 4 and the drive rod 7 in FIG. 1 is shown in FIG. As shown in Fig. 2, the drive rod 7 made of SUS and the movable electrode rod 14 made of copper are mechanically connected and electrically disconnected by a ceramic insulator 12 made of alumina. As an example, the joining method between the drive rod 7 made of SUS and the ceramic insulator 12 made of alumina having a smaller thermal expansion coefficient will be described. From the original structure, the outer diameter D1 of the drive rod 7 is larger than the outer diameter D2 of the ceramic insulator 12, but as the first configuration example of the present embodiment, the outer diameter of the joining surface of the drive rod 7 ( D3) is made 0.2 mm or more smaller than the outer diameter D2 of the ceramic insulator 12. For this reason, the groove | channel 15 of 1 mm or more in depth is manufactured in the joining edge part of the drive rod 7, and the joining surface 16 inside this groove | channel is heated through the brazing material (for example, silver brazing material) 17. It bonded by.

In addition, the projection 18 is provided on the joining end surface of the driving rod 7 toward the cylindrical alumina insulator 12 having a hollow portion to facilitate the high temperature soldering operation. It has a joining structure that can be inserted into an inner hole (hollow part) of the cuff and easily positioned.

In addition, the joining method of the alumina insulator 12 and the movable electrode rod 14 made of copper also includes the driving electrode 7 made of SUS and the movable electrode rod 14 made of copper as compared with the thermal expansion rate of the alumina. Since the thermal expansion coefficients are almost the same, the joint structure and the joining method of the driving rod 7 and the alumina should be the same.

In addition, in the 1st structural example which concerns on this embodiment as shown in FIG. 2, it is a joining surface of a metal rod and a ceramic cylindrical body, and the outer diameter of a metal rod side is 0.2 mm or more smaller than the outer diameter of a ceramic cylindrical body. It is a structure which manufactures and abuts with the ceramic cylindrical body, and joins the junction part through a brazing material, and also arrange | positions a protrusion in a metal rod, and fits in the inner hole of a ceramic cylindrical body.

Actions and effects according to the first configuration example will be described with reference to FIG. 4 (1) shows the distribution of the residual stress in the metal rod and the alumina insulator, the whiter urban distribution shows a higher stress range, and the blacker urban distribution shows a lower stress range. In addition, the detail expansion structure of the outer edge part (referred to as a fixed end part in FIG. 4) of a joining surface is shown in the circle | round | yen. 4 is a residual stress distribution in the case where the diameter of the metal rod and the alumina insulator are the same, and the right view shows that the diameter of the metal rod is slightly smaller than that of the alumina insulator as in this configuration example. The experimental result of residual stress distribution in one case is shown. Referring to Fig. 4 (1), it can be seen that the stress range in which the whiter portion is higher is smaller especially in the alumina insulator, and the low stress range is expanded.

4 (2) shows the maximum principal stress characteristics in the three junction structures in the metal rod and the alumina insulator. According to this, it can be seen that the stress applied to the alumina insulator is reduced by making the metal rod (the material of Cu in the experiment of FIG. 4) slightly smaller than the outer diameter of the alumina insulator. As shown, the residual stress in the first structural example is significantly smaller than the other two structural examples even in the vicinity of the bonding surface in the alumina insulator.

From the experimental results shown in FIG. 4, it can be seen that by reducing the outer diameter of the joining surface of the metal rod slightly smaller than the outer diameter of the ceramic cylindrical body, the ranges showing the maximum stress and the high stress can both be significantly reduced. According to the experimental results, when the diameter of D3 shown in FIG. 2 is 0.2 mm smaller than the diameter of D2, the maximum stress and the high stress range are drastically smaller. As the cause, it is thought that the tensile stress caused by the shrinkage of the metal during the cooling process is caused by the dispersion of the tensile stress because the volume subjected to the stress increases significantly on the ceramic insulator side. Referring to the left side of Fig. 4 (1), since the reduction of the metal rod is applied directly to the alumina insulator of the same diameter, the maximum stress and high stress range can be widely distributed or lead to the destruction of the alumina insulator.

Next, a second configuration example of the bonding structure of the vacuum switch according to the embodiment of the present invention will be described with reference to FIGS. 1 and 3. Fig. 3 shows a detailed dimensional relationship in the bonding between the fixed electrode base 10 and the alumina insulator 9 in Fig. 1. According to the second structural example as shown in FIG. 3, the fixed electrode base 10 made of copper, the ceramic cylindrical body 9 made of alumina, and the stress relief composite member 19 are constituted. The joint part of the fixed electrode base 10 made of copper and the ceramic cylindrical body 9 made of alumina is provided with a pre-fabricated stress relaxation composite member 19 and is provided on both joint surfaces of the stress relaxation composite member 19. It joins by heating through the brazing material 20. A protrusion (for example, the load side conductor 11) is provided at the center of the bonding surface of the fixed electrode rod 5. Moreover, the center hole is provided in the center part of the 2nd ceramic member 9, and the said projection part 11 is inserted in the said center hole.

The stress relief composite material 19 uses the same material (eg, alumina) as the center member 21 as the ceramic cylindrical body 9 of the mating partner, and the outer ring member 22 made of copper on the outer circumferential side thereof. It is fitted. The outer diameter D5 of the center member 21 is configured to be smaller than the outer diameter D4 of the fixed electrode base 10 and larger than the outer diameter D6 of the ceramic cylindrical body 9.

In addition, in the 2nd structural example which concerns on this embodiment as shown in FIG. 3, the disk-shaped composite member which fitted the center member with small thermal expansion coefficient to the inner hole of the outer ring member with large thermal expansion coefficient was stressed. As a member for relaxation, it interposes between a metal member and a ceramic member, and joins them.

In the second configuration example, since the ceramic insulator is bonded to the center member (for example, alumina, W, Mo) having the same or smaller thermal expansion rate, the difference in thermal expansion rate on both sides of the bonding interface becomes smaller, and the ceramic insulation Generation of high thermal residual stress in the ruler can be suppressed. Therefore, peeling of a joining surface and the crack of a ceramic insulator can be prevented effectively.

In addition, as a composite member for stress relaxation, in the surface where the center member and the outer ring member are joined by high temperature soldering, in addition to the shrinkage fitting effect caused by the thermal expansion rate of the center member being smaller than the thermal expansion rate of the outer ring member, sufficient bonding interface strength is achieved. Can be obtained. In addition, due to the reduction of the fixed electrode base during the cooling process, the outer ring member 22 (for example, Cu) bonded to the fixed electrode base generates tensile stress, but is less likely to be destroyed because it is a metal member ( Since the metal has an elongation characteristic) and a compressive stress is generated in the center member, a center member made of alumina or the like tends to be cracked in the tensile stress but strong in the compressive stress. Further, in the method of bonding the stress relief composite member to the ceramic insulator and the fixed electrode base, low temperature solder bonding, diffusion bonding, friction welding bonding or glass bonding may be used instead of the high temperature solder bonding (in the first configuration example described above). Is also the same).

Next, the manufacturing method of the composite member for stress relaxation which is a 2nd structural example which concerns on this embodiment is demonstrated, referring FIG. In the vacuum path 23, the outer ring member 25, the center member 26, the weight 31, and the cylinder guide 27 are provided on the sample stage 24 as shown in FIG. In order to facilitate the removal operation after the heat treatment, the outer ring member 25 is combined through the carbon sheet 28 between the guide 27 and the weight 31 and the like. A corner 29 is formed obliquely inside the end of the cylindrical outer ring member 25, and a suitable amount of the brazing material 30 is filled in the gap between the center member 26 and the corner 29.

At room temperature, the inner diameter d1 of the outer ring member 25 is made smaller than the outer diameter d2 of the center member 26 (d1 <d2), and the center member 26 is not dropped. At a high temperature, the outer ring member (for example, Cu) 25 having a high thermal expansion rate expands larger than the center member (for example, alumina) 26 with a small thermal expansion rate, so that d2 < ), The center member 26 falls into the center hole of the outer ring member 25. At the same time, the molten solder material 30 flows downward along the inner wall surface of the outer ring member to fill the gap between the outer ring member 25 and the center member 26.

When it returns to room temperature, the joining of the outer ring member 25 and the center member 26 is completed, and a shrinkage fitting force can be applied to the joining strength by the brazing material 30, and a highly reliable joining interface can be obtained. Thereafter, the rod-shaped stress relaxation composite material prepared as shown in Fig. 5 is cut, and the cut surface is polished and metallized to produce a disk-shaped stress relaxation composite member. In this way, the stress relief composite member 19 as shown in Fig. 3 can be mass-produced by cutting the manufacturing method by cutting after fitting the rod-shaped center member inside the elongated cylindrical outer ring member, thereby reducing the cost. We can plan. The disk-shaped center member may be formed to fit into the inner hole of the outer ring member by any one of high temperature solder bonding, low temperature solder bonding, diffusion bonding, shrink fitting, and integral sintering using a green compact.

As described above, in the vacuum switch according to the embodiment of the present invention, the outer diameter of each of the metal member and the ceramic member in the joint surface is specified so as not to generate a large residual stress in the ceramic member in contact with the metal member. Or (particularly, the outer diameter of the metal rod side is made 0.2 mm or more smaller than the outer diameter of the ceramic cylindrical body at the joining end, and abuts the ceramic cylindrical body and joins the butt part through the brazing material) Intervening between them (specifically, a disk-shaped composite material formed by fitting a center member having a low thermal expansion coefficient into an inner hole of an outer ring member having a large thermal expansion coefficient is interposed between a metal member and a ceramic member as a stress relaxation material. To prevent damage such as cracking of the ceramic member.

According to the present invention, it is possible to reliably reduce the residual stress and to realize a highly reliable ceramic and metal bonding structure, and to improve the reliability of the vacuum circuit breaker to which the bonding structure is applied.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view showing a joining structure of a vacuum switch according to an embodiment of the present invention and showing first and second structural examples.

Fig. 2 is a detailed cross sectional view showing a first structural example of the bonding structure of the vacuum switch according to the present embodiment.

Fig. 3 is a detailed sectional view showing a second structural example of the bonding structure of the vacuum switch according to the present embodiment.

Fig. 4 is a diagram showing the bonded structure according to the present embodiment and the maximum principal stress characteristic in the bonded structure compared with the prior art.

FIG. 5 is an explanatory diagram illustrating a method of manufacturing a stress relief composite member, which is a second structural example of the present embodiment. FIG.

Fig. 6 is a sectional view showing a general internal structure of a vacuum switch in the prior art.

Fig. 7 is a diagram showing a bonding cross section between a ceramic and a metal in the vacuum switch according to the prior art.

8 is a diagram showing a stress distribution in a joint structure of a ceramic and a metal of the prior art.

<Explanation of symbols for the main parts of the drawings>

1: vacuum vessel

2: fixed electrode

3: movable electrode

4, 14: movable electrode rod

5: fixed electrode rod

6: flexible conductor

7: switchgear drive rod

8, 9, 12, 21: ceramic member (for example, alumina insulator)

10: fixed electrode base

11: load side conductor

13, 19: stress relief composite member

15: home

16: joint surface

17, 20, 30: soldering material

18: protrusion

21, 26: center member of the stress relief composite member

22, 25: outer ring member of the stress relief composite member

23: vacuum furnace

24: sample stand

27: guide

28: carbon sheet

29 corners

31: weight

Claims (12)

A plurality of electrode pairs in which a vacuum container, a plurality of movable electrodes and a fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and In a vacuum switch comprising a flexible conductor for connecting a plurality of movable electrode rods to each other, and a drive rod for driving the movable electrode rod, A first ceramic member interposed between the drive rod and the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod, The bonding structure between the first ceramic member and the metal rod made of the driving rod and the movable electrode rod has an outer diameter of the metal rod 0.2 mm or more smaller than the outer diameter of the ceramic member, and solders the metal rod and the ceramic member. A vacuum switch characterized in that the bonding to the ash. A plurality of electrode pairs in which a vacuum container, a plurality of movable electrodes and a fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and In a vacuum switch comprising a flexible conductor for connecting a plurality of movable electrode rods to each other, and a drive rod for driving the movable electrode rod, A first ceramic member interposed between the drive rod and the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod, Between the second ceramic member and the fixed electrode rod is a stress relief composite member in which the bonding structure between the second ceramic member and the fixed electrode rod relaxes the stress of the second ceramic member due to the reduction of the fixed electrode rod. A vacuum switch, characterized in that bonded to the intervening. The said stress relief composite member is comprised from the disk shaped center member which has an outer diameter larger than the outer diameter of the said 2nd ceramic member, and the outer ring member fitted to the outer peripheral side of the said center member, The inner diameter of the outer ring member is a vacuum switch, characterized in that less than the outer diameter of the fixed electrode rod. The disk-shaped center member is made of a material having a coefficient of thermal expansion equal to or less than that of the second ceramic member. And the outer ring member is made of a material having a small difference from the thermal expansion rate of the fixed electrode rod. The inner hole of the outer ring member according to claim 3 or 4, wherein the disk-shaped center member is formed by any one of high temperature solder bonding, low temperature solder bonding, diffusion bonding, shrink fitting, and integral sintering by a green compact. A vacuum switch characterized in that it is formed to fit in. A plurality of electrode pairs in which a vacuum container, a plurality of movable electrodes and a fixed electrode housed in the vacuum container face each other, a movable electrode rod connected to the movable electrode, a fixed electrode rod fixing the fixed electrode, and The vacuum switch in the vacuum switch provided with a flexible conductor connecting the plurality of movable electrode rods to each other, a drive rod for driving the movable electrode rod, and a second ceramic member interposed between the vacuum vessel and the fixed electrode rod. It is a stress relaxation composite member that relaxes the stress of the second ceramic member, The stress relief composite member is composed of a disk-shaped center member having an outer diameter larger than the outer diameter of the second ceramic member, and an outer ring member fitted to the outer circumferential side of the center member, The inner diameter of the outer ring member is smaller than the outer diameter of the fixed electrode rod stress relief composite member. The disk-shaped center member is made of a material having a coefficient of thermal expansion equal to or less than that of the second ceramic member. And the outer ring member is made of a material having a small difference from the thermal expansion rate of the fixed electrode rod. It is a manufacturing method of the composite member for stress relaxation of Claim 6 or 7, Fit the long rod-shaped center member in advance into the inner hole of the tubular outer ring member of the same length, The composite member which consists of the said rod-shaped center member and the outer ring member is cut | disconnected, and the disk type stress relaxation composite member of the appropriate thickness is manufactured, The manufacturing method of the stress relaxation composite member characterized by the above-mentioned. The vacuum switch as claimed in claim 1, wherein the vacuum switch is a low temperature solder joint, a diffusion joint, a friction welding joint, or a glass joint instead of the high temperature solder joint for joining the metal rod and the ceramic member. The method according to any one of claims 2 to 4, wherein the bonding between the stress relieving composite, the second ceramic member, and the fixed electrode rod is performed by high temperature solder bonding, low temperature solder bonding, diffusion bonding, friction welding, or the like. A vacuum switch, characterized in that the glass bonding. The method of claim 1, wherein a protrusion is provided at the center of the joining surface of the metal rod, and a center hole is provided at the center of the first ceramic member. And the protrusion is inserted into the central hole. The projection part is provided in the center part of the joining surface of the said fixed electrode rod, The center hole is provided in the center part of the said 2nd ceramic member, And the protrusion is inserted into the central hole.