JPH07172946A - Joined product between ceramic part and metallic part - Google Patents

Abstract

PURPOSE:To relax the residual stress in a joined product and secure the insulation properties and the air tightness in the joined part by adjusting the value obtained by dividing the product of the melting point of a brazing material, the difference in thermal expansion coefficient between a ceramic and a metal and the wall thickness of the ceramic material by the thickness of the metallic material to lower than a specific value in the joined material where the metallic material is brazed to a cylindrical ceramic part on both ends with the brazing material. CONSTITUTION:When the wall thickness of the ceramic part (1/2 of the difference between the outer and inner diameters) is represented by D; the wall thickness of the metallic part, C; the difference in thermal expansion coefficient between the ceramic and the metal (the average thermal expansion coefficient from room temperature to the melting point of the brazing material, DELTAalpha(/ deg.C); the melting point M( deg.C) of the brazing material, M.DELTAalpha.D/ deg.C, their product is adjusted to be less than 6X10<-3>. A metallic part of a disk having a round hole (2a) on its center such as kovar 2 of low thermal expansion is applied to the cylindrical ceramic part 1 on its both ends. The joining is done by arranging the foil of the active brazing metallic foil between the ceramic body 1 and the disks 2 and heating them at 950 deg.C for 5 minutes in vacuum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable bonded body of a ceramic member and a metal member in which a residual stress in a brazed bonded body is relaxed, and particularly to an insulating property and an airtightness of a bonded portion. Regarding things that can ensure sex.

[0002]

2. Description of the Related Art Ceramics such as silicon nitride and alumina have excellent insulating properties and mechanical properties, and a bonded body of such ceramics and a metal having excellent workability has an insulating property, airtightness of the bonding portion and high bonding. The need as a joining member that requires strength is increasing. For example, a joining member having a structure in which a metal member such as a disk having a hole in the center or a pipe with a flange is joined to both ends of a cylindrical silicon nitride member has a wide range of applications as a device component.

When an organic adhesive or the like is used for joining silicon nitride and metal, the joining strength and reliability are low. Therefore, brazing using a brazing material containing an active metal such as titanium and metallizing the joining surface of silicon nitride. It is performed by silver brazing or the like after processing. However, due to residual stress caused by the difference in the thermal expansion coefficient between silicon nitride and the metal generated during the cooling process after heating and joining during brazing, the silicon nitride is destroyed or the silicon nitride and metal are separated. In some cases, the airtightness of the bonded body cannot be maintained. This residual stress increases as the melting point of the brazing material increases and the difference in thermal expansion coefficient between silicon nitride and metal increases.

In order to prevent the destruction of the silicon nitride and the separation of the metal from the silicon nitride, Kovar having a low coefficient of thermal expansion is used as the metal to be joined, or the joining surface of the metal member is extremely made depending on the structure and shape of the metal member. A method such as a narrow structure has been adopted.

[0005]

However, even if Kovar is used as the metal to be joined, ceramics such as silicon nitride will be destroyed if brazing is performed without devising the structure of the joined body, resulting in airtightness of the joined body. May not be retained. Even if the ceramics are not immediately destroyed, a large residual stress exists in the bonded body, cracks may develop in the ceramics during use, and the airtightness of the bonded body may deteriorate. Further, the fact that the metal to be bonded is limited to a low thermal expansion metal such as Kovar may cause a problem in the design of the bonded body.

Further, in the method of brazing and joining to a ceramic such as silicon nitride by making the joining surface of the metallic member extremely narrow depending on the structure and shape of the metallic member, the ceramic and the metal are joined in a very small area. Because it will be
The mechanical strength and the like during use may destroy the joints, making it impossible to maintain airtightness.

The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a highly reliable bonded body of a ceramic member and a metal member in which residual stress in the bonded body is relaxed. To aim.

[0008]

A joined body of a ceramic member and a metal member of the present invention is a joined body in which a metal member is brazed to both ends of a cylindrical ceramic member, and the meat of the cylindrical ceramic member is formed. Thickness (1 / the difference between the outer diameter and the inner diameter)
2) is D, the thickness of the metal member is C, the difference in coefficient of thermal expansion between ceramics and metal (average coefficient of thermal expansion from room temperature to the melting point of the brazing material) is Δα (/ ° C), and the melting point of the brazing material is M ( C)), M · Δα · D / C is 6 × 10 ⁻³ or less.

In the joined body of the ceramic member and the metal member of the present invention, examples of ceramics include silicon nitride and alumina. Further, examples of the metal member include Kovar, stainless steel and the like.

When a ceramic member such as silicon nitride or alumina and a metal member such as Kovar or stainless steel are brazed and joined, a heat treatment is performed at a temperature higher than the melting point of the brazing material. At the following temperatures,
The joint surface is constrained, and the residual stress due to the difference in thermal expansion coefficient between the ceramic and the metal increases in the joint body as the temperature decreases. In particular, ceramics have low toughness, so
The residual stress in the ceramic may cause the ceramic to break.

Generally, the magnitude of this residual stress is proportional to the melting point M (° C.) of the brazing material and the difference Δα (/ ° C.) in the coefficient of thermal expansion between the ceramic and the metal. That is, also in the joined body of the ceramic member and the metal member, the higher the melting point of the brazing material, the larger the difference in the coefficient of thermal expansion between the ceramic and the metal,
Residual stress becomes large, and in order to produce a bonded body with high reliability without destruction of ceramics, peeling of the bonded portion between ceramics and metal, special measures must be taken in the bonded body structure.

The present inventors have found that FIG. 1 and FIG. 2 or FIG.
And a circular plate 2 having a circular hole 2a with a diameter of 6 mm at the center as a metal member at both ends of the main body 1 as a cylindrical ceramic member shown in FIG. 4 (FIGS. 1 and 2).
Alternatively, the tubular body 3 (FIGS. 3 and 4, the tubular portion 3a, in which the disc-shaped flange portion 3b is integrally provided at the end of the cylindrical tubular portion 3a)
Length: 20 mm, wall thickness of tube portion 3 a: 2 mm, inner diameter: 6
mm) for a joined body, the thickness D (D: 1/2 of the difference between the outer diameter and the inner diameter) of the cylindrical main body 1 and the disk 2 or the metal member as the metal members at both ends. By limiting the thickness C of the flange portion 3b of the tubular body 3, the joined body having high reliability without breakage of the main body 1, separation of the joined portion 4 between the main body 1 and the disc 2 or the flange portion 3b, etc. It was found that the production of

That is, the smaller the wall thickness D of the main body 1 is, and the larger the thickness C of the disk 2 or the flange portion 3b at both ends is, the more the residual stress in the bonded body is relaxed and the ceramic body is made of ceramics. The destruction of the main body 1 and the peeling of the joint portion 4 are suppressed. At this time, when the metal to be joined is stainless steel or the like having a large thermal expansion coefficient as compared with Kovar or the like which is a low thermal expansion metal, the wall thickness D of the cylindrical main body 1 is smaller and the discs 2 at both ends are Thickness C of flange 3b
Needs to be larger.

Here, the cylindrical main body 1 made of silicon nitride is used.
The effect of the wall thickness D and the thickness C of the disk 2 or the flange portion 3b made of metal at both ends is expressed by the ratio D / C of both, and further, ceramics that significantly affects the residual stress in the joined body. Taking into consideration the difference Δα in the coefficient of thermal expansion of metal (average coefficient of thermal expansion from room temperature to the melting point of the brazing material) and the melting point M of the brazing material, and defining the value M · Δα · D / C, From the results of the comparative example, if the bonded body is designed so that this value is 6 × 10 ⁻³ or less, it becomes possible to manufacture a highly reliable bonded body of the cylindrical ceramic member and the metal member.

[0015]

EXAMPLES Next, the present invention will be described in detail with reference to Examples and Comparative Examples. As shown in FIGS. 1 and 2, Examples 1 to 8 and Comparative Examples 1 to 10 of the present invention have a circular shape having a diameter of 6 mm at the center of both ends of a main body 1 made of silicon nitride as a cylindrical ceramic member. 2 is an example in which the disc 2 as a metal member having the hole 2a is joined, and Examples 9 to 11 and Comparative Examples 11 to 13 are both end portions of the same main body 1 as described above, as shown in FIGS. 3 and 4. Further, as the metal member, the flange portion 3b of the tubular body 3 in which the disk-shaped flange portion 3b is integrally provided at the end of the cylindrical tubular portion 3a (the length of the tubular portion 3a: 20 m
m, the tube portion 3a has a wall thickness of 2 mm, and an inner diameter of 6 mm.

In these bonded bodies, the length A (mm) and the wall thickness D (mm) of the main body 1 made of silicon nitride (D:
The difference between the outer diameter and the inner diameter is ½), the diameter B (mm) and the thickness C (mm) of the disc 2 or the flange portion 3b are changed, and bonded bodies having various structures are manufactured. Where body 1
And the diameter B of the disc 2 or the flange portion 3b joined to both ends of the main body 1 are the same.

The metal constituting the disk 2 or the flange portion 3b is Kovar (composition:
Iron 54% by weight-Nickel 29% by weight-Cobalt 17% by weight) or stainless steel SUS430 (composition:
Iron 81.75 wt% -Chromium 17 wt% -Molybdenum 1
Wt% -0.75 wt% silicon) was used. The average coefficient of thermal expansion from room temperature to 800 ° C. (melting point of the brazing material) is 10.5 × 10 ⁻⁶ / ° C. for Kovar and SUS430.
Is 12.5 × 10 ⁻⁶ / ° C. Further, the average thermal expansion coefficient of silicon nitride forming the main body 1 is 3.5 × 10 ⁻⁶ / ° C.
Is.

The thickness of the joint is 0.05 m according to the joint surface.
m ring-shaped active metal wax (composition: silver 70.5% by weight)
-Copper 26.5% by weight-Titanium 3% by weight, melting point: 800
(° C) foil was placed between the main body 1 and the disk 2 or the flange portion 3b, and the test was performed in vacuum at 950 ° C for 5 minutes.

The bonded body was evaluated as follows. That is, for a bonded body of the main body 1 made of silicon nitride, which is not observed to be broken at room temperature, the bonded disk 2 and one hole 2a and the tube portion 3a of the tube body 3 are closed, and the other hole 2a and the tube portion 3a are filled with helium. It was connected to a detector and checked for air tightness. Further, with respect to the bonded body which kept airtightness at room temperature, after immersing the bonded body in liquid nitrogen, observation of breakage of the main body 1 and inspection of airtightness by a helium detector were performed.

Here, after the evaluation at room temperature, the evaluation after immersion in liquid nitrogen was carried out. At the liquid nitrogen temperature, the residual stress in the bonded body was enlarged as compared with the residual stress at room temperature. This is because the bonded body was evaluated under more severe conditions and it was thought that this was related to the reliability of the bonded body. That is, the bonded body that maintains airtightness even after immersion in liquid nitrogen is
It is assumed that there is almost no possibility that a crack will develop in the main body 1 or the airtightness of the bonded body will deteriorate during use at room temperature. The results of Examples and Comparative Examples are as shown in Table 1.

[0021]

[Table 1]

(Example 1 and Comparative Examples 1 and 2)
Using Kovar's disk 2 as the metal member, A is 30 m
In this example, m and B are fixed to 30 mm and C is fixed to 2 mm, and the thickness D of the main body 1 made of silicon nitride is changed to 2, 6, and 10 mm. In this case, Example 1 in which D was 2 mm retained airtightness even after immersion in liquid nitrogen, but Comparative Examples 1 and 2 in which D was increased to 6 and 10 mm broke the main body 1 by immersion in liquid nitrogen. When the wall thickness D of the main body 1 is reduced, the residual stress in the bonded body is relieved.

(Examples 2 and 3) In these examples, Kovar's disc 2 was used as a metal member, and A was 30 mm and B was 30 mm.
mm and C are fixed to 10 mm, and the thickness D of the main body 1 is set to 2, 1
In this example, the length is changed to 0 mm. In this case, both of them maintained airtightness even after immersion in liquid nitrogen. From the results of Comparative Example 2 and Example 3, when the thickness C of the disc 2 to be joined is increased, the residual stress in the joined body is relaxed.

(Examples 4 and 5 and Comparative Example 3)
The disk 2 of SUS430 is used as the metal member, and A is 3
In this example, 0 mm, B is 30 mm, D is fixed to 2 mm, and the thickness C of the disc 2 is changed to 10, 6, and 2 mm. In this case, in Examples 4 and 5 in which C was 10 and 6 mm, the airtightness was maintained even after immersion in liquid nitrogen, but in Comparative Example 3 in which C was reduced to 2 mm, the main body 1 was broken by immersion in liquid nitrogen. If the thickness C of the discs 2 to be joined is reduced, the residual stress in the joined body increases.

Furthermore, Comparative Example 3 (SU having the same bonded structure)
When S430 is used) and Example 1 (using Kovar) is compared, Example 1 maintains airtightness even after immersion in liquid nitrogen, and thus SUS430 having a large difference in thermal expansion coefficient from silicon nitride.
The residual stress of the joined body using is increased.

(Comparative Examples 4 and 5) In these, the disc 2 of SUS430 was used as the metal member, A was fixed to 30 mm, B was 30 mm, and C was 2 mm, and the thickness D of the main body 1 was 6,
In this example, the length is changed to 10 mm. In Comparative Example 3 in which D was 2 mm, the silicon nitride did not break at room temperature, but in this case, Comparative Examples 4 and 5 were both silicon nitride main body 1 at room temperature.
Was destroyed. Increasing the thickness D of the main body 1 made of silicon nitride increases the residual stress in the bonded body.

(Comparative Example 6) This is SU as a metal member.
Using the disc 2 of S430, A is 30 mm, B is 30 m
In this example, m and C are 10 mm and D is 10 mm. In this case, the main body 1 of silicon nitride was broken by immersion in liquid nitrogen. In Example 3 (using Kovar) having the same bonded structure, airtightness was maintained even after immersion in liquid nitrogen. Therefore, as compared with this, SUS having a large difference in thermal expansion coefficient from silicon nitride.
The bonded body using 430 has an increased residual stress.

(Example 6 and Comparative Example 7) These use Kovar's disc 2 as a metal member. Example 6 is compared with Example 1, Comparative Example 7 is compared with Comparative Example 1, and main body 1 is Only the height A is changed from 30 mm to 60 mm. In this case, as in Example 1 and Comparative Example 1, Example 6
The airtightness was maintained even after immersion in liquid nitrogen, but Comparative Example 7
Then, the main body 1 was broken by immersion in liquid nitrogen. The height A of the cylindrical body 1 to be joined does not seem to have a great influence on the residual stress.

(Example 7 and Comparative Example 8) These use Kovar's disc 2 as a metal member. Example 7 is used for Example 1, Comparative Example 8 is used for Comparative Example 1, and disc 2 is used. It is also possible to change only the diameter B and the outer diameter of the main body 1 from 30 mm to 60 mm. In this case, like Example 1 and Comparative Example 1, in Example 7, the airtightness was maintained even after immersion in liquid nitrogen, but in Comparative Example 8, the main body 1 was broken by immersion in liquid nitrogen. The diameter B of the disc 2 to be joined and the outer diameter of the main body 1 do not seem to have a great influence on the residual stress.

(Example 8 and Comparative Example 9) These use Kovar's disc 2 as a metal member, and Example 8 is for Example 1, Comparative Example 9 is for Comparative Example 1, A, B , C,
D is doubled. In this case, like Example 1 and Comparative Example 1, in Example 8, the airtightness was maintained even after immersion in liquid nitrogen, but in Comparative Example 9, the main body 1 was broken by immersion in liquid nitrogen. Even if the dimensions of the bonded body are changed, if the ratio is the same, the residual stress does not seem to be significantly affected.

(Comparative Example 10) In this example, a Kovar disk 2 is used as a metal member, and the thickness C of the disk 2 bonded to both ends of the main body 1 made of silicon nitride is 2 mm for one side and 1 for the other side.
It is 0 mm. Comparative Example 2 (the thickness C of the disk 2 is 2 mm at both ends) except for the thickness C of the disk 2 bonded to one end of the main body 1, Example 3 (the thickness C of the disk 2 at both ends is 10 m)
Same as m). In this case, the main body 1 broke on the side where the thickness C of the disc 2 was 2 mm by immersion in liquid nitrogen. When the discs 2 having different thicknesses are joined to both ends of the body 1, the disc 2 having the smaller thickness C seems to dominate the destruction of the body 1.

(Example 9 and Comparative Examples 11 and 12) In these examples, a tube body 3 having a flange portion 3b made of Kovar is used as a metal member, A is 30 mm, B is 30 mm, and C is 30 mm.
Is fixed to 2 mm, and the thickness D of the main body 1 made of silicon nitride is changed to 2, 6, and 10 mm. In this case, D
In Example 9 having a diameter of 2 mm, the airtightness was maintained even after immersion in liquid nitrogen, but Comparative Examples 11 and 1 in which D was increased to 6 and 10 mm.
In No. 2, the main body 1 of silicon nitride was broken by immersion in liquid nitrogen. When the wall thickness D of the main body 1 is reduced, the residual stress in the bonded body is relieved. This result is shown in Example 1 in the case of the disc 2.
And the same as Comparative Examples 1 and 2.

(Examples 10 and 11 and Comparative Example 13) In these, a tubular body 3 made of SUS430 with a flange portion 3b was used as a metal member, and A was 30 mm and B was 30 m.
In this example, m and D are fixed to 2 mm, and the thickness C of the flange portion 3b of the SUS430 to be joined is changed to 10, 6, and 2 mm. In this case, Examples 10 and 1 in which C is 10 and 6 mm
No. 1 kept airtightness after immersion in liquid nitrogen, but C was 2m
In Comparative Example 13 having a small m, the silicon nitride main body 1 was broken by immersion in liquid nitrogen. When the thickness C of the flange portion 3b made of metal to be joined is reduced, the residual stress in the joined body increases. The results are the same as those of Examples 4 and 5 and Comparative Example 3 in the case of the disc.

As is clear from the above Examples and Comparative Examples,
Factors that greatly affect the destruction of ceramics such as silicon nitride due to the residual stress in the bonded body are the wall thickness D of the cylindrical ceramic member and the thickness C of the metal member bonded to both ends. The smaller the wall thickness D of the cylindrical ceramic member and the larger the thickness C of the metal members bonded to both ends, the more the residual stress in the bonded body is relaxed, and the destruction of ceramics such as silicon nitride is suppressed. It

Here, the tubular body 3 with the flange portion 3b
When the flange portion 3b is regarded as the circular plate 2, the pipe portion 3a becomes a portion associated with it. That is, the present invention can be applied to a metal member having a portion associated with the disc. In this case, the thickness C of the metal member is the thickness of the disc portion such as the flange portion 3b. In addition, since the magnitude of the residual stress related to the fracture of ceramics is proportional to the difference in the coefficient of thermal expansion of the metal to be joined to the ceramics, compared to the joined body in which Kovar is joined, the one in which SUS430 is joined is The body structure will be more limited.

Further, the residual stress associated with the destruction of ceramics such as silicon nitride reaches the melting point of the brazing filler metal during the cooling process at the time of bonding, the bonding surface is constrained, and the shrinkage of the ceramics and metal in the subsequent cooling process. Will increase as a result of the mismatch, and its size at room temperature will be approximately proportional to the melting point of the braze. Here, the effect of the thickness (1/2 of the difference between the outer diameter and the inner diameter) D (mm) of the cylindrical silicon nitride member and the thickness C (mm) of the metal member bonded to both ends thereof is compared with each other. It is expressed by D / C, and further, the difference Δα (/ in the coefficient of thermal expansion between ceramics and metal (the average coefficient of thermal expansion from room temperature to the melting point of the brazing material) that significantly affects the residual stress in the joined body.
℃) and the melting point M (℃) of the brazing filler metal are taken into consideration.
Define the value D / C. In the case of this example and the comparative example,
M is 800 ° C., Δα of the joined body using Kovar is 7.
0 × 1 ⁻⁶ , Δα of the joined body using SUS430 is 9.0 × 10 ⁻⁶ . As shown in Table 1, M ・ Δα ・
If the bonded body is designed so that the value of D / C is 6 × 10 ⁻³ or less, the silicon nitride does not break even after immersion in the liquid chamber,
It is possible to produce a highly reliable cylindrical bonded body of a silicon nitride member and a metal member that maintains airtightness.

[0037]

As described above, according to the present invention, it is possible to provide a highly reliable bonded body structure of a ceramic member such as silicon nitride and a metal member in which residual stress in the brazed bonded body is relaxed. It will be possible. A joined body using this joined body structure is used as a joined member or the like that requires airtightness and insulation.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a joined body of a ceramic member and a metal member of the present invention.

FIG. 2 is a vertical cross-sectional view of the joined body of FIG.

FIG. 3 is a plan view showing another example of a joined body.

4 is a vertical cross-sectional view of the joined body of FIG.

[Explanation of symbols]

1 Main Body as Ceramics Member 2 Disc as Metal Member 3 Tubular Body as Metal Member 3b Flange Part of Tubular Body 4 Joint between Ceramics Member and Metal Member A Length of Main Body 1 as Ceramics Member (mm) B Diameter of the disk 2 or the flange 3b of the tube 3 as a metal member C Thickness of the disk 2 or the flange 3b of the tube 3 as a metal member D Thickness of the main body 1 as a ceramic member

Claims (4)

[Claims] 1. A joined body in which metal members are brazed to both ends of a cylindrical ceramic member, wherein the thickness (1/2 of the difference between the outer diameter and the inner diameter) of the cylindrical ceramic member is D. Let C be the thickness of the member, Δα (/ ° C) be the difference between the coefficient of thermal expansion of ceramics and metal (average coefficient of thermal expansion from room temperature to the melting point of the brazing material), and M be the melting point of the brazing material.・
Δα · D / C is 6 × 10 ⁻³ or less, a joined body of a ceramic member and a metal member. 2. The joined body of a ceramic member and a metal member according to claim 1, wherein the ceramic member is made of silicon nitride. 3. The joined body of a ceramic member and a metal member according to claim 1, wherein the metal member is made of Kovar. 4. The joined body of a ceramic member and a metal member according to claim 1, wherein the metal member is made of stainless steel.