JPH01141881A - Method for bonding porous ceramic to metal - Google Patents

Abstract

PURPOSE:To firmly bond a porous ceramic to a metal without producing cracking, etc., by interposing a ceramic having about the same thermal expansion coefficient as the porous ceramic and higher strength between the bonding surfaces. CONSTITUTION:A ceramic 20 (e.g., high-strength alumina ceramics) having a thermal expansion coefficient equivalent or similar to that of a porous ceramic 1 (e.g., porous alumina ceramics) and higher strength than the ceramic 1 is interposed between the ceramic 1 and a metal 3 (e.g., copper sheet). In this case, the porous ceramic 1 is firstly bonded to the ceramic 20, and then the ceramic 20 is bonded to the metal 3. As a result, thermal stress is not developed between the porous ceramic 1 and the ceramic 20 during the bonding, and the thermal stress developed between the ceramic 20 and the metal 3 is absorbed by the high-strength ceramic 20.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for joining ceramics and metal.

[Prior Art] Porous ceramics are often used in conjunction with metals in various fields that take advantage of their properties.

When joining ceramics and metals, it is particularly important to use various methods to relieve thermal stress caused by the difference in coefficient of thermal expansion between the two. In general, a soft metal is interposed between ceramics and metal to buffer thermal stress through its deformation.
Techniques disclosed in JP-A-0-246276, Japanese Patent Laid-Open No. 60-231476, etc. have been proposed.

These technologies propose methods for buffering thermal stress, and the gist of these technologies is to buffer thermal stress by interposing a metal with a coefficient of thermal expansion intermediate between ceramics and metal. be.

[Problems to be solved by the invention] However, porous ceramics generally have a drawback of low strength due to their low density, and it is difficult to obtain a bonding strength that can be used in practical use even if the above-mentioned method of buffering the thermal stress generated during bonding is used. Furthermore, if the thermal stress is not sufficiently relaxed, cracks may occur in the porous ceramic due to the thermal stress, and the bonded body may be destroyed. The aim is to provide a method for joining ceramics and metal.

[Means for Solving the Problems] When joining porous ceramics and metal, the present invention provides a bonding surface between the porous ceramics and the metal with a coefficient of thermal expansion equal to or similar to that of the porous ceramics. The above-mentioned problems are to be solved by a method of joining porous ceramics and metal, which is characterized by interposing and joining ceramics having a higher strength than the porous ceramics.

[Operations] The specific configuration and operations of the present invention will be explained based on the drawings.

FIG. 1 is a cross-sectional view for explaining the joining method based on the present invention, in which 1 represents porous ceramics, 2 represents an intervening layer to be described later, and 3 represents metal. The intervening layer 2 is made of a dense fired ceramic having the same composition as the porous ceramic 1, for example, having a coefficient of thermal expansion equal to or similar to that of the porous ceramic 1, and having a higher strength than the porous ceramic 1. . (The ceramic forming this intervening layer is hereinafter referred to as intervening ceramic 20).

When joining the porous ceramic 1 to the metal 3, the intervening ceramic 20 is formed in advance by means such as press molding or processing of fired ceramics. Next, the metal 3 and the intervening ceramic 20 are bonded using, for example, an active metal brazing material, or by metallizing (active metal paste method, Mo-Mn method, etc.) to join the intervening ceramic in advance.
After that, they are joined using ordinary brazing material or the like. After holding,
Intermediate ceramic 20 and porous ceramic 1 are oxide soldered.

Alternatively, an intervening layer having the above function can be formed on the bonding surface between the metal 3 and the porous ceramic 1 by bonding using active metal wax or the like.

Note that the joining of the metal 3 and the intervening ceramic 2o described above,
Although it is desirable that the intervening ceramic 2o and the porous ceramic 1 be bonded in descending order of bonding temperature, they may be bonded simultaneously in some cases.

FIG. 2 is a sectional view showing another joining method according to the present invention.

In this example, a thermal stress buffering layer 4 made of copper, which is a soft metal, or a metal having a coefficient of thermal expansion intermediate between that of the intervening ceramic and the metal, is interposed on the bonding surface between the metal 3 and the intervening ceramic 2o. Porous ceramics 1
This is particularly effective when the expansion coefficients of the metal 3 and the metal 3 are significantly different.

As described above, the present invention forms the intervening layer 2 made of the intervening ceramic 20 on the joint surface between the porous ceramic 1 and the metal 3, so that the thermal expansion coefficients of the ceramic 1 and the intervening layer 2 are equal or almost equal. Therefore, no thermal stress is generated between the porous ceramic 1 and the intervening layer 2 during bonding, or even if thermal stress is generated, only a very weak stress is generated.

On the other hand, in the configuration of the present invention, between the intervening layer 2 and the metal 3,
Thermal stress that occurs when ceramics 1 and metal 3 are laminated and bonded, or ceramics 1 and thermal stress buffer layer 4
A thermal stress approximately equal to the thermal stress generated when the metal 3 and the metal 3 are laminated and bonded is generated. However, this thermal stress, which may destroy the porous ceramic 1, is absorbed by the intervening layer 2, which is stronger than the porous ceramic 1, and therefore has almost no effect on the brittle porous ceramic 1. As a result, a bonded body of porous ceramics and metal with strength suitable for practical use can be obtained.

Of course, in the present invention, the thermal stress buffer layer 4 whose structure is shown in FIG.
Although it is desirable to use this, it is not an essential condition as long as the intervening layer 2 can be used that has sufficient strength to absorb the thermal stress generated during bonding.

[Example 1] Porous alumina ceramics (purity 95%, porosity 27
%2 bending strength 4.23kgf/m@”, 20mmX2
0mm x 5mat) and SUS 316 (30mm
25mm x 12mmt) was joined. Porous alumina ceramics and very dense high strength alumina ceramics with the same composition as this porous alumina ceramics (purity 95%, porosity 3%2 bending strength 31kgf/m)
s'', 20mm x 20mm x 2mmt) was coated with oxide solder kneaded with screen oil, and after drying, both sides were bonded together and heated at 900°C.

Heat treatment was performed for 10 minutes to bond the ceramics together.

Next, an Ag-Cu-Ti based paste was applied to the surface of the dense alumina ceramics of the ceramic bonded body, and after drying, a metallizing treatment was performed for 30 minutes in a vacuum furnace at 850°C. On the metallized surface of this ceramic,
B Ag-8 (JIS 2.3261-76) plate brazing material and thermal stress buffer layer 20am x 20mm x
O, a 5m+nt copper plate is arranged, and this copper plate and 5US316
Similarly, BAg-8 and plate brazing material were charged and laminated at 840°C.

Brazing was performed in an Ar atmosphere for 10 minutes. In the case of a bonded body without intervening dense alumina ceramic, which was carried out in parallel, cracks occurred in the porous ceramic after brazing, and the porous ceramic was more broken than the porous ceramic and could not be bonded. The bonded body of porous alumina ceramics and metal, which is composed of ceramics, dense high-strength alumina ceramics, copper plate, and SO3316 material, was firmly bonded without any cracks, and a bonded body with sufficient strength for practical use was obtained. .

[Example 2] Porous alumina ceramic cylinder with fine pores (purity 92%, porosity 28%2 bending strength 3.29 kgf/m
92% Al1, the same as porous alumina ceramics, on one end surface of the
Dense alumina ceramics with ゜03 purity and same diameter thickness 3+am (porosity 3%9 bending strength 26kgf/ma)
+'') Next, 5US316 disks (35 mm+φ, thickness 5 mm+) were placed, a washer brazing material of BAg-8 composition containing 1% Ti was inserted into each gap, and the mixture was heated at 860°C in a vacuum furnace.

Brazing was performed for 10 minutes. Porous alumina ceramics is connected to SO53 through a dense alumina ceramic ring.
A bonded body was obtained which was completely bonded to the No. 16 disc and had sufficient strength for practical use.

[Effects of the invention Porous ceramics made from not only core alumina but also silicon nitride and other ceramics can be used in various fields such as separation materials for solid-liquid and solid-gas mixtures, insulation materials, and sensor materials. It is thought that this number will continue to increase. As for how to use it, it is required to use it under higher temperature and pressure, and the requirements for the bonding strength between porous ceramics and metal bonded bodies are becoming even more severe.

The present invention provides a method for joining porous ceramics and metal that fully meets these industrial demands, and is very effective in practice.

[Brief explanation of the drawing]

FIGS. 1 and 2 show typical cross-sectional structures of the joined body of the present invention. 6 1. Porous ceramics, 2. Intervening layer, 3. Metal 4, thermal stress buffer layer patent applicant Nippon Steel Corporation

Claims (1)

[Claims] When joining porous ceramics and metal, a ceramic having a coefficient of thermal expansion equal to or similar to that of the porous ceramic and having a higher strength than the porous ceramic is interposed on the joining surface of the porous ceramic and the metal. A method for joining porous ceramics and metal, which is characterized by mounting and joining.