JPH01179770A - Method for bonding metal and ceramic - Google Patents

Abstract

PURPOSE:To reduce the residual thermal stress and to improve the bonding strength by superposing a metal and a ceramic on each other, heating the laminate to a specified temp., and simultaneously exerting a fluctuating pressure on the contact surface. CONSTITUTION:A metal 22 and a ceramic 24 are pinched between the opposed end faces of the upper anvil 16 and lower anvil 18 connected through the load cell 14 of a crosshead 12 connected to a strut 10, and a silicon glass tube 26 is inserted into the holes of members 28 and 30 and hermetically sealed with sealing materials 32 and 34 to enclose the peripheries of the anvils 16 and 18. A specified gas is introduced into the glass tube 26 from a gas supply pipe 38 provided on the member 28, and heated by an IR image heating furnace 44 to a temp. lower than the m.p. of the metal and higher than the recrystallization temp. An actuator piston 20 is simultaneously actuated to exert a fluctuating pressure at 10-100Hz frequency in the direction intersecting orthogonally with the contact surfaces of the metal 22 and the ceramic 24, and the gas is cooled under such conditions to a temp. lower than the recrystallization temp.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for joining metal and ceramics.

(b) Conventional Techniques A conventional method for bonding ceramics to metal is disclosed in Japanese Patent Laid-Open No. 174582/1982. The joining method shown in this paper overlaps metal and ceramics,
It is characterized by placing a metal oxide layer between them, maintaining the temperature below the melting point of the metal in vacuum or an inert gas atmosphere, and pressurizing at a constant pressure.

(c) Problems to be Solved by the Invention However, the conventional method of joining metal and ceramics as described above has a problem in that the joining strength is not sufficient. That is, in the cooling process after joining the ceramic and metal, large thermal stress is generated due to the difference in coefficient of thermal expansion between the ceramic and the metal. Therefore, the strength of the joint decreases. Further, since the joint between the ceramic and the metal is merely pressurized with a constant pressure, diffusion in the joint is insufficient, and sufficient joint strength cannot be obtained. The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention solves the above problems by applying variable pressure to the joint surface between metal and ceramics. That is, the method for joining metal and ceramics according to the present invention is as follows:
A stack of metal and ceramic is heated to a temperature lower than the melting point of the metal and higher than the recrystallization temperature, and a fluctuating pressure is applied in a direction perpendicular to the contact surface between the metal and ceramic, followed by cooling 3. The effect of the fluctuating pressure is maintained until the temperature drops below the recrystallization temperature of the metal.

(e) Working metal and ceramics are stacked on top of each other, heated to a temperature below the melting point of the metal, and a fluctuating pressure perpendicular to the joint surfaces is applied to promote the diffusion effect at the joint. This is because the fluctuating pressure causes lattice defects such as dislocations and atomic vacancies to multiply and become more likely to diffuse. By promoting the diffusion effect in this way, the bonding force of the bonding surfaces increases. Next, by cooling while applying a fluctuating pressure, it is possible to reduce the thermal stress caused by the difference in coefficient of thermal expansion between the metal and the ceramic. This is due to local plastic deformation caused by fatigue due to repeated fluctuating pressure. In this way, the residual thermal stress can be reduced, thereby increasing the bonding strength.

(f) Example FIG. 1 shows an apparatus for joining metal and ceramics. An upper ankle 16 is connected to a crosshead 12 connected to a column 10 via a load cell 14. One anvil 18 is provided coaxially with the upper anvil 16. The lower anvil 18 is configured to receive pressurizing force from an actuator piston 20 disposed below it.

The actuator piston 20 (not shown) generates a variable load using hydraulic pressure from a hydraulic source. A metal 22 and a ceramic 24 to be joined to each other, which will be described later, are sandwiched between the opposing ends of the upper anvil 16 and the lower anvil 18. A silicon glass tube 26 is installed so as to surround the outer periphery of the lower underhill 16 and the lower underhill 18. The upper end of the silicon glass tube 26 is inserted into the hole of the member 28, and the lower end of the silicon glass tube 26 is inserted into the hole of the member 30. Note that the insertion portions of the silicon glass tube 26 and the members 28 and 30 are respectively sealed by seal members 32.
and sealed by 34. The member 30 is attached to a fixed base 36. A predetermined gas can be supplied to the inside of the silicon glass tube 26 from an air supply pipe 38 provided on the member 28, and can be exhausted from an exhaust pipe 40 provided on the member 30. In addition, the silicon glass tube 26
A thermocouple 42 is placed adjacent to the metal 22 and ceramics 24 inside. Silicon glass tube 26
An infrared image heating furnace 4 surrounds the outer periphery of the infrared image heating furnace 4.
4 is provided. The infrared image heating furnace 44 is on stand 3
It is supported on a stand 46 fixed to 6. The infrared image heating furnace 44 can also be cooled by cooling water supplied from a cooling water pipe 47. A bellows 4 is provided between the flange portion on the lower end side of the lower anvil 18 and the member 30.
8 is provided, which allows the silicon glass tube 26
This allows relative movement between the member 30 and the lower ankle 18 while maintaining an internal airtight state. The upper anvil 16 can be cooled by flowing cooling water from the cooling water pipe 50, and the lower anvil 18 can also be cooled by flowing cooling water from the cooling water pipe 50.
Cooling is possible by flowing cooling water from 2.

Next, a specific example in which a metal 22 and a ceramic 24 are bonded using the apparatus shown in FIG. 1 will be described with reference to A. Oxygen-free copper with a purity of 99.98% was used as the metal 22, and alumina with a purity of 95.4% was used as the ceramic 24. The metal 22 and ceramic 240 dimensions are both 10 mm in diameter and 10 mm in length. Three conditions were set for the atmosphere inside the silicon glass tube 26: argon gas, air, and vacuum. Under the above conditions, heating is started from room temperature TA using the infrared image heating furnace 44 according to the pattern shown in FIG. Apply fluctuating pressure to the Note that the constant pressure PO is applied until the variable pressure is applied. Further, the temperature TB is the metal 22
recrystallization temperature T. temperature is lower than that of P as a fluctuating pressure. The fluctuation value of ±P1 is added to the reference value of .

That is, a fluctuating pressure of Po±P1 will act. The frequency of the fluctuating pressure is 10 to 100 Hz (test results when changing the frequency will be described later). In this state, the temperature of the metal 22 and the ceramic 24 is set to a predetermined value Tc.
for a predetermined time t. Hold for a while. In addition, the temperature T
c is a temperature lower than the melting point of the metal 22 and higher than the recrystallization temperature. Predetermined time t. After that time, start cooling and metal 2
Recrystallization temperature T of 2. Afterwards, when the temperature drops, the application of the fluctuating pressure is stopped. As a result, the metal 22 and the ceramic 24 are joined. Note that t1 in the figure indicates the total time during which the fluctuating pressure was applied. In addition, although the fluctuating pressure is applied from the moment the temperature reaches TB, the fluctuating pressure may start acting earlier than this (for example, from the beginning).
, or may be delayed (for example, after reaching the heating temperature Tc).

A test for joining the metal 22 and the ceramic 24 as described above was carried out using heating temperature Tc, fluctuating pressure po +p, frequency of the fluctuating pressure, and holding time t of heating temperature Tc. The strength of the joints was compared by changing the , and ambient atmosphere.

Effects of Heating Temperature and Vibration Frequency Figure 3 shows the results when the heating temperature Tc and vibration frequency were varied. The horizontal axis in the figure represents the frequency of the fluctuating pressure, and the vertical axis represents the ratio of the bending strength σ of the bonded body to the alumina bending strength σ6.

Note that the applied fluctuating pressure was 15±2.5 MPa (mechapascal), and the heating temperature Tc was maintained for a time t. is 15
It's a minute. The bending strength was determined by a three-point bending test in which both ends of the joined body were supported (with a span of 15 mm) and a load was applied to the joint at the center.

From the results shown in FIG. 3, it can be seen that, for example, the bending strength at a frequency of 25 Hz is significantly improved compared to the case where the frequency is 0, that is, when a constant load is applied.

For example, at 600°C, under constant load, the bending strength ratio σt/
σ. was about 0.03, but when variable pressure is applied, it becomes 0.15, which is about 5 times as large. Similarly 70
At 0°C, 0.11 becomes 0.16, and at 800°C, 0.19 improves to 0.25. Also, as shown in Figure 3, the frequency of the fluctuating load is 15 to 35H.
z is most preferred. However, even if the frequency is 10 to 100 Hz, the bonding strength can be improved. Furthermore, regarding the influence of heating temperature, it can be seen that the bonding strength improves as the heating temperature increases. However, the increase in strength as the heating temperature increases saturates at around 800°C. This can also be understood from FIG. 4, which shows the results of tensile strength tests conducted at different heating temperatures.

Holding time of heating temperature and influence of ambient air Holding time t of heating temperature Tc. The results of a tensile strength test with different
As shown in the figure. As can be seen from FIG. 5, the heating temperature Tc
retention time t. It is preferable that the time is around 15 minutes; if the time is too long, the bonding strength will gradually decrease. In the test shown in FIG. 5, the atmosphere inside the silicon glass tube 26 was changed to three conditions: air, argon gas, and vacuum. In the case of argon gas, the strength tends to be somewhat higher, or there is not a large difference.

Effect of fluctuating pressure Reference value P of fluctuating pressure. Figure 6 shows the test results when the size of . In this test, P was kept constant at -2°5MPa, and the bending strength was compared by changing Po.

It can be seen from this that the larger the reference value Po of the fluctuating pressure is, the stronger the bonding strength tends to be.

(G) As described in detail, according to the present invention, the metal and ceramic are heated and a fluctuating pressure is applied between them, so that the metal is effectively diffused into the ceramic. Sufficient bonding strength can be obtained. Furthermore, by cooling while applying a varying pressure, residual thermal stress can be reduced, and from this point as well, the strength of the joint can be improved.

4. Brief explanation of the drawings □ Figure 1 shows a device for joining metal and ceramics, Figure 2 shows the effect of fluctuating pressure and changes in temperature over time, and Figure 3 shows temperature and fluctuations. Figure 4 shows the relationship between the welding temperature and tensile strength. Figure 5 shows the relationship between the holding time of the heating temperature and the ambient air and the tensile strength. A diagram showing the relationship, FIG. 6 is a diagram showing the relationship between the frequency of the fluctuating pressure and the bending strength.

22...Metal, 24...Ceramics.

Patent applicant: Nikki Steel Works Co., Ltd. Educational corporation Hiroshima Denki Gakuen

Claims (2)

[Claims] 1. A stack of metal and ceramic is heated to a temperature lower than the melting point of the metal and higher than the recrystallization temperature, and a fluctuating pressure is applied in a direction perpendicular to the contact surface between the metal and ceramic, followed by cooling. A method of joining metal and ceramics that maintains the effect of fluctuating pressure until the temperature drops below the recrystallization temperature of the metal. 2. The method for joining metal and ceramics according to claim 1, wherein the frequency of the fluctuating pressure is 10 to 100 times per second.