JPS63239164A - Method of joining ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Prior Art] Ceramics are generally bonded by applying a bonding agent that melts at high temperatures, abutting the bonded surfaces, and heating the bonded portion. Electric furnaces and gas burners are commonly used heating means.

Since heating in an electric furnace is performed by housing the entire ceramic in the electric furnace, not only the joint portion but also the entire ceramic is exposed to high temperature.

Heating with a gas burner involves blowing gas burners (generally a plurality of gas burners) onto the joint and igniting the joint with a gas flame. In the heating method using a gas burner, temperature unevenness tends to occur at the joint, so in order to suppress this,
It is necessary to periodically change the position where the gas flame hits, and a moving (or rotating) device is provided on the ceramic side or the gas burner side.

The present inventors have also proposed a method of joining ceramics by passing current through the bonding agent portion while heating the bonding portion with a gas burner, and melting the bonding agent using Joule heat generated by the current flow. (Patent application Sho 6l-78697).

In this bonding method, a bonding agent that is conductive at high temperatures is used.

[Problems to be Solved by the Invention] Heating using the electric furnace described above exposes the entire ceramic to high temperatures, which causes significant thermal shrinkage and thermal distortion, leading to problems such as thermal deterioration of the base material. .

When heating with a gas burner, it is difficult to control the temperature of the joint, and the positional temperature difference or temporal temperature change at the joint may become excessive.This causes considerable thermal stress to be applied to the joint, causing the joint to fail. Cracks may occur in the parts.

In addition, in the method of heating the joint part with a gas burner while supplying electricity to the joint part and heating the joint part with Joule heat, the binder must be electrically conductive at high temperatures.

An object of the present invention is to provide a method for joining vine ceramics that has low thermal shrinkage, thermal distortion, thermal deterioration, etc., does not cause problems due to thermal stress, and can be used with a bonding agent that is not conductive at high temperatures. It's about doing.

[Means for Solving the Problems] A bonding agent having a dielectric loss greater than that of ceramics is used, this bonding agent is interposed between the bonding surfaces of the ceramics, and the bonding surfaces are abutted against each other.

Next, a high frequency electric field in a short wave band or a microwave band is applied to the vicinity of the bonding portion or to the entire ceramic, and dielectric heating is used to heat and melt the bonding agent to bond the ceramics.

[Action] A dielectric placed under an alternating electric field generates dielectric loss and heats up. The loss generated per unit volume of the dielectric is P(w/(
To) 3), then P= (5/9) f E 2e t an δX
It is given by 10 -12.

Here, f, E, ε, and tanδ are the frequencies (
Hz), electric field strength (V/cm), relative dielectric constant, and dielectric power factor.

Further, εtanδ is called a loss coefficient and indicates the degree of loss generated in a dielectric material, and a substance with a large loss coefficient produces a large dielectric loss. When bonding ceramics, a bonding agent with a larger loss coefficient than the ceramic is used in order to reach the maximum temperature at the bonded part.

The frequency of the heating power source is a short wave band or a microwave band, and the usable frequencies are determined by the Radio Law. The frequencies allocated for industrial, chemical, and medical purposes in Japan are 13.56゜27.12, 40.68M in the shortwave band.
Hz, and in the microwave band, 2450.5800M
Hz, etc., so the frequency to be used is selected from these. When a short wave power source is used, the ceramics to be bonded are placed between plate-shaped electrodes in the vicinity of the joint, and when a microwave power source is used, the ceramics to be bonded are housed in a metal box that is irradiated with microwaves.

In such an arrangement, by applying a high-frequency voltage between the plate-shaped electrodes or by irradiating high-frequency power into the metal box, a high-frequency electric field is applied to the vicinity of the ceramic joint or the entire ceramic, and the above equation is expressed. Produces fever as shown.

Since the loss coefficient of the bonding agent is larger than that of the ceramic, the bonding agent portion is heated more strongly than the ceramic portion, and so-called selective heating occurs in the bonding agent portion.

In this way, the adhesive part can be efficiently heated and melted.
Ceramics can be joined.

Note that the dielectric constant (ε) and dielectric power factor (tan
δ) usually changes depending on temperature and frequency even if the material and composition are the same. Therefore, the loss factor (ε
It is also common for the tan δ) to change depending on temperature and frequency, and it is desirable to use a bonding agent with an understanding of these behaviors.

[Example] Embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(A) and 1(B) are schematic diagrams showing a bonding apparatus for carrying out the method of the present invention, and show a plan view and a front view, respectively. In this embodiment, a case will be described in which rectangular ceramics la and lb are vertically butt-jointed obliquely.

Ceramics la and lb have surfaces to be joined that are inclined with respect to the thickness direction, and are butted together with a bonding agent 2 interposed therebetween. It is necessary that the loss coefficient of the bonding agent is larger than that of the wave bonded material, and for this reason, a material with a large loss coefficient is mixed into the powder of the ceramic material components LA and LB, and other suitable auxiliary agents are used.

Add water or the like and knead to form a sheet or pellet shape to obtain a bonding agent 2. Materials that increase the loss coefficient include KAISiO, NaA1SiO, and Li.
O, SiO, MgO, Ti0, B a O, A
10, ZnO, B 203, etc., and by mixing an appropriate type of ffi material from these, the loss coefficient of the bonding agent 2 can be changed to that of ceramics la, l.
It can be made several times to several tens of times larger than the loss coefficient of b.

Tables 1 and 2 show examples of dielectric properties of ceramics, glasses, etc.

Table 1 Examples of dielectric properties of ceramics and glasses (room temperature) Table 2 Examples of dielectric properties of glass ceramics (at room temperature) Ceramics 1. a and lb are held in place by a support jig (not shown). Electrodes 3a and 3b are disposed facing each other on the left and right sides of the joint near the joint, and are held in place by a support jig (not shown). Electrodes 3a, 3b
In order to withstand high temperatures, metals with extremely high heat resistance (such as molybdenum) are used.

The length of the electrodes 3a, 3b in the vertical direction and the length in the front-rear direction are made larger than the length of the ceramics la, lb in the vertical direction and the length of the joint part of the ceramics la, lb in the vertical direction, respectively. The ends of the electrodes 3a and 3b in the front-rear direction are opened in a trumpet shape, so that the distance between the opposing electrodes increases. The purpose of this is to reduce the heat generation density by lowering the electric field strength in the part farther away from the joint in the front-rear direction than in the joint part, and to make the temperature distribution in the front-rear direction of the ceramics smoother during bonding. It is.

The high-frequency power generator 4 is composed of a self-excited oscillator, etc., and rectifies commercial frequency alternating current into direct current, and further performs frequency conversion and voltage conversion of the high frequency, and an application line 5 using a coaxial line or the like.
A high frequency voltage is applied to the electrodes 3a and 3b through. The frequency to be used is selected from among the frequencies approved for use under the Radio Law as shown in the section ``Operations'' above.

The outline of the ceramic bonding procedure is as follows.

A bonding agent 3 is interposed between the bonding surfaces of the ceramics la and lb, and the bonding surfaces are pressed and fixed together using a support jig (not shown). The electrodes 3a and 3b are placed on the left and right sides of the joint between the ceramics la and lb, and the gap between the electrodes and the ceramics at the center of the electrodes is about 2 to 3 mm, and the electrodes are fixed in place using a support jig (not shown). A high frequency voltage is applied from the high frequency power generator 4 between the electrodes 1a and lb.

An electric field is applied between the electrodes 1a and 1b, and dielectric heating occurs at the ceramic joint, causing a temperature rise with the bonding agent 2 at the highest temperature. After a few minutes to a few minutes after energization, the temperature suitable for bonding will be reached (the temperature at which the bonding agent melts, generally 1,000-odd degrees), so at this point the energization is stopped and the heated part is allowed to cool naturally. In addition, in the final stage of energization, pressure is applied in the direction of pressing the ceramics la and lb together, so that the normal pressure on the joint surface is 0. 05-2 kg/mu
2) By discharging the excess bonding agent and voids to the outside, a thin and dense bonding metal is formed, so that the bonding strength can be increased. Also, perform intermittent control of energization,
The bonding stress can be further reduced by performing slow cooling by reducing the energization rate and finally stopping the energization. Further, dielectric heating may be performed in the vicinity of the bonding portion and the electrode under an inert gas atmosphere. This prevents oxidative deterioration of the ceramics due to high temperatures during bonding, and improves the appearance of the bonded portion.

Other Examples Preheating method using an auxiliary heat source In general, the loss coefficient of a dielectric tends to be smaller at room temperature than at high temperature. In such cases, dielectric heating alone may cause problems such as a slow rise in temperature.
Preheating the joint using an auxiliary heat source eliminates these problems. As an auxiliary heat source, a radiant heat radiation type electric heater may be attached near the top and bottom surfaces of the ceramic joint in FIG. 1(B) to preheat the ceramic joint.

Furthermore (or) a contact heating type electric heater may be embedded in the electrodes 3a, 3b, and this heat may be transferred to the electrode-ceramic junction.

When the temperature of the ceramic joint reaches several hundred degrees due to these auxiliary heat sources, the input of the auxiliary heat sources is cut off. next,
To avoid problems when applying high-frequency voltage, take measures such as separating the electric heaters placed on the top and bottom surfaces of the ceramic joint from the joint surface, and separating the input lead wire to the electrode embedded heater from the electrode part. and then dielectric heating.

Dielectric heating method in a metal box When using a microwave band frequency, the ceramics to be bonded are placed inside a metal box (one side is approximately several times the wavelength), and high-frequency power is irradiated into the metal box. Ceramics can be bonded using this method.

In this method, high frequency power generated by a magnetron is guided through a waveguide or the like, an opening is provided in the metal box, and the high frequency power is irradiated into the metal box from this opening.

In this method, it is necessary to pay attention to the structure and arrangement of the ceramic support jig (made of metal) so that it does not generate discharge or shadow the electric power irradiation on the joint.

In addition, in order to uniformly heat the joint, it is necessary to avoid fixation of the electric field distribution in the joint, and for this purpose, it is necessary to use a metal starch fan or the materials to be joined (ceramics and measures such as irradiating high-frequency power while rotating the support material, etc.).

[Effects of the Invention] According to the present invention, since the bonding agent and its vicinity can be intensively heated, thermal deterioration and thermal deformation of ceramics accompanying bonding can be reduced.

Furthermore, since the joint portion is heated uniformly over time, the thermal stress during joining becomes extremely small, and the joint strength improves.

Furthermore, even a bonding agent that has low conductivity and cannot be used for electrical bonding using Joule heat can be used as a bonding agent according to the method of the present invention.

[Brief explanation of the drawing]

FIGS. 1A and 1B are a plan view and a front view, respectively, schematically showing a bonding apparatus for carrying out the method of the present invention. la, lb...ceramics, 2...
Bonding agent 3a, 3b...electrode, 4...
High frequency power supply.

Claims (1)

[Claims] A method of bonding ceramics by interposing a bonding agent between the bonding surfaces of ceramics, heating the bonded portion, and melting the bonding agent, resulting in a dielectric loss greater than the dielectric loss of the ceramics. A method for bonding ceramics, using a bonding agent, applying a high frequency electric field in a short wave band or microwave band to the vicinity of the bonding portion or the entire ceramic to dielectrically heat the bonding agent, thereby melting the bonding agent.