JPH10236842A - Sealing glass for nitride ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing glass which has good wettability with a nitride ceramic material, contains no lead oxide and can tightly seal a nitride ceramic material at low temp. even in an oxidizing atmosphere, inert atmosphere, reducing atmosphere or vacuum by mixing ZnO and B2 O3 and fusing and vitrifying the mixture. SOLUTION: ZnO by 55 to 63mol% and B2 O3 by 45 to 37mol% are mixed, fused by heating to vitrify, and then kept at 580 to 800 deg.C for 10 to 120min to slowly crystallize to obtain a sealing glass for a nitride ceramic material. The obtd. sealing glass has 580 to 620 deg.C softening point and 650 to 780 deg.C peak temp. (DTA) of crystallization. A powder of the sealing glass is dispersed in a vehicle to obtain a glass paste, which is then applied on a nitride ceramic material, dried and heat treated at a temp. over the softening point and <=780 deg.C to seal the nitride ceramic material. Thereby, the obtd. sealed part of the nitride ceramic material has excellent sealing property, heat resistance and thermal shock resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass material used for sealing and sealing nitride-based ceramics, and a method for sealing nitride-based ceramics using the same.

[0002]

2. Description of the Related Art Since nitride-based ceramics such as silicon nitride, aluminum nitride, boron nitride, and titanium nitride have excellent mechanical strength, heat resistance, oxidation resistance, and the like, high-temperature structural materials, insulating materials, and mechanical materials. Attention has been paid to engineering ceramics such as component materials, and substrate materials for ceramic heaters and various electronic devices. Particularly, silicon nitride having high Young's modulus, high thermal conductivity and excellent thermal shock resistance is used for mechanical parts used at high temperatures such as gas turbines and parts for automobile engines. Hot press method, active metal method, etc. are mainly used for bonding and sealing between nitride-based ceramics or between nitride-based ceramics and other materials such as metals, but all require heat treatment at high temperature. And

Conventionally, low-melting glass has been used to seal and seal oxide-based ceramics and glass at a relatively low temperature. This is low melting glass powder and this is resin,
A glass paste dispersed in a vehicle made of a solvent or the like is applied to a material to be sealed, and is baked to soften the glass and adhere hermetically. Typical examples of the glass used for this purpose include various types of amorphous or crystalline solder glass, or a composite material obtained by adding an oxide filler to amorphous solder glass.

[0004] However, it is generally known that nitride-based ceramics have extremely poor wettability with glass, and they do not adhere at all or shrink during firing to produce a gap between the ceramic and the adherend. Further, it reacts with a glass material to generate ammonia gas or nitrogen gas, which may cause foaming and peeling. Furthermore, nitride-based ceramics have a lower coefficient of thermal expansion than oxide-based ceramics.
In the range of 30 to 35 × 10 ⁻⁷ / ° C. with silicon nitride.
About 45 to 60 × 10 ⁻⁷ / ° C. for aluminum nitride. For this reason, when sealing is performed with ordinary glass for oxide ceramics, peeling and cracking occur due to thermal strain at the time of sealing, resulting in impaired airtightness and reliability. Therefore, glass used for sealing oxide-based ceramics and glass cannot be used for nitride-based glass as well.
Low-temperature sealing of nitride ceramics has been extremely difficult. As a low-temperature sealing of such a nitride ceramic, a resin material such as an epoxy resin or a polyimide resin has been studied. However, resin materials have poor heat resistance, cannot be subjected to repeated heat treatment after sealing, and cannot be used for high-temperature parts and the like.

Accordingly, the present inventors have studied sealing with a glass material having a low coefficient of thermal expansion. As the low thermal expansion glass, lead borosilicate, zinc borate and the like are known as amorphous glass, and lead zinc borate, zinc borosilicate and zinc borate are known as crystalline glass. Of these, amorphous glass often has poor wettability and adhesion to nitride ceramics. Further, when the heat resistance is relatively low and high-temperature treatment at a temperature higher than the softening point after sealing is required, the material cannot be used because of softening and flowing. If an attempt is made to increase the heat resistance, the sealing temperature also increases, and sealing cannot be performed at a low temperature. If an oxide filler is added to increase the heat resistance after sealing, the wettability between the filler and the glass is poor, and the liquid phase at the time of bonding is reduced, so that the adhesiveness is poor.

[0006] The crystalline glass that precipitates crystals during sealing is
High heat resistance after sealing. However, glass containing lead oxide generally reacts easily with nitride ceramics, especially when fired in a non-oxidizing atmosphere, lead oxide is reduced and oxygen replaces nitrogen in nitride ceramics, generating nitrogen gas. Therefore, it cannot be used for sealing a component that needs to be fired in a non-oxidizing atmosphere, for example, a component using an oxidizing metal. Further, since lead has a bad effect on living bodies and the environment, it is desirable not to use lead-based glass.

On the other hand, B ₂ O as described in British Patent No. 899901 and JP-A-48-43408.
₃ -SiO ₂ -ZnO-based crystalline glass is used for coating a Si semiconductor having a small coefficient of thermal expansion or for sealing Kovar or molybdenum, but the sealing property for nitride-based ceramics is insufficient. Since the softening point is relatively high, a bond having high adhesive strength cannot be formed particularly at a low temperature, for example, at a temperature of 700 ° C. or less.

[0008] Saio Sakuhana et al., "Glass Handbook", No. 14
7 to 149 pages (Asakura Shoten, 1975)
-B ₂ O ₃ based crystal glass is described. However, ZnO-B ₂ O ₃ based crystalline glass the vitrification range, the crystallization range is extremely narrow, composition, large variations in characteristics due to heat treatment or the like working conditions, because control is difficult, as the sealing of the ceramic conventional It is not used, and the fact is that no particular study has been made on its use for sealing nitride-based ceramics.

Further, in British Patent No. 1205652, various solder glasses are described, and a sealing solder glass comprising ZnO and B ₂ O ₃ is also described. Here, ZnO and B ₂ O ₃ are also described. There is no specific description of crystallizing this using glass made of and sealing the nitride ceramics. In addition, the value of the coefficient of thermal expansion described here is relatively large, and this value indicates that this value is not satisfactory as a sealing glass of nitride ceramics. .

[0010]

In such a situation,
The present inventors, in order to find a sealing material that has good wettability with the nitride-based ceramics and a suitable thermal expansion coefficient, and does not contain lead oxide, at a low temperature, not only in an oxidizing atmosphere but also in an inert atmosphere, In order to obtain a glass material that can hermetically seal nitride-based ceramics even in a reducing atmosphere or in a vacuum, we have been working on obtaining a glass material. We know that there is very suitable in a ZnO-B ₂ O ₃ based glass which has not been used in, the present invention has been attained.

[0011]

That is, the present invention provides a ZnO
55-63 mole%, is a B ₂ O ₃ 45~37 mol% sealing glass of the nitride-based ceramic consisting intended to be subject matter. Hereinafter, the present invention will be described in detail.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The composition of the glass of the present invention is ZnO.
It is necessary to adjust the 55 to 63 mol% and B ₂ O ₃ 45~37 mol%. Note that this ratio is such that the ratio between Zn and B is Z
It means the ratio when converted to nO and B ₂ O ₃ . If the ZnO component in the glass is more than 63 mol%, the glass will not be vitrified. On the other hand, if it is less than 55 mol%, the phase separation of the glass is likely to occur, and the bonding becomes unstable and the reliability is impaired.
ZnO in the range of 55 to 63 mol% is most suitable for hermetic sealing of the nitride ceramic from the viewpoints of sinterability, degree of crystallization, crystallization rate and the like. The glass of the present invention may be used in the form of a powder, but desirably, the glass powder is dispersed in a vehicle and used as a paste.

The vehicle may be one usually used for a glass paste, and is obtained by adding a resin, a dispersant, a surfactant and the like to water or an organic solvent as needed. Glass powder or glass paste is used in a usual manner, for example, filling between sealing materials, or applying to one sealing material, and then placing the other sealing material on top of this. Sealing is performed by applying a heat treatment at a temperature equal to or higher than the softening point of glass, which is applied to ceramics. The heat treatment can be performed in any atmosphere such as an oxidizing atmosphere such as air, an inert atmosphere such as nitrogen or argon, a reducing atmosphere such as hydrogen or hydrogen-nitrogen, or a vacuum.

The glass of the present invention has a softening point of about 580-62.
0 ° C., and the peak temperature Tc of crystallization by DTA is about 650 to 780 ° C. Since crystallization occurs gradually even at a temperature lower than the crystallization temperature, the heat treatment for crystallization is performed at a temperature in the range of 580 to 800 ° C, preferably 600 to 780 ° C, for 10 to 120 minutes, preferably 30 to 120 ° C. 6
It is desirable that the crystal be slowly precipitated by holding for 0 minutes. In the glass of the present invention, the glass softened by the heat treatment is fluidized, and after increasing the contact area with the nitride-based ceramic, a solid-phase reaction is performed to cause crystallization and sintering slowly while forming a bond, Very good adhesion to nitride ceramics. Also, the coefficient of thermal expansion is small. Therefore, the obtained nitride-based ceramics sealing portion bonded by the glass of the present invention has excellent airtightness, heat resistance, and thermal shock resistance.

[0015]

【Example】

Example 1 A glass paste was manufactured by kneading 75.5% by weight of a glass powder composed of 60% by mole of ZnO and 40% by mole of B ₂ O ₃ and 24.5% by weight of a vehicle. A mixture of an acrylic resin and butyl carbitol acetate was used as a vehicle. Two silicon nitride plates were prepared, and the obtained glass paste was applied to one silicon nitride plate to a thickness of 100 μm, and the other silicon nitride plate was placed on the silicon nitride plate.
After keeping the solvent at 0 ° C. for 30 minutes to evaporate the solvent, the temperature was raised in vacuum, and the glass was kept at a peak temperature of 650 ° C. for 60 minutes to soften and crystallize the glass. An airtight sealed body with no gap was obtained. Table 1 shows the glass transition point, softening point, crystallization temperature, coefficient of thermal expansion, bonding strength with silicon nitride of this glass. Regarding the bonding strength, a glass paste was applied on a silicon nitride plate in a circular shape having a diameter of 20 mm and a thickness of 100 μm, and then baked at 650 ° C.
The joining strength was evaluated from the peeled state when a 200 g steel ball was dropped from a height of 30 cm.

Comparative Example 1 A glass paste was produced in the same manner as in Example 1 except that ZnO—B ₂ O ₃ —SiO ₂ based glass powder containing no PbO (FG16 manufactured by Asahi Glass Co., Ltd.) was used. The same process was used to seal the two silicon nitride plates, but the glass was not sintered. When the heat treatment temperature was set to 700 ° C,
Although air-tightly sealed, a sealed body could not be formed. Table 1 shows the physical properties of the glass and the bonding strength with silicon nitride. The bonding strength was measured using a material that was heat-treated at 700 ° C.

Comparative Example 2 A glass paste was produced in the same manner as in Example 1 except that a PbO—SiO ₂ —B ₂ O ₃ based glass powder (F1370 manufactured by Asahi Glass Co., Ltd.) was used. The sealing of the two silicon nitride plates was carried out, but some deviation of the glass and bubbles were observed, and a good sealed body could not be formed. Table 1 shows the physical properties of glass and the bonding strength with silicon nitride.

[0018]

[Table 1]

Example 2 Using a glass powder having the same composition as in Example 1, two aluminum nitride plates were sealed in the same manner as in Example 1, and an airtight sealed body was obtained.

[0020]

By using the low expansion crystalline glass of the present invention, a nitride ceramic can be hermetically sealed at a low temperature. Also, since it has excellent bonding strength and heat resistance, it can withstand repeated heat treatment and severe use environment. Furthermore, since the crystalline glass of the present invention does not contain lead oxide, there is little harm to living bodies and the environment. From the above results, it is expected that the use of nitride ceramics as a high-temperature mechanical material can be greatly expanded by the present invention.

Claims (4)

[Claims] 1. 55 to 63 mol% of ZnO, B ₂ O ₃ 45
A glass for sealing nitride-based ceramics of up to 37 mol%. 2. A glass paste for sealing nitride-based ceramics, wherein the glass powder according to claim 1 is dispersed in a vehicle. 3. The nitride-based ceramic is sealed by applying the glass paste according to claim 2 onto a nitride-based ceramic, drying the glass paste, and then performing a heat treatment at a temperature in a range from a softening point to 780 ° C. how to. 4. The method according to claim 1, wherein the nitride-based ceramic is ZnO 55-6.
A sealed portion sealed with crystallized glass consisting of ₃ mol% and 45 to 37 mol% of B ₂ O ₃ .