JPH039075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a sintered ceramic body, and more particularly to a sintered non-oxide ceramic body having a conductive coating.

[Technical Background of the Invention and Problems Therewith] Conventionally, a conductive film has been formed on the surface of a ceramic sintered body in order to bond the ceramic sintered body to a metal member.

A common method for forming this conductive coating is to apply a molybdenum-manganese metallization paste containing molybdenum powder and manganese powder as main components to the surface of the ceramic sintered body, and to sinter the paste in a reducing atmosphere.

These methods have all been successfully applied to sintered oxide-based ceramics such as alumina, but in recent years, silicon nitride and other materials have been attracting attention due to their good abrasion resistance and high-temperature properties. There is room for consideration regarding non-oxide ceramic sintered bodies; for example, it is difficult to form a conductive film with this method, so this method cannot necessarily be applied to non-oxide ceramic sintered bodies. I know there isn't.

Therefore, for example, a method has been attempted in which the surface of a porous silicon nitride ceramic sintered body obtained by a reactive sintering method is impregnated with ammonium molydebenate salt and reduced to form a conductive film made of molydebenate.

However, this method is effective when bonding sintered ceramic bodies because the conductive film is made of molybdenum, which has a coefficient of thermal expansion almost equal to that of silicon nitride ceramics. Because it does not chemically react with non-oxide ceramics such as, there is a limit to the bonding strength, and it is said that joining a non-oxide ceramic sintered body with metal parts, especially steel materials, is even more difficult. There was a problem.

[Purpose of the Invention] The present invention was developed as a result of intensive research to address these points.
We have discovered that a composite of a group transition metal with a nitride is effective for joining non-oxide ceramic sintered bodies containing nitrogen as a constituent element.

The present invention was made based on such knowledge, and an object of the present invention is to provide a non-oxide ceramic sintered body that can be strongly bonded to metal members.

[Summary of the Invention] That is, the non-oxide ceramic sintered body of the present invention has at least one of tungsten and molydeben and a group IVa transition metal on the surface of the non-oxide ceramic sintered body containing nitrogen as a constituent element. Mainly composed of a mixture with nitride, and the ratio (atomic ratio) of group IVa transition metal to the total amount of tungsten and molydeben and group IVa transition metal is 0.4 or more and 0.8
It is characterized by having the following conductive coating.

Specific examples of the non-oxide ceramic sintered body to which the present invention is applied include aluminum nitride ceramics and silicon nitride ceramics. The former has high thermal conductivity and high insulation properties, and the latter has high high-temperature strength and is therefore highly practical. The conductive film formed on the surface of the nitrogen-containing ceramic sintered body in this way is
Because it contains nitrides of group IVa transition metals such as TiN, the nitrogen in the ceramic sintered body can be used as a raw material during the reaction process, and it can firmly bond even non-oxide ceramics. Can be done.

Further, the conductive film may be mainly composed of a mixture of at least one of tungsten and molydeben and a nitride of a group IVa transition metal,
Other substances may also be contained in small amounts.

When obtaining this conductive coating, in the case of molybdenum, metal salts of molybdic acid such as lithium molybdate, potassium molybdate, calcium molybdate, sodium molybdate, and lead molybdate, and molybdenum accompanying these are used. You can use the ones that exist.

In the case of tungsten, metal salts of tungstic acid such as potassium tungstate, calcium tungstate, sodium tungstate, and magnesium tungstate, and those in which tungsten is present in combination with these metal salts can be used.

As the IVa group transition metal used in the present invention, titanium and zirconium are more suitable, and among them, titanium is preferable. Further, as the compound containing a group IVa transition metal, a compound containing titanium or zirconium is similarly suitable, and among these, a compound containing titanium is suitable. These compounds can be used as long as they eventually become titanium nitride or zirconium nitride when applied to silicon nitride and fired in a non-oxidizing atmosphere, especially a reducing atmosphere. Compounds include titanium oxide (TiO ₂ ), titanium boride (TiB, TiB ₂ ), titanium carbide (TiC), or basic titanium sulfate (TiOSO ₄ .nH ₂ O: n
is 0 or a positive integer), isopropyl orthotitanate [Ti[COH(CH ₃ ) ₂ ] ₄ ], and the like. The sintered body of the present invention is obtained by depositing a mixture of at least one of tungsten and molydeben and a nitride of a group IVa transition metal on the surface of a non-oxide ceramic sintered body.

In the present invention, a liquid or paste-like compound is suitable as the composite to be adhered to the surface of the ceramic sintered body. This can be done by coating or immersing it in water.

Although other substances may be dispersed or dissolved in these liquids or pastes, the conductive film that is formed is composed of at least one of tungsten and molybdenum and a nitride of a group IVa transition metal. It is desirable that the total amount of nitrides of tungsten, molybdenum, and group IVa transition metals be 50 mol % or more, and 2 mol % or more each of nitrides of tungsten, molybdenum, and group IVa transition metals.

After this, the liquid or paste is dried,
Furthermore, it is heated in air at a temperature higher than the temperature at which the metal salt of tungsten or molybdenum dissolves, and in a non-oxidizing atmosphere (for example, a reducing atmosphere containing nitrogen).
A conductive film is formed by heating and baking to a temperature of 1100°C or higher.

For example, when the non-oxide ceramic is silicon nitride, firing in a non-oxidizing atmosphere causes the silicon in the ceramic sintered body that is the base material to react with at least one of tungsten and molybdenum, and Nitrogen in ceramic sintered bodies and
This method involves reacting the group IVa transition metal in the oxide of the group IVa transition metal, and the firing temperature required for this differs depending on the type of deposit, but the liquid material that is the starting material is lithium molybdate (Li). ₂ MoO ₄ ) and titanium oxide (TiO ₂ ), it is preferable to fire at 1200 to 1400°C.

In the present invention, the reason why the ceramic sintered body coated with each of the above compounds is heated in air to melt it is to strengthen the adhesion with the ceramic sintered body and improve wettability.

Although it is currently unknown why the conductive film formed by such a method has a high adhesion strength to the base material, the formation mechanism is presumed to be as follows.

For example, assuming that lithium molybdate and titanium oxide are applied in liquid form to Si ₃ N ₄ and fired, the lithium first reacts with the Si ₃ N ₄ base material, and the surface of Si ₃ N ₄ Activate. This allows molybdenum and silicon in Si ₃ N ₄ to react relatively smoothly. It is thought that nitrogen in Si ₃ N ₄ is liberated by this reaction, and this nitrogen and titanium react to form titanium nitride, forming a conductive film with higher adhesion strength.

[Embodiments of the invention] The following embodiments of the present invention will be described.

Example 1 Appropriate amounts of nitrocellulose and butyl acetate were added to a mixed powder of lithium molybdate (Li ₂ MoO ₄ ) and titanium oxide (TiO ₂ ) to prepare a slurry. The obtained slurry was applied to the surface of an AlN sintered body containing Y ₂ O ₃ . After drying this,
Lithium molybdate was dissolved by heating in air at 750°C for 5 minutes, and then fired at 1300°C for 60 minutes in a mixed gas of nitrogen:hydrogen=1:1 to form a conductive film. This conductive film consists of TiN, Mo, and γ
-It consisted of a spinel phase similar to Al ₂ O ₃ .

In this way, two conductive films were formed.
Ni electrolytic plating is applied to each AlN sintered body,
Both were joined using silver solder. The obtained bonded body had a bond strength (shear) of 12.3 Kg/mm ² .

Example 2 0.3 g of lithium molybdate was applied to the surface of an AlN ceramic sintered body made by hot pressing.
A liquid mixture consisting of 0.3 g of titanium oxide and 1.6 cc of water was applied. After drying this, 750℃ in air,
Dissolve the lithium molybdate by heating for 5 minutes,
Then, at 1300℃ with a mixed gas of nitrogen:hydrogen=1:1.
It was heated and baked for 60 minutes to form a conductive film. This conductive coating consisted of TiN, Mo, and a spinel phase similar to γ-Al ₂ O ₃ .

In this way, two conductive films were formed.
Ni plating was applied to each AlN sintered body, and the two were joined using silver solder. The bonding strength of the resulting bonded AlN sintered bodies was approximately approximately
It was 14Kg/ ^mm2 .

Example 3 A mixed powder of lithium molybdate (Li ₂ MoO ₄ ) and titanium oxide ₍ TiO ₂ ) was applied in the form of a slurry liquid to the surface of a ceramic sintered body made of silicon nitride containing Y ₂ O 3 and Al ₂ O ₃ did.

In this case, the amount of titanium oxide was changed from 0 to 0.45 g in increments of 0.05 g with respect to 0.3 g of lithium molybdate. After drying the coated material at room temperature, it was heated in air at 750°C for 5 minutes to dissolve the lithium molybdate, and then heated in a homing gas of nitrogen:hydrogen = 1:1 at 1300°C for 60 minutes. A conductive film was formed by firing.

This coating consists of TiN, Mo, Y ₂ O ₃ 2SiO ₂ and a small amount of unknown phase, and its thickness is approx.
It was 7 μm. Note that this thickness can be controlled over a fairly wide range (for example, 1 to 20 μm).

The conductive film thus formed on the ceramic sintered body is subjected to nickel electroplating,
A 0.3 mm thick copper plate was interposed as a buffer material, and it was bonded to the copper material using silver solder. The results of measuring the bonding strength of the obtained ceramic sintered body are shown in the drawing.

As is clear from the figure, when the atomic ratio of the conductive film is in the range of 0.4<Ti/Mo+Ti<0.8, it has a preferable bonding strength. This relationship is broadly applicable to the present invention. That is, when the conductive coating has the following relationship, preferable bonding strength is obtained.

0.4<B/A+B<0.8 (atomic ratio) A: Tungsten, molybdenum B: Group IVa transition metal [Effects of the invention] As explained above, according to the present invention, ceramic sintered bodies, especially non-oxide ceramics sintered It is possible to form a conductive film with extremely high adhesion strength on the body, and therefore it is possible to more firmly bond not only ceramic sintered bodies to each other but also ceramic sintered bodies and metal parts. It is.

[Brief explanation of the drawing]

The drawing is a graph showing the bonding strength of steel materials bonded using the non-oxide ceramic sintered body of the present invention.

Claims (1)

[Scope of Claims] 1. The surface of a non-oxide ceramic sintered body containing nitrogen as a constituent element is mainly composed of a mixture of at least one of tungsten and molybdenum and a nitride of a group IVa transition metal. Based on the total amount of molybdenum and group IVa transition metals
A non-oxide ceramic sintered body characterized by having a conductive coating having a ratio (atomic ratio) of a group IVa transition metal of 0.4 or more and 0.8 or less. 2. The mixture of at least one of tungsten and molybdenum and nitride is a mixture containing at least 50 mol% or more of both in total, and 2 mol% or more of each of them, according to claim 1 non-oxide ceramic sintered body. 3. The non-oxide ceramic sintered body according to claim 1, wherein the IVa group transition metal is titanium. 4. The non-oxide ceramic sintered body according to claim 1, wherein the conductive film is mainly composed of a mixture of molybdenum and titanium nitride. 5. The non-oxide ceramic sintered body according to claim 1, wherein the non-oxide ceramic sintered body is an aluminum nitride ceramic. 6. The non-oxide ceramic sintered body according to claim 1, wherein the non-oxide ceramic sintered body is silicon nitride ceramic.