JPH075405B2 - Metallization method for non-oxide ceramics - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metallization method for non-oxide ceramics, and more particularly to a metallization method suitable for application to a silicon carbide sintered body.

[Prior Art] By joining a ceramic with a metal or another ceramic, a new function not found in a single ceramic is created, and the range of application of the ceramic is further expanded. For example, when joining ceramics and metal, various methods are known, but considering the characteristics of each ceramic,
It is necessary to select a joining method suitable for it.

As a method of joining a non-oxide ceramics such as silicon carbide ceramics and a metal or other ceramics, as described in JP-A-58-135180, between the ceramics and the metal or other ceramics, There is a method of inserting an Al-Si alloy insert and heating it to about 600 ° C while applying pressure in a vacuum to directly bond it.

Many methods have been proposed for ceramic metallization.

JP-A-59-203780 describes a method in which the surface of a non-oxide ceramics sintered body is coated with aluminum, an alumina layer is formed, and the alumina layer is metallized. This method requires two metallization steps and is uneconomical. In JP-A-55-51775, high-melting-point metal powders such as Mo and W are placed on non-oxide ceramics and metallized by firing under pressure in a non-oxidizing atmosphere.

The method of joining by pressurizing in a non-oxidizing atmosphere as described in JP-A-58-135180 or JP-A-59-203780 is not suitable for joining members having complicated shapes, and mass productivity is high. Also has a problem.

On the other hand, as a method for metallizing nitride ceramics, for example, as described in JP-A-59-195590, at least one metal component of Fe, Ni, Cr, Mn and C, Si, B are used. 10% or less of at least one of these components is mixed, and the composition is placed on the surface of the nitride-based ceramics body in the form of powder or particles, and the composition is placed in a non-oxidizing or weakly oxidizing atmosphere. There is a method of melting the above, but the silicon carbide ceramics are not mentioned.

Moreover, since this metallizing method is characterized by melting the composition, the metallization temperature is high, and when it is applied to silicon carbide ceramics, the bonding reaction with the ceramics proceeds excessively, and a brittle compound layer is formed. It was confirmed by an experiment that the metallization was so thick that a sufficient metallization strength could not be obtained.

A method for metallizing silicon carbide ceramics is disclosed in
In the one described in JP-A-58-89154, powders of W, Mo, Ti, Mn, etc. are applied to the surface of ceramics, and this is
It is baked above 00 ℃.

In the conventional metallizing methods described in JP-A-59-195590 and JP-A-58-99184, the metallization thickness is formed to be approximately the same as the thickness of the metal powder applied to the ceramic surface.

On the other hand, in the case of joining a ceramic and a metal having a different thermal expansion coefficient or another ceramic, as a method for reducing the thermal strain of the joined body, the metallization temperature and the subsequent joining temperature should be as low as possible in addition to the metallization layer thickness. It should be as thin as possible. Coefficient of thermal expansion 4.5 × 10 ^-6 /
In the case of a silicon carbide ceramic having a small temperature of 0 ° C., it was confirmed by an experiment that when the thickness of the metallized layer is 10 μm or more, the ceramic may be broken by the thermal strain only.

Conventionally, there is also a method of thinly applying or printing a metal powder paste having a small particle size on the ceramic surface as a method of reducing the thickness of the metallized layer, but even in this case, it is extremely difficult to control the thickness of the metallized layer to 10 μm or less. Have difficulty.

As a method of forming the metallized layer thin, there are methods such as vapor deposition and ion plating, but high bonding strength cannot be obtained by this method.

[Problems to be Solved by the Invention] In the above-mentioned prior art, no particular consideration is given to the thickness of the metallized layer and its control. When a silicon carbide ceramic and a metal or the like are joined, thermal stress fracture occurs in the silicon carbide ceramic. There is a problem that a highly reliable bonded body cannot be obtained.

An object of the present invention is to provide a metallizing method for forming a strong and heat-resistant metallized layer on the surface of non-oxide ceramics, particularly silicon carbide ceramics.

[Means for Solving Problems] The present invention has been made to achieve the above object, and a method for metallizing a non-oxide ceramic according to the present invention is
A step of forming a chromium powder layer on the surface of the non-oxide ceramic sintered body, and a layer containing a reaction product of ceramics and chromium on the surface of the sintered body, which is fired in an inert atmosphere or a reduced pressure atmosphere, and chromium oxidation thereon. It is characterized by including a sequential step of forming an unreacted layer containing a substance and a step of removing the unreacted layer containing the chromium oxide.

Hereinafter, the background to the completion of the present invention and examples will be described in detail.

The present inventors found that the following new phenomenon was found as a result of investigating the reaction state between the ceramic and the metal when various metal powders were applied to the surface of the silicon carbide ceramic and heated in a non-oxidizing atmosphere. did.

That is, when a metal of Group IVa and Group Va such as Ti, Zr, Nb, and V is applied, the reaction does not proceed at a heating temperature of 1000 ° C., and the temperature exceeds 1000 ° C. to cause a binding reaction. It is necessary to raise the heating temperature to near the melting point of the metal. However, when the heating temperature is raised to near the melting point, a brittle compound layer such as carbide and silicide of the metal is formed thickly at the metallized interface,
It was found that sufficient metallization strength could not be obtained.

When Fe, Ni, Mn, Co, etc. are coated with a Group VIIa or Group VIIIa metal, the bonding reaction with the ceramics proceeds excessively at a heating temperature of 1000 ° C., and brittle silicide or It was found that the carbide layer and the free carbon were formed thick and sufficient metallization strength could not be obtained. The thickness of the metallized layer formed of the metal powder was 10 μm or more, which was comparable to the thickness of the metal powder coated or printed on the silicon carbide ceramic surface. For this reason, the ceramics were also destroyed by the thermal stress generated on the surface of the ceramics.

On the other hand, especially when Cr powder is applied among the Group VIa metals such as Cr, Mo, W, etc., a mixed layer of Cr silicide and Cr carbide is formed on the base material of the ceramic, and further on the outer side thereof. It was found that the Cr reaction layer including the metallic chromium layer was formed to be 1 to 10 μm thin as a whole. The Cr silicide, Cr carbide, and Cr layer are firmly bonded to the ceramics, and their thickness is not affected by the thickness of the applied Cr powder, and the heating temperature is 900 to 130.
It was found that an extremely thin Cr metallized layer of 1 to 10 μm was formed at 0 ° C. Therefore, the thermal stress generated on the surface of the ceramic is also reduced, and the thermal stress destruction of the ceramic does not occur, which is a cause of improving the metallization strength. That is, in the conventional metallizing method, the thickness of the metallized layer is determined by the thickness of the metal powder applied in advance, but in the present invention, the thickness of the metallized layer is not affected by the thickness of the applied Cr powder, and the thickness of the metallized layer depends on the firing conditions. I have found that I can control.

On the other hand, an unreacted Cr layer containing a part of a chromium oxide layer such as Cr ₂ O ₃ is formed relatively thickly on the outer side of the metallic chromium layer. The unreacted Cr layer has a weak bond with the reactive Cr layer or the ceramics, and its thickness increases in proportion to the thickness of the chromium powder applied. Such an unreacted chromium layer can be removed before joining the metal member to the metallized surface of the chromium reaction layer so that the joining strength of the metal member is not adversely affected. The unreacted Cr layer may be removed by a method such as polishing, brush removal, or honing.

The formation of the Cr meta-fried layer on the surface of the ceramic of the present invention is performed by coating or printing a metal Cr powder of 10 μm or more on the surface of the silicon carbide based ceramic, and an atmosphere of activated gas such as Ar or He or a vacuum degree of 10 ^{−. In} a non-oxidizing atmosphere below ² Torr
It is obtained by heating at 900 ° C or higher and 1300 ° C or lower for 10 minutes or longer.

The outermost layer of the Ta metallized layer formed by the above method
Since an unreacted Cr layer containing a part of chromium oxide such as Cr ₂ O ₃ is also formed, the chromium oxide layer is removed by brushing or the like, and the total thickness of Cr silicide, Cr carbide, or Cr is 10 μm or less. A strong metallized layer can be obtained by using only a reaction layer consisting of.

It was found that a strong Cr metallized layer can be obtained by the above method, which is unique to silicon carbide ceramics.
Further, among silicon carbide ceramics, 1 as a sintering aid
A silicon carbide ceramics containing ~ 2 wt% (hereinafter also referred to as "wt%") BeO was obtained as a particularly strong Cr metallized layer.

Furthermore, the present invention has an electric resistance of about 2 × 10 4 containing 40 to 60 wt% of ZrB _2.
^It can also be applied to electrically conductive silicon carbide of ^-4 Ω · cm.

Since the Cr metallized layer formed on the ceramic surface is not sufficient in brazing property or soldering property for joining with another metal, after forming a Cu or Ni layer on the chromium reaction layer surface, It is desirable to join the metal or other ceramics with a brazing material. It was found by various experiments that a Cu or Ni layer can be easily formed in the case where a reaction layer mainly composed of chromium silicide and chromium carbide contains a small amount of metallic Cr on its surface. To form a Cu or Ni layer on the surface of the Cr reaction layer, methods such as electroplating, chemical plating, vapor deposition, and sputtering can be used. Further, it is desirable to perform the diffusion treatment again at a temperature of 500 to 800 ° C. in order to enhance the bonding state between the Cr layer and the Cu or Ni layer, but this can be omitted when heating to this temperature range during bonding.

By forming a metallized film of chromium on the surface of the silicon carbide-based ceramics by the above method, and by joining with another metal member by a brazing material, a bending strength of 20 kg / mm ² or more is obtained,
The heat resistance is 600 ℃ or more.

The particle size of the chromium powder applied to the surface of the silicon carbide ceramics is 100 μm or less, preferably 50 μm or less. If the particle size is larger than this, as a result, a portion of the ceramic surface that is not covered with the formed metal chromium layer is likely to occur. Also, the coating thickness of the chromium powder is preferably 10 μm or more, and if it is too small, a ceramic surface portion which is not covered with the metal chromium layer is likely to be formed as a result. . The chromium powder is preferably applied in a paste form together with an appropriate paste form.

If the chromium powder is 5 wt% or less, the joining strength is not particularly reduced even if metals such as Ni, Fe, Mn, Mo, Ti, W are mixed,
The amount is preferably 5 wt% or less. It is desirable to heat the ceramics coated with chromium powder to 900 to 1300 ° C. for 10 minutes to 1 hour. When the Cr firing temperature is 900 ° C or lower, the Cr metallized layer is not formed, and when it is 1300 ° C or higher.
The thickness of the Cr metallized layer becomes 10 μm or more, and the strength of the Cr metallized layer is extremely reduced.

Next, a method of joining with metal or ceramics through the Cr metallized layer formed by the above method will be described in detail.

As described above, the surface of the silicon carbide ceramic, which is provided with the Cu or Ni layer after being metallized with Cr, can be easily joined to the metal or the metallized ceramic or glass by soft solder or hard solder.

When joining the silicon carbide ceramics to a metal or ceramics having a different coefficient of thermal expansion, it is desirable to join the silicon carbide ceramics to the metal or ceramics via a third metal having a thermal stress relaxation action. .

This thermal stress relaxation material has a longitudinal elastic modulus of 12 × 10 ³ kgf / m
A metal material of m ² or less or a composite material thereof is preferable. Specifically, copper or a composite material containing copper as a main component or silver or a composite material containing silver as a main component is preferable. The thickness of these is preferably 100 to 1000 μm.

[Embodiment] Embodiment 1 An embodiment of the present invention will be described below with reference to FIG.

Figure 1 shows that by adding about 1% by weight BeO, the thermal conductivity is 270 W / m · ° K and the electrical insulation resistance is 10 ¹³ Ω · cm. Silicon 1
The cross section of the joined body which joined the alumina ceramics 2 of the same shape is shown.

The present invention is particularly effective when applied to silicon carbide having a thermal conductivity of 240 to 270 W / m · ° K and an electric insulation resistance of 10 ¹⁰ to 10 ¹³ Ω · cm.

On one surface of the silicon carbide ceramics plate, Cr powder having a particle size of 10 μm, which was made into a paste by dimethyl ethyl cellulose, was applied to the entire surface in a thickness of about 30 μm, and this was applied in an Ar atmosphere.
After firing at 1100 ° C. for 30 minutes, it was naturally cooled. As a result, a mixed layer of Cr silicide and Cr carbide having a thickness of about 4 μm and a metal Cr layer are partially formed on the surface of the ceramic mother plate, and an unreacted Cr layer having a thickness of about 20 μm is further formed on the surface. It was
Next, the unreacted Cr layer is removed with a knife, and a Ni film 4 is electroplated on the reaction Cr layer 3 on the ceramic surface to a thickness of about 5 μm.
m formed.

On the other hand, the one in which the Mo-Mn metallized layer 5 and the Ni plating layer 6 were formed on one surface of the alumina ceramics 2 was used.

A silver foil 7 having a thickness of 0.6 mm was used between the two ceramics, the surfaces of which were metallized by the above method, in order to reduce thermal stress. Two ceramics having different thermal expansion coefficients, which were metallized by the above method through the silver foil, were joined by silver braze 8. The thickness of the silver solder of this joint is about 30 μm and JIS
Was brazed at 800 ° C. in N ₂ containing 10% hydrogen.

As a result of measuring the tensile strength of the joined body joined by the above method, a strength of about 20 kgf / mm ² was obtained.

Further, the tensile strength was measured after heating the bonded body bonded by the above method to 700 ° C., and it was found that the bonding strength was not decreased and the heat resistance was high.

Example 2 About 5 wt% AlN as a sintering aid, thickness 2 mm, length and width 20 mm
Approximately 50μ of Cr powder with a particle size of 10μm, which was made into the same paste as above, was applied to one surface of the hot-pressed silicon carbide ceramic plate.
It is applied to the entire surface with a thickness of m, and this is applied in an argon atmosphere for 90
After firing for 30 minutes at 0 to 1500 ° C., it was naturally cooled. As a result, on the surface of the ceramic, a Cr silicide and Cr carbide mixed layer having a thickness of about 1 to 15 μm and a portion of metal Cr, which is Cr, are formed.
A reaction layer was formed, and an unreacted layer having a thickness of about 30 μm was further formed thereon. Next, the unreacted Cr formed in the outermost layer
The layer was removed with a metal brush and the metal Cr layer on the surface of the ceramic was electroplated with Ni to about 5 μm.

After a copper wire having a diameter of 2 mm was bonded to the metallized film formed by the above method with silver solder at 800 ° C., a tensile test was performed in the vertical direction.

FIG. 2 shows the relationship between the heating temperature and the bonding strength obtained as a result, and FIG. 3 shows the relationship between the thickness of the Cr layer and the bonding strength. When the heating temperature is 900 to 1300 ° C., , Reaction Cr
It can be seen that high-strength bonding can be performed with a layer thickness of 1 to 10 μm. In FIGS. 2 and 3, the mark ● indicates fracture of the ceramic base material, and the mark ○ indicates fracture of the joint.

Example 3 Electric resistance containing about 40 wt% ZrB ₂ having a thickness of 1 × 10 ⁴ Ω · cm 1
mm, 3 mm x 50 mm conductive SiC ceramics, a part of one surface is coated with Cr powder of about 30 μm to a thickness of about 500 μm, and this is applied under reduced pressure of 5 × 10 ⁴ Torr at 1050 ° C. , 30
It was naturally cooled after firing for 1 minute. Then Cr on the metallized surface
The oxide layer was removed and Ni plating was performed to about 3 μm. That Ni
A Ni film having a diameter of 1 mm was brazed with silver on the surface of the plating and used as a heater for ignition.

Even when the heat cycle test of this ignition heater was conducted 1000 times in the temperature range of 600 ° C to 20 ° C, no decrease in bonding strength was observed.

[Effects of the Invention] According to the present invention, by forming a Cr reaction layer strongly bonded to the surface of a silicon carbide-based ceramic, another metal member or ceramic member can be formed on the Cr reaction layer surface via a Cu or Ni film. It is possible to firmly bond and obtain a bonded body having high heat resistance and high strength.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between the temperature at which a silicon carbide ceramics plate coated with chromium powder is heated and the bonding strength obtained as a result, FIG. 3 is a characteristic diagram showing the relationship between the thickness of the Cr metallized layer and the bonding strength.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Rikuo Kamoshida 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitate Manufacturing Co., Ltd.In Hitachi Research Laboratory (72) Inventor Akira Matsuzaka 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Nitate Manufacturing Co., Ltd. Inside Hitachi Research Laboratory (56) References Japanese Patent Publication No. 3-62674 (JP, B2)

Claims (6)

[Claims] 1. A step of forming a chromium powder layer on the surface of a non-oxide ceramic sintered body, and a layer containing a reaction product of ceramics and chromium on the surface of the sintered body, which is fired in an inert atmosphere or a reduced pressure atmosphere. A method for metallizing non-oxide ceramics, comprising a sequential step of forming an unreacted layer containing chromium oxide thereon and removing the unreacted layer containing chromium oxide. . 2. The method for metallizing non-oxide ceramics according to claim 1, wherein the non-oxide ceramics is made of carbide ceramics. 3. The method of metallizing non-oxide ceramics according to claim 2, wherein the carbide ceramics is made of silicon carbide. 4. A method of metallizing non-oxide ceramics according to claim 1, wherein the pressure of the reduced pressure atmosphere is 10 ⁻² Torr or less. 5. The method for metallizing non-oxide ceramics according to claim 1, wherein the layer containing the reaction product of the ceramic and chromium is formed to a thickness of 1 to 10 μm. 6. The method for metallizing non-oxide ceramics according to claim 1, wherein the chromium powder is applied in a paste form on the surface of the sintered body.