JPH11329676A - Joined ceramics and metal body, ceramic heater using same, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stable joint of high strength, by providing, on a surface of nitride ceramics, a metallized layer including a V compound such as vanadium nitride or vanadium carbide and a metallic layer having Ni and/or a Ni compound as main constituent and a specific porosity, and joining a metallic member to the metallic layer. SOLUTION: Porosity of a metallic layer is 5 to 20%. A mixture of V fine powder of 1 to 30 wt.%, preferably 2 to 10 wt.%, Ni fine powder, an organic binder, etc., is prepared and spread on a surface of nitride ceramics 4, and heated to 1000 to 1200 deg.C in a vacuum atmosphere of 1×10<-3> Torr or under for 15 minutes. A lusterless silvery metallic layer 5 and a metallized layer 3 which is a boundary face between the layer 5 and the ceramics 4, are thereby obtained. The metallic layer 5 and a metallic member 1 to be joined are supplied with a brazing filler metal 2 therebetween, and heated/brazed, thus a joined body of a structure including cushioning materials is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-metal bonded body and a ceramic heater using the same, and more particularly to a method for forming a metal layer useful for bonding ceramic and metal simultaneously with metallizing the ceramic surface. Things.

[0002]

2. Description of the Related Art Conventionally, ceramics and metals have been joined by metallizing (metallizing) the ceramics surface by the Mo-Mn method and then Ni plating and then brazing to the metal with a silver brazing material. The active metal method and the like are widely and generally used.

However, the Mo-Mn method is widely used for oxide ceramics such as alumina, but is difficult to apply to non-oxide ceramics such as silicon nitride ceramics. In the active metal method, since the metallization and the brazing are performed simultaneously, the active metal Ti
Ag-Cu-Ti system containing Ag-Cu-In-
Improvements have been seen, such as joining directly by reacting with ceramic using a brazing filler metal such as Ti-based, but a joint having sufficient strength and excellent oxidation resistance and heat resistance has not been obtained. It is the current situation.

When a ceramic and a metal are joined by heating, residual stress acts near the joint during the cooling process due to a difference in thermal expansion between the ceramic and the metal, so that the joint strength of the joined body is reduced and the ceramic is cracked. Therefore, in order to reduce the residual stress, a low thermal expansion metal such as Mo, W, or Fe-Ni-Co alloy is inserted between the two to join them, or a soft metal plate such as Ni, copper, or aluminum is sandwiched. We are trying to join.

[0005] Among these soft metals, copper has a low proof stress, and therefore, when used for a joint to which stress is applied, the copper portion is deformed. Similarly, aluminum cannot be used for a joined body used at high temperature because of its low melting point. On the other hand, Ni has a proof stress and has excellent characteristics in terms of oxidation resistance and heat resistance, so that it is suitable as a buffer material for joining ceramics and metal. However, even if a Ni plate is simply inserted between a high-purity nitride-based ceramic having low thermal expansion and a metal to be joined, the two (Ni plate and ceramic)
Residual stress during the cooling process greatly affects the thermal expansion difference, and cracks occur in the ceramics, so that a joined body having high joining strength cannot be obtained.

[0006] As described above, in the metallization by the active metal method, in the Ag-Cu-based brazing material, Ti is used as an active metal.
Often used. Here, this Ag-Cu-Ti
The joining mechanism and actual problems will be considered by taking as an example the joining of three kinds of materials, ie, a brazing material, a nitride ceramic (here, silicon nitride ceramics), and a metal plate.

[0007] As shown in FIG. 3 Ag- Cu- is metallized layer 3 by the reaction layer of TiN and Ti ₅ Si ₃ is generated a Ti-based brazing material 2 and the silicon nitride at the interface between the ceramics 4 mainly, By forming this layer, Ag-Cu-Ti
It is considered that the surface of the silicon nitride ceramics in contact with the brazing material is metallized (metallized).

An Ag—Cu alloy brazing material 2 flows on the metallized layer 3 of TiN and Ti ₅ Si ₃ , and the brazing material 2 and the metal member 1 are further brazed to form three types of substances. A conjugate is obtained.

However, if the difference in thermal expansion between the metal and ceramic to be heated and joined is large, residual stress is generated near the joint during the cooling process. In this case, the metal plate to be joined is Ni
Even in the case of a plate, the residual stress generated due to the difference in thermal expansion between the silicon nitride ceramic and the Ni plate acts in the brazing material or on the ceramic surface, which causes problems such as a decrease in bonding strength of the joined body and cracking of the ceramic.

[0010]

As described above, Ni has excellent properties as a cushioning material used for joining ceramics and metal, but it cannot be said that a Ni plate as such is a sufficiently satisfactory cushioning material. This is because the residual stress generated due to the difference in thermal expansion between the ceramic and the Ni plate described above acts in the brazing material or on the ceramic surface, and the bonding strength of the bonded body is reduced and the bonding strength varies due to cracking of the ceramic.

Further, other soft metals (such as copper) have problems in heat resistance and corrosion resistance, and do not provide a sufficiently satisfactory buffer material or buffer layer.

[0012]

An object of the present invention is to provide a method for forming a buffer layer necessary for performing high-strength and stable bonding between ceramics and a metal,
And a joined body of metal and ceramic having the buffer layer.

[0013]

SUMMARY OF THE INVENTION In the present invention, in joining a ceramic and a metal, vanadium nitride and vanadium carbide are applied to the surface of a nitride ceramic to absorb and relax residual stress caused by a difference in thermal expansion between the two. Metallized surface containing a compound of V and Ni and / or Ni
Porosity of 5 as a main component (such as nickel silicide)
It is characterized by having a metal layer and a ceramic member formed by bonding a metal member on the metal layer.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows a cylindrical ceramic 4 mainly composed of silicon nitride (Si ₃ N ₄ ) joined to a metal member 1 of a metal fitting made of Ni wire, Fe—Ni—Co alloy or the like. In this joint structure, a metallized layer 3 containing a compound of V is provided on the surface of a ceramic 4, a metal layer 5 having pores is formed thereon, and a metal member 1 is joined on the metal layer 5 by a brazing material 2. Things.

In order to obtain such a joint structure, V (vanadium) is contained as an active metal in an amount of 1 to 30% by weight, preferably 2 to 10% by weight, the balance being Ni metal fine powder, and further containing an organic binder. A mixture is prepared, and the mixture is applied on the ceramics 4 and heated to about 1050 ° C. in a vacuum atmosphere and held for 15 minutes. It is to be noted that the treatment temperature is optimally from 1000 to 1200 ° C. At a temperature higher than this, the Ni fine powder is melted and a metal layer 5 having effective pores cannot be obtained. Is not enough to metallize.

As a result, the above-mentioned mixture applied to the surface of the ceramics 4 was obtained as a dull silver metal layer 5 and a metallized layer 3 at the interface with the ceramics 4.
A brazing material 2 (for example, Ag-Cu based, Au-Cu based, etc.) is added between the metal layer 5 and the metal member 1 to be joined, and is heated and brazed, so that a buffer material is sandwiched therebetween. Thus, a joined body of ceramic and metal can be obtained.

As for the breaking strength of the joined portion of the joined body, a high joining strength of 380 MPa was obtained in a four-point bending test.
The fracture at this time occurred inside the metal layer 5 having pores partially including the metallized layer 3 at the interface with the ceramics 4.
When the bonding was performed without the metal layer 5 for comparison, the fracture occurred inside the ceramics 4 including a part of the bonding interface, and the strength was as low as 210 MPa.

The cross section of the dull silver metal layer 5 obtained on the surface of the ceramics 4 is observed with a scanning electron microscope (SEM), and the cross section and the surface are analyzed for crystal structure by XRD (X-ray diffraction). As a result, a V compound such as vanadium nitride (VN) or nickel silicide (N
It was confirmed that the metallized layer 3 including iSi or the like was formed, and the metal layer 5 having pores was formed on the metallized layer 3.

From these results, it is found that the mixture of the active metal V powder and the Ni powder applied to the surface of the ceramics 4 is heated in a vacuum atmosphere, so that the ceramics 4
The highly reactive active metal V in contact with the surface of the silicon nitride reacts with silicon nitride (Si ₃ N ₄ ) to form vanadium silicide (V ₃ S).
i ₅ , VSi ₃ ) and vanadium nitride (VN), and free Si generated during the reaction reacts with the Ni powder to produce low-melting nickel silicide (NiSi or the like). The above reaction proceeds further using nickel as a liquid phase, and as a result, the active metal V collects on the surface of the ceramics 4, and a dense metallized layer 3 made of vanadium silicide and vanadium nitride is coated on the surface of the metallized layer 3 with nickel silicide. It is considered that the metal layer 5 is formed by the mixed Ni particles.

It was also found that the metal layer 5 containing nickel silicide and Ni as main components was not dense but had pores. Image analysis of the previous SEM photograph of the pores revealed that the pores had an average diameter of about 10 μm and had a porosity of 5 to 5.
It was 20%, and it was found that the four-point bending strength was high and stable particularly in the range of 8 to 16%.

This reaction requires that the active metal V having a high reactivity first reacts with silicon nitride (Si ₃ N ₄ ) to form vanadium silicide and vanadium nitride, and this reaction is sufficiently promoted. It was found that heat treatment in a vacuum was effective. This is a highly reactive active metal V
Is presumed to react with a substance in the atmosphere (for example, oxygen, hydrogen, or the like) first, so that the reactivity of V is weakened and the reaction force with silicon nitride ceramics is insufficient. Further, a heat treatment temperature in a vacuum is important in order to have a porosity of 5 to 20%. As described above, the treatment temperature is optimally 1000 to 1200 ° C. lower than the melting point of Ni. At temperature, nickel silicide is used
The fine powder is melted and only a metal layer having a low porosity is obtained. At a low temperature, the reaction between the active metal V and the silicide ceramic is insufficient, so that the metallization cannot be performed satisfactorily.

Since the metal layer 5 having the pores is present between the ceramics 4 and the metal member 1 to be bonded, residual stress due to a difference in thermal expansion at the time of heat bonding is absorbed, and the bonding strength is high and stable. A conjugate can be obtained. Further, since the metal layer 5 is a reaction layer made of Ni and nickel silicide, it has excellent heat resistance and oxidation resistance, and can be used at high temperatures.

Actually, after the bonded body of the present invention was left in an oxidizing atmosphere at 600 ° C. for about 200 hours, a high value which was not much different from that in the initial state immediately after bonding was obtained even when the four-point bending strength was measured. .

The porosity of the metal layer 5 having a porosity of 5 to 20% containing Ni and nickel silicide as main components is measured as follows.

1. The joint is cut with a diamond cutter so that the porous metal layer 5 can be seen.

2. Cut the cut surface with 5% dilute nitric acid solution
Immerse for 0 second to remove polishing sagging.

3. 500 for the processed cut surface
Take a SEM photograph at 2x.

4. Based on the SEM photograph, the metal layer 5
The porosity is measured by image analysis.

The porosity of the metal layer 5 having pores is 5 to 20.
% Is preferable because if the porosity is less than 5%, the metal layer 5
This is because the stiffness is high and a stress relaxation effect cannot be expected. On the other hand, if the porosity is larger than 20%, the strength of the metal layer 5 having pores becomes weak, and the metal layer 5 is broken from the metal layer 5 portion.

The thickness of the metal layer 5 is 0.05 to 0.50 m
m is preferable. If the thickness is less than 0.05 mm, sufficient stress relaxation cannot be expected. Although there is no upper limit of the thickness of the metal layer 5 as the stress relaxation layer, the upper limit is 0.5
The reason why the thickness is set to 0 mm is to take into consideration processing restrictions for overlaying the paste.

The fact that the ceramics 4 is a nitride ceramic means that silicon nitride, aluminum nitride, and a mixed system of aluminum nitride and silicon nitride are also included in the category. Preferably, it is desirable to use a silicon nitride ceramic which can be expected to have high strength.

The joined body of ceramics and metal of the present invention is
It can be used as an electrode take-out part of a ceramic heater, a joint part of a metal and a ceramic of a ceramic tappet, a joint part of a terminal of a ceramic semiconductor package, and the like.

FIG. 2 shows an example in which the present invention is applied to a ceramic heater.

As shown in FIG. 2, an electrode extraction portion of the heating resistor is formed in a part of the nitride-based ceramics 4 in which the heating resistor is buried. Then, a lead wire can be joined as the metal member 1 using the brazing material 2.

[0036]

EXAMPLE A test was conducted to evaluate the joint strength of the ceramic-metal joint of the present invention.

First, a test sample as shown in FIG. 4 was prepared. A columnar ceramic member 4 composed mainly of silicon nitride having the same shape and a columnar metal member 1 made of Ni
Is prepared, and the end faces to be joined are ground and finished with a # 600 grindstone. Thereafter, a paste obtained by mixing 96% by weight of fine powder Ni, 4% by weight of fine powder V, and a small amount of an organic binder or the like is applied to the bonding surface of the ceramics 4 by 0.20 mm. After drying, bake at 1000-1200 ° C. in a vacuum furnace. Thereafter, the brazing material 2 was applied on the obtained metal layer 5, the metal member 1 was overlapped and fixed, dried sufficiently, and then brazed in a vacuum furnace to prepare a test sample.

On the other hand, as a comparative example, Au—Ni was directly applied to the joint surface of the ceramics 4 having a columnar silicon nitride as a main component.
After applying the brazing, a columnar Ni-made metal member 1 was overlaid and fixed, dried sufficiently, and then brazed in a vacuum furnace.

The baking temperature of the metal layer 5 of each sample;
The brazing temperature of the metal member 1 is shown in Table 1. The metallized strength of the joint was evaluated by a four-point bending strength.

As shown in Tables 1 and 2, it can be seen that those having the porous metal layer 5 within the scope of the present invention have high bending strength and high bonding strength.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

As described above, according to the present invention, it is possible to prevent a decrease in bonding strength due to residual stress caused by a difference in thermal expansion and to provide a bonded body of ceramics and metal having excellent durability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a joined body of a ceramic and a metal of the present invention.

FIG. 2 is a perspective view showing a ceramic heater of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a conventional joined body of ceramic and metal.

FIG. 4 is a diagram showing a test sample of the present invention.

[Explanation of symbols]

 1: Metal member 2: Brazing material 3: Metallized layer 4: Ceramics 5: Metal layer

Claims (4)

[Claims] 1. A metallized layer containing a compound of V such as vanadium nitride or vanadium carbide on a surface of a nitride-based ceramic, and a porosity of 5 to 20% containing Ni and / or a compound of Ni as a main component thereon. A joined body of a metal and a ceramic, comprising a metal layer of (1) and a metal member joined to the metal layer. 2. The method according to claim 1, wherein the surface of the nitride-based ceramic is
A mixture of a fine powder of V, a fine powder of Ni, an organic binder and the like in a weight percentage is applied, and heated to 1000 to 1200 ° C. in a vacuum atmosphere of 1 × 10 ⁻³ torr or less, so that the ceramic surface is coated. After simultaneously forming a metallized layer containing a compound of V such as vanadium nitride and vanadium carbide, and a metal layer having a porosity of 5 to 20% mainly containing Ni and / or a compound of Ni so as to be in contact therewith And a method for manufacturing a bonded body of metal and ceramic, comprising a step of bonding a metal member to the metal layer. 3. A heating resistor is buried inside a nitride ceramic, a metallized layer containing a compound of V such as vanadium nitride or vanadium carbide is formed on the surface of the ceramic, and Ni and / or Ni is formed thereon. A ceramic heater comprising a metal layer mainly composed of a compound and having a porosity of 5 to 20%, and a metal terminal portion joined to the metal layer. 4. The method according to claim 1, wherein the surface of the nitride-based ceramic is
A mixture of a fine powder of V, a fine powder of Ni, an organic binder and the like in a weight percentage is applied, and heated to 1000 to 1200 ° C. in a vacuum atmosphere of 1 × 10 ⁻³ torr or less, so that the ceramic surface is coated. A metallized layer containing a compound of V, such as vanadium nitride or vanadium carbide, and a metal layer having a porosity of 5 to 20% containing Ni and / or a compound of Ni as a main component are formed at the same time so as to be in contact therewith. A method for manufacturing a ceramic heater, comprising a step of joining a metal terminal portion to a metal layer.