JPS6357394B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for metallizing carbide ceramic bodies used for applications such as high temperature resistant, high strength materials, and wear resistant materials. Metallization of ceramic bodies, especially alumina (Al ₂ O ₃ ) ceramic bodies, has been used for a long time as a metal sealing technique for attaching electrodes to ceramic capacitors and for vacuum tubes and airtight terminals. With this transition, its use as a wiring conductor has rapidly progressed, and recently it has become an indispensable and important technology for forming conductor parts of ceramic multilayer wiring boards. Known methods for metallizing ceramic bodies include thick film or thin film methods, electroless plating methods, heat-resistant metallized powder sintering methods using high temperature treatment, and active metal methods. The method for metallizing alumina ceramic bodies is as follows:
Generally, metals are formed into active ultrafine particles in a high vacuum using vapor deposition and physically deposited on the ceramic surface, or metallization including, for example, molybdenum (Mo) powder and manganese (Mn) powder. The paste composition is made into a paste using a binder and solvent, which is made of a suitable binder and solvent, and after this is applied onto a ceramic body, it is placed in a weakly acidic hydrogen atmosphere containing water vapor or a mixed atmosphere of hydrogen and nitrogen. A method of forming a metallized layer by firing inside is adopted. In the latter method, Mn is oxidized to MnO during the firing process in an atmosphere containing hydrogen containing water vapor or nitrogen, and the
A fluid glass of MnO- _{Al2O3 - SiO2} is formed by reacting with _Al2O3 and _SiO2 , and this penetrates between the _{Al2O3 particles} to form a matrix, so that the metallized _layer and
Strong adhesion with Al ₂ O ₃ sintered body can be obtained. For this reason, it is common practice to add glass components such as Al ₂ O ₃ , SiO ₂ , CaO, etc. to the metallization composition to promote glass formation and obtain stronger adhesion. The metallization layer formed by the method described above is
After Ni plating has been applied, soldering and brazing can be performed. In this way, many methods have been developed for metallizing oxide-based ceramic bodies such as alumina and beryllia, which have been widely used in the past.Basically, the method using highly activated vapor-deposited metal fine particles as described above has been developed. The method of adhering metal components through glass, which is compatible with oxide ceramics, has been technically established. However, in recent years, with the development of new ceramic materials, materials with excellent properties not found in conventional oxide ceramics, such as high strength at high temperatures, high thermal shock resistance, chemical resistance, and physical and chemical stability, have been developed. Carbide ceramic materials such as silicon carbide came into use,
Its uses are not limited to electronic component materials, but are also expanding to materials for industrial machinery such as gas turbines and sealing. When carbide ceramics are used as industrial machine parts, ceramic bodies may be joined together,
It is essential to join a ceramic body and a metal member, and one effective method is to apply a metallized layer to the joint portion of the ceramic body and then bond the metal. However, with respect to carbide-based ceramic bodies, strong adhesion between the ceramic body and the metallized layer cannot be obtained using the metallization compositions and methods using the same, which have been used in conventional alumina ceramic bodies. For example, according to the vapor deposition method, the adhesive strength is weak because it is basically a physical adhesive in addition to the special process, and when heated to improve the strength, carbide is generated due to the high reactivity, resulting in brittle reactions. A phase is formed, further reducing adhesive strength. In addition, in the method of adhering through glass, the glass has poor wettability with carbide ceramics, and when fired at high temperatures, the bonds in the glass
Since SiO ₂ is reduced by carbide and its strength is reduced, strong adhesive strength cannot be obtained and it is difficult to form an excellent metallized layer.Therefore, an effective metallization method for carbide ceramics has been long-awaited. Ta. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for forming a strongly adhered metallization layer on the surface of a carbide-based ceramic body. According to the present invention, 80 to 30 parts by weight of W powder and Si powder
After applying a metallizing composition paste containing 20 to 70 parts by weight and a binder to the required locations of the carbide ceramic body, it is heated within the range of 1300 to 1600°C in a non-oxidizing atmosphere other than a nitrogen atmosphere. A method for metallizing a carbide ceramic body is provided, which comprises firing at a temperature of . Carbide ceramics generally have a small coefficient of thermal expansion, and although it varies somewhat depending on the sintering method, it has the following coefficient of thermal expansion in the temperature range from room temperature to about 400°C. Silicon carbide (SiC) ceramic
:3.5 to 5.5 (×10 ^-6 /℃) Tantalum carbide (TaC) ceramic
: 6.6 to 8.4 Titanium carbide (TiC) ceramic: 7.4 Boron carbide (B ₄ C) ceramic: 4.5 Tungsten carbide (WC) ceramic: 4 to 6.2 Therefore, in the metallization method of these carbide ceramics, Since it is necessary to reduce the difference in thermal expansion coefficient between the composition and the ceramic, a high melting point metal with a low thermal expansion coefficient is used as at least one metal powder for metallization, and furthermore, strong adhesion between the carbide ceramic and the metallized layer is obtained. The inventors have found that the most important factor for this purpose is to mix carbide ceramic and a metal with good wettability. In the present invention, the high melting point metal with a low coefficient of thermal expansion has a coefficient of thermal expansion of 4.3×10 ^-6 /°C at room temperature.
W is used. Metals that have good wettability with carbide ceramics include Cu, Zn, B, Al, Si, Co, and Ni, among which Si is selected. Si is SiC ceramic, TaC ceramic, TiC
It is suitable for carbide ceramics such as ceramic, B ₄ C ceramic, and WC ceramic. The above W and Si are 80 parts by weight to 30 parts by weight of W,
These powders are mixed at a blending ratio of 20 parts by weight to 70 parts by weight of Si. The above compounding ratio may be appropriately set within the above range while taking into account the thermal expansion coefficient of the carbide ceramic to be metallized. Next, to give a specific example of a method for metallizing the surface of silicon carbide ceramic using the above-mentioned metallization composition, the above-mentioned W and Si powder is mixed with a well-known solvent such as α-terbinol or water, A binder consisting of a well-known binder such as ethyl cellulose or polyvinyl alcohol is added to form a fluid paste, which is then carbonized by means such as screen printing, feather painting, brush banding, spraying, or dipping. After coating the surface of the siliceous ceramic body to be metallized, it is fired at an appropriate temperature in the range of 1300°C to 1600°C in a non-oxidizing atmosphere such as argon gas or hydrogen under reduced pressure. If the blending ratio of the metallizing powder is outside the above range, the metallization state on the carbide ceramic surface will be poor and sufficient bonding strength will not be obtained. Regarding the firing temperature, if it is less than 1300℃, it will be W.
A liquid phase consisting of Si is not generated, and the wettability with the carbide ceramic is insufficient, and good metallization does not proceed.On the other hand, when the temperature exceeds 1600℃, the reaction with the carbide ceramic becomes intense and WC is formed. This becomes noticeable and a porous layer is formed on the surface layer of the carbide ceramic, making it impossible to obtain a metallized layer with sufficient adhesive strength. If a nitrogen atmosphere is adopted as the non-oxidizing firing atmosphere, Si in the metallized composition will be removed during firing.
(silicon) reacts with N ₂ (nitrogen) to form silicon nitride, which prevents the formation of a good metallization layer. According to the method of the present invention, a metallized layer having a bending strength of 6 kg/mm ² or more as determined by the test method described below is formed on the surface of a carbide ceramic body. Examples of the present invention will be described below. (Example 1) Tungsten (W) powder and silicon (Si) powder were blended in the proportions (wt%) shown in Table 1, and an organic binder was added to make a metallization composition (metallization paste). Screen printing was performed on a silicon carbide ceramic body, which is a typical type of carbide ceramic, and the surface of the ceramic body was metallized by firing at 1400°C in a furnace with an argon atmosphere. The metallization states listed in Table 1 are the results of visual observation of the metallized surface. Since the results are graded according to the degree of occurrence of cracks and voids on the surface of the metallized surface, it is possible to judge whether the adhesion of the metallized surface is good or bad based on the results of the surface condition.

【table】

[Table] Based on the results of the above experiments, tungsten is 80 to 30%
It has been found that metallizing pastes with a ratio of 20-70% silicon to tungsten give excellent metallized surfaces, and metallizing pastes with a ratio of 40-60% silicon to 60-40% tungsten are optimal. Next, after applying the metallizing paste of sample No. 4 in Table 1 to the end surfaces of two silicon carbide ceramic bodies, the test pieces were fired and bonded under the above conditions with the coated surfaces in contact with each other. The bending strength was measured with stress applied to the joint surface, and the result was 18Kg/mm.
A value of ² was obtained. Also, No. 3 has 9Kg/
mm ² , No. 5 showed a strength of 16 Kg/mm ² .
For comparison, we conducted the same experiment as above using sample No. 1 metallized paste, and found that it was 2Kg/mm.
It was ² . In addition, the method for producing the above-mentioned test piece and the method for measuring the bending strength are as follows. After applying metallizing paste to the 3.5 mm x 20 mm end faces of two 3.5 mm x 20 mm x 15 mm flat silicon carbide ceramic bodies, the coated surfaces were fired with the coated surfaces facing each other, and then the joined Cut out the ceramic body with a diamond cutter, 3mm x
A test piece measuring 3 mm x 30 mm and having a joint at the center of its length was prepared. The bending strength of this test piece was measured by a three-point bending method in which the joint was used as the upper load point and the distance between the lower supports was 20 mm. Furthermore, the surface of the silicon carbide ceramic body was metallized using the metallization paste of Sample No. 3 (W70% by weight, Si 30% by weight) at 1200℃ in Ar atmosphere 1200℃ N ₂ 〃 1400℃ Ar 〃 1400℃ under reduced pressure (10 ^-2 torr) As a result of carrying out experiments at 1700°C Ar, 1700°C N ₂ , the results were that the metallization state was: ×, 〇, △, and ×. As described above, according to the metallization method of the present invention, a strong metallization layer can be easily formed on a carbide-based ceramic body, particularly a silicon carbide-based ceramic body, in the same manner as on an oxide-based ceramic body such as alumina. After that, it became possible to plate the metallized surface with nickel, copper, etc., and then join the metals using existing techniques such as soldering and silver brazing. In this way, using the metallization technology according to the present invention,
By combining conventional brazing and other techniques, carbide ceramic bodies can be used as high-temperature mechanical components or wear-resistant parts such as mechanical seals, and can be used as electrode terminals for electrical and electronic components. It is possible, and the effects are tremendous.

Claims (1)

[Claims] 1. After applying a metallizing composition paste containing 80 to 30 parts by weight of W powder, 20 to 70 parts by weight of Si powder, and a binder to the required locations of the carbide-based ceramic body, 1. A method for metallizing a carbide-based ceramic body, which comprises firing at a temperature within the range of 1300 to 1600°C in a neutral atmosphere.