JPH0152347B2 - - Google Patents

Description

[Detailed description of the invention]

"Field of Industrial Application" The present invention establishes a method for manufacturing a composite sintered body suitable for IC boards, multilayer wiring boards, etc. that require high insulation resistance and thermal conductivity. ``Prior art'' As a manufacturing method for this type of composite sintered body, the present applicant previously filed Japanese Patent Application No. 175597-1982 (Japanese Patent Application No. 69468-1988).
``A fine powder of an insulating ceramic raw material is mixed with an organic solvent that is poorly soluble in water, along with an emulsifier that emulsifies water, and while stirring the dispersed oil-based slurry O, the slurry is mixed with metal or reduction firing. Therefore, a slurry W in which fine powder of a metal compound to be metallized is dispersed in water is poured into a W/O emulsion in which the slurry W is dispersed in the form of particles in the slurry O, and this emulsion is molded and non-oxidized. ``A method for producing highly thermally conductive ceramics characterized by firing in a warm atmosphere.''"Problems to be Solved by the Invention" The invention of Japanese Patent Application No. 175597/1987 succeeded in producing a composite sintered body with generally satisfactory characteristics, but there are still some points to be improved. was. That is, the water-based slurry dispersed in particulate form is separated by the oil-based slurry. Although the thickness dimensions of these isolated films are approximately the same, it is difficult to achieve complete uniformity, so during drying, the thickness of the partition layer between the water-based slurry particles varies, which impairs the structural uniformity, so mechanical There was a risk that variations would occur in various characteristic values such as strength, thermal conductivity, and insulation resistance. "Means for Solving the Problems" A metal alkoxide is used as an insulating ceramic raw material component in slurry O. "Operation" The water in the aqueous slurry W dispersed in the form of particles comes into contact with the metal alkoxide in the slurry O, causing a hydrolysis reaction between the water and the metal alkoxide on the surface of the slurry W, forming a film of the hydrolysis product. formation,
This becomes an insulating barrier layer, maintains structural uniformity, and stabilizes various properties of the sintered product. For example, titanium alkoxide, "titanium tetraethoxide" Ti(OC ₂ H ₅ ) ₄ reacts with water to form Ti(OC ₂ H ₅ ) ₄ +2H ₂ O → 4C ₂ H ₅ OH + TiO ₂ , and aluminum alkoxide, "Aluminum isopropoxide" Al [OCH
In the case of (CH ₃ ) ₂ ] ₃ , Al[OCH(CH ₃ ) ₂ ] ₃ + 3H ₂ O→ 3(CH ₃ ) ₂ CHOH + Al(OH) ₃ on the surface of the aqueous slurry dispersed in the above particle form. is coated with an insulating layer of metal oxide or hydroxide. “Example” (1) Add 109 g of the above aluminum isopropoxide to 700 c.c. of kerosene and add alumina (Daimei Chemical TM
-5 silane coupling treated product with Nihon Unica A-162 silane coupling agent) 109g
were mixed at 80 RPM for 24 hours using a No. 2 alumina ball mill and 2 kg of 20 mmφ alumina ball stone to obtain an oil-based slurry O. Separately, add 500 ml of FeO (particle size 1μ, commercially available) to 400 c.c. of water.
g and 660 g of metal Mo (particle size 0.5 μ, commercially available),
Along with 400g of 15% aqueous solution of binder PVA, 2 alumina balls and 2Kg of alumina ball of 20mmφ
Aqueous slurry W was obtained by mixing at 80 RPM for 24 hours. Next, the oil-based slurry O obtained through the above process was transferred to a polyethylene beaker (No. 2), and the water-based slurry W was added at a rate of 2 c.c. per second while stirring with a propeller (3 blades, 50 mmφ, 1800 RPM). When poured, the slurry W becomes fine particles of 50 to 100 μΦ and is dispersed in the oil-based slurry. After pouring all the slurry W into slurry O to generate mixed slurry W/O, propeller stirring is started.
The stirring speed was lowered to 500 RPM, and stirring was performed gently for 10 minutes to promote the hydration reaction of the aluminum isopropoxide in the slurry O to the surface of the fine particles of the slurry W. Mixed slurry W/O obtained in this way
A small amount of the slurry was collected on a 350-mesh sieve, and the oil-based slurry O surrounding the fine-particle water-based slurry W was gently washed off using kerosene, resulting in a near-transparent gel-like substance on the surface of the particles of the slurry W. A hydrolyzed coating layer estimated to be aluminum hydroxide with a thickness of about 10 μm was confirmed by fluorescence X-ray analysis. This mixed slurry W/O was formed into a sheet on a polyester film by the doctor blade method, and dried in a forced exhaust chamber using a fan to obtain a green sheet with a thickness of 0.78 mm. ℃、1500℃、
Firing was performed under conditions of holding for 1 hour. This sintered body has a thickness of about 0.6 mm, and is made of a film of countless metal particles of about 40 to 80 μφ sintered in a powder metallurgy manner under a sintered alumina layer of about 50 μ thick formed on the top surface. It exhibited a dense cross-sectional shape that was firmly bonded to a thin layer of sintered alumina with a thickness of approximately 5 to 8 microns through a metallization reaction. Table 1 shows the above-mentioned samples produced according to the present invention and the patent application filed in
175597 (Japanese Unexamined Patent Application Publication No. 59-69468), the results of measuring variations in thermal conductivity and volume resistivity are shown. However, as a comparative product, the sample according to the above-mentioned Japanese Patent Application No. 175597/1980 was prepared by adding 109 g of the aluminum isopropoxide used in the present invention as the alumina in the slurry W to the above-mentioned alumina TM-- which was subjected to silane coupling treatment. 5, the alumina TM-5 was changed to 136 g, and 3.5 g of an emulsifier (NOF, Nonion OP-80R, HLB value 4.3) was added.

[Table] From Table 1, it can be seen that the samples manufactured according to the present invention have less variation in both thermal conductivity and volume resistivity than the comparative product manufactured based on Utility Application No. 175597/1983. In addition to significantly reducing the amount of aluminum, the average values of both properties were further increased, an effect that can be attributed to aluminum isopropoxide. (2) Add aluminum alkoxide, 112 g of aluminum isopropoxide, silicon alkoxide, 42 g of ethyl silicate to 700 c.c. of kerosene to produce a mullite composition and alumina (Nippon Unicar Co., Ltd. with Sumitomo Aluminum Refining A-HPS-30). A-162 silane coupling treated product) 56g, silicic anhydride (particle size
24g of 1μ (commercially available Nihon Unica A-162 silane coupling treated product) was processed using 2 alumina ball mills and 2Kg of 20mmφ alumina ball stone.
Oil-based slurry O by mixing at 80RPM for 24 hours.
I got it. Separately, in 400 c.c. of water, 480 g of silicon carbonate (particle size 0.5 μ, Schütarch, β type), 5 g of boron nitride (sintering aid, particle size 0.5 μ, Denki Kagaku Kogyo), and 15% PVA as a binder. 160 g of the aqueous solution was blended and mixed at 80 RPM for 15 hours using a No. 2 alumina ball mill and 2 kg of alumina ball having a diameter of 20 mm to obtain an aqueous slurry W. Next, the slurry W is poured into the oil-based slurry O at a rate of 5 c.c. per second using the same propeller stirrer as in the previous example, and the slurry W is dispersed in the slurry O in the form of fine particles of 50 to 70 microns. After pouring all of the slurry to form a mixed slurry W/O, the propeller stirring speed was lowered to 600 RPM, and gentle stirring was continued for 10 minutes to transfer the aluminum and silicon alkoxides/aluminum isopropylene in the slurry O to the surface of the fine particles of the slurry W. Promoted the hydration reaction of poxide and ethyl silicate. A small amount of the W/O slurry thus obtained was collected on a 350-mesh sieve, and the oil-based slurry O surrounding the particulate water-based slurry W was gently washed off using kerosene.
A hydrolyzed coating layer with a thickness of about 8 μm was formed on the surface of the particles, which appeared in a gel-like state and was estimated to be made of aluminum hydroxide and silicic acid by fluorescent X-ray analysis. This mixed slurry O/W was heated at a gas temperature of 170°C.
Granulation was carried out by spray drying under the conditions of a disk diameter of 110 mm, 7200 ROM, and 2 c.c./sec. The granulated granules are made of fine particles of silicon carbide mixed with a trace amount of boron nitride, and the 25-35 μm lumps with the above-mentioned hydrolyzed coating layer formed on the surface are mixed with fine particles of alumina and silicate ceramics in slurry O. It was coated with a thin film of powder having a thickness of 3 to 5 microns and had an average particle size of 40 microns. The granules were molded into a 50 x 30 mm plate with a thickness of 5 mm using a die press at a pressure of 1500 Kg/cm ² , and then fired in an argon atmosphere at 1780°C for 1 hour to form a 40 mm x 24 mm plate. A sintered product with a thickness of 4 mm was obtained. This sintered product consists of 30-33μ grains made of finely sintered silicon carbide powder using boron nitride as an auxiliary agent, which is solidified by a thin layer of sintered mullite with a thickness of 2-4μ. It exhibited a dense cross-sectional shape that was combined with . Table 2 shows the above-mentioned samples produced according to the present invention and the patent application filed in
175597 (Japanese Patent Application Publication No. 175597 (1982)) The results of measuring the variation in thermal conductivity and volume resistivity are shown for samples manufactured according to Japanese Patent Application Publication No. 175597 (1983). ,
As the mullite component in slurry W, 112 g of the aluminum isopropoxide used in the present invention was replaced with the above-mentioned alumina A-HPS-30 treated with silane coupling to give 86 g, and 42 g of ethyl silicate was also treated with silane coupling. Replaced with the above commercially available silicic anhydride subjected to 36
g, and an emulsifier (NOF/Nonion OP)
-80R・HLB value 4.3) It was manufactured under the same conditions as Example 1 of the present invention except that 1.5 g was blended.

[Table] In the second example, the sample manufactured according to the present invention was also superior in both thermal conductivity and volume resistivity compared to the comparative product manufactured according to Utility Model Application No. 57-175597. We succeeded in significantly reducing the variation and maintaining thermal conductivity close to that of silicon carbide porcelain, while increasing the volume resistivity, which is a weak point of silicon carbide porcelain, to a level close to that of mullite porcelain. As clarified by the above examples, the composite sintered body obtained according to the present invention can be produced by directly manufacturing a sheet from the prepared mixed slurry by the doctor blade method or by once spray drying it. Even if press molding is performed after granulation, a great effect of the metal alkoxide in the slurry O can be seen. In both examples, alkoxides of Al and Si are used as representatives, but alkoxides such as Ti, Ca, Mg, Zr, Li, Sr, Be, etc. shown in the chemical formula above can also be used, so desired results can be obtained. An insulating layer consisting of the composition can be formed. In addition, in both examples, the alumina and silicic anhydride that have been subjected to the silane coupling treatment and are blended into the slurry O compensate for the large firing shrinkage of the main components, aluminum isopropoxide and ethyl silicate. This can be omitted since it is used to emulsify the slurry by imparting lipophilic properties, but in this case it is preferable to add an emulsifier such as sorbitan monooleate or HLB4.3. Therefore, the main component fine powders in slurry O and slurry W are sintered fine powders of inorganic raw materials such as highly thermally conductive metals, and sintered highly insulating and chemically stable ceramics. Since the material is bonded and coated as a matrix, the blending ratio of both starting materials is determined depending on the desired properties, but unless there is a special request, the final product (after sintering)
Slurry W which becomes the latter minute core in terms of capacity ratio
The ratio of the highly insulating and chemically stable ceramic raw material of the former slurry O to the highly thermally conductive inorganic raw material is preferably about 0.1 to 0.3, and in order to completely disperse the slurry W in the former slurry O. The latter slurry W is 1/5 in volume ratio
~2/3, particularly about 1/3 is preferred. Note that slurry O and slurry W have different solutions and main components, so it is difficult to make the specific gravity of both slurries the same. However, when granulating a W/O mixed slurry by spray drying, there is no problem and it is possible to directly Even when sheet molding, the difference in specific gravity between the two is
Since a layer of slurry O is formed on either side of the bottom, there is no problem, and it may be preferable in some cases. Next, preferred embodiments regarding the raw materials, blending ratios, etc. used in slurry O and slurry W are shown below. (1) Slurry O The main metal alkoxide can be freely selected along with an oxide of the same element to compensate for the firing shrinkage, if necessary, and oxidation of two or more metal alkoxides and the same metal element as these. The desired compositions such as mullite, cordierite, and forsterite shown in the examples can be obtained by using the following materials.If these main components require high-temperature firing, a small amount of mineralizing agent may be added according to conventional techniques. It may be added, and known binders and plasticizers may be added to press mold products of granulated products by sheet casting with mixed slurry W/O or spray drying, or to increase the strength during these processes. However, from the viewpoint of dispersibility, the average particle size of these main components and mineralizing agents is preferably 3μ or less, and the desirable blending amount is 15 to 30 parts by volume per 100 parts of the organic solvent that is sparingly soluble in water. be. (2) The highly thermally conductive inorganic raw material that is the main component of slurry W is not limited to the metals used in the examples and oxides that can be metalized by reduction firing, but also stable oxides such as beryllia can be used. These also require fine particles for dispersibility, but unlike the main component in Slurry O, they aggregate into particles, so the average particle size is allowed up to 5μ, and the mixing ratio with water as a solution is 100 parts water. 15 to 35 parts by volume based on the slurry O is preferable, and like slurry O, a known binder,
Additions of small amounts of plasticizers and dispersants that reduce viscosity at low moisture levels are effective. Further, in order to approximate the firing shrinkage rate of slurry W to that of slurry O, the ceramic main component used in slurry O or other oxides or hydroxides may be added. "Effects of the Invention" As described above, the present invention, which uses a metal alkoxide as the main component of the slurry O, forms a hydrolyzed coating layer of the metal alkoxide on the surface of the fine particles of the slurry W dispersed in the slurry O. By acting as an insulating layer between the fine particles, it is possible to improve the variation in characteristic values as clarified in the examples, and the water in the particles of slurry W is converted into an oil based alcohol in the form of alcohol according to the chemical reaction formula described above. Because it is absorbed into the slurry O, it dries the molded object from the inside, so even large, complex shapes molded by casting, rubber press, etc. can be dried uniformly.
It has an excellent effect of eliminating the fear of distortion, cuts, etc. that occur during drying.

Claims (1)

[Claims] 1 Oil-based slurry O made by dispersing and dissolving fine metal alkoxide powder in an organic solvent that is poorly soluble in water.
and, while stirring, pour into this slurry a water-based slurry W prepared by dispersing fine powder of a highly thermally conductive inorganic raw material in water, and disperse the water-based slurry W in the oil-based slurry O. At the same time, a hydrolyzed coating layer of the metal alkoxide is formed on the surface of the dispersed fine particles of slurry W, and the fine particles of the aqueous slurry W coated with this hydrolyzed coating layer and the surrounding oil-based fine particles are formed. A method for producing a composite sintered body, which comprises molding and firing a mixed slurry consisting of slurry O.