JPS6332743B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing ceramics that significantly improves thermal conductivity and maintains high insulation properties. For example, printed wiring boards made of thin plates of high alumina porcelain have become more heat dissipating due to the increased packaging density of electronic circuits in recent years, so there is a strong demand for materials with high heat dissipation. In the case of high alumina porcelain, which is commonly used due to its high thermal conductivity, the upper limit is set from the perspective of mass production.
0.07 cal/cm・sec・ even for 99.5% high purity products
The temperature remained at about ℃, and the above requirements could not be met. The present invention has established a method for manufacturing highly thermally conductive ceramics that significantly improves thermal conductivity without significantly reducing the insulation resistance of various ceramics, including the above-mentioned printed wiring boards. explain. Example 1 (a) Alumina sol (#200 alumina content 10% Nissan Chemical) 130g CaCO ₃ (commercially available) average particle size 0.2μm 0.2g MgCO ₃ (commercially available) average particle size 0.1μm 0.1g Silicic anhydride (commercially available) Product) A nonionic surfactant (Nonion E-230,
HLB value 17.3, NOF) 4.5 g water 2160 c.c. was blended and mixed using a magnetic stirrer to prepare the first dispersion W ₁ . ( _{b )} Polyethylene oxide (water _- soluble (3) ethylene tetrachloride (water-insoluble _solvent ) 1460g non-ionic surfactant (OP-80R, HLB value
4.3, Nippon Oil & Fats & Oil Co., Ltd.) 9g of both were mixed using a magnetic stirrer as before to make the non-aqueous solvent O. (d) The above O and W ₂ were mixed while stirring to form a non-ionic surfactant. A dispersion of the second raw material powder is emulsified in a non-aqueous solvent to produce a W ₂ -O emulsion in which anhydrous W ₂ lumps are dispersed in O. (E) The W ₂ -O emulsion and the above W ₁ are mixed while stirring, and the nonionic surfactants with different HLB values blended into the W ₂ -O emulsion and the first dispersion W ₁ are used. Make a W ₂ -O-W ₁ composite emulsion. This W ₂ -O-W ₁ composite emulsion is the first
A second dispersion W ₂ coated with a non-aqueous solvent O is dispersed in the dispersion W ₁ . (f) W ₂ -O-W ₁ composite emulsion at gas temperature
170℃, disk diameter 120mm, 7200RPM, 4 per second
Spray drying was performed under cc conditions. In the granulated granules, Fe ₂ O ₃ and MoO ₃ lumps were coated with gel-like alumina fine powder, and the average particle size was 100 μm. (g) The granules were press-molded with a die at a pressure of 1500 Kg/cm ² . (h) The press-formed product is held at 1500℃ for 1 hour in a hydrogen atmosphere with a dew point of 35℃ and fired to form a 9mmφ×1mm
A sintered product of t was obtained. The sintered product has a film thickness of 497μ, consisting of countless polyhedrons of 40 to 60μ made of fine powders of Fe and Mo sintered in a powder metallurgical manner.
It had a dense cross-sectional shape that was firmly connected by the front and rear sintered alumina insulating layers. Table 1 shows the results of measuring various properties of the sintered product thus obtained.

[Table] From the above table, it can be seen that the sintered product obtained by the above embodiment of the present invention has a negligible decrease in insulation resistance compared to conventional high purity (99.5%) alumina porcelain. In order to significantly increase the target thermal conductivity, and especially for the printed wiring board mentioned earlier that requires high heat dissipation, glass is applied to the iron plate, which is considered to be the best material in the past. The thermal conductivity of baked enamel boards is 0.1 cal/cm・sec・℃, which is 70% higher, and it is possible to significantly increase the packaging density of electronic circuits. In the above Example 1, CaCO ₃ and mineralizers were added to alumina sol as the first raw material powder.
Although trace amounts of MgCO ₃ and SiO ₂ were added, some or all of these were replaced with water-insoluble organic compounds such as calcium stearate, magnesium stearate, and ethyl silicate, and the non-aqueous solvent was added to the non-aqueous solvent O. To further improve the adhesion between the sintered Fe and Mo fine powder and the alumina insulating layer covering it by enhancing the function of the water solvent and generating CaO-MgO-SiO ₂ glass in the firing process. In addition, a trace amount of a water-soluble particle binder such as methylcellulose (0.5% based on water) is added to the first dispersion _W1.
By adding the following), the thin layer of gel-like alumina fine powder that coats the surface of the granules granulated by spray drying is hardened, making it easier to handle, and making it easier to handle. Similarly, it is also effective to add a trace amount of ethyl cellulose as a water-insoluble particle binder. Example 2 Forsterite porcelain (2MgO・SiO ₂ ) raw material fine powder Average particle size 0.5μm 10g Nonionic surfactant (Noigen EA-170,
First dispersion W ₁ consisting of a mixture of 4 g water (2000 c.c.) (HLB value 17, Daiichi Kogyo Seiyaku) and 113 g polyvinyl alcohol (Denka B-05) Fe ₂ O ₃ (commercial product, average particle size 0.3μ) ) (water-soluble particle binder) 1g water 400c.c. second dispersion W ₂ consisting of a mixture of 990g ethylene dichloride (water-insoluble solvent) non-ionic surfactant (Neugen EA-33,
As in the previous example, a W ₂ -O-W ₁ emulsion was made using a mixture of 8 g of HLB value 4 (Daiichi Kogyo Seiyaku) and the non-aqueous solvent O, and after spray drying and press molding, the dew point The 9mmφ x 1mmt sintered product obtained by firing at 1400℃ for 1 hour in a hydrogen atmosphere at 30℃ consists of countless 50-60μ polyhedra made of a sintered body of fine powder of metallic iron. It exhibited a cross-sectional shape that was firmly connected by an insulating layer of forsterite porcelain with a diameter of about 5μ. As shown in Table 2, this sintered product showed remarkable effects in greatly improving the thermal conductivity without causing any adverse effects on the properties of forsterite porcelain.

[Table] Although Examples 1 and 2 above were both intended for printed wiring boards, the present invention is not limited to thin plates, and is applicable to ICs that require particularly high heat dissipation properties as well as insulation resistance and other properties of ceramics. It can be applied to the production of not only plate-shaped bodies but also cylinders and rod-shaped bodies, including thick-walled ceramics such as packages. In addition, by using beryllia, which has particularly high thermal conductivity, as the highly insulating first raw material fine powder, it is possible to further improve heat dissipation.
The second raw material fine powder with high thermal conductivity is not limited to the oxides that are metallized by firing, such as Fe ₂ O ₃ and MoO ₃ shown in the examples, but other compounds or metals may also be used directly. In addition, carbides and nitrides such as SiC and BN that are stable in a non-oxidizing atmosphere can also be used, but these first and second raw material fine powders should be a combination of materials with similar thermal expansion coefficients and sintering temperatures. preferable. Therefore, the insulating layer formed from the above-mentioned first raw material fine powder exhibits sufficient specific characteristics even at an extremely thin film thickness of about 2 μm, and even when the film is thick, it exhibits heat dissipation properties corresponding to the film thickness. From this point of view, although not particularly limited, it is preferably about 3 to 8 μm, and the blending ratio of the first raw material fine powder and the second raw material fine powder is determined depending on the desired film thickness. Next, the preferred conditions for producing a satisfying W ₂ -O-W ₁ emulsion are: First, the total amount of W ₂ and O is equal to or 1/4 of W ₁ (volume ratio, the same applies hereinafter); The relationship between W ₂ and O is such that W ₂ is equal to or 1/4 of O, and the first and second raw material powders are the first dispersion W ₁ and the second dispersion, respectively.
The mixing ratio of water is determined so that it can be dispersed in W ₂ as a slurry, but in both cases 10 to 10% of the total amount
It is about 40% by weight. Furthermore, the surfactant in the first dispersion W ₁ is in the range of 0.1 to 0.5% by weight based on water, and the surfactant in the non-aqueous solvent O is in the range of 0.2 to 2% by weight based on the non-aqueous solvent. %. As mentioned above, the nonionic surfactants added to W ₁ and O are emulsified by adding oil to water, and the latter is emulsified by adding water to oil, depending on their HLB value. The HLB value of the nonionic surfactant added to the former W ₁ for emulsification is 15 or higher.
HLB, a nonionic surfactant added to the latter O
The value is preferably 5 or less.

Claims (1)

[Claims] 1 (a) A fine powder of a ceramic raw material having high insulation properties is used as a first raw material powder, and a nonionic surfactant and water are added and mixed to form a first dispersion. The process of making W ₁ . (b) One or more types of fine powder selected from inorganic materials such as metals, compounds of metals that can be metallized by firing, carbides, and nitrides, which have a higher thermal conductivity than the first raw material powder, are added to the powder. A step of preparing a second dispersion liquid _W2 by adding and mixing a water-soluble particle binder and water to the raw material powder of No.2. (c) A step of preparing a non-aqueous solvent O by mixing a non-aqueous solvent and a non-ionic surfactant with a lower HLB value than the non-ionic surfactant in (a). (d) A step of mixing and emulsifying the above W ₂ with O to produce a W ₂ -O emulsion. (E) Mix the above W ₂ -O emulsion and W ₁ , W ₂
-The process of making O-W ₁ . (F) A step of spray drying the composite emulsion W ₂ -O-W ₁ . (g) A process of press forming into the desired shape. (h) Sintering process in a non-oxidizing atmosphere. A method for producing highly thermally conductive ceramics consisting of