JPS6319470B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a significantly improved method for producing various types of highly thermally conductive ceramics, particularly highly thermally conductive alumina porcelain that greatly increases the degree of integration as an IC substrate. Alumina porcelain is widely used as a ceramic substrate for ICs due to its excellent mechanical strength, electrical insulation, and good thermal conductivity. However, as the integration density of ICs tends to increase year by year, It started to cause dissatisfaction. In other words, the upper limit of the thermal conductivity of industrially produced alumina porcelain is about 0.08 cal/cm・sec・℃, but a value of 0.1 cal/cm・sec・℃ or higher is desired.
In response to this, enamel substrates or beryllia porcelain are attracting attention, but since the former enamel substrate is made by baking glass onto a thin metal plate, not only can it not be expected to significantly improve the overall thermal conductivity, but the glass The layer has the disadvantage of being easily scratched,
In the case of beryllia porcelain, the raw material powder is highly toxic and requires strict control, making it difficult to mass-produce, and it has been limited to special uses. The present invention does not rely on the above-mentioned enamel substrate or harmful beryllium porcelain, but instead uses the powder of alumina porcelain, which has been subjected to lipophilic surface treatment, in a first slurry in which raw material powder such as alumina porcelain is dispersed in a water-insoluble organic solvent. Disperse in water one or more fine powders selected from metals with higher thermal conductivity than the insulating ceramic raw material of slurry 1 or inorganic materials such as metal oxides, carbides, and nitrides that can be metalized by reduction firing. The resulting second slurry is emulsified and dispersed, and this emulsion is used as a starting material to obtain the desired shape and shape according to a conventional method.
We have established a manufacturing method for highly thermally conductive ceramics, which is characterized by firing in a non-oxidizing atmosphere after molding to a certain size, and which significantly improves thermal conductivity without significantly reducing other properties. ,
The details will be explained below along with examples. Example 1 Ethylene tetrachloride (water-insoluble organic solvent) 500c.c.
Alumina powder made lipophilic by surface treatment with silane coupling agent (Showa Light Metal, UA)
008・Average particle size 0.4μ) 20g, mineralizer (magnesium silicate, reagent grade 1) and emulsifier (NOF・
Nonion OP-80R/HLB value 4.3) 0.9g to 1000c.c.
Mixed by alumina ball mill & ball stone,
Fine alumina powder subjected to lipophilic treatment is dispersed in ethylene tetrachloride to form a first slurry. Separately, add 66 g of ferric oxide (Fe ₂ O ₃ , reagent, particle size 0.5 μ) and 120 g of molybdenum trioxide (MoO ₃ , reagent, particle size 0.1 μ) to 300 c.c. of water. Mixed by alumina ball mill & ball stone,
Particles of Fe ₂ O ₃ and MoO ₃ are dispersed to form a second slurry. Next, transfer the first slurry obtained through the above process to a beaker and add a magnetic stirrer.
While rotating and stirring at a speed of 1200 RPM, the second
Gradually pour in the slurry at a rate of 5 c.c. per second,
Add 50~100μ of the second slurry into the first slurry.
A W/O emulsion was obtained by uniformly dispersing the following particles into particles. This W/O emulsion was heated to a gas temperature of 190°C.
Spray drying was carried out under the conditions of a disk diameter of 120 mm, 7200 RPM, and 3 c.c. per second. The granulated granules are made by turning a 20 to 40 μm block of Fe ₂ O ₃ and MoO ₃ fine powder into a 4 to 10 μ thick thin film of alumina fine powder that has been surface-treated with silane coupling. The average particle size of the coated material was 45μ. The granules were molded into a 90mm x 90mm plate with a thickness of 3mm using a die press at a pressure of 1500Kg/cm ² , and then heated with ammonia decomposition gas at 1500℃ for 1 hour at a dew point.
A sintered product measuring 60 mm x 60 mm x 2 mm was obtained by firing at 30°C. This sintered product is made of powder metallurgically sintered Fe and Mo.
Numerous polyhedrons of 15 to 27 μm in size made of fine powder are tightly bonded to an insulating layer of sintered alumina with a thickness of 2 to 5 μm through a metallization reaction, forming a dense cross-sectional shape. The characteristics were shown.

[Table] From Table 1, it can be seen that the sintered product obtained in Example 1 of the present invention has a higher volume resistivity and transverse rupture strength than conventional high-purity (99.9%) alumina porcelain. The reduction in thermal conductivity was kept to a negligible level, and the thermal conductivity was increased by approximately 54%, making it possible to significantly increase the integration density. Example 2 In exactly the same manner as in the above example, first and second slurries, and these first and second slurries W/
This emulsion is made into a carrier film (Toray Co., Ltd.) using the doctor blade method.
A green sheet with a thickness of about 1 mm is formed by sheet casting on a green sheet (luminar), and after drying, it is baked in ammonia decomposition gas at 1490℃ for 0.8 hours with a dew point of 32℃ to a thickness of 0.6mm and 50mm in length and width. A sintered product of ×50 mm was obtained. In the sintered product according to this example, the first and second slurries have different specific gravity depending on the solution (ethylene tetrachloride and water); the former first slurry has a specific gravity of 1.65, and the latter second slurry has a specific gravity of Because of the lower 1.42,
In the green sheet that is sheet-casted in the state of W/O emulsion, the granular second slurry dispersed in the first slurry gradually floats up over time and separates into two layers, and the lower layer is sintered by firing. An alumina porcelain layer of about 0.04 mm, and a thin alumina film of 2 to 4 μm are made of sintered iron and molybdenum that are firmly bonded to each other and to the underlying alumina porcelain part by the metallization reaction as in the previous example. It consisted of a metal layer with a thickness of about 0.56 mm, and exhibited the characteristics shown in Table 2.

[Table] However, the volume resistivity was measured in the thickness direction.
This example also shows remarkable effects like the previous example, and in particular, the final product forms two layers consisting of highly insulating alumina porcelain and insulated metal. It can exhibit insulation properties similar to porcelain. As described above, the present invention imparts high dispersibility to organic solvents by subjecting an insulating ceramic raw material to lipophilic surface treatment in advance, and skillfully utilizes this lipophilicity to make the insulating ceramic raw material A W/O emulsion is created by dispersing water in which metal components are dispersed into particles in a water-insoluble solvent, and this emulsion can be used as it is as a slurry for doctor blades or cast molding, or can be spray-dried. The ceramics having the extremely high thermal conductivity shown in each example are produced by molding them into the desired shape as granules for press molding by a conventional method and then firing them in a non-oxidizing atmosphere. The manufacturing method has been established. Note that in the above example, oxides Fe ₂ O ₃ and MoO ₃ that are metallized by reduction calcination were used as the starting material powders to be dispersed in water in the second slurry W.
The starting raw material powder for this second slurry is coated with the fine powder of the insulating ceramic raw material blended in the first slurry and is fired in a non-oxidizing atmosphere, so that the oxidation of these powders is prevented. The material is not limited to a material, but may be a metal as long as it satisfies the required thermal conductivity and fire resistance, or may be a non-oxide ceramic such as silicon carbide or silicon nitride. Furthermore, the insulating ceramic raw material used for the first slurry 0 is not limited to the alumina used in the examples, but can be selected depending on desired characteristics. As explained in the examples, the fine powder of highly thermally conductive raw materials including insulating ceramics and metal components, which are the main components of the first and second slurries, is a fine powder of sintered metal. Since it is insulated and coated with a thin layer of sintered ceramics, the materials and blending ratio of both starting materials are first determined according to the desired properties such as insulation and thermal conductivity. Unless there is a requirement, the volume ratio of ceramics to metal in the final product (after sintering) is preferably about 0.2 to 0.5 equivalents, and after adjusting the first and second slurries accordingly, The slurry is mixed. The ratio of the insulating ceramic as the final product to the highly thermally conductive inorganic material such as metal is determined by the mixing ratio of the first and second slurries. The volume ratio of the second slurry to the slurry is preferably 1/5 to 2/3, particularly about 1/3. Note that since the first and second slurries have different solutions and main components, it is difficult to make the specific gravity of both slurries the same, but there is no problem in granulating the emulsion-formed slurry by spray drying. If this is directly sheet casted, Example 2
As described above, since two layers consisting of an insulating layer and a highly thermally conductive layer are formed on the same plate, it is rather preferable as a highly thermally conductive insulator. Next, preferred embodiments regarding the raw materials, blending ratios (volume ratios), etc. used in the first and second slurries will be described below. (A) First slurry Insulating ceramic raw material Not limited to alumina, powders of other compositions can be used depending on the purpose, such as forsterite, mullite, zircon, wollastonite, etc. Coupling for lipophilic treatment In addition to silane-based agents, aluminate- and titanate-based agents can also be used depending on the ceramic powder, but from the viewpoint of dispersibility, the average particle size of the raw material is preferably 3 μm or less. For handling organic solvents, it is preferable to use a high boiling point, but if the boiling point is too high, heating is required, so a temperature of 50 to 120℃, or 70 to 90℃ is preferable, and the blending ratio (volume ratio) with the insulating ceramic solvent
A suitable range is 2 to 30 parts of the above ceramic per 100 parts. Emulsifier This emulsifies the second slurry, that is, the aqueous slurry, into the first slurry, and if it is an organic substance or a liquid, it must be selected with an HLB value of 6 or less. can be replaced with a solid emulsifier such as fine powder of aluminum stearate or magnesium stearate, and the solid emulsifier functions as a strong protective film at the boundary between the first and second slurries and also acts as a mineralizer. In some cases, it is more effective than in the case of organic liquids for working, but in any case the amount is in the range of 1 to 5 parts by volume per 100 parts of organic solvent. Others The first slurry is completely slurried with the above lipophilic-treated ceramic fine powder, an organic solvent that is incompatible with water, and an emulsion that emulsifies water, and mixed with the second slurry. In addition to sheet casting molding, which is performed in that state after being made into an emulsion,
Even in granules granulated by spray drying for press molding, the coating layer exhibits the necessary strength, but it is also effective to add known binders and plasticizers according to conventional methods. For casting molding, it is preferable to use a binder such as polyethylene oxide that is compatible with water in order to volatilize the water in the second slurry to the outside after molding, but the amount added is less than 100 parts of the ceramic raw material. The thickener is 30
The plasticizer is 25 parts by volume or less, and the ceramic raw material is 30 parts by volume per 100 parts of the organic solvent.
less than the capacity part. Further, if the main raw material ceramic is alumina or the like which requires high temperature firing, a small amount of mineralizing agent can be added according to a conventional technique. (B) Second slurry High thermal conductivity component The core high thermal conductivity component is not limited to oxides that are metallized by reduction firing, but also other compounds such as chlorides such as ferric chloride, hydroxides, etc. It is possible to use hydroxides such as ferric iron, fine metal powders, and even non-oxide ceramics such as silicon carbide and silicon nitride, but these also require fine particles in terms of dispersibility. However, unlike the case of the ceramic raw material powder in the first slurry, since it aggregates into particles, an average particle size of up to 5μ is allowed, and the blending ratio (volume ratio) with water as a solution is 100 parts of water. In contrast, a range of 5 to 30 parts is appropriate. Others It is sufficient to form a slurry only with highly thermally conductive components such as metals, but as in the case of the first slurry, it is preferable to add a small amount of a binder and plasticizer, and also a commercially available dispersant to lower the viscosity at low moisture levels. , for example microsol (KE-
412・Compatible Chemistry) etc. are also effective, and the binder is 30 parts by volume or less per 100 parts of the metal component, the plasticizer is also 20 parts by volume or less, and the dispersant is used to achieve low viscosity at low moisture levels. The amount is 2 parts by volume or less per 100 parts of the total slurry. Furthermore, the ceramic raw material powder used in the first slurry or other oxides or hydroxides may be added to the second slurry in order to approximate the firing shrinkage rate to that of the first slurry.

Claims (1)

[Claims] 1. A first slurry O is prepared by dispersing a fine powder of an insulating ceramic raw material that has been subjected to a lipophilic surface treatment in an organic solvent that is not compatible with water, together with an emulsifier that emulsifies water. While stirring,
A second slurry is prepared by dispersing in water one or more fine powders selected from metals having high thermal conductivity, metal compounds that can be metalized by reduction firing, or inorganic materials such as carbides and nitrides. Adjust the W and pour it in, disperse the second slurry in the form of particles in the first slurry, and add W/O.
A method for producing highly thermally conductive ceramics, which comprises forming an emulsion, molding the emulsion, and firing it in a non-oxidizing atmosphere.