JP2748961B2 - Method for producing surface-modified alumina ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing surface-modified alumina ceramics, and particularly to a method for producing a semiconductor integrated circuit substrate or an engineering ceramic by increasing the specific surface area of the surface. The present invention relates to improving the adhesion to metals and the like or obtaining a novel catalyst carrier.

[Conventional technology]

Alumina ceramics are widely used in various industrial fields because of their excellent mechanical strength, thermal properties, electrical properties, and the like. In particular, the demand for substrates for semiconductor integrated circuits is increasing, but firing and then printing or bonding a desired conductive material such as metal on alumina ceramics to form connecting electrodes and electrical circuits on the substrate doing. However, if the surface of the alumina ceramic is smooth, the metal or the like formed on the surface is easily peeled off.Therefore, in order to improve the adhesion between the alumina ceramic and the metal, the surface of the alumina ceramic is mechanically removed by sandblasting or the like. Surface roughening is performed by a method or chemical etching that elutes crystal grain boundaries with an acid or an alkali such as hydrofluoric acid, phosphoric acid, or sodium hydroxide.

[Problems to be solved by the invention]

Roughening of alumina ceramics by mechanical or chemical methods is uneven in surface texture structure,
Since it is difficult to obtain fine grooves and projections, not only the adhesion to metal and the like tends to decrease, but also it takes a long time to roughen the surface.

[Means for solving the problem]

The inventors of the present invention used a conventional technique to partially machine the surface of alumina ceramics in order to increase the specific surface area and increase the adhesion to metals and the like formed on the surface, in order to make the roughness of the surface structure of alumina ceramics uniform. It was noted that the purpose could be achieved by forming a layer having extremely high strength and a large specific surface area on the surface of the ceramics instead of removing it by a mechanical or chemical method. Intensive examination of the layers formed on alumina ceramics revealed that three-dimensional growth of mullite crystals containing alumina, which is the main component of alumina ceramics, and where the sintering temperature of alumina and the growth temperature of needle-like crystals almost match. It has been found that a layer having a large specific surface area and a large bonding force can be obtained by densification.

That is, a clay mineral containing aluminum oxide and silicon dioxide as main components, a mixture of aluminum oxide powder or aluminum hydroxide powder and silicon dioxide powder or silicate glass powder, or at least one substance selected from aqueous slurries thereof is converted to alumina. 1200 to 1700 after coating on the surface of the compact or alumina ceramics
This is to form acicular mullite on the surface of the alumina ceramic by firing at ℃ and eluting the glass component remaining on the surface of the obtained alumina ceramic.

In addition, the alumina molded body in the present invention includes not only a molded body composed of only alumina as a ceramic component but also a molded body mainly composed of alumina containing a component other than alumina, such as silica and magnesia, and similarly an alumina ceramic. In addition to ceramics composed only of alumina, ceramics mainly composed of alumina and containing silica, magnesia, and the like are included. Further, the present invention can be used for both unsintered alumina compacts and sintered alumina ceramics.

Hereinafter, a case where an unsintered alumina molded body is used will be described.

As the alumina, a powder having a particle size of 0.1 to 10 μm substantially containing no other component, for example, an alumina powder having an average particle size of 0.5 μm (α-type alumina, manufactured by Sumitomo Chemical Co., Ltd., trade name ABS-12, impurity Fe ₂ O ₃ : 0.01, SiO ₂ : 0.02, Na ₂ O: 0.03 content, each unit is wt%, alumina powder with an average particle size of 5 μm (α-type alumina, manufactured by Sumitomo Chemical Co., Ltd., trade name AM- Two
5. Impurity Fe ₂ O ₃ : 0.01, SiO ₂ : 0.02, Na ₂ O: 0.03 content, each unit is wt%, alumina powder with average particle size 10μm (α-type alumina, manufactured by Sumitomo Chemical Co., Ltd.) Name AM-28, impurities Fe ₂ O ₃ : 0.01, SiO ₂ : 0.02, Na ₂ O: 0.27 contained, all units are weight%), etc., methylcellulose, polyvinyl alcohol, wax, thermosetting as binder resin,
A thermoplastic resin or the like is added in an amount of 2 to 30% by weight, formed into a pellet, honeycomb, or thin plate by extrusion molding, casting, or the like, and then sufficiently dried to obtain an alumina molded body.

Subsequently, a mullite-forming substance is applied or immersed on the surface of the molded body to adhere the mullite-forming substance to the surface.Examples of the mullite-forming substance include clay minerals such as kaolin and porcelain clay for porcelain, and quartz. Powder, cristobalite powder, tridymite powder, plate glass powder, silicate glass such as colloidal silica or water glass, or a powdery mixture of aluminum oxide powder or aluminum hydroxide powder and silicon dioxide powder can be used. When a powdery mixture of silicon dioxide and aluminum hydroxide, aluminum oxide or the like is used as a raw material, it is selected in the range of 0.1 to 100 μm, but aluminum oxide or aluminum hydroxide is 0.1 to 10 μm, and silicon dioxide is 0.5 to 50 μm. The degree is preferred.

When using a powder of silicate glass or a mixed powder of silicon dioxide and aluminum oxide or aluminum hydroxide, raw powder 1 to 10 as it is or in a weight ratio,
A slurry in which the raw material powder having a water content of 99 to 90 is dispersed is used.

Alumina compacts or alumina ceramics to which mullite-forming substances are attached can be used at a temperature of 1200 to 1700 ° C for 0.1 to 1
After firing for 0 hour, preferably 1 to 3 hours, the glass component or glass phase remaining in the fired body is eluted with an acid or alkali. When using hydrofluoric acid as the acid, it is immersed in an acid having a concentration of 2 to 20% at a temperature of 20 to 50 ° C. for 10 minutes to 3 hours. When using an alkali such as sodium hydroxide or potassium hydroxide, use an alkali having a concentration of 0.1 to 2N in an autoclave at a temperature of 100 to 200 ° C.
Soak for minutes to 10 hours. After these elution treatments, post-treatment is carried out by a common method such as washing with water.

According to such a method, fine acicular mullite grows three-dimensionally in close contact with the surface of the alumina ceramics, and densely grown surface modified alumina ceramics are obtained by intermingling the acicular crystals. The resulting needle-shaped mullite is usually 1 to
It has the form of a whisker-like crystal having a diameter of 30 μm and a minor diameter of 0.1 to 2 μm, and has thermal stability up to about 1750 ° C. and is not easily deformed.

The obtained surface-modified alumina ceramics had a pore size of 0.
The porous material has pores of 1 to 1 μm, and its porosity is proportional to the thickness of the acicular mullite layer, and can be adjusted in the range of 5 to 40%. In addition, since acicular mullite is strongly adhered to the underlying alumina ceramics,
It is difficult to peel off even if it is cooled rapidly after heating at 500 ℃.

Although the case of using the alumina molded body has been described above, in addition to the alumina molded body, glass that is not easily melted and deformed at 1200 ° C. to 1400 ° C., such as quartz glass, is used, and alumina powder, water A mixture of several percent of alkali components such as sodium oxide and potassium oxide added to aluminum oxide powder and kneaded are applied, baked, and treated with hydrofluoric acid to prevent needle mullite from growing on the surface of quartz glass. It is possible.

(Operation) The method of the present invention can easily and efficiently homogenize the surface texture structure of alumina ceramics and increase the specific surface area.
It becomes possible to enhance the adsorption of ions and the like and the permeability of solder and the like.

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Alumina powder having an average particle size of 0.5 μm (α-type alumina, manufactured by Sumitomo Chemical Co., Ltd., trade name: AHS-12, impurity Fe ₂ O ₃ : 0.01, Si
_{O 2: 0.02, Na 2 O} : 0.03 containing, with respect to both the unit weight%), methyl cellulose was extruded into a thin plate after kneaded 10% by weight as a binder. The obtained molded body was sufficiently dried, and the alumina molded body having a weight of 50 g (thickness 2 mm, width 50 mm,
160 mm in length).

As a mullite-forming substance, 90 parts by weight of water was added to 10 parts by weight of a clay mineral powder having an average particle diameter of 1 μm to prepare a slurry in which the mullite-forming substance was dispersed. 100m of this slurry
After the alumina compact was immersed and impregnated in l, the alumina compact was fired at 1650 ° C. for 2 hours. The glass component or glass phase remaining in the obtained alumina ceramics is
Elution was carried out with 4.6% hydrofluoric acid for 1 hour, followed by washing with water to obtain a surface-modified alumina ceramic having acicular mullite densely grown on the surface.

The 3500-fold electron micrograph of acicular mullite crystals densely grown on the surface of the obtained surface-modified alumina ceramics
FIG. 2 shows an electron micrograph at 1500 times of the cross-sectional structure of the ceramic.

After immersing the sheet-shaped surface-modified alumina ceramic in a 0.1 mol / L ferric nitrate solution for 2 hours for impregnation, the iron supported on the ceramic was eluted with hydrochloric acid and determined by absorption spectrometry. It was 2.7 mg per 1 g of the ceramic.

After nickel was vapor-deposited for 10 minutes by vacuum evaporation, nickel was eluted with 1N hydrochloric acid, and the amount of nickel deposited was determined by absorption spectroscopy to be 34 mg.

Melt solder was applied to the nickel-deposited ceramics, and the wettability was examined. As a result, the solder penetrated well.

On the other hand, mechanical strength is 50mm long, 10mm wide, 1m thick
The thin ceramic plate having a thickness of m was bonded with a cyanoacrylate-based resin, and the flexural strength was determined to be 20.5 kg / mm ² .

[Example 2] Pellets of surface-modified alumina ceramics having a diameter of 0.5 to 1 mm were produced in the same manner as in Example 1, and the concentration of the pellets was adjusted to 0.
After immersion in a 1 mol / L ferric nitrate solution for 2 hours for impregnation, the iron supported on the ceramic was eluted with hydrochloric acid and determined by absorption spectroscopy. As a result, it was 6.5 mg / g of the ceramic.

[Example 3] A honeycomb ceramic carrier having a wall thickness of 0.2 mm for a catalyst support was produced in the same manner as in Example 1, and the concentration was 0.1 mm.
After being immersed in a mol / L ferric nitrate solution for 2 hours for impregnation, the iron supported on the ceramic was eluted with hydrochloric acid and determined by absorption spectroscopy. As a result, it was 3.5 mg / g of the ceramic.

(Comparative example)

The amount of the metal supported on the alumina ceramic before the surface was modified with the mullite needle crystals was measured by the same method as in Examples 1, 2, and 3. 0 per g of ceramics.
8 mg, 2.2 mg and 1.2 mg.

The bending strength of a sheet-like alumina ceramic whose surface had not been modified was examined in the same manner as in Example 1.
It was 11.4 kg / mm ² .

〔The invention's effect〕

As described in detail above, according to the method of the present invention, the roughness of the surface structure of alumina ceramics can be made uniform, and the specific surface area can be increased, so that the adhesion of various metals and the like and the adsorption of ions and the like can be improved. Surface-modified alumina ceramics with enhanced permeability such as solder can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an electron micrograph instead of a drawing for explaining the structure of acicular mullite crystals densely grown on the surface of the surface-modified alumina ceramic of the present invention, and FIG. 2 is a cross-sectional structure of the alumina ceramic of FIG. FIG. 3 is an electron micrograph showing the crystal structure of the surface of the non-modified alumina ceramics.

────────────────────────────────────────────────── (5) References JP-A-2-137789 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 41/80-41/91 B01J 37 / 00

Claims (2)

(57) [Claims] An acicular mullite is formed by applying a substance containing silicon dioxide to the surface of a molded body of alumina or alumina ceramics, followed by firing, and eluting the glass component remaining on the surface of the obtained ceramics to convert the acicular mullite into alumina ceramics. A method for producing surface-modified alumina ceramics, characterized in that it is formed on the surface of a ceramic. 2. A clay mineral whose silicon dioxide-containing substance is mainly composed of aluminum oxide and silicon dioxide, a mixture of aluminum oxide powder or aluminum hydroxide powder and silicon dioxide powder or silicate glass powder, or an aqueous solution thereof. 2. The method for producing surface-modified alumina ceramics according to claim 1, wherein the method is at least one substance selected from slurries.