JPS59156962A - Manufacture of alumina sintered substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for manufacturing an alumina sintered substrate.
In particular, the present invention provides a method for manufacturing an alumina sintered substrate with a smooth surface. The alumina sintered substrate obtained by the present invention is useful as a substrate for thin films such as vapor deposited films and sputtered films.

2. Description of the Related Art Conventional configurations and their problems With the miniaturization and higher performance of electronic equipment, attempts have been made to reduce the thickness of circuit elements used, and several thin film elements have been put into practical use. A glass substrate is generally used as a thin film substrate essential for forming these thin film elements. However, glass substrates have poor heat resistance, such as barium titanate, which requires thin film formation at a high temperature of 1000°C or higher.

It cannot be used as a substrate for forming thin films such as lead titanate. This is a drawback common to alumina sintered substrates whose surfaces are smoothed by glazing.

Conventionally, an alumina sintered substrate has been used as a thin film substrate having high heat resistance of 1000° C. or higher, and is a substrate material with excellent electrical insulation and high mechanical strength. However, in an alumina sintered substrate with an alumina purity of about 96%, the surface smoothness is 0.6 to 1 μm in terms of center line average roughness.
It cannot be used as a substrate for forming a thin film with a thickness of 1 μm or less. As substrate materials having high heat resistance and excellent surface smoothness, there are sapphire substrates and alumina sintered substrates subjected to surface polishing treatment, but these substrate materials are expensive.

OBJECTS OF THE INVENTION The object of the present invention is to provide a method for manufacturing an inexpensive alumina sintered substrate with excellent surface smoothness.

Structure of the Invention The present invention provides a method for manufacturing an alumina sintered substrate in which a slurry is prepared by mixing a mixed powder of alumina raw material powder and magnesium oxide with an organic binder, and then the slurry is heated and fired in air. By using a material having a spherical shape, an alumina sintered substrate with good surface smoothness can be produced.

The alumina sintered substrate with excellent surface smoothness according to the present invention is realized by a green sheet in which alumina raw material powder and an organic binder are uniformly mixed, and the dispersibility of the alumina raw material powder and organic binder in the green sheet is It has been found that green sheets in which the alumina raw powder and organic binder are uniformly dispersed can be obtained by using spherical powder particles, in particular, depending on the shape of the alumina raw powder. Alumina green sheets with uniformly dispersed spherical particles have a uniform pore distribution even after the organic binder decomposes when heated and fired.
The solid phase reaction of the alumina particles proceeds uniformly, making it difficult for abnormal grain growth and local depression of surface particles to occur.

When the alumina green sheet of the present invention is fired in air at a temperature lower than 1600'C, the bulk density of the sintered body becomes 3.9q/cηλ or less, which is not preferable. On the other hand, heat treatment at high temperatures impairs the surface smoothness of the sintered body, and heat treatment at temperatures higher than 1600°C causes the center line average roughness of the sintered body surface to become more than 0.06 μm, and at temperatures lower than 1500°C. It is not unpleasant like baking.

Description of examples The present invention will be specifically explained below using examples.

Example 1 The shape of the raw material powder is spherical and well-shaped, angular and relatively uniform, spherical, angular, and other complex-shaped particles mixed together, and spherical. Four types of alumina powder, each with a purity of 99.
99.9% each was added to 997.5g of these four types of alumina powder prepared using raw material powder with an average particle size of 0.4μm.
9% magnesium oxide with an average particle size of 0.19 μm.
5q was added, and 4009 g of a liquid mixture of n-butanol and methanol was added to each mixed raw material powder, and 1-80 g of dibutyl phthalate and 120 g of polyvinyl butyral fat were added.
q was added and mixed for 96 hours in a fluororesin pot. Each of the four types of S:y')- obtained was
Figures 1 to 4 show surface electron micrographs of 04 types of green sheets, which were formed by coating onto an 8 μm thick polyester film using a doctor blade to form green sheets with a thickness of 0.35 mm. Figure 1 shows a graphite obtained from raw material powder that is spherical and well-shaped.
Figure 2 shows the surface of a green sheet obtained from raw material powder that has an angular shape and is relatively uniform. Figure 3 shows a mixture of spherical, angular, and other complex-shaped particles. Figure 4 shows the surface of a green sheet obtained from raw material powder that is irregularly shaped, and Figure 4 shows the surface of a green sheet obtained from raw material powder that has a mixture of spherical, angular, and cotton-like powders. It is.

As seen in Figure 1, when using spherical powder,
A green sheet with a dense and uniform surface is obtained, and cracks are less likely to occur during drying. On the other hand, Figure 2~
As seen in FIG. 4, when a powder having a shape other than spherical is used as the raw material powder, a green sheet having an uneven surface with many pores is obtained. The four alumina green sheets shown in Figures 1 to 4 were cut into 361L square shapes, placed in an electric furnace, and placed in air for 2 hours.
The temperature was raised to 1550°C at a heating rate of 00°C/hour, held at this temperature for 2 hours, and then heated to 300°C/hour at a rate of 500°C.
After the temperature had cooled down for a while, it was cooled in the furnace. The bulk density and center line average roughness (Ra) of the obtained alumina sintered substrates are shown in the table below.
4 correspond to FIG. 1, FIG. 2, FIG. 3, and FIG. 4, respectively.

As is clear from the above table, when using alumina raw material powder with spherical grain shape, the bulk density is 3.93 g/cyA.
It has the highest density, and the center line average roughness is as small as o, o5 μm. On the other hand, when using alumina raw material powder with a particle shape other than spherical, the bulk density is 3.9q/cd or less.
Also centerline average roughness. , the roughness is 1 μm or more.

Example 2 Purity 99.9%, average particle size. , 2.59% of magnesium oxide having a purity of 99.9% and an average particle size of 0.19 μm was added and mixed as an accessory component to 997.69% of alumina raw powder having a spherical powder particle shape of 4 μm. This raw material mixed powder has n
- After adding 400q of an isostatic mixture of butanol and methanol, dibutyl phthalate BQq and 120q of polyvinyl butyral resin were added and mixed for 96 hours in a fluororesin pot. The slurry thus obtained is 1
A green sheet with a thickness of 3 sm was formed by coating on a polyester film with a thickness of 88 .mu.m using a doctor plaid. After drying and cutting into 36M square shapes, they were placed in an electric furnace at 1000°C.

1450°C, 1500°C, 1550°G, 1600°C
, six firings were performed at six firing temperatures of 1650°C. The temperature was raised at a heating rate of 200°C/hour to each temperature, and after holding at that temperature for 2 hours,
The temperature was lowered at a rate of 1.5°C/hour and then furnace cooled to room temperature. FIG. 5 shows the bulk density and center line average roughness Ra of the obtained alumina sintered substrates plotted against each firing temperature.

As is clear from FIG. 6, the bulk density shows a high value of 3.9 q/tst or more at temperatures above 1500°C, but becomes lower than 3.9 q/cd at temperatures below that. In addition, the center line average roughness is 0.04 ~ 0.04 at 1000℃ or less
It exhibits excellent smoothness of 0.06 μm, but becomes rough at 0.08 μm at 1650'C.

The Narumina sintered substrate fired at a temperature within the range of 1500 to 1600°C has a bulk density of 3.9 g/r, a high density of more than a, and excellent smoothness with a center line average roughness of less than 0.06 μm. It is.

Effects of the Invention As seen in the examples above, the method of the present invention uses alumina raw material powder with spherical particle shapes and is fired at a temperature within the range of 1500 to 1600°C, thereby producing alumina sintered with excellent surface smoothness. A body substrate can be manufactured. The alumina sintered substrate produced by this method is useful as a substrate for high-temperature formed thin film devices, and its application to high-frequency devices is considered, and its industrial value is great.

[Brief explanation of the drawing]

Figures 1, 2, 3, and 4 are surface electron micrographs of alumina green sheets made of different raw material powders, and Figure 5 is a photograph obtained using a spherical raw material powder with a uniform shape. Bulk density and center line average roughness R of alumina sintered substrate
It is a figure showing the relationship with a). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 opm

Claims (1)

[Claims] Aluminum oxide powder particles having a spherical shape are mixed with an organic binder to form a slurry, this slurry is formed into a sheet shape, and then heated in air for 150 to 160 mm.
A method for manufacturing an alumina sintered substrate, characterized by heating and firing at a temperature within a range of 0'C.