JPS623065A - Manufacture of magnesia ceramic - 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 [Field of Industrial Application] The present invention relates to a method for manufacturing magnesia porcelain, and particularly to a method for manufacturing magnesia porcelain with low dielectric loss.

"Prior Art" Magnesia is known as a material with excellent properties such as electrical insulation at high temperatures, high frequency properties such as dielectric loss, and thermal conductivity. On the other hand, with advances in electronic technology, materials with particularly low dielectric loss are required for microwave integrated circuit boards, microwave transmission windows, and the like. As mentioned above, magnesia has excellent properties and is one of the most suitable materials, but its poor sinterability and water compatibility make it difficult to use for microwave integrated circuit boards, etc. was difficult.

In order to improve this sintering property and hydration property, S
It has been proposed to add i02, for example, in JP-A-51-25508 and JP-A-53-126009.
No. 142419, Japanese Patent Publication No. 1983-142419, Japanese Patent Application Publication No. 1983
It is described in Japanese Patent Publication No. 3602, Japanese Patent Publication No. 56-24964, etc.

[Problems to be solved by the invention] However, these proposals are not suitable for S! Since 02 is added to magnesia in powder or sol form, magnesia and S! Mixing with 02 is not complete. As a result, formation of coarse crystal grains, generation of vacancies, etc. occur, and I
The surface smoothness required for the base for C (Ra is 0.2μ
It has not been possible to obtain magnesia porcelain that has sufficient properties such as low dielectric loss, water resistance, etc. for use in microwave integrated circuit boards, microwave transmission windows, etc.

[Means for Solving the Problems] The present invention relates to a method for manufacturing magnesia porcelain that solves the above-mentioned problems, and the method for manufacturing magnesia porcelain according to the present invention has the following advantages: 0.05 to 0.05 in terms of Si 02 The present invention is characterized in that magnesia powder treated with an alkoxysilane compound or a silazane compound having a concentration of 2.0 x Φ% is sintered.

As the alkoxysilane compound, for example, the compounds shown in Table 1 can be used. In the molecular formula, Me represents a methyl group, Et represents an ethyl group, Vi represents a vinyl group, and Ph represents a phenyl group.

Examples of the silazane compound include the compounds shown in Table 2.

Table 2 The treatment of magnesia powder with an alkoxysilane compound or silazane compound can be carried out by, for example, a) dissolving a predetermined amount of the alkoxysilane compound or silazane compound in a volatile solvent, and spraying the solution on the magnesia powder; Method of heating and drying.

b) A method in which the solution used in method a) and magnesia powder are mixed in a mixer such as a V-type blender, and then heated and dried.

C) A method in which magnesia powder is added to the solution used in method a), heated in a slurry state, and then the solvent is filtered off and dried.

etc.

In the treatment of an alkoxysilane compound or a silazane compound, the amount used must be 0.05 to 2.0% by weight calculated as SiO2 based on the magnesia powder, but if the layer used is less than this range. If the amount is too small, the treatment effect will not be sufficiently improved, and if it is more than this range, the surface smoothness will be impaired, making it impossible to obtain magnesia porcelain with excellent properties.

As mentioned above, magnesia powder treated with an alkoxysilane compound or a silazane compound is molded by a method similar to that of ordinary ceramics, such as a mold press, a doctor blade method, a rubber press, etc.
The product is sintered at 00'C.

[Function] By treating magnesia powder with an alkoxysilane compound or a silazane compound, the above compound is uniformly bonded to the surface of each magnesia powder particle. Therefore, when the magnesia powder is sintered, the surface of the magnesia powder particles is
Si02 produced by the decomposition of the above compound at the molecular level
The sintering reaction progresses uniformly because it is covered homogeneously by
A very dense sintered body with well-uniformed grain sizes can be obtained.

In addition, because dense sintering with uniform particle sizes is possible in this way, the resulting magnesia porcelain does not lose the excellent electrical properties and thermal conductivity of magnesia, and has improved water resistance. However, the surface becomes rough and smooth.

[Effects of the Invention] The present invention produces magnesia porcelain using magnesia powder treated with an alkoxysilane compound or a silazane compound. , materials with smooth surfaces such as microwave integrated circuit boards and microwave transparent windows) can be used.

[Example] An embodiment of the present invention will be described.

In this example, first, toluene 2720CI and the processing agent shown in Table 3 were added to a 5Ω separable flask.
(The maximum calculated as hffi. (In the case of methyltrimethoxysilane, 0.5% by weight as S! 02 is 11.7
g, in the case of hexamethyldisilazane, Sio is 0.1
After stirring and mixing these, 1020 g of magnesia powder was added and refluxed for 2 hours while stirring. After cooling, the supernatant liquid was removed, and the resulting slurry was left in a vacuum dryer at 60° C. for one day and night to dry. Magnesia was treated with an alkoxysilane compound or a silazane compound (hereinafter abbreviated as silane treatment). A powder was obtained.

Next, 300 g of the silane-treated magnesia powder,
200 mQ of tertiary butyl alcohol and 15 g of polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name Kosuretsuk BMS) were placed in a 2Q polyethylene container together with a plastic ball stone with a diameter of 15 mm, and mixed at 84R, P, and M for 72 hours.

The slurry thus obtained was passed through a 250-mesh sieve, then vacuum freeze-dried for 5 hours, and passed through a 32-mesh sieve to obtain a raw material powder.

The raw material powder was molded into a shape according to the measurement at a pressure of 1500 kg/cm2, and fired in an electric furnace at 1480 to 1680°C in the atmosphere to obtain samples for measuring water resistance, dielectric loss, dielectric constant, and specific gravity.

Also, a part of the slurry was formed into a sheet on an acetate film by the doctor blade method, and exposed to air for 1 hour.
Sinter it in an electric furnace at 480-1680'C to obtain samples for measuring surface smoothness and thermal conductivity.

Water resistance was determined by leaving a 4 x 8 x 30 mm sample in the vapor phase at 10 atmospheres and 180° C. for 11 hours in an autoclave, and measuring the change in surface area per unit surface area before and after measurement.

The dielectric loss (tanσ) and the dielectric constant were determined using a dielectric double-column camera method (measured at 8 GHz using a Yokogawa Hewlett Card Model 8408B) using a sample with a diameter of 15 mm and a length of 8 mm.

The surface smoothness is determined by the measurement length 4 mm cutoff value Q, 8
It was measured as center line average roughness Ra> based on J15BO601 under the condition of mm.

Thermal conductivity was determined by the laser flash method.

As comparative examples, measurements were made in the same way when magnesia powder without silane treatment was used and when powdered silica and silica sol were added to magnesia powder.

From the above experiments, water resistant compatibility (0.04mg/cm2-H
(below), surface smoothness (Rag, 20 μm or less), and dielectric loss (2,6x"10-4 or less), in order to obtain magnesia porcelain that is comprehensively excellent, 0.05 to 3i02
It has been found necessary to use magnesia powder treated with 2.0% by weight of an alkoxysilane or silazane compound. As is clear from Table 3, the treatment of this example does not impair the excellent thermal conductivity and dielectric constant of magnesia porcelain.

Furthermore, Fig. 1 is an electron micrograph showing the surface structure of magnesia porcelain using magnesia powder treated with 0.5% methyltrimethoxysilane in terms of SiO2, and Fig. 2 is an electron micrograph showing the structure of the surface of magnesia porcelain. Electron micrograph showing the surface structure of magnesia porcelain using magnesia powder mixed with .5% powder wrinkle strength. FIG. 3 is an electron micrograph showing the surface structure of magnesia porcelain using magnesia powder mixed with 0.5% by weight of silica sol.

As can be seen from these photographs, the structure of the magnesia porcelain according to this example has a uniform grain size and is very dense.

Note that Samples No. 3 to 8.11.12 and No. 14 to 19 had similarly dense structures.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph showing the structure of the surface of magnesia porcelain according to an example of the present invention, and FIGS. 2 and 3 are electron micrographs showing the structure of the surface of magnesia porcelain according to a comparative example.

Claims (1)

[Claims] A method for producing magnesia porcelain, comprising sintering magnesia powder treated with an alkoxysilane compound or a silazane compound in an amount of 0.05 to 2.0% by weight in terms of SiO_2.