JPS58217480A - Magnesia ceramic and manufacture - 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 The present invention relates to magnesia porcelain with improved water resistance and a method for producing the same.

Magnesia porcelain generally has higher thermal conductivity than other porcelains, and also has high high frequency electrical insulation resistance.

It is one of the most suitable materials for microwave and other integrated circuit boards. However, magnesia porcelain has a major drawback in that it is inferior in water resistance, which is a requirement for a substrate material, and for this reason it is currently not in practical use.

Various attempts have been reported to improve the water resistance of magnesia porcelain.9 For example, a method of sintering using various additives (calcium phosphate, magnesium, magnesium phosphorus, etc.) as a sintering aid has been reported. However, sufficient water resistance has not yet been achieved.

In view of the current state of the conventional methods as described above, the present invention aims to provide magnesia porcelain with improved water resistance and a method for producing the same.

That is, according to the present invention, water-resistant phase-separated magnesia porcelain can be obtained by forming a coating layer using ceramics mainly composed of forsterite. This water-resistant magnesia porcelain is manufactured by the following steps (a) to (e).

(a) A step of preliminarily firing a preformed magnesia raw material to form a porous body; (b) Impregnating the porous body with an organic silicon compound liquid or a diluted solution thereof and burning it on the surface of the porous body to form a porous body. Step of forming a fine particle silicon dioxide coating layer on □(C)
A step of sintering the silicon dioxide-coated porous body to form a ceramic coating layer mainly composed of forsterite on the surface.

The present invention will be explained in detail below.

The present invention provides a magnesia sintered body with a forsterite-rich ceramic coating layer formed on its surface.
Its water resistance has been improved. Forsterite (2Mg0
-8 i 02 ) is generated by the reaction between silicon dioxide and magnesium oxide in the fine particle silicon dioxide coating layer formed on the surface of the magnesia molded body during sintering.

The magnesia molded body is preformed by a known method and first made into a porous body by preliminary sintering (or calcination).

A silicon dioxide coating layer is formed on the surface of this porous magnesia body as follows. That is, after impregnating a porous body with an organic silicon compound liquid (ethyl silicate, trimethyl ethyl 7rane, phenyl triethoquinosilane, or a diluted solution thereof), the impregnating liquid is burned on the surface of the impregnated porous body. . This combustion causes the organic components to disappear (or carbonize), and silicon dioxide fine particles are deposited on the surface. The impregnating liquid inside the porous body moves to the surface by capillary action and combustion continues, producing silicon dioxide which is deposited on the surface. Finally, the impregnation liquid inside the porous body rises in temperature (usually 100 to 25
(which is understood to reach approximately 0°C) also evaporates, reaches the surface, and burns. In this way, the impregnating liquid disappears and
A thin coating layer made of silicon dioxide fine particles is formed on the surface of the porous body.

An organic silicon compound is an organic compound having a silicon-carbon bond in its molecule, and the organic silicon compound liquid is preferably ethyl silicate, trimethyl ethyl silane,
Phenyl triethoxysilane is used, and if necessary, it is diluted with a diluent such as ethyl alcohol or methyl ethyl ketone to a viscosity suitable for impregnation. These organosilicon compounds are volatile and contribute to the continuation of combustion on the surface of the porous material, thereby contributing to the deposition of a fine particle coating layer of silicon dioxide.

The porous body has a brightness of 1.0 to allow impregnation with the impregnating liquid. In addition, it is sufficient that the material is made porous in a range that can be sufficiently densified in the subsequent sintering, and that the porosity is about 10% or more. Usually, these conditions are such that a magnesia raw material of 0.1 to o, F; μ is molded by a conventional method such as a doctor blade method, and
It is obtained by preliminary sintering at a temperature of 0 to 1100°C. It can be used as a molding aid, but it can also be used in an inert gas atmosphere with an oxygen concentration of 5 vol% or more.

The magnesia sintered body having the silicon dioxide layer formed in this way is then fired and sintered. That is, temperature 1
By firing in an air atmosphere at 850 to 1450°C, dense i-forsterite is also generated on the surface. For the production of forsterite, the firing temperature, holding time, and reactivity of the magnesia used must be considered.

In the present invention, magnesia porcelain is mainly composed of magne/lamb oxide, for example, 90% by weight or more of Mg0,
Or B eQ as an unavoidable impurity during manufacturing,
CaOI S 102r A12os + Fe20
It includes those containing up to 10% by weight of 3+Cr2O3+ or clay, talc, etc., alone or in combination.

Forsterite used as a coating layer is characterized by the fact that its dense sintered body has high hydration resistance, its coefficient of thermal expansion is smaller than that of the base magnesia porcelain, and the difference is slight, and like magnesia porcelain it can be used at high frequencies. It is optimal because it has excellent electrical insulation properties and the same sintering temperature range as magnesia, and due to the presence of the forsterite coating layer, the water resistance of magnesia porcelain is better than that of conventional porcelain. Yoshi has also been greatly improved.

The thickness of the forsterite coating layer required to achieve good water resistance is typically on the order of 2 to 100 microns, but may vary depending on the properties of the base magnesia porcelain. For magnesia porcelain having an apparent density of about a8 to a5 after sintering, a thickness on the above order is sufficient.

As an indicator of water resistance compatibility, when increasing the amount of water used in tests such as those shown in the examples, the preferable lower limit is approximately 0.04.
mW/crtl hr, which can be achieved with a forsterite layer thickness of about 2 μm or more. Also, the most preferred α0
A value of less than 1 .mu./car hr can be achieved with a forsterite layer thickness of about 10 .mu.m.

Examples of the present invention will be shown below.

The following raw material mixture was mixed for 15 hours in an alumina ball mill with an internal volume of 8 tons to form a slurry.

Next, the slurry was degassed under vacuum for 10 minutes, then cast onto an acetate film using a doctor blade method, and air-dried for 15 hours to a thickness of 1 cm and 2 widths of 320 I11.
I got a ++1 green sheet. This size is 150X
Cut it to 1875wm and heat it in an electric furnace at 1150℃.
A Madanesia calcined substrate having an open porosity of about 20% was obtained by time calcining. Next, ethyl silicate (Si(OC2Hs)4)
(1st grade chemical reagent) is prepared, and 1 portion of the calcined body is added to it.
It was soaked for 0 seconds for impregnation.

This impregnated body was ignited and ethyl silicate was burned over the entire surface, producing silicon dioxide particles of about 0.1 μm. Some of these particles were released into space, but most of them were deposited on the surface of the substrate, forming a silicon dioxide fine particle layer with a thickness of about 20 μm on the surface of the substrate.

This was fired in an electric furnace at 1450°C for 1 hour. The resulting substrate had a layer of about 3-5 μm thick, similar to forsterite, formed on the surface by the reaction between MgO and 5i02. It had been. The size of the sintered product is 100x125x
It was α67tmm.

The thermal conductivity, water resistance, bending force, dielectric constant, and dielectric loss tangent of this sintered product were measured in comparison with those of the sintered product made by the conventional method, and the results shown in Table 1 were obtained.

Measure the increase in weight per unit area (MgO hydrates,
As described above, the magnesia porcelain according to the present invention has been recognized to have significantly improved water resistance, and other characteristics are also satisfactory.

The present invention can be used for products with complex shapes, and is also effective not only for sheets and molded products, but also for products made by pouring press molding, extrusion molding, etc., and has great advantages.

Furthermore, the magnesia porcelain of the present invention can be used not only as a material for integrated circuit boards, but also for other purposes requiring water resistance and water resistance.

Sender: Nippon Tokushu Tokugyo Co., Ltd. Agent: Patent attorney Asamichi Kato

Claims (1)

[Scope of Claims] 1) Water-resistant magnesia porcelain having a ceramic coating layer mainly composed of forsterite on its surface. 2) A method for manufacturing magnesia porcelain having a ceramic coating layer mainly composed of forsterite on its surface, which comprises the following steps (a) to (C). (a) Preliminary firing of the preformed magnesia molded body to form a porous body; (b) Impregnation of the porous body with an organosilicon compound liquid or its diluted liquid and burning it on the surface of the porous body to form a porous body. (c) sintering the silicon dioxide-coated porous body to form a ceramic coating layer mainly composed of forsterite on the surface.