JPH03177352A - Production of ceramics green sheet - Google Patents

Abstract

PURPOSE:To obtain the subject ceramics green sheet excellent in surface smoothness and nonporousness and capable of burning at low temperatures by blending powdery inorganic substances with a sol or a gel prepared from metallic compounds for formation of a slurry and molding the resultant slurry. CONSTITUTION:One or more powdery inorganic substances are blended with a sol or a gel prepared using one or more metallic compounds selected from metallic alkoxides, metallic carboxylates, metallic nitrates, metallic oxychlorides and metallic chlorides and a binder is added thereto, as necessary, to form a slurry followed by molding of the resultant slurry. As the above-mentioned powdery inorganic substances, e.g. alumina, silica, mullite, titanium, titania, zinc oxide, iron oxide, zirconia, etc., can be used. As the binder, both the organic and inorganic substances can be used.

Description

[Detailed Description of the Invention] The present invention relates to a method for producing a ceramic green sheet, and more specifically to a ceramic green sheet that has excellent surface smoothness and non-porosity and can be fired at low temperatures. Concerning sheet manufacturing method.

The ceramic green sheet obtained by the method of the present invention can be applied to electronic component substrates, sensor substrates, optical materials, functional ceramic materials, etc.

Most of the ceramic green sheets currently on the market are made by manufacturing inorganic powder as a raw material, then repeatedly crushing, mixing, and calcining, and performing operations such as classification to obtain fine powder. To this, an organic binder and additives such as a sintering aid, a deflocculant, and a plasticizer are added to form a slurry, which is then shaped into a sheet.

The green sheet produced in this way is made into a sintered body by firing the particles at a temperature higher than the Tamman temperature (two-thirds of the melting point expressed in absolute temperature) of the substance at the bottom of the tank, so that the particles fuse together and become a sintered body. A certain ceramic sheet is obtained. However, sintering at the Tamman temperature is only possible when the particles are extremely small, and if the particle size obtained by normal grinding is several microns or submicron order, the sintered body must be sintered at an even higher temperature. -0 For example, in the case of aluminum whose melting point is 2323, the Tamman temperature is 1553, but in terms of -M it is 2.
It is fired at a temperature of 000 to 2100. Firing at such high temperatures not only requires a firing furnace with extremely high heat resistance, but also poses the problem that the energy cost required for firing is extremely high.

Moreover, even when fired at such high temperatures, the particles are still not completely fused together, leaving many pores and uneven areas in the sintered body, and the physical properties of the strength hat are also dependent on the material. Only properties that are significantly lower than physical properties can be obtained. In addition, the surface smoothness is poor, and if, for example, a conductor or resistor circuit is formed on such a ceramic sheet by screen printing to create an electronic component board, the width and thickness of the circuit will be uneven. There was a problem in that it was not possible to obtain a constant electric resistance.

In order to solve these problems, low-temperature fired ceramic sheets are commercially available, which are made by mixing a substance with a lower melting point or glassy powder with an inorganic substance powder as a main component. This method can be fired around 1273, and the firing cost can be greatly reduced, but it is definitely a mixture of powders, and as a result, non-porosity and surface smoothness are improved compared to conventional methods. There isn't. In addition, since the substances added to lower the firing temperature are limited, in most cases,
It is inevitable that the performance originally possessed by the main component will deteriorate.

An object of the present invention is to solve the above-mentioned problems of conventional ceramic green sheets, and to provide a ceramic green sheet that has excellent surface smoothness and non-porosity, and can be fired at low temperatures. It is something to do.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a powder of one or more inorganic substances and metal alkoxides, metal carboxylates, metal nitrates, metal oxychlorides, and metal chlorides can be used. By mixing a sol or gel prepared from one or more metal compounds selected from the group consisting of two or more metal compounds, adding a binder as necessary to form a slurry, and shaping the slurry, the desired ceramic green sheet can be obtained. The present inventors have discovered that the present invention can be obtained, and have completed the present invention.

The inorganic substance powder used in the present invention is not particularly limited, but -
Second, one or more metal oxides are used. In addition, in the conventional method, the particle size, which has an important effect on the sintering temperature, the non-porosity of the sintered body, the surface smoothness, etc.
In the present invention, there is no particular limitation, and the thickness can be freely selected and used from sub-micron to several tens of microns. As for inorganic substance powders, alumina-coated silica, mullite, titanium, titania, zinc oxide, iron oxide, zirconia, etc., which are currently commonly used for electronic component substrates, sensor substrates, etc., can be used.

Furthermore, the sol or gel used in the present invention refers to a colloid in which fine particles of a metal compound, which is a precursor of ceramics, are dispersed in a dispersion medium. This is an amorphous non-g9. It can be prepared by applying a known method known as the so-called Bluegel method or the alkoxide method, which is a method for preparing oxides at a temperature far lower than their melting point. Specifically, metal alkoxides formed by reacting metals with alcohols, or metal compounds such as metal carboxylates, metal nitrates, metal oxychlorides, and metal chlorides, are hydrolyzed in a dispersion medium. Obtainable.

In the present invention, metal alkoxides that can be used include aluminum trimethoxide, argonium triethoxide, aluminum isopropoxide, aluminum tributoxide, tetraethoxysilicate, tetraisopropoxysilicate, tetrabutoxysilicate, tetraethoxytitanium, and tetraethoxysilicate. Isopropoxy titanium, tetrabutoquinotitanium, tetramethoxyzirconium, tetraethoxyzirconium, tetraisopropoquine zirconium, tetrabutoxyzirconium, triethoxyiron, triisopropoxyiron, tryptoxyiron,
Jetoxy barium, diisopropoxy barium, dibutoxy barium, jetoxy copper, diisopropoxy copper,
Dibutoxy copper, jetoxy nickel, diisopropoxy nickel, dibutoxy nickel, jetoxy cobalt,
Diisopropoxycobalt, dibutoxycobalt, jetoxyzinc, diisopropoxyzinc, dibutoxyzinc,
Jetoxystrontium, diisopropoxystrontium, dibutoxystrontium, triethoxyindium, triisopropoxyindium, tributoxyindium, pentaethoxyniobium, pentaisopropoxyniobium, pentabutoxyniobium, triethoxyyttrium, triisopropoxyyttrium, Examples include trypoxyythtrium. In addition, metal carboxylates include lead acetate, yttrium stearate, barium oxalate, and metal nitrates include aluminum nitrate, nickel nitrate,
Yttrium nitrate, metal oxychloride, aluminum oxychloride, zirconium oxychloride, metal chloride,
Aluminum chloride, titanium tetrachloride, etc. can be used. In addition to this, a metal alkoxide consisting of two types of metals can also be used.

Furthermore, when a sol or gel of the same metal as the inorganic substance powder is used, it is possible to obtain a green sheet that becomes a highly pure ceramic after firing.

To combine the N-free powder and the sol or gel of the metal compound, after preparing the sol or gel of the metal compound, add and stir the inorganic substance powder, or,
When preparing a sol or gel of a metal compound, powder of an inorganic substance may be mixed in advance in a dispersion medium. Alternatively, an inorganic substance powder and a metal compound may be mixed in advance to form a sol or gel. mixed). Although there is no particular restriction on the mixing ratio of the inorganic substance powder and the metal compound sol or gel, it is appropriate that the ratio after firing is 50:50 to 95:5. If the amount of inorganic material powder is less than 50%, cracks are likely to occur due to large shrinkage during the drying process (which is undesirable), while if the amount of sol or gel is less than 5%, the pores between the inorganic material powders are completely closed. This is not desirable because it cannot be filled in and the density deteriorates.

The slurry prepared as described above is coated on a carrier by, for example, a doctor blade method, with a binder added thereto if necessary, dried with warm air, and then peeled off from the carrier.
The desired ceramic sugerene sheet can be manufactured.

Both organic and inorganic materials can be used as binders. Kaolinite, montmorinite, pyrophyllite, etc. can be used as the inorganic binder. Further, as the organic binder, a polymeric substance soluble in a water-containing organic solvent such as polyvinyl alcohol, methyl cellulose, polyvinyl butyral, etc. can be used. Adding a binder improves the flexibility of the bottom-shaped green sheet, making it possible to wind it up into a roll after forming, and facilitating secondary processing such as cutting and die-cutting.

Ceramic gel sheets produced in this way can be fired at temperatures as low as 1273°C or less, similar to those produced by the sol-gel method, reducing firing costs by significantly lowering the firing temperature compared to conventional green sheets. can do. In addition, since the components generated from the sol or gel are filled between the inorganic powders, it is possible to obtain a ceramic sheet that is dense without the pores that were unavoidable with conventional methods and has an extremely smooth surface. .

EXAMPLES The present invention and its effects will be specifically explained below with reference to Examples.

Example 1 (Manufacture of Algona Green Sheet) 15 g of commercially available alumina powder (average particle size: 10 Gron) and 60 g of aluminum isopropoxide, which is the raw material for alumina sol.
220 g of water and 70 g of ethanol were added as a dispersion medium, and the mixture was heated and stirred. The heating temperature at this time is
The temperature was 90°C, and the composition ratio (molar ratio) of water and aluminum isopropoxide was 40:1. After heating and stirring for several hours, a small amount of nitric acid was added as a deflocculant, and when heating and stirring were continued for about 1 hour again, the mixture became viscous. This indicates that alumina sol was produced by hydrolysis of aluminum isopropoxide. Regarding this fact, it was previously confirmed that an alumina sol was produced as a result of performing the above method using only aluminum isopropoxide.

Polyvinyl alcohol was added to the above mixture of alumina powder and alumina sol, and the mixture was stirred with a homogenizer for 2 to 3 hours to prepare a stock solution of alumina green sheet. Since this stock solution exhibits thixotropic properties, it was stirred to adjust the viscosity and form a bottom shape when it was cast onto a carrier. The melt cast onto a carrier exhibits thixotropic properties and loses fluidity within a few minutes. This was dried with warm air under normal pressure to obtain an alumina green sheet. Drying time required 1 hour.

The alumina green sheet thus obtained had a film thickness of about 50 microns. Also, this sheet is very flexible and can be made into various shapes.

The green sheet was fired at 1273° C. for 4 hours to obtain an alumina film with a surface roughness of 0.25 μm and excellent surface smoothness.

This alumina film was confirmed to be both T and α-alumina by X-ray diffraction. Furthermore, it was confirmed that all of the samples fired at 1473 for 4 hours were α-alumina.

Example 2 (Manufacture of alumina green sheet) An alumina green sheet was manufactured using alumina powder and aluminum nitrate as raw materials.

First, 15 g of alumina powder was dispersed in 50 g of water, mixed with an aqueous aluminum nitrate solution, stirred, and then mixed with 35 g of ethanol.
g was added thereto, and the mixture was heated and stirred. The molar ratio of aluminum nitrate to aluminum was 1:2. After stirring for several hours, a small amount of nitric acid was added as a deflocculant, and the mixture was heated and stirred again for several hours until it became viscous.

To the above mixture, polyvinyl alcohol was added as a binder, other additives were added, and the mixture was stirred with a homogenizer for 2 to 3 hours to prepare an alumina green sheet stock solution. When this stock solution was cast onto a carrier, it was stirred to adjust the viscosity, shaped into a bottom shape, and dried with warm air under normal pressure to obtain an alumina green sheet. Drying time required 1 hour.

After drying, the green sheet was fired at 1473 for 4 hours.
An alumina film with a surface roughness of 0.3μ and good surface smoothness was obtained.

This alumina film was confirmed to be entirely α-alumina by X-ray diffraction.

Example 3 (Production of mullite green sheet) 20.4 g of tetraethoxysilicate was mixed with 7.2 g of water and a small amount of nitric acid, stirred in an atmosphere at a temperature of 90'C until it became a homogeneous phase, and mixed with this and 270 g of water. Mix 62.4g of aluminum isopropoxide and heat at 90° again.
The mixture was stirred under a temperature atmosphere of C until viscosity was generated.

Mullite powder and polyvinyl alcohol as a binder were added to the above mixture, and other additives were added and stirred for 2 to 3 hours using a homogenizer to prepare a stock solution of mullite green sheets.

When this stock solution was cast onto a carrier, it was stirred to adjust the viscosity and shaped into a bottom shape, and then dried with warm air under normal pressure to obtain a mullite green sheet. Drying time required 1 hour.

The green sheet was fired at 1273° C. for 4 hours to obtain a mullite film with a surface roughness of 0.3 degrees Cron and a good surface smoothness.

This film was confirmed to be mullite by X-ray diffraction.

Comparative Example 1 (Comparison of surface roughness between the alumina film according to Example 1 and the alumina film produced by the powder method) A method for producing an alumina film by the powder method is shown below.

First, alumina powder (average particle size 10ξcrons) 300
g, magnesium oxide 3g, trichlorethylene 120
30 g of polyvinyl butyral was added and kneaded again for 24 hours to obtain a slurry, which was bottom-shaped by the doctor blade method and dried with hot air to obtain an alumina green sheet. During drying time,
It took an hour.

This alumina green sheet was fired in 1973 for 4 hours to obtain an alumina film with a thickness of 200ξcm. This film exhibited a surface roughness of 1.0 micron (Figure 1B). In contrast, the alumina film according to Example 1 had a surface roughness of 0.25. (FIG. 1A), and was found to have very excellent surface smoothness.

[Brief explanation of drawings]

FIG. 1A shows the measured values of the surface roughness of the alumina film obtained in Example 1. FIG. 1B shows the measured values of the surface roughness of the alumina film obtained in Comparative Example 1.

Claims (1)

[Claims] (1) Prepared from one or more powders of inorganic substances and one or more metal compounds selected from the group consisting of metal alkoxides, metal carboxylates, metal nitrates, metal oxychlorides, and metal chlorides. A method for producing a ceramic green sheet, which comprises mixing a sol or a gel, adding a binder as necessary to form a slurry, and forming the slurry.