JPH05337911A - Manufacture of ceramic green sheet - Google Patents

Abstract

PURPOSE:To provide the manufacturing method for a ceramic green sheet in which a uniform green sheet can be manufactured easily when powders of different specific gravity are used as a raw material. CONSTITUTION:When a green sheet is manufactured by molding suspension composed of inorganic powders of different specific gravity dispersed in liquid and drying, the viscosity of slurry in a mixture is increased gradually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic green sheet, and more specifically, it can be applied to a ceramic member used for a ceramic circuit board,
In particular, the present invention relates to a method for producing a ceramic green sheet that can easily obtain a uniform green sheet when powders having different specific gravities are used as raw materials.

In recent years, along with the demand for higher performance of electronic devices, there has been an increasing demand for materials having properties that have not been heretofore known, and various combinations of composite materials have been investigated.

[0003]

2. Description of the Related Art A conventional method for manufacturing a ceramic green sheet will be described. First, a ceramic powder, an organic binder, and an organic solvent are mixed in a ball mill or the like to prepare a suspension (hereinafter referred to as a slurry), and the slurry is thinly spread on a carrier film by a doctor blade method or the like and dried to obtain green. Get the sheet. Then, the obtained green sheet was subjected to various processes and then fired to obtain a ceramic member.

[0004]

However, in the above-mentioned conventional method for producing a ceramic green sheet, when powders having different specific gravities are used as raw materials, the settling speeds until the slurry is dried are different, so that a homogeneous slurry is obtained. There was a problem that it was difficult to obtain a green sheet. In particular, when a powder having a specific gravity larger than that of the slurry solvent is mixed with a powder having a smaller specific gravity, a powder having a specific gravity larger than the slurry solvent sinks below the water surface during drying, while a powder having a specific gravity smaller than the slurry solvent floats above the water surface. It was extremely difficult to obtain a uniform green sheet because the powders were separated by different powders. Therefore, in order to prevent the powders having different specific gravities from being separated from each other, it is conceivable to set the slurry viscosity high, but if the viscosity is increased from the beginning to mix, it becomes difficult to uniformly mix.

Therefore, an object of the present invention is to provide a method for producing a ceramic green sheet, which can easily obtain a homogeneous green sheet when powders having different specific gravities are used as raw materials.

[0006]

In order to achieve the above object, the method for producing a ceramic green sheet according to the present invention is carried out when a slurry in which inorganic powders having different specific gravities are dispersed in a liquid is molded and dried to produce a green sheet. The viscosity of the slurry during mixing is gradually increased. In the present invention, gradually increasing the viscosity of the slurry during mixing may be performed by gradually decreasing the temperature of the slurry, or gradually evaporating the liquid of the slurry during mixing. It may be carried out by adding the organic binder gradually to the slurry being mixed.

[0007]

In the present invention, the viscosity of the slurry is low at the start of kneading and then gradually increased when uniformly mixed,
Since I tried to stretch it while the viscosity was high,
The number of agglomerated particles is small, the powder can be kneaded while maintaining a uniform dispersion state without separation of the powder, and a uniform green sheet can be obtained. The viscosity of the slurry can be easily controlled by three types of methods: controlling the slurry temperature, controlling the solvent amount, and controlling the binder addition amount.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Hollow silica powder with a specific gravity of 0.5 (average particle size 20μ
m) 100 g and 500 g of alumina Al ₂ O ₃ powder with a specific gravity of 2.5 (average particle size 5 μm) are used, and ethanol, polyvinyl butyral resin and dibutyl phthalate are added to this and kneaded with a mixer equipped with a vacuum degassing device. Then, a slurry was prepared. The figure shows the amounts of the solvent and the organic component in Examples 1 to 3 and Comparative Example described later. (Example 1) Each material of hollow silica, glass, ethanol, PVB, and DBP shown in FIG. 1 was enclosed in a mixer,
The internal temperature was adjusted to 50 ° C. and the mixture was kneaded for 2 hours. After that, when the temperature was lowered to 20 ° C. at a rate of 0.5 ° C./min and kneading was continued for another hour, the slurry viscosity gradually increased during mixing as shown in FIG. Then, after degassing the obtained slurry in a vacuum, a thickness of 300 is obtained by the doctor blade method.
A green sheet of μm was formed. And this is 20c
Cut into m-square pieces, measure thickness and weight, calculate density, and
When examining the change in the density of the green sheet in the batch,
As shown in FIG. 3, it was found that the variation of the green sheet density in the batch was extremely small. Example 2 The raw materials of hollow silica, glass, ethanol, PVB and DBP shown in FIG. 1 were put in a mixer and kneaded at room temperature and atmospheric pressure for 2 hours. Next, when the interior was evacuated and kneading was continued for another hour while evaporating ethanol at a rate of 5 cc / min, the slurry viscosity gradually increased during mixing, as shown in FIG. Then, after degassing the obtained slurry in a vacuum, a thickness of 300 is obtained by the doctor blade method.
A green sheet of μm was formed. And this is 20c
Cut into m squares, measure thickness and weight, calculate density, and
When examining the change in the density of the green sheet in the batch,
As shown in FIG. 3, it was found that the variation of the green sheet density in the batch was extremely small. Example 3 The raw materials of hollow silica, glass, ethanol, PVB and DBP shown in FIG. 1 were placed in a mixer and kneaded at room temperature and atmospheric pressure for 2 hours. Next, when kneading was continued for another hour while adding 10 g of polyvinyl butyral resin every 10 minutes, the slurry viscosity gradually increased during mixing, as shown in FIG. Next, after degassing the obtained slurry under vacuum, a green sheet having a thickness of 300 μm was formed by a doctor blade method. Then, this was cut into 20 cm squares, the thickness and weight were measured, the density was calculated, and the change in the green sheet density in one batch was examined. As shown in FIG. 3, the green sheet density in the batch was It was found that the variation of was extremely small. (Comparative Example) The raw materials of hollow silica, glass, ethanol, PVB and DBP shown in FIG. 1 were put in a mixer and kneaded at room temperature and atmospheric pressure for 3 hours. Then, the obtained slurry is degassed in vacuum and then the thickness is 300 μm by the doctor blade method.
Green sheet was molded. Then, this was cut into 20 cm squares, the thickness and weight were measured, the density was calculated, and the change in the density of the green sheets in one batch was examined.
As shown in, it was found that the variation in the green sheet density in the batch was extremely large. Moreover, the curve tends to rise to the right, that is, the green sheet density gradually increases as a whole. This can be interpreted as the composition itself of the green sheet gradually changes due to the separation of the powder.

As described above, in the case where the slurry viscosity of the comparative example was not changed, the dispersion of the green sheet density in the batch was extremely large, whereas the slurry viscosity was controlled by controlling the slurry temperature in Example 1 of the present invention. When gradually increasing the slurry viscosity by increasing the slurry solvent amount control in Example 2,
In all cases where the slurry viscosity was increased by controlling the slurry binder addition amount, the variation in the green sheet density in the batch was extremely smaller than that in the comparative example.
Therefore, a uniform green sheet can be obtained.

[0010]

According to the present invention, when powders having different specific gravities are used as raw materials, it is possible to easily obtain a homogeneous green sheet.

[Brief description of drawings]

FIG. 1 is a diagram showing amounts of a solvent and an organic component in Examples 1 to 3 and a comparative example.

FIG. 2 is a diagram showing changes in slurry viscosity in Examples 1 to 3.

FIG. 3 is a diagram showing changes in green sheet density in one batch in Examples 1 to 3 and Comparative Example.

[Explanation of symbols]

Claims (4)

[Claims] 1. A ceramic green sheet characterized by gradually increasing the viscosity of a slurry during mixing, when forming a slurry in which inorganic powders having different specific gravities are dispersed in a liquid and molding and drying the slurry. Production method. 2. The method for producing a ceramic green sheet according to claim 1, wherein the slurry viscosity during the mixing is gradually increased by gradually decreasing the slurry temperature. 3. The method for producing a ceramic green sheet according to claim 1, wherein the slurry viscosity during the mixing is gradually increased by gradually evaporating the liquid of the slurry. 4. The method for producing a ceramic green sheet according to claim 1, wherein the slurry viscosity during the mixing is gradually increased by gradually adding an organic binder to the slurry.