JPH04325453A - Production of ceramic green sheet - Google Patents

Abstract

PURPOSE:To produce a ceramic green sheet capable of reducing the size of a laminated ceramic capacitor and increasing the capacity. CONSTITUTION:Ceramic powder is dispersed by 100 pts.wt. in 50-100 pts.wt. org. solvent, 3-15 pts.wt. binder, 2-10 pts.wt. plasticizer and 0.1-2 pts.wt. dispersant. The resulting slurry is molded in <=100mum film thickness to produce a ceramic green sheet. The binder is preferably polyvinyl acetal.

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 particularly to a method for manufacturing a ceramic green sheet for use in, for example, multilayer ceramic capacitors.

0002

2. Description of the Related Art Conventionally, when producing ceramic green sheets, organic solvents, binders, plasticizers, dispersants, etc. were added to ceramic powder, and the mixture was kneaded for a required period of time to prepare an organic slurry. Then, using this organic slurry, ceramic green sheets were manufactured by a doctor blade method or the like. The ceramic green sheet thus obtained is used, for example, in a multilayer ceramic capacitor.

In recent years, electronic components have been desired to be smaller, lighter, and more dense, and chip components such as multilayer ceramic capacitors are becoming smaller. Therefore, in multilayer ceramic capacitors, efforts are being made to make the ceramic green sheets thinner in order to achieve smaller size and larger capacity.

0004

[Problems to be Solved by the Invention] However, if the ceramic powder and the binder are non-uniform, small pores will be formed in the sintered body when the thin ceramic green sheet is fired, and reliability such as withstand voltage will deteriorate. I don't have good sex. In order to produce a ceramic green sheet from which a highly reliable sintered body can be obtained, it is necessary to improve the dispersibility of the slurry.

[0005] Furthermore, as the number of layers increases, an increase in the cost of noble metal products used for internal electrodes has become a problem, and efforts are being made to use base metals for internal electrodes. When a ceramic green sheet and an internal electrode are simultaneously fired as in a multilayer ceramic capacitor, if a base metal is used for the internal electrode, the electrode is likely to be oxidized during firing. Therefore, when using a base metal for the internal electrodes, firing in a non-oxidizing atmosphere is required. When fired in such a non-oxidizing atmosphere, the carbon remaining after binder removal is difficult to burn. The remaining carbon causes vacancies.

[0006] Therefore, the main object of the present invention is to provide a method for producing a ceramic green sheet that can produce a highly reliable sintered body.

[0007]

[Means for Solving the Problems] The present invention is a method for producing a ceramic green sheet using a slurry obtained by adding an organic solvent, a binder, a plasticizer, and a dispersant to ceramic powder and kneading the mixture. The powder is dispersed in an organic solvent, a binder, a plasticizer, and a dispersant.
This is a method for manufacturing ceramic green sheets that is formed into a film thickness of μm or less. Here, 100 parts by weight of ceramic powder, 50 to 100 parts by weight of organic solvent, and 3 to 3 parts by weight of binder.
15 parts by weight, 2 to 10 parts by weight of plasticizer, 0.1 part of dispersant
It is desirable to use a slurry obtained by adding ~2 parts by weight. Further, it is desirable that the binder is made of polyvinyl acetal.

[0008]

According to the method of the present invention, the slurry has high dispersibility, so that the ceramic powder and the binder are mixed uniformly. Furthermore, it is easy to decarbonize even in a non-oxidizing atmosphere. Therefore, the ceramic green sheet can be made into a thin film, and moreover, even when fired, pores are less likely to be generated in the sintered body. Therefore, it is possible to obtain a highly reliable ceramic having a reduced thickness.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments.

0010

[Example] First, as a ceramic powder, BaCO3
, CaCO3, and SiO2 were weighed to have a composition ratio of 1:2:1 to prepare a weighed material. After mixing this weighed material for 1 hour in a Raikai device,
The mixture was dissolved at ℃ to obtain a melt. This melt was rapidly cooled and pulverized to obtain a powder. 8 parts by weight of this powder and BaCO3
, 100 parts by weight of BaTiO3 powder calcined and crushed from TiO2 were wet mixed in a ball mill, dehydrated, dried, calcined at 1100° C. for 2 hours, and crushed to obtain a ceramic powder. In addition, as a binder, polyvinyl alcohol is converted into butyral with a butyral degree of 65 ± 3.
Mol% of S-LEC B and BL manufactured by Sekisui Chemical Co., Ltd.
-1 (product name) was prepared. Furthermore, dibutyl phthalate (DBP) was prepared as a plasticizer. Further, as an organic solvent, a mixture of toluene and ethanol in a composition ratio of 1:1 was prepared.

(Example) 100 parts by weight of ceramic powder, 6 parts by weight of binder, 5 parts by weight of plasticizer, 80 parts by weight of organic solvent, and a hydrophilic-lipophilic balance of 4 as a nonionic dispersant.
．． 0.5 parts by weight of the sorbitan ester No. 3 was added thereto and mixed for 15 hours in a ball mill containing PSZ cobblestones with a diameter of 10 mm to obtain a mixture. After degassing this mixture under vacuum, a ceramic green sheet with a thickness of 50 μm was produced using a doctor blade method. A paste containing nickel powder dispersed in an organic vehicle was applied to one side of the molded body by screen printing. 100 layers of these were stacked and thermocompression bonded at 100°C and 50kg/cm2. Furthermore, after burning the binder in a natural atmosphere at 300°C, it was fired in N2 + H2 at 1250°C for 2 hours to obtain a multilayer dielectric ceramic composition.

(Comparative Example 1) A multilayer dielectric ceramic composition was obtained under the same conditions as in the example without using a dispersant.

(Comparative Example 2) A multilayer dielectric ceramic composition was obtained under the same conditions as in the example, using Poval 205 (trade name), a polyvinyl alcohol manufactured by Kuraray Co., Ltd., as a binder.

Regarding each ceramic green sheet obtained, the discharge viscosity, average particle size distribution D50,
The molded density, tensile strength, elongation rate, and microscopic transmission observation were investigated, and after sintering, the withstand voltage reliability NG number was investigated, and the results are shown in Table 1.

[0015]

[Table 1]

[0016] Here, the discharge viscosity is the viscosity taken out after mixing the materials in a ball mill, and was measured using a BH type viscometer. It can be seen that the viscosity is reduced by adding the dispersant. The average particle size distribution D50 is measured using Microtrack (manufactured by Nikkiso Co., Ltd.), which measures particle size distribution using light scattering.
This is the measured value of the average particle size distribution. It can be seen that the smaller the value, the finer the ceramic powder. The molded density is the molded density of the ceramic green sheet, and was measured from the relationship between weight and volume. If the dispersibility improves, the degree of filling of the ceramic increases and the molding density increases. The tensile strength was measured at a tensile speed of 1 cm/min. The elongation rate was measured by a tensile test. For microscopic transmission observation, a ceramic green sheet with a thickness of 20 μm or less was irradiated with transmitted light from below and observed from the opposite side with a lens of about 100 times magnification to examine the dispersibility of the ceramic. If the dispersibility is poor, agglomeration of the ceramic or binder may be observed. In addition, "○" in the table indicates that the dispersibility is good, and "x" indicates that the dispersibility is poor. First, the number of failures in voltage resistance reliability is as follows:
A conductive paste consisting of silver, glass frit, and vehicle was applied to the side surface of the multilayer dielectric porcelain and dried. This was baked in the air at 550° C. for 20 minutes to obtain a multilayer ceramic capacitor. A voltage of 16 V was applied to this in a constant temperature bath at 85° C., and the number of short circuits after 1000 hours was defined as the number of failures in voltage resistance reliability.

Next, the reason for limiting the numerical values in the claims will be explained. If the organic solvent is less than 50 parts by weight,
The ceramic powder may not get wet and the binder may not completely dissolve. Moreover, when the organic solvent exceeds 100 parts by weight, the viscosity of the slurry becomes too low, making it difficult to form it into a sheet. When the amount of binder is less than 3 parts by weight, the tensile strength of the ceramic green sheet becomes weak. Furthermore, if the binder exceeds 15 parts by weight, the volumetric shrinkage before and after sintering will increase, making it impossible to obtain dense ceramic crystals. By adding 2 parts by weight or more of a plasticizer, the elongation rate of the ceramic green sheet increases, making it suitable for practical use. However, if the plasticizer exceeds 10 parts by weight, the elastic modulus of the ceramic green sheet will be too small, making it difficult to work with. If the amount of the dispersant added is less than 0.1% by weight, there is no effect of the addition of the dispersant. Furthermore, if the amount of the dispersant added exceeds 2.0% by weight, the ceramic green sheets become flexible, making it difficult to perform lamination work.

As can be seen from Table 1, the multilayer dielectric ceramic composition of the example has better dispersibility than Comparative Examples 1 and 2, has high withstand voltage reliability, can be made into a thin film, and is suitable for multilayer ceramic capacitors. can be made smaller and larger in capacity.

Claims (3)

[Claims] 1. A method for producing a ceramic green sheet using a slurry obtained by adding an organic solvent, a binder, a plasticizer, and a dispersant to ceramic powder and kneading the mixture, the method comprising: binder,
Dispersed in the plasticizer and the dispersant to a diameter of 100 μm
A method for manufacturing ceramic green sheets that is formed to the following thickness. 2. The slurry comprises 100 parts by weight of the ceramic powder, 50 to 100 parts by weight of the organic solvent,
3 to 15 parts by weight of the binder and 2 to 10 parts by weight of the plasticizer
The method for producing a ceramic green sheet according to claim 1, which is obtained by adding 0.1 to 2 parts by weight of the dispersant and the dispersant. 3. The method for producing a ceramic green sheet according to claim 1, wherein the binder is made of polyvinyl acetal.