JPH07201652A - Composition for ceramic green sheet - Google Patents

Abstract

PURPOSE:To provide a composition for ceramic green sheet by which the internal defect, i.e., pores, of a sintered ceramics obtained by firing a press molded laminate can be reduced. CONSTITUTION:The composition for ceramic green sheet contains at least a ceramic material powder and a binder. A polyvinylbutyral resin is employed as the binder and the product of the degree of polymerization of polyvinylbutyral resin and the quantity (g) of polyvinylbutyral resin to be used for 100g of ceramic material powder is set in the range of 2000-5500.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic capacitor, a laminated inductor, and a laminated ceramic capacitor having a ceramic laminated structure.
The present invention relates to a composition for a ceramic green sheet used for laminated composite electronic parts and the like.

[0002]

2. Description of the Related Art For example, a monolithic ceramic capacitor is manufactured as follows. First, a ceramic green sheet is molded, and a conductive paste to be internal electrodes is applied and formed on the ceramic green sheet by means of screen printing or the like. Next, an arbitrary number of ceramic green sheets coated with the conductive paste are stacked and pressure-bonded to obtain a laminated body. At this time, dummy ceramic green sheets serving as protective layers may be arranged above and below the laminated body. Then, after the obtained laminated body is fired to obtain a ceramic sintered body, a conductive paste to be an external electrode is applied to the end surface of this sintered body and fired to form an external electrode. A cross-sectional view of the monolithic ceramic capacitor thus obtained is shown in FIG.
Shown in. In FIG. 1, 1 is a monolithic ceramic capacitor, 2 is a ceramic sintered body, 3 is an internal electrode layer, 4 is an external electrode layer, and 5 is a pore in the ceramic sintered body.

By the way, the ceramic green sheet is prepared by mixing an appropriate ceramic raw material powder, a binder, a plasticizer, an organic solvent and the like into a slurry having a constant viscosity, and then a doctor blade method, a three-roll reverse coater method or the like. It is made by making a sheet by the method of. In particular, when forming a thin ceramic green sheet of 20 μm or less, a three-roll reverse coater is often used.

A ceramic green sheet composition for this three-roll reverse coater has already been disclosed as an example in JP-A-3-170361. In the present invention, at least the ceramic raw material powder and the binder are used for the purpose of providing a composition having sufficient transfer of shear stress to a carrier such as a surface-treated PET (polyethylene terephthalate) film and having good transferability in a reverse coater. In the composition for a ceramic green sheet containing, a polyvinyl butyral resin is used as the binder, and the product of the polymerization degree of the polyvinyl butyral resin and the usage amount (g) of the polyvinyl butyral resin per 100 g of the ceramic raw material powder is 5500 or more. The present invention provides a composition for a ceramic green sheet, characterized in that

[0005]

However, when a laminated ceramic capacitor produced by using the conventional composition for ceramic green sheets is produced, the sinterability is poor,
Grain growth of ceramic particles is suppressed, many pores remain in the sintered body, and the pore area ratio in the ceramic sintered body is 1
Therefore, when a DC voltage is applied, the electric field concentrates on the pores, the insulation resistance deteriorates, and the breakdown voltage decreases. Further, there is a problem that the dielectric constant is lowered and it becomes difficult to make the dielectric layer thinner. As shown in FIG. 1, the pores formed in the ceramic sintered body are exaggerated.

[0006]

In order to solve the above problems, the present invention provides a ceramic green sheet composition containing at least a ceramic raw material powder and a binder,
A ceramic green, wherein a polyvinyl butyral resin is used as the binder, and the product of the polymerization degree of the polyvinyl butyral resin and the usage amount (g) of the polyvinyl butyral resin per 100 g of the ceramic raw material powder is 2000 or more and less than 5500. A sheet composition is provided.

If the lower limit value 2000 of the product is below that value, the adhesion between the ceramic green sheets will be impaired in the pressure bonding of the ceramic green sheets, and peeling defects will occur. The upper limit value of 5500 is a limit so that the number of pores, which are internal defects of the ceramic sintered body, does not become too large when the upper limit value is more than 5500.

Here, the polyvinyl butyral resin used in the present invention has a polymerization degree of 200 to 900 as a means for achieving the product of 2000 or more and less than 5500.
It is preferable to use a resin having a lower limit of 200, below which the physical properties of the resin will not be exhibited, and the upper limit of 900 is too high when a resin solution is used. This is a limitation to prevent the occurrence, and more preferably 700 to 900 is desirable. Further, it is preferable to use the polyvinyl butyral resin in an amount (g) of 6 to 15 g with respect to 100 g of the ceramic raw material powder. If the lower limit value of 6 g is less than that value, it is easy to handle the ceramic green sheet in post-processing. The shape cannot be retained, and the mechanical strength is a limitation to prevent this. The upper limit value of 15 g does not increase the internal defects of the ceramic sintered body obtained by firing the ceramic green sheet. This is a limitation.

As the polyvinyl butyral resin used in the present invention, two or more kinds of polyvinyl butyral resins having different polymerization degrees may be used when it is necessary to adjust the viscosity of the resin solution. However, also in the composition for ceramic green sheets in that case, the total product of the polymerization degree of each polyvinyl butyral resin and the usage amount (g) of each polyvinyl butyral resin to 100 g of the ceramic raw material powder is 2000 or more and 5500 or more.
It goes without saying that it should be less than.

[0010]

When a polyvinyl butyral resin is used in the composition for ceramic green sheets and the product of the polymerization degree and the amount (g) of the polyvinyl butyral resin used with respect to 100 g of the ceramic raw material powder is set to 2000 or more and less than 5500, at the time of firing. As the grain growth of the ceramic particles progresses, it is possible to obtain a ceramic sintered body having a dense structure with a pore area ratio of 0.5% or less in the ceramic sintered body. Moreover, there is no problem in the adhesion between the ceramic green sheets of the laminate obtained by pressure bonding.

[0011]

EFFECT OF THE INVENTION The ceramic sintered body obtained by pressure-bonding and molding the ceramic green sheet composition of the present invention after firing has a pore area ratio of 0.
Since it is as small as 5% or less, deterioration of insulation resistance and reduction of breakdown voltage due to conventional pores are small, and high reliability can be obtained. In addition, the decrease in dielectric constant is small, and
Since the layer thickness of the dielectric layer can be made thinner than before, it is possible to further increase the acquisition capacity while achieving size and thickness reduction. Furthermore, delamination and other delamination are not observed.

[0012]

EXAMPLES Examples of the present invention will be described below. First, barium titanate-based fine powder 10 as a ceramic raw material powder
To 0 g, the degree of polymerization of polyvinyl butyral resin as a binder and the amount used (g) were used according to Examples 1 to 11 in Table 1 below, and toluene, ethanol as a solvent, and an appropriate amount of an ester plasticizer as a plasticizer were added. , And mixed with a ball mill to obtain a slurry having a constant viscosity. Then, it supplied to the three roll reverse coater and created the ceramic green sheet. The butyralization degree of the polyvinyl butyral resin used here is 63 ± 3. The degree of butyralization is expressed by mol% of polyacetal occupying the whole of the polyvinyl alcohol, polyvinyl acetate, and polyacetal single molecules forming polyvinyl butyral.

Confirmation of the adhesion between the ceramic green sheets of the laminate obtained by stacking a plurality of ceramic green sheets obtained by the above-mentioned method and press-molding, and confirming the ceramic sintered body after firing the laminate. The results of measuring the pore area ratio are shown in Table 1 below. The adhesion between the ceramic green sheets of the laminate was determined by cutting the laminate and visually observing the cross section with a magnifying glass to confirm that there was no layer peeling. The pore area ratio of the ceramic sintered body is the ratio of the pore area to the ceramic polishing surface area, the measuring method is to polish the ceramic sintered body, the pore area of the ceramic polishing surface is measured by image processing, The pore area ratio was calculated.

[0014]

[Table 1]

From the results shown in Table 1 above, the polymerization degree (a) of the polyvinyl butyral resin and the ceramic raw material powder 100 g
In Example 3 and Examples 5 to 10 in which the product (a) × (b) of the amount of polyvinyl butyral resin to be used (b) is 2000 or more and less than 5500, there is no problem in the adhesion between the ceramic green sheets. , Shows that the ceramic sintered body has a small pore area ratio of 0.5% or less. However, in Examples 1, 2 and 4 in which the product was less than 2000, layer peeling was observed between the ceramic green sheets. Further, it can be seen that in Example 11 in which the product is 5500 or more, the pore area ratio of the ceramic sintered body is as high as about 2.0%.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional monolithic ceramic capacitor.

[Explanation of symbols]

 1 Multilayer Ceramic Capacitor 2 Ceramic Sintered Body 3 Internal Electrode Layer 4 External Electrode Layer 5 Pore

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Claims (1)

[Claims] 1. A composition for a ceramic green sheet containing at least a ceramic raw material powder and a binder, wherein polyvinyl butyral resin is used as the binder, and the polymerization degree of the polyvinyl butyral resin and polyvinyl butyral resin per 100 g of the ceramic raw material powder are used. The composition for a ceramic green sheet is characterized by having a product of 2000 or more and less than 5500 with the amount (g) of used.