JPH0774047A - Manufacture of monolithic ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a manufacturing method, of a monolithic ceramic capacitor, wherein, when dielectric ceramic layers between internal electrodes for the monolithic ceramic capacitor are thin, a crack and a delamination are not caused in its manufacture and a withstand-voltage defect and an insulation- resistance defect are not caused. CONSTITUTION:The manufacturing method of a monolithic ceramic capacitor refers to a monolithic ceramic capacitor in which a plurality of dielectric ceramic layers in a thickness of 15mum or lower, a plurality of internal electrodes formed between the dielectric ceramic layers and external electrodes formed so as to be connected electrically to the exposed internal electrodes are contained. Films which constitute the internal electrodes are formed in such a way that they are formed on ceramic green sheets, that their central-line average roughness is at 0.5mum or lower and their 10-point average roughness is at 1/4 or lower with reference to the thickness of the ceramic green sheets regarding their surface roughness and that their thickness as a metal is at 1.5mum or lower and at 1/7 or lower with reference to the thickness of the ceramic green sheets. Then, a laminated body which is obtained by laminating a plurality of ceramic green sheets is fired.

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 laminated ceramic capacitor, and more particularly to a method for manufacturing a laminated ceramic capacitor having a dielectric ceramic layer with a thickness of 15 μm or less.

[0002]

2. Description of the Related Art A monolithic ceramic capacitor has a plurality of dielectric ceramic layers, a plurality of internal electrodes formed between the dielectric ceramic layers, and is connected to these internal electrodes at each end face of the dielectric ceramic layer. Including external electrodes.

Conventionally, a monolithic ceramic capacitor has been manufactured through the following steps.

First, a ceramic green sheet formed into a sheet by a doctor blade method or the like is prepared. Then, a conductive paste containing a metal to be an internal electrode such as palladium, silver-palladium, or nickel is screen-printed on the upper surface of the ceramic green sheet in a predetermined pattern. At this time, it is usual to manufacture a plurality of laminated ceramic capacitors by using a large ceramic green sheet and cutting it after laminating in a later step. Therefore, the conductive paste layer for forming the internal electrodes is formed in a plurality of regions dispersed in the ceramic green sheet.

Next, a plurality of ceramic green sheets each having a conductive paste layer formed thereon are laminated and pressed in the thickness direction to be pressure-bonded. After that, the pressure-bonded laminated body is cut so as to obtain a laminated body for obtaining individual monolithic ceramic capacitors.

Next, the obtained individual laminated bodies are fired,
Obtain a sintered body. After that, the laminated ceramic capacitor is completed by baking external electrodes that are electrically connected to the internal electrodes on the end faces of the sintered body.

[0007]

With the recent development of electronics, miniaturization of electronic parts is rapidly progressing,
The trend toward miniaturization of monolithic ceramic capacitors has become remarkable. As a method of miniaturizing a monolithic ceramic capacitor, a method of reducing the thickness of a dielectric ceramic layer between internal electrodes is known.

However, in the conventional method for manufacturing a monolithic ceramic capacitor, as the dielectric ceramic layer between the internal electrodes is made thinner, the ratio of the thickness of the conductive paste layer serving as the internal electrode to the thickness of the dielectric ceramic layer increases. Therefore, during firing, the contraction of the conductive paste layer governs the contraction of the dielectric ceramic layer, and there is a problem that cracks or delamination occurs.

Further, since the surface of the conductive paste layer has irregularities, voids are likely to occur during firing, and the thickness of the internal electrodes becomes non-uniform, and the internal electrodes become ball-shaped. Then, when the dielectric ceramic layer between the internal electrodes is made thinner, electric field concentration is more likely to occur in the voids and the ball-shaped portions of the internal electrodes, resulting in the problem of breakdown voltage failure and insulation resistance failure. there were.

Therefore, the main object of the present invention is to produce cracks and delamination during the production of a thin dielectric ceramic layer between the internal electrodes of a monolithic ceramic capacitor, especially when the dielectric ceramic layer is 15 μm or less. It is an object of the present invention to provide a method for manufacturing a monolithic ceramic capacitor that does not have a withstand voltage defect or an insulation resistance defect.

[0011]

The present invention has a thickness of 15
A plurality of dielectric ceramic layers having a thickness of μm or less, a plurality of internal electrodes formed between the dielectric ceramic layers so that one end of each is exposed on each end face of the dielectric ceramic layer, and the exposed internal electrodes are electrically connected. A method for manufacturing a monolithic ceramic capacitor including external electrodes formed so as to be electrically connected to each other, wherein a film for forming internal electrodes is provided on a ceramic green sheet with respect to its surface roughness and a center line average. The roughness (Ra) is 0.5 μm or less, the ten-point average roughness is ¼ or less of the thickness of the ceramic green sheet, and the metal thickness is 1.5 μm.
Below, 1 / the thickness of the ceramic green sheet
A step of forming a laminated body by laminating a plurality of ceramic green sheets on which films for forming internal electrodes are formed, and a step of firing the laminated body. It is a manufacturing method of a monolithic ceramic capacitor.

[0012]

The inventors of the present application have earnestly studied to obtain a laminated ceramic capacitor having a dielectric ceramic layer having a thickness of 15 μm or less, which is free from cracks and delamination, and has neither breakdown voltage nor insulation resistance. As a result, by limiting the surface roughness and the metal thickness of the film containing the metal that will be the internal electrodes formed on the ceramic green sheet, there is no defective withstand voltage or defective insulation resistance, and the dielectric ceramic layer is thin, small and large. It has been found that a monolithic ceramic capacitor having a capacity can be obtained.

That is, the center line average roughness (Ra) of the surface roughness of a film, which is an internal electrode formed of a metal powder and an organic substance, formed by screen printing on a ceramic green sheet is 0. Below 5 μm,
By limiting the ten-point average roughness to 1/4 or less of the thickness of the ceramic green sheet, voids are less likely to occur during firing, and continuity of the internal electrodes can be secured. Therefore, the internal electrodes do not become ball-shaped, and even if the dielectric ceramic layer is thinned, electric field concentration is less likely to occur between the internal electrodes, and withstand voltage failure and insulation resistance failure can be reduced in the multilayer ceramic capacitor. .
Further, since the continuity of the internal electrodes is improved, the variation in the capacitance is reduced, and the capacitance failure such as the capacitance reduction is eliminated.

Further, by limiting the thickness of the metal film of the internal electrode to 1.5 μm or less, which is 1/7 or less of the thickness of the ceramic green sheet, the internal electrode during firing is limited. It is possible to reduce the influence of the shrinkage of the film that becomes the above on the shrinkage of the dielectric ceramic layer. Therefore, it is possible to manufacture a small-sized and large-capacity monolithic ceramic capacitor without the problem of cracks and delamination.

[0015]

According to the present invention, even if the thickness of the dielectric ceramic layer is as thin as 15 μm or less, cracks and delamination do not occur at the time of manufacture, and the occurrence of voids is suppressed. , It is possible to reduce the breakdown voltage failure.

Further, since the continuity of the internal electrodes is improved, the variation in capacitance is reduced. Therefore, it is possible to obtain a small-sized and large-capacity monolithic ceramic capacitor with high reliability and quality, low manufacturing cost.

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

[0018]

Example (Example 1) First, B having a purity of 99.8% or more
aCO ₃ , CaCO ₃ , TiO ₂ , ZrO ₂ , MnO ₂
Is prepared, {(Ba _0.9 Ca _0.1 ) O} _1.01 (Ti _0.8
Zr _0.2 ) O ₂ +0.25 wt% MnO ₂ were blended to obtain a blended raw material. The blended raw materials are wet mixed in a ball mill, pulverized, dried and then dried in air 1
It was calcined at 100 ° C. for 2 hours to obtain a calcined product. The calcined product was crushed by a dry crusher to obtain a raw material powder having a particle size of 1 μm or less.

A polyvinyl butyral binder and an organic solvent such as ethanol were added to this raw material powder, and the mixture was wet mixed by a ball mill to prepare a ceramic slurry. After that, the ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular ceramic green sheet having a thickness of 20 μm.

Next, the ceramic green sheet was screen-printed with a conductive paste of several kinds of Ni powders containing Ni having different particle sizes and particle size distributions to screen-print the surface roughnesses A to F shown in Table 1. Also, a plurality of ceramic green sheets having conductive paste layers for forming internal electrodes having different metal thicknesses were obtained.

[0021]

[Table 1]

A plurality of ceramic green sheets on which conductive paste layers having different surface thicknesses and Ni metal thicknesses are formed are laminated so that the sides from which the conductive paste layers are drawn out are staggered, and a laminated body is formed. Got

The obtained laminated body was subjected to 40% N ₂ atmosphere.
After heating to a temperature of 0 ° C. to burn the binder, it is heated at 1300 ° C. in a reducing atmosphere composed of H ₂ —N ₂ —H ₂ O mixed gas with an oxygen partial pressure of 10 ⁻⁹ to 10 ⁻¹² MPa at 2300 ° C. It was fired for a time to obtain a ceramic sintered body.

After firing, silver paste was applied to each end surface of the obtained ceramic sintered body, and the silver paste was heated to 600 in an N ₂ atmosphere.
Baking was performed at a temperature of ° C to form an external electrode electrically connected to the internal electrode.

The external dimensions of the monolithic ceramic capacitor thus obtained are 1.6 mm in width and 3.2 m in length.
m, the thickness was 1.2 mm, and the thickness of the dielectric ceramic layer interposed between the internal electrodes was 15 μm. The total number of effective dielectric ceramic layers was 19, and the area of the counter electrode per layer was 2.1 mm ² .

5000 pieces of each sample, capacitance (C)
In order to measure the dielectric loss (tan δ) and an automatic bridge type measuring instrument, the frequency is 1 KHz, 1 Vrms.
Was applied and the temperature was measured at 25 ° C.

Next, a DC voltage of 25 V was applied for 1 minute using an insulation resistance tester to 5000 samples,
The insulation resistance value (R) at ° C was measured, and the product of the electrostatic capacitance (C) and the insulation resistance value (R), that is, the CR product was obtained. C, which is the product of the electrostatic capacitance (C) and the insulation resistance value (R)
The number of samples whose R product was 1000 MΩ · μF or less was regarded as defective and the number thereof was shown.

For the measurement of withstand voltage, 20 samples of each sample were used.
A DC voltage of 75 V was applied to each of the 000 samples for 3 seconds, and a sample having an insulation resistance value of 10 ⁸ Ω or less at that time was regarded as defective and the number thereof was shown.

Further, the laminated capacitor chips obtained as described above were fixed by 200 pieces of each sample with a resin and polished, and observed under a microscope at a magnification of 200 times to inspect for the presence of delamination.

The results of the above tests are also shown in Table 2.

[0031]

[Table 2]

(Example 2) BaT having a purity of 99.9% or more
iO ₃ and CeO ₂ , TiO ₂ , or BaZ with a purity of 98% or more
Prepare and rO _3, MnO _2, with respect to BaTiO ₃ 100 molar parts, a CeO ₂ 3 molar parts, the TiO ₂ 4.5 parts by mole, 3 parts by mole of BaZrO _3, and the MnO ₂ 0.15 molar parts The ingredients were blended to obtain a blended raw material. The blended raw materials were wet mixed in a ball mill, pulverized and dried to obtain raw material powder having a particle size of 1 μm or less.

A polyvinyl butyral binder and an organic solvent such as ethanol were added to this raw material powder, and the mixture was wet mixed by a ball mill to prepare a ceramic slurry. After that, the ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular ceramic green sheet having a thickness of 10 μm.

Next, on this ceramic green sheet, a conductive paste of Pd powder mainly composed of several kinds of Pd having different particle sizes and particle size distributions was screen-printed to give surface roughnesses F to J shown in Table 3. Also, a plurality of ceramic green sheets having conductive paste layers for forming internal electrodes having different metal thicknesses were obtained.

[0035]

[Table 3]

A plurality of ceramic green sheets on which the conductive paste layers having different surface thicknesses and Pd metal thicknesses are formed are laminated so that the sides from which the conductive paste layers are drawn out are alternately staggered to form a laminate. Got

The obtained laminated body was heated to a temperature of 400 ° C. in the atmosphere to burn the binder, and then fired in the atmosphere at 1300 ° C. for 2 hours to obtain a ceramic sintered body.

After firing, silver paste was applied to each end surface of the obtained ceramic sintered body and baked at a temperature of 750 ° C. in the atmosphere to form an external electrode electrically connected to the internal electrode.

The external dimensions of the monolithic ceramic capacitor thus obtained are 1.6 mm in width and 3.2 m in length.
m, the thickness was 1.2 mm, and the thickness of the dielectric ceramic layer interposed between the internal electrodes was 7.5 μm. The total number of effective dielectric ceramic layers was 19, and the area of the counter electrode per layer was 2.1 mm ² .

The characteristics of each of the obtained samples were measured in the same manner as in the examples. The results of the above tests are also shown in Table 4.

[0041]

[Table 4]

As is clear from Tables 2 and 4, the laminated ceramic capacitor manufactured by the manufacturing method of the present invention can prevent the occurrence of fatal defects such as delamination without impairing the capacitor characteristics. In addition, there are no breakdown voltage failures, insulation resistance failures, etc., and variations in capacitance and dielectric loss are small.

On the other hand, outside the scope of the present invention, the following characteristics are not preferable.

The centerline average roughness Ra like E is 0.5 μ.
In a multilayer ceramic capacitor using a ceramic green sheet having a conductive paste layer larger than m, defective insulation resistance and defective withstand voltage occur, resulting in large variations in capacitance and dielectric loss.

A laminated ceramic capacitor using a ceramic green sheet on which a conductive paste layer having a metal thickness t of more than 1.5 μm, such as F, causes delamination failure, which causes insulation resistance failure.
A breakdown voltage occurs. Further, the value of the electrostatic capacitance becomes small and the variation becomes large. Further, the value of the dielectric loss becomes large, and the variation also becomes large.

A multilayer ceramic capacitor using a ceramic green sheet having a conductive paste layer having a thickness of 10-point average roughness Rz larger than ¼ of the thickness of the ceramic green sheet, such as J, has a poor insulation resistance. ∙ Defects in withstand voltage occur, resulting in large variations in capacitance and dielectric loss.

In a laminated ceramic capacitor using a ceramic green sheet having a conductive paste layer in which a metal thickness t such as K is greater than 1/7 of the ceramic green sheet thickness, delamination failure occurs, and As a result, insulation resistance defects and breakdown voltage defects occur. Further, the value of the electrostatic capacitance becomes small and the variation becomes large. Further, the value of the dielectric loss becomes large, and the variation also becomes large.

In the embodiments of the present invention, the film forming method for forming the internal electrodes is shown by the screen printing method, but the forming method is not limited to this. The same effect can be obtained by a method of forming a film formed on a carrier film in advance by transferring it onto a ceramic green sheet or a forming method by gravure printing.

Claims (1)

[Claims] 1. A plurality of dielectric ceramic layers having a thickness of 15 μm or less, and a plurality of internal electrodes formed between the dielectric ceramic layers such that one edge of each is exposed at each end face of the dielectric ceramic layer. And a method for manufacturing a laminated ceramic capacitor including an external electrode formed so as to be electrically connected to the exposed internal electrode, wherein a film for forming the internal electrode is formed on a ceramic green sheet, Regarding the surface roughness, the center line average roughness (Ra) is 0.5 μm or less and the ten-point average roughness (Rz) is 1/4 or less of the thickness of the ceramic green sheet, and Thickness as metal is 1.5μm
In the following, a step of forming the ceramic green sheet to have a thickness of 1/7 or less with respect to the thickness of the ceramic green sheet, stacking a plurality of the ceramic green sheets having the film for forming the internal electrodes, and stacking the stacked layers. A method of manufacturing a monolithic ceramic capacitor, comprising the steps of obtaining a body and firing the laminate.