JPH07297073A - Multilayered ceramic capacitor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a multilayered ceramic capacitor with for defects like shorting, and its manufacturing method. CONSTITUTION:Inner electrodes 3 are formed on a ceramic green sheets 2, and 70-80% of solvent component in the inner electrodes are evaporated for drying. A ceramic green sheet 4 is thermocompression bonded to obtain a sheet of three-layered structure. The sheets of three-layered structure are stacked and then baked, and external electrodes are formed.

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 and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, it has been demanded that the monolithic ceramic capacitors become smaller and larger in capacity.

In the conventional manufacturing method, first, a ceramics slurry obtained by kneading a ceramics raw material powder, an organic binder and an organic solvent is prepared, and the ceramics slurry is formed on a polyethylene terephthalate film by a doctor blade method or a reverse roll coater method. Was coated and dried to obtain a ceramic green sheet. next,
A metal powder paste of palladium, silver-palladium, or the like was printed as an internal electrode on the ceramic green sheet by a screen printing method, and a plurality of these were stacked and pressure-bonded to form a ceramic laminate block. Then, this was cut into a ceramic laminate green chip having a predetermined shape, which was sintered and porcelain at a specified firing temperature. After that, a conductive material such as silver was applied to the exposed end faces of the internal electrodes to form external electrodes, and thus a monolithic ceramic capacitor was obtained.

[0004]

SUMMARY OF THE INVENTION In the above conventional configuration,
When the thickness of the ceramic green sheet is reduced to increase the capacity, there is a problem that the surface roughness of the ceramic green sheet and the surface roughness of the internal electrode layers may cause a short circuit (short circuit defect) between the upper and lower layers. Was there.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned conventional problems and provide an excellent monolithic ceramic capacitor and a manufacturing method thereof.

[0006]

In order to achieve this object, the present invention forms an internal electrode on a green sheet and then dries and volatilizes 70 to 80% of a petroleum solvent contained in the internal electrode. Make it semi-wet. Next, another green sheet is stacked on the green sheet having the internal electrode formed thereon with the internal electrode sandwiched therebetween, and the sheet is pressed and pressure-bonded to form a three-layer structure sheet. Then, the sheet having the three-layer structure is laminated, pressure-bonded, and additionally dried so that the internal electrodes are alternately led out to the opposite ends of the sheet to form a laminated body. After this laminated body is sintered, external electrodes are provided so as to electrically connect the derived internal electrodes.

[0007]

As described above, according to the present invention, since the internal electrode formed on the ceramic green sheet forms a three-layer structure ceramic sheet in a semi-wet state, even if there are some protrusions on the internal electrode surface. , It is possible to reduce the damage given to the ceramic green sheet. Since the two ceramic green sheets are present between the internal electrodes, defects such as surface roughness and pinholes of the ceramic green sheets can be covered, and short-circuit defects can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, a polyvinyl butyral type organic binder is added to a ceramic powder containing barium titanate as a main component,
Dibutyl phthalate as a plasticizer and methyl ethyl ketone as an organic solvent were mixed in predetermined amounts, and alumina balls were used as a dispersion medium for ball milling for 48 hours to obtain a ceramics slurry. Next, as shown in FIG. 1, this ceramic slurry was obtained by applying a ceramic green sheet 2 having a thickness of 7 μm on a polyethylene terephthalate film 1 by a roll coating method and drying.
Thereafter, as shown in FIG. 2, the internal electrodes 3 were formed in a predetermined shape on the ceramic green sheet 2 by a screen printing method using a palladium paste. And about 7 petroleum solvent components contained in the internal electrode 3
After volatilizing and drying 5%, another ceramic green sheet 4 having a thickness of 7 μm and having no internal electrode formed thereon is sandwiched between the internal electrodes 3 as shown in FIG. 80 ℃, 50
A sheet having a three-layer structure was obtained by thermocompression bonding under a pressure of kg / cm ² . The sheet having the three-layer structure was further dried to volatilize and dry the remaining petroleum solvent.

Thereafter, the unprinted thickness 50 of the electrodes
Seventy sheets of three-layer structure were stacked on three sheets of ceramic green sheets having a thickness of 70 μm so that the internal electrodes 3 were respectively led out to opposite ends. Then, three ceramic green sheets to which the internal electrodes 3 have not been applied are stacked on top of this and pressure 600 k is applied.
The ceramic laminate block was formed by pressure bonding under the main pressurization condition of g / cm ² .

Next, the ceramic laminated body block is cut into a predetermined shape with a cutting blade to obtain an independent ceramic laminated body green chip.

Further, the ceramic laminated green chips are aligned with the setter for firing, put into a burnout furnace, burned out from room temperature to 400 ° C. for about 30 hours, and then put into the fired furnace to obtain the maximum. Baking was performed for about 20 hours up to a temperature of 1280 ° C. for sintering.

Thereafter, a silver electrode to be an external electrode was formed on the exposed end surface of the internal electrode 3, and a plating process was performed to improve solderability to obtain a laminated ceramic capacitor.

The laminated ceramic capacitor thus obtained and the conventional laminated ceramic capacitor were measured for delamination occurrence rate, initial short circuit defect rate, withstand voltage, humidity resistant load life and high temperature load life when the conventional value was 100%. did. Moisture resistance load life is 85 ℃, 85 according to JIS standard.
% Rh, 1000 times the voltage twice the rated voltage (25V)
The number of deterioration of insulation resistance after taking time was measured. Also, the high temperature load life was measured according to the JIS standard, and the number of deterioration of the insulation resistance was measured after applying a voltage four times the rated voltage at 85 ° C. for 1000 hours.

The results are shown in (Table 1).

[0016]

[Table 1]

As can be seen from Table 1, delamination and short-circuit defects are almost absent in this embodiment. In addition, the withstand voltage and moisture resistance load life are improved, and the high temperature load life is comparable to conventional ones.

It should be noted that even if the combination of the short-circuit thickness, the firing conditions and the like shown in this embodiment is changed, the effect is not affected at all.

[0019]

As described above, according to the present invention, since the internal electrode formed on the ceramic green sheet forms a ceramic sheet having a three-layer structure in a semi-wet state, some protrusions are present on the internal electrode surface. However, the damage given to the ceramic green sheet can be reduced. Since the two ceramic green sheets are present between the internal electrodes, defects such as surface roughness and pinholes of the ceramic green sheets can be covered, and short-circuit defects can be reduced. In addition, the three-layer structure makes it possible to reduce the level difference due to the presence / absence of electrodes, which is conventionally present, and when stacking, it is possible to easily achieve high stacking and improve the adhesion between the ceramic green sheets. Since the solvent component left in the internal electrodes improves the adhesion between the ceramic green sheets, it is possible to prevent the internal electrodes from shrinking during firing and prevent the capacity from decreasing.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the same manufacturing process.

FIG. 3 is a cross-sectional view showing the same manufacturing process.

[Explanation of symbols]

 1 Film 2 Ceramics Green Sheet 3 Internal Electrodes 4 Ceramics Green Sheet

Claims (2)

[Claims] 1. A laminated body in which a sheet having a three-layer structure in which internal electrodes are sandwiched between ceramic green sheets from the upper and lower surfaces is laminated so as to lead out to the end portions where the internal electrodes are alternately opposed to each other, and at the end portions of the laminated body. A monolithic ceramic capacitor provided with an external electrode adapted to electrically connect the led out internal electrode. 2. An internal electrode is formed on the upper surface of the ceramic green sheet, the petroleum solvent contained in the internal electrode is dried and volatilized by 70 to 80%, and then the ceramic green sheet is placed on the internal electrode. Is laminated and pressed to form a sheet having a three-layer structure of a ceramics sheet and an internal electrode, and the sheets having the three-layer structure are laminated so that the internal electrodes are alternately led out to opposite ends, and pressure-bonded. A method for producing a laminated ceramic capacitor, comprising: obtaining a laminated body, then firing the laminated body, and forming external electrodes by electrically connecting the derived internal electrodes.