JPH08298228A - Laminated capacitor - Google Patents

Abstract

PURPOSE: To prevent a decrease in acquisition capacitance caused by the generation of a gap due to the agglutination of an inner electrode by firing by a method wherein the withstand voltage of this capacitor is improved by decreasing the field density generated on the end part of the inner electrode, and the inner electrode is formed thin. CONSTITUTION: In this laminated capacitor which is composed of a laminated part, where an internal electrode and a ceramic sheet are alternately stacked, a protective layer which protects the laminated part, and an external part 2, at least the internal electrode printed on the outermost layer of the ceramic sheet 1 is formed thicker than the other internal electrode (thin internal electrode 4) as shown in the diagram as an internal electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer capacitor capable of relaxing electric field concentration and improving withstand voltage characteristics.

[0002]

2. Description of the Related Art A multilayer capacitor has, inside a ceramic laminated body, internal electrodes that are alternately drawn out one by one on opposite end faces, and external electrodes are provided on both end faces where the internal electrodes are exposed. Have a structure.

In such a multilayer capacitor, a plurality of sheets, each of which is formed by applying a conductive paste by a method such as screen printing, is stacked on a green sheet, which is a slurry formed by kneading ceramic powder and an organic binder, and is heated and pressed. It is obtained by forming a laminated body, dividing this laminated body into individual chips, firing them, and then baking external electrodes.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
There are a laminated portion in which internal electrodes and ceramic sheet layers are alternately stacked, and a protective layer formed of a plurality of ceramic sheets that protects the laminated portion. Since a multilayer capacitor can obtain a large capacity per unit volume, the demand for larger capacity has increased, and in recent years the number of laminated internal electrodes has increased, which has led to an increase in the proportion of internal electrode parts in the laminated body. It was

Since the ceramic sheet layer and the metal layer of the internal electrode shrink differently, the difference in shrinkage between the laminated portion and the protective layer becomes large, and cracks or the like may occur between the two. In order to prevent this, the thickness of the internal electrode has been reduced, but this also has a problem. That is, when the conductive paste is thinly applied to form the electrode thinly, the metal particles of the conductive paste are aggregated during firing and a gap is generated in the internal electrode. Also, FIG.
As shown in the partial cross-sectional view of the conventional multilayer capacitor, the thinner the internal electrode, the higher the density of the electric field at the edge portion of the internal electrode. Between the internal electrodes in the center of the laminated part,
Although the electric field is dispersed to the adjacent inner electrodes on both sides and the degree of concentration is small, the innermost electrode in the outermost layer has only one adjacent inner electrode, so that the electric field density is higher than the other portions and the degree of concentration is large. Therefore, there has been a problem that the withstand voltage characteristic is deteriorated.

Therefore, an object of the present invention is to improve the withstand voltage characteristics by reducing the density of the electric field generated at the end portions of the internal electrodes to reduce the concentration, and further, by forming the internal electrodes thin, An object of the present invention is to provide a multilayer capacitor capable of preventing a reduction in acquisition capacity due to aggregating of electrodes during firing to form a gap.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted research to achieve the above-mentioned object, and as a result, in a multilayer capacitor in which internal electrodes and ceramic sheet layers are alternately stacked, at least the concentration of an electric field is relaxed. If the thickness of the innermost electrode of the outermost layer is made thicker than the thickness of the other inner electrodes, the withstand voltage characteristics can be improved, and further, by accumulating thick and thin inner electrodes alternately, the obtained capacitance The present invention has been reached by finding that the decrease of the above can be prevented.

Therefore, according to the present invention, firstly, the internal electrodes are alternately drawn out one by one on both end surfaces of a chip element body formed by stacking the internal electrodes alternately facing each other with a ceramic sheet interposed therebetween. A multilayer capacitor having external electrodes formed on both end surfaces where the internal electrodes are exposed, wherein at least the outermost internal electrode of the laminated internal electrodes is formed relatively thicker than the other internal electrodes. Secondly, a multilayer capacitor characterized in that
The internal electrodes are alternately drawn out one by one on both end surfaces of a chip element body formed by stacking internal electrodes that are alternately opposed to each other with a ceramic sheet sandwiched between them, and external electrodes are provided on both end surfaces where these internal electrodes are exposed. Of the internal electrodes to be laminated, the relatively thick internal electrodes and the thin internal electrodes are alternately stacked, and the thick internal electrodes are stacked so as to be the outermost layer. And a multilayer capacitor characterized by the above.

[0009]

By changing the thickness of a part of the internal electrodes of the multilayer capacitor as required, the problems of contraction, acquisition capacitance or electric field concentration can be solved. That is, as shown in the partial cross-sectional view of FIG. 4, by forming the thickness of the internal electrodes printed on the outermost ceramic sheet 1 to be thicker than the others (thick internal electrodes 3 and thin internal electrodes 4), The density of the electric field generated at the ends of the internal electrodes can be reduced to reduce the concentration, and the withstand voltage characteristics can be improved.

Further, by alternately stacking the thick internal electrodes and the thin internal electrodes, even if one internal electrode has a large gap, the other thick electrode becomes an electrode having a small gap, so that the acquisition capacity is reduced. Can be reduced.

[0011]

[Embodiment 1] FIG. 1 is a schematic vertical sectional view showing an internal structure of a multilayer capacitor prepared in this embodiment, which will be described below with reference to this drawing.

The ceramic powder is mixed with an organic binder, a solvent,
A ceramic slurry is prepared by kneading with a dispersant or the like. This ceramic slurry is applied onto a support such as a PET film to prepare a ceramic sheet. Screen printing method (screen emulsion thickness 8μ
m) apply the conductive paste (viscosity 300PS),
An internal electrode pattern to be the thin internal electrode 4 is formed. At this time, some ceramic sheets have a thick emulsion (10 μm).
m) Print using a screen to prepare the ceramic sheet 1 on which the thick internal electrodes 3 are printed.

Next, the ceramic sheets on which the internal electrode patterns are formed are punched into a certain shape and stacked, and at this time, the sheet on which the thick internal electrodes 3 prepared above are printed is the outermost layer of the laminated portion and its vicinity. Stack so that it becomes a layer of. Then, a ceramic sheet to be a protective layer is stacked on the stacked sheets, placed in a mold and heated and pressed to obtain a laminate. This laminated body is cut and divided into individual chips having a predetermined size, the chips are sintered in a firing furnace, and a conductive paste is baked on the exposed surface of the internal electrodes to form the external electrodes 2, thereby obtaining a laminated capacitor.

[0014]

[Embodiment 2] FIG. 2 is a schematic longitudinal sectional view showing the internal structure of the multilayer capacitor produced in this embodiment, which will be described below with reference to this drawing.

A ceramic sheet was prepared in the same manner as in Example 1 and screen-printed (screen emulsion thickness 8 μm).
Then, a conductive paste (viscosity 300 PS) is applied to form an internal electrode pattern to be a thick internal electrode 3. At this time, some of the ceramic sheets have a thin emulsion thickness (5 μm).
A ceramic sheet 1 having a thin internal electrode 4 printed thereon is prepared by printing using a screen.

Next, the ceramic sheets on which the internal electrode patterns are formed are punched into a certain shape and stacked, and at this time, the sheets on which the thin internal electrodes 4 prepared previously are printed and the normal printed sheets alternate. In this way, stacking is performed (in this case, the sheet on which the thick internal electrodes 3 are printed is stacked as the outermost layer on the sheet of the thin internal electrodes). After that, a multilayer capacitor is obtained in the same manner as in Example 1.

[0017]

Comparative Example A ceramic sheet was prepared in the same manner as in Example 1 and screen-printed (screen emulsion thickness 8 μm).
Conductive paste (viscosity 300 PS) is applied to form internal electrode patterns. The printed sheets obtained are stacked, and then a multilayer capacitor is obtained in the same manner as in Example 2.

In order to compare the insulation failure between Examples 1 and 2 and the comparative example, 200 finished products were each subjected to 80 ° C.
After applying a load of −100 V and a humidity of 95% for 12 hours, the presence or absence of insulation insoluble was examined. As a result, the number of occurrences of insulation failure was 0/200 in Example 1, 0/200 in Example 2, and 3 in Comparative Example. /
It was 200, and when the cause of the insulation failure in the comparative example was examined, it was found that all three had a short circuit between the innermost outer electrode and the electrode next to it.

In Example 2 and Comparative Example, the capacitance of 50 finished products was measured, and the average value was calculated to compare the capacitance values. The capacity value of 2 was 97.6%.

[0020]

As described above, according to the present invention,
It is possible to prevent a decrease in withstand voltage characteristics due to the concentration of an electric field, and further to prevent a decrease in acquisition capacity that is caused by a thin internal electrode aggregating during firing to form a gap.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing the internal structure of a multilayer capacitor produced according to an example of the present invention.

FIG. 2 is a schematic vertical cross-sectional view showing the internal structure of a multilayer capacitor manufactured according to another embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing that in the conventional multilayer capacitor, the electric field density generated at the inner electrode end portion is more likely to be concentrated in the innermost electrode of the outermost layer than in other portions.

FIG. 4 is a partial cross-sectional view of the multilayer capacitor of the present invention in which the thickness of the innermost electrode of the outermost layer is made thicker than the others to reduce the concentration of the electric field density generated at the end of the inner electrode.

[Explanation of symbols]

 1 Ceramic Sheet 2 External Electrode 3 Thick Internal Electrode 4 Thin Internal Electrode

Claims (2)

[Claims] 1. The internal electrodes are alternately drawn out one by one on both end faces of a chip body formed by stacking internal electrodes that are alternately opposed to each other with a ceramic sheet interposed therebetween, and the internal electrodes are exposed. A multilayer capacitor having external electrodes formed on both end faces, wherein at least the inner electrode of the outermost layer among the laminated inner electrodes is formed relatively thicker than the other inner electrodes. And multilayer capacitors. 2. The internal electrodes are alternately drawn out one by one on both end faces of a chip body formed by stacking internal electrodes that are alternately opposed to each other with a ceramic sheet interposed therebetween, and the internal electrodes are exposed. A multilayer capacitor having external electrodes formed on both end surfaces, wherein among relatively stacked internal electrodes, relatively thick internal electrodes and thin internal electrodes are alternately arranged, and a thick internal electrode is an outermost layer. A multilayer capacitor characterized by being stacked.