JPH08273971A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE: To improve the insulation breakdown voltage value of a laminated ceramic capacitor for middle/high voltages and to reduce its scattering. CONSTITUTION: A sharp part is provided on opposite sides of inner electrodes 2a and 2b which oppose with a certain distance within the same plane, the concentration of electric field is induced at this part when a high voltage is applied so that insulation breakdown constantly occurs from this part, thus suppressing the scattering of the insulation breakdown voltage and simultaneously improving level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic ceramic capacitor, and more particularly to a monolithic ceramic capacitor for medium and high voltage which requires a high withstand voltage.

[0002]

2. Description of the Related Art A general monolithic ceramic capacitor is
After stacking the ceramic green sheets and sheets with internal electrodes formed on the ceramic green sheets so that the internal electrode layers are alternately displaced by a certain size and crimping, cutting into chips of the desired shape and firing the obtained laminated body It is manufactured by connecting the internal electrodes appearing at both ends of the sintered body to the external electrodes, and the structure is such that individual capacitors are connected in parallel.

On the other hand, in a medium- and high-voltage monolithic ceramic capacitor (particularly 1 KV class or higher), in order to improve the withstand voltage, the ends are connected to the external electrodes 4a and 4b as shown in the sectional view of FIG. Internal electrodes 2a, 2b
(Hereinafter referred to as a counter electrode), the end portions are external electrodes 4a, 4
The internal electrode layers 3 (hereinafter, referred to as floating electrodes) which are not connected to b and overlap with each of the counter electrode layers are alternately arranged with the dielectric layer 1 interposed therebetween, so that the electric field strength applied per layer is increased. Is generally used as a general means.

[0004]

However, in the above configuration, when dielectric breakdown of the dielectric occurs under high voltage, the location of the breakdown is greatly influenced by the microstructure of the ceramic sintered body, so that the location of the breakdown is specified. As a result, the withstand voltage greatly varies, which causes problems in manufacturing and quality.

In view of the above problems, the present invention is intended to provide a high-quality medium- and high-voltage monolithic ceramic capacitor in which variations in dielectric breakdown voltage are suppressed.

[0006]

Therefore, a laminated ceramic capacitor of the present invention comprises a laminated body in which a first internal electrode layer and a second internal electrode layer are laminated so as to alternately face each other with a dielectric layer interposed therebetween. And an external electrode provided on an end surface of the laminated body, wherein the first internal electrode layer includes two internal electrodes,
The two internal electrodes face each other at a distance on the surface of the dielectric layer and are formed so that one ends thereof are connected to the external electrode, and at least one layer of the first internal electrode layers is The two internal electrodes have at least one sharp portion at the end portion on the opposite side, and the second internal electrode layer has an end portion not connected to the external electrode and an end portion of the dielectric layer. It is provided so that it does not reach.

[0007]

With this configuration, when a high voltage is applied, electric field concentration is induced in the sharp portion provided on the counter electrode, and as a result, dielectric breakdown always occurs at this point as the starting point.
It is possible to specify the breakdown point and suppress variations in the dielectric breakdown voltage.

[0008]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. First, the shapes of the counter electrodes 2a and 2b used in this example are shown in FIG. 1A, and the shape of the floating electrode 3 disposed in the central portion is shown in FIG. 1B as a plan view.
For the dielectric layer 1, a dielectric slurry is prepared and a reverse roll coater is used to form a 100 μm thick film on the carrier film.
Was prepared by molding.

Next, the internal electrodes 2a, 2b and 3 having the shapes shown in FIGS. 1 (a) and 1 (b) are respectively formed on the green sheet by screen printing using a commercially available paste containing palladium as a main component. A predetermined quantity was formed, and this green sheet was cut into a predetermined size to be laminated.

Next, a pallet for lamination is prepared, and a predetermined number of green sheets on which the internal electrodes 2a, 2b and 3 are not printed are laminated as shown in the schematic construction of FIG. After forming the lower layer 5 that does not contribute to the capacitance, the internal electrode 2 shown in FIGS.
The green sheets on which a, 2b and 3 are formed are peeled from the carrier film, and a predetermined number of layers are alternately laminated by thermocompression bonding, and finally the upper layer 6 which is equivalent to the lower layer 5 and does not contribute to the capacitance of the capacitor is formed. Then, a laminated molded body was produced.

Next, the above-mentioned laminated molded body is cut into a desired chip shape and 350 ° C. for degreasing the organic binder in an electric furnace.
After being held for 5 hours on the way, it was baked at 1300 ° C. for 2 hours. After firing, external electrodes 4a and 4b containing silver as a main component were formed on the exposed end faces of the internal electrodes 2a and 2b of the device, as shown in FIG. 6, to produce a laminated ceramic capacitor.

As a comparative example, the counter electrodes 10a and 10b having the pattern shown in FIG. 5 are used instead of the counter electrodes 2a and 2b shown in FIG. 1A, and the floating electrode shown in FIG. A multilayer ceramic capacitor was manufactured in the same manner as described above in combination with No. 3 and used as a sample of a conventional product.

The two types of monolithic ceramic capacitors thus obtained were subjected to a DC breakdown test, and the dielectric breakdown voltage was measured for each 100 samples.
The results of the average value and standard deviation are shown in (Table 1).

[0014]

[Table 1]

As is apparent from Table 1, the product of the present invention has a very small variation in the dielectric breakdown voltage, and the level is improved. Regarding this, as a result of observing the inside of the sample after destruction, in the conventional product, a crack was running three-dimensionally in the dielectric layer 1 between the counter electrodes 10a and 10b and the floating electrode 3, whereas In the product of the present invention, the breakage was concentrated in the plane of the electrodes 2a and 2b facing each other. That is, by intentionally concentrating the electric field according to the present invention, it has succeeded in causing breakdown in the plane between the counter electrodes 2a and 2b having a larger thickness than the dielectric layer 1 forming the capacitor, and as a result, the breakdown voltage Is considered to have improved.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In the first embodiment, the pattern shown in FIG. 1A was used as the pattern for the counter electrodes 2a and 2b, but in this embodiment, as shown in FIG. 2, the pattern shown in FIG. The difference from the first embodiment is that sharp points equivalent to the above are provided at symmetrical positions.
The shape of the floating electrode 3 is the same as that in FIG. The manufacturing method for manufacturing the laminated ceramic capacitor and the sample for comparison are the same as those in the first embodiment.

The results of measuring the dielectric breakdown voltage using the thus obtained monolithic ceramic capacitor in the same manner as in Example 1 are shown in Table 2.

[0018]

[Table 2]

In this case as well, it is understood that the improvement of the dielectric breakdown voltage value and the reduction of the variation are achieved as in the first embodiment. Further, the internal observation result of the destroyed sample also showed the same tendency as in the first embodiment.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings. In the first and second embodiments, the internal electrode layer patterns facing each other are shown in FIG.
As shown in (a) and FIG. 2, sharp portions are provided on both sides facing each other, but in this embodiment, as shown in FIG. 3, a sharp portion equivalent to the conventional one is provided on only one of the facing sides. They differ in that they show an equal electric field.

The shape of the floating electrode 3, the manufacturing method for manufacturing the laminated ceramic capacitor, and the sample for comparison are all the same as those in the first embodiment.

The results of measuring the dielectric breakdown voltage using the thus-obtained monolithic ceramic capacitor in exactly the same manner as in Example 1 are shown in Table 3.

[0023]

[Table 3]

As is clear from this (Table 3), in the product of the present invention, the dielectric breakdown voltage was improved and its variation could be reduced.

In each of the first to third embodiments, at least one sharp portion is provided in all layers in which each counter electrode is formed, but at least one sharp portion is provided in one or more layers of counter electrodes. By providing it, it is possible to suppress the variation in the dielectric breakdown voltage value and improve the level at the same time.

In the internal electrode layer, the counter electrodes 2a,
The counter electrodes 2a and 2b and the floating electrode 3 are connected to the dielectric layer 1 so that the layer on which the layer 2b is formed is located on the lower layer 5 and upper layer 6 sides.
It is preferable to alternately stack the layers.

[0027]

As described above, according to the present invention, the sharp portions are provided on the opposite sides of the internal electrodes facing each other at a constant distance in the same plane, and when a high voltage is applied, electric field concentration is induced in these portions and insulation is performed. By specifying that the breakdown always occurs from this part, it is possible to suppress the variation in the dielectric breakdown voltage value and at the same time improve the level.

[Brief description of drawings]

FIG. 1A is a plan view of an internal electrode according to a first embodiment of the present invention. FIG. 1B is a plan view of an internal electrode according to a first embodiment of the present invention.

FIG. 2 is a plan view of internal electrodes according to a second embodiment of the present invention.

FIG. 3 is a plan view of internal electrodes according to a third embodiment of the present invention.

FIG. 4 is an exploded perspective view of a laminated body according to an embodiment of the present invention.

FIG. 5 is a plan view of a conventional internal electrode.

FIG. 6 is a cross-sectional view of a general medium / high voltage monolithic ceramic capacitor.

[Explanation of symbols]

 1 Dielectric Layer 2a Counter Electrode 2b Counter Electrode 3 Floating Electrode 4a External Electrode 4b External Electrode

Claims (1)

[Claims] 1. A laminated body in which a first internal electrode layer and a second internal electrode layer are laminated so as to alternately face each other with a dielectric layer in between, and an external electrode provided on an end face of the laminated body. And the first internal electrode layer is composed of two internal electrodes.
Two internal electrodes are formed so as to face each other at a distance on the surface of the dielectric layer, and one end sides thereof are connected to the external electrode, and two internal electrodes are provided in at least one layer of the first internal electrode layers. The inner electrode has at least one sharp portion at the end on the opposite side, and the end of the second inner electrode layer is not connected to the outer electrode and does not reach the end of the dielectric layer. Multilayer ceramic capacitor provided in this way.