JPH09129416A - Laminated ceramic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated ceramic device where a current is prevented from concentrating locally on a spot and which is protected against damage caused by a corona discharge by a method wherein an inner electrode pattern provided onto a ceramic green sheet is formed conforming to the curvature of the ceramic device. SOLUTION: A laminated ceramic device is equipped with an inner electrode pattern 2 which includes a rectangular effective inner electrode 1 and a ceramic green sheet 3 provided in the periphery of the inner electrode pattern 2, wherein the inner electrode pattern 2 provided in the green sheet 3 is formed conforming the curve of the ceramic device. The inner electrode pattern 2 is printed on the green sheet 3 conforming to the shape of the device. Then, the green sheets 3 each with the inner electrode pattern 2 printed on them and the other green sheets with no inner electrode pattern 2 are laminated as many as required, all the laminate is thermocompressed, degreased, sintered, and chamfered, and outer electrodes are provided in the burned laminate by application. By this setup, a laminated ceramic device of this constitution is capable of enhancing inner electrodes in effective area and being improved in solderability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic element, and more particularly to a laminated ceramic element having a property that a large current flows on its surface.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional laminated ceramic element includes an internal electrode pattern 4 including a rectangular effective internal electrode 1 and a ceramic grain sheet 3 provided outside the internal electrode pattern 4. Have

The effective internal electrode 1 has a corner portion. In a multilayer ceramic element of this type, when a steep surge is applied, a large current flows on the surface, and temporarily flows into a corner portion of the electrode portion before all the electrode surfaces are turned on.

Further, in the conventional laminated ceramics element, as shown in FIG. 7, the shortest distance t1 between the theoretical end portion of the body and the end portion of the inner electrode pattern 4 which is curved by chamfering is calculated from the theoretical inner electrode pattern 7. I am considering.

Furthermore, in the laminated ceramics element, in the shape of the element body obtained by chamfering, as shown in FIG. 8, the corner portion remains in the zinc oxide 6 element body, and the film thickness t4 of the external electrode 5 is thin. There is a portion where the thickness t4 of the external electrode 5 is small (the relationship of t4 <t5).

As a prior art, Japanese Patent Laid-Open Publication No. Hei 2-5501 discloses a multilayer chip varistor in which internal electrodes are provided and laminated between sheets mainly composed of zinc oxide.

[0007]

However, in the laminated ceramics element shown in FIG. 6, the local current concentration and the corona which temporarily flow into the corners of the electrode portion before all the electrode surfaces are turned on. There is a problem of causing discharge breakdown.

Further, the laminated ceramics element shown in FIG. 7 has a problem that the effective internal electrode area is reduced because the formation position of the rectangular internal electrode pattern 4 is shifted to the inside of the element body.

Further, in the laminated ceramics element shown in FIG. 8, if the corner portion remains in the zinc oxide element body 6, the film thickness t4 of the external electrode 5 becomes thin, and the film thickness t4 of the external electrode 5 becomes thin. Has a problem that solderability becomes weak.

Therefore, an object of the present invention is to prevent local current concentration and corona discharge destruction, to increase the effective internal electrode area, and to obtain a uniform and thick external electrode film with improved accuracy. Accordingly, it is an object of the present invention to provide a multilayer ceramic element capable of improving solderability.

[0011]

According to the present invention, an internal electrode formation of a laminated ceramic element having an internal electrode pattern including an effective internal electrode and a ceramic grain sheet provided outside the internal electrode pattern. At
A laminated ceramics element is obtained in which the effective internal electrode has a shape that matches the curvature of the body shape.

Further, according to the present invention, in forming an internal electrode of a laminated ceramic element having an internal electrode pattern including an effective internal electrode, and a ceramic grain sheet provided outside the internal electrode pattern, the ceramic is formed. A laminated ceramics element is obtained in which the internal electrode pattern formed on the green sheet is formed into an electrode pattern conforming to the curvature of the body shape.

Further, according to the present invention, there is provided a multilayer ceramic element wherein the internal electrode pattern is rectangular and the corners are curved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical method of manufacturing a multilayer ceramic element is as follows. First, a powder obtained by adding several kinds of subcomponents to an oxide as a main component is mixed, calcined, and then reground to obtain a mixed powder. And Next, several kinds of organic solvents are added to the mixed powder to form a slurry and form a film. After printing an internal electrode on this film, punching it out, stacking an appropriate number of these while reversing left and right one by one to form a laminated structure, and then pressing by hot pressing. Further, this is cut into a predetermined size, degreased and sintered to obtain a sintered body and to perform corner cutting. An external electrode is applied and baked to obtain a multilayer ceramic element.

In the present invention, an electrode pattern formed on the ceramic green sheet is formed in accordance with the curvature of the elementary body in the step of forming the internal electrode during such a manufacturing process.

The first embodiment of the laminated ceramic element of the present invention will be described below with reference to the drawings. The present embodiment shows an example in which a multilayer ceramic chip varistor is used.

Referring to FIG. 1, the laminated ceramic element has an internal electrode pattern 2 including an effective internal electrode 1 having a rectangular shape, and a ceramic grain sheet 3 provided outside the internal electrode pattern 2. .

The laminated ceramic element is formed by an internal electrode pattern 2 formed on a ceramic green sheet 3.
Are formed in the electrode pattern 2 which is adapted to the curvature of the element shape.

In order to form a multilayer ceramic element, an internal electrode pattern 2 conforming to the curvature of the element body is printed on a ceramic green sheet 3. Then, when a required number of the ceramic green sheets 3 and the ceramic green sheets 3 without the internal electrode patterns 2 are laminated, and the whole is subjected to necessary steps such as hot pressing, degreasing, sintering, chamfering, and external electrode coating, A multilayer ceramic chip varistor as shown in FIG. 4 is obtained.

In this multilayer ceramic chip varistor, since the effective internal electrode 1 has no corners as compared with the conventional internal electrode pattern 4 shown in FIG. 7, all electrode surfaces are exposed when a sharp surge occurs. In order to prevent the local current concentration and the corona discharge breakdown that are turned on and flow into a part of the electrode, the conventional internal electrode pattern 4 has a surge withstand capability of 6 or 6 when the current waveform is 8/20 μs.
0A to 100A, but surge withstand 100A
It has the above.

In the formation of the internal electrodes according to the first embodiment, as shown in FIG. 2, the distance t2 between the end of the conventional internal electrode pattern 4 and the end of the ceramic green sheet 3 is 350 μm. Then, the distances t1 'and t3' between the end of the internal electrode pattern 2 and the end of the ceramic green sheet 3 are all 350 μm to form the internal electrode pattern 2 conforming to the curvature of the elementary body. FIG. 5 shows the size of the effective internal electrode 1 at this time, and the area S ′ of the effective internal electrode 1 is 2.4 mm ² , which is compared with the conventional effective internal electrode S = 2.2 mm ² shown in FIG. Since the area ratio is 1.1 times, the surge withstand capability is 1.1 times.
In the case of a conventional multilayer chip varistor having a surge withstand capability of 10 A, the surge immunity is 11 A, which is approximately 10% higher than the conventional surge varistor.

Further, in the formation of the internal electrodes of the first embodiment, the internal electrode pattern 2 is formed so that the area of the effective internal electrodes is the same as that of the prior art, and the corners are cut with a centrifugal barrel for 30 minutes. By performing the treatment for 50 minutes, the zinc oxide hexagonal body has no extremely convex portions as shown in FIG.
The film thickness accuracy of the external electrode 5 is improved, and the film thickness t4 ', t5' of the external electrode 5 is uniform and thicker than the film thickness t4, t5 = 10 μm to 40 μm of the conventional external electrode 5 shown in FIG. Three
Since 0 μm to 40 μm can be obtained, it is possible to prevent electrode erosion which has conventionally occurred at the external electrode film thickness of 10 μm to 20 μm during soldering.

[0023]

As described above, according to the present invention, the internal electrode pattern formed on the ceramic green sheet is formed in accordance with the curvature of the element body, so that the effective internal electrode has no corner portion. It is possible to prevent local current concentration and corona discharge breakdown.

Further, since it is possible to increase the effective internal electrode area by forming an internal electrode pattern in a portion where no internal electrode pattern is conventionally formed, for example,
In the case of the effective internal electrode, the effective internal electrode area is 1.1 times as large as that of the conventional pattern, so that the surge withstand capability is improved.

In addition, since it is possible to sufficiently treat the corners of the element body without taking the internal electrode pattern formation position into consideration and without reducing the effective internal electrode area ratio, there is no extremely convex portion. Since the accuracy of the external electrode film thickness is improved and a uniform and thick external electrode film thickness can be obtained, there is an effect that the solderability of the multilayer ceramic element is improved.

Although the above embodiment describes only the multilayer ceramic chip varistor, it is apparent that other multilayer ceramic parts having the same structure have similar effects.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which internal electrodes are formed on a ceramic green sheet according to an embodiment of the present invention.

In FIG. 1, the distance between the end of the internal electrode pattern and the end of the body is defined as t2 based on the shortest distance t2 between the end of the conventional internal electrode pattern and the end of the body. FIG. 4 is a plan view showing a state in which internal electrodes are formed in accordance with the curvature of FIG.

FIG. 3 is a cross-sectional view showing a multilayer ceramic chip varistor according to one embodiment of the present invention.

FIG. 4 is a perspective sectional view of a multilayer ceramic chip varistor.

FIG. 5 is an explanatory diagram showing effective internal electrode dimensions according to an embodiment of the present invention.

FIG. 6 is a horizontal plan view showing a state in which internal electrodes are formed on a conventional ceramics green sheet.

FIG. 7 is a plan view showing a state in which internal electrodes are formed on a conventional ceramic green sheet and a theoretical formation position.

FIG. 8 is a cross-sectional view of a conventional monolithic ceramic chip varistor.

FIG. 9 is an explanatory diagram showing conventional effective internal electrode dimensions.

[Explanation of symbols] 1 Effective internal electrode 2, 4 Internal electrode pattern 3 Ceramic green sheet 5 External electrode 6 Zinc oxide element 7 Theoretical pattern

Claims (3)

[Claims] 1. In forming an internal electrode of a laminated ceramic element having an internal electrode pattern including an effective internal electrode and a ceramic grain sheet provided outside the internal electrode pattern, the effective internal electrode is formed into a body shape. A laminated ceramics element characterized by being shaped to match the curvature of the. 2. In forming an internal electrode of a laminated ceramic element having an internal electrode pattern including an effective internal electrode and a ceramic grain sheet provided outside the internal electrode pattern, the internal electrode pattern is formed on the ceramic green sheet. A laminated ceramics element, wherein the internal electrode is formed into an internal electrode pattern that matches the curvature of the element shape. 3. The multilayer ceramic element according to claim 2, wherein the internal electrode pattern is rectangular and the corners are curved.