JPH0338810A - Laminated ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent damage by a fire by producing an electrically open state even when a defect by a short circuit is caused by installing a bimetal which is fitted into a cutout, whose shape is nearly the same as that of the cutout at room temperature and which is provided with a characteristic that it is deformed largely at about 300 deg.C or higher. CONSTITUTION:While a laminated body 6 is being moved horizontally, it is cut one after another while a cutout is being formed on the surface of a cutout position 41 nearly in the central part of cutting positions 22 by using a rotary cutting blade 21 which is moved up and down; after that, a baked body 7 is obtained by a baking operation. A so-called bimetal 5, formed by pasting different kinds of metals, whose shape is nearly the same as that of a formed cutout 4 at room temperature, which is not deformed by heating at a mounting operation and which is bent largely at about 300 deg.C or higher is fitted into and bonded to the cutout 4. Thereby, even when a short circuit is caused after this assembly has been mounted on a board 8, an electrically open state is produced and it is possible to prevent a laminated ceramic capacitor from being damaged and an electronic component near it and a printed-circuit board from being damaged by a fire.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multilayer ceramic container and a method for manufacturing the same, and particularly has a structure that destroys the main body and interrupts the current in the event that a wooden component is short-circuited. The present invention relates to a multilayer ceramic capacitor and its manufacturing method.

[Conventional technology]

Conventionally, a multilayer ceramic capacitor is manufactured by printing internal electrodes 1 on a dielectric ceramic sheet 1 as shown in FIG. It is obtained by integrating by firing, and then electrically connecting both end surfaces where the internal electrodes 11 are exposed to form the external electrodes 12.

[Problem to be solved by the invention]

In conventional double-layered multilayer ceramic capacitors, the external electrode 12 is generally made of a paste consisting of a metal powder mainly composed of silver, glass frit, and a substance to improve the bond between the ceramic and the internal mold fi1. The structure is miniaturized with good volumetric efficiency by applying and baking it onto the exposed end face and a part of the adjacent face.

However, in recent chip-shaped electronic components such as multilayer ceramic capacitors, a large number of electronic components are mounted on a printed circuit board, and each electronic component is now required to have high reliability. In particular, short-circuit defects are extremely rare in multilayer ceramic capacitors, but if they occur, not only will the electronic component be defective, but the entire printed circuit board will also be defective.
There was a serious drawback in that there was a risk of a major accident resulting in burnout.

An object of the present invention is to create a structure that maintains the volumetrically efficient structure of the conventional laminated ceramic capacitor and also has the function of creating an electrically open state and preventing burnout even if a short circuit occurs. Our objective is to provide a multilayer ceramic codenser with

[Means to solve the problem]

The multilayer ceramic capacitor of the first aspect of the present invention is constructed by alternately laminating and burying internal electrode layers facing each other with dielectric ceramic sheets interposed in between, and cutting and sintering the internal electrode layers so that the internal electrodes are alternately exposed at both ends to be integrated. In a multilayer ceramic capacitor in which an external electrode for taking out the electrode is subsequently attached, a notch is provided in a portion of the surface of the capacitor element that is substantially central, where there is no electrode, and is provided approximately parallel to the external electrode; It is characterized by having a bimetal which has almost the same shape as the notch at normal temperature into which it is inserted, and which has the property of being significantly deformed at temperatures above about 300°C.

Note that the present invention can be effectively implemented by making the cross-sectional shape of the cut an acute angle.

Further, the method for manufacturing a multilayer ceramic capacitor according to the second aspect of the present invention includes a step of forming a notch approximately parallel to an external electrode in a portion of the surface of the capacitor where there is no electrode at approximately the center; The structure is characterized in that it includes a step of fitting a bimetal having substantially the same shape as the bimetal, which has a characteristic of being significantly deformed at temperatures above about 300°C.

〔Example〕

Next, the present invention will be explained with reference to the drawings. Figures 1 (a> and (b) are perspective views and cross-sectional views of one embodiment of the present invention, and Figures 2 (a) to (d) are cross-sectional views shown in order of steps to explain the manufacturing method of the present invention. FIG. 3(a) is an intermediate and perspective view.

(b) is a perspective view showing the shape of a bimetal component used in the present invention at normal temperature and at 300° C. or higher.

The manufacturing method for multilayer ceramic capacitors is as follows: First, fine ceramic powder and organic binder are kneaded together, a raw sheet is created using the doctor blade method, an internal mold 8i1 is created on the surface of the raw sheet by screen printing, and then the desired number of sheets are created. Figure 2 (a) is formed by stacking and thermocompression bonding.
) A laminated body 6 is formed in which the internal electrodes 1 are alternately shifted.

Next, as shown in FIG. 2(b), the rotary cutting blade 21, which moves vertically while horizontally moving the laminate 6, cuts to a cutting position N22.
Figure 2 (
A fired body 7 as shown in c) is obtained. Here, as in the conventional case, a paste made of a substance for improving the bond between the metal powder mainly composed of silver, the glass frit, and the ceramic is attached to both end surfaces of this fired body 7 and baked, as shown in FIG. A ceramic capacitor element 3 having a notch 4 approximately in the center of the surface as shown in d) is obtained.

Further, in this notch 4, a shape is formed that has almost the same shape at room temperature as shown in FIG. 3(a), does not deform when heated during mounting, and is shown in FIG. 3(b) at about 300° C. or higher. By fitting and gluing the so-called bimetal 5, which is made by pasting together different metals that can bend greatly,
A multilayer ceramic capacitor element 3 of the present invention as shown in FIGS. 1(a> and 1b) is obtained.

Next, the operation of the present invention will be explained using FIG. 5(a)(1)). First, as shown in FIG. 5 (a), after the bimetal 5 is fitted into the notch 4 at the approximate center of the surface of the multilayer ceramic capacitor element 3 and mounted on the board 8, if a short circuit occurs. In this case, the ceramic element is heated due to heat generation due to overcurrent, deforms the bimetal 5, pushes the capacitor element 3 up from the substrate, and completely separates the ceramic element through the notch 4, resulting in an electrically open state. This can prevent damage to the multilayer ceramic capacitor, as well as nearby electronic components and burnout of the printed circuit board.

Figures 41a and 41a are perspective views of bimetals used in other embodiments of the present invention, Figure 4a is the shape at room temperature, and Figure 4b is the shape at 300°C or higher. The construction method is generally the same as that of the first embodiment, but it has the advantage that it incorporates a plurality of bimetals 5], which makes the displacement force caused by heat even larger and more uniform, and that it is more reliably effective. be.

〔Effect of the invention〕

As explained above, according to the present invention, the bimetal is fitted into the notch in the approximate center of the surface of the multilayer ceramic capacitor element, and if a short circuit occurs after it is mounted on the board, the ceramic will not heat up due to overcurrent. When the element is heated, the bimetal is deformed, pushing the capacitor element away from the substrate, and the ceramic element is completely separated through the notch, creating an electrical open state, which can damage the multilayer ceramic capacitor and damage the surrounding area. In electronic components, it has the effect of preventing printed circuit boards from burning out.

In addition, despite having such excellent effects, the shape is completely different from that of conventional multilayer ceramic capacitors, and the handling of supply, mounting, etc. remains the same without compromising the advantages of conventional capacitors. Maintained.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams showing a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 1(a) is a perspective view, and FIG.
FIG. 2(b) is a cross-sectional view, FIGS. 2(a) to 2(d) are views showing the manufacturing process of an embodiment of the present invention, and FIGS. , a cross-sectional view and a perspective view of the step of forming the notches, FIG. 2(c) is a cross-sectional view of the capacitor element after cutting and forming the notches, and FIG. 2(d) is a perspective view after firing and forming external electrodes. shows. Figure 3 (a), (
b) is a perspective view of a bimetallic component of a multilayer ceramic capacitor according to an embodiment of the present invention, and (a) is the shape at room temperature (
b) is a diagram showing the shape of 9 at temperatures above about 300°C, and FIGS. Figure 4 (2L) shows the shape at room temperature, Figure 4 (1)) shows the shape at temperatures above about 300 °C, and Figures 5 (a) and (b) show the effects of the multilayer ceramic capacitor of the present invention. Figure 5(a) is a cross-sectional view showing the normally mounted state, Figure 5(b) is a diagram showing the state when a short circuit occurs, and Figure 6 is an example of a conventional multilayer ceramic capacitor. A cross-sectional view is shown. 1, ] 1. Internal electrode, 2.12. External electrode, 3. Capacitor element, 4 Notch, 5, 51. Bimetal, 6. Laminated body, 7. Sintered body, 8.. Substrate, 21・
... Cutting blade, 22 ... Cutting position, 4] ... Cutting position.

Claims (3)

[Claims] 1. Internal electrode layers facing each other are alternately laminated and buried through dielectric ceramic sheets, cut so that the internal electrodes are exposed alternately at both ends, and then sintered and integrated, and then external electrodes are electrically connected to the internal electrodes. a notch provided substantially parallel to the external electrode in a substantially central portion of the surface of the capacitor where there is no electrode;
A multilayer ceramic capacitor comprising: a bimetal fitted into the notch and having a shape substantially the same as the shape of the notch at room temperature, and having a property of being significantly deformed at temperatures above about 300°C. 2. 2. The multilayer ceramic capacitor according to claim 1, wherein the cut has a cross-sectional shape having an acute angle. 3. A process of forming a notch almost parallel to the external electrode in a part of the surface of the capacitor that has no electrodes in the center, and a characteristic that the notch has almost the same shape as the notch at room temperature, and is significantly deformed at temperatures above about 300°C. A method for manufacturing a multilayer ceramic capacitor, comprising the step of fitting a bimetal having the following properties.