JPH03163810A - Laminated ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To produce an electrically open state when short failure is generated, and prevent burnout, by arranging shape memory alloy set in a notch which alloy has almost the same shape as the notch at a normal temperature, and largely changes the shape at a temperature higher than or equal to about 300 deg.C. CONSTITUTION:In a notch 4, a nickel-titanium based or stainless based shape memory alloy 5 is set and bonded as shown in figure (a). Said alloy has almost the same shape as the notch at a normal temperature, and are not deform by heating at the time of mounting. Said alloy is made to store a shape which bends up to nearly right angle in the center as shown in figure (b), at a temperature higher than or equal to about 300 deg.C. When short is generated after the alloy is mounted on a board 8, a ceramic body is heated by the generated heat due to excess current, the shape memory alloy 5 changes the shape and pushed up a capacitor element 3 from the board 8, and the ceramic body is completely divided from the notch 4. Thereby an electrical open state is produced, and the damage of a laminated layer ceramic capacitor and the bournout of adjacent electronic parts and, further, of a printed board can be prevented.

Description

[Detailed Description of the Invention] r# Business 1-. Field of Application] The present invention relates to a multilayer ceramic capacitor and a method for manufacturing the same, and more particularly to a multilayer ceramic capacitor having a structure that destroys the main body and interrupts current when the component is short-circuited, and a method for manufacturing the same.

[Conventional technology]

Conventionally, multilayer ceramic capacitors are manufactured by printing internal electrodes 11 on a dielectric ceramic sheet, stacking the desired number of sheets as shown in FIG. The internal electrodes 11 are then integrated by forming the external electrodes 12 by electrically connecting them at both end surfaces where they are exposed.
Problems to be Solved by the Invention] The conventional multilayer ceramic capacitor described above has an external electric rod 1.
2) A base 1 made of a metal powder whose main component is generally silver, etc., a glass frit 1 to 3, and a ceramic material and a substance for improving consolidation. By attaching heat to a part of the material and making it compact, it can be miniaturized with volume efficiency.
) However, recent chip-shaped electronic components such as multilayer ceramic capacitors have a large number of electronic components mounted on a printed circuit board, so each electronic component is required to have high reliability. It's starting to look like this. In particular, as for the defect in Show 1, the multilayer ceramic = 1 den "J3"(Ha-II; This had a serious drawback in that it could cause the entire printed circuit board to become defective, leading to a serious accident such as burnout.

It is an object of the present invention to maintain the volumetrically efficient structure of conventional multilayer ceramic capacitors while reducing the volumetric efficiency. -) It is an object of the present invention to provide a multilayer ceramic capacitor having a structure having a function of creating an electrically open state and preventing burnout even if a short-circuit failure occurs.

``Means for Solving the Problems'' The multilayer ceramic capacitor of the first aspect of the present invention has inner electrode layers alternately laminated and buried opposite each other via the power receiving body ceramic seam 1 to In a multilayer ceramic capacitor in which external electrodes 2 are cut and sintered so as to be exposed alternately and then integrated, and external electrodes 2 for taking out the electrodes are attached thereto, the external electrodes are placed in the black part of the electrodes approximately in the center of the surface of the capacitor element. and a shape memory alloy fitted into the notch that has almost the same shape as the notch at room temperature and has the property of deforming significantly at temperatures above about 300°C. Constructed as a feature.

Note that the present invention can be effectively carried out 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 the steps of forming a notch substantially parallel to the 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 shape memory alloy having substantially the same shape as the shape memory alloy, which has the property of deforming significantly at temperatures of 30° C. or higher.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Figure 1(a). (Ll) is a perspective view and a cross-sectional view of an actual cell example of the present invention, and Figures 2 (a) to (1) are cross-sectional views and FIGS. 3(a) and 3(b) are perspective views showing the shapes of parts used in the present invention, including shape memory, at room temperature and at 300° C. or higher.

The method for manufacturing a multilayer ceramic capacitor is to first knead finely divided ceramic powder and an organic binder, then create a green sheet using the doctor blade method, create internal electrodes 1 on its surface by screen printing, and then print the desired number of sheets. Figure 2 (a)
A laminate 6 is formed in which internal electrodes 1 are alternately shifted as shown in FIG.

Next, as shown in FIG. 2(b), the rotary cutting blade 21, which moves vertically while horizontally moving the stacked body 6, cuts to a cutting position 22.
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 containing silver, the glass frit, and the ceramic is attached to both end surfaces of this fired body 7 and baked. A ceramic capacitor element 3 having a notch 4 approximately at the center of its surface as shown in FIG. 3(d) is obtained.

Furthermore, this notch 4 has almost the same shape at room temperature as shown in FIG.
) As shown in Figures 1(a) and 1(b), by fitting and bonding a nickel-titanium or stainless steel shape memory alloy 5 that memorizes the shape of bending to an approximately right angle in the middle, the shape shown in Figures 1(a) and (b) A multilayer ceramic capacitor element 3 of the present invention is obtained.

Next, the operation of the present invention will be explained using FIGS. 5(a) and 5(b). First, as shown in FIG. 5(a), a shape memory alloy 5 is fitted into a notch 4 at approximately the center of the surface of the multilayer ceramic capacitor element 3, and after it is mounted on a substrate 8, if a short circuit occurs. In this case, the ceramic element is heated due to heat generated by the overcurrent, the shape memory alloy 5 is deformed, and the capacitor element 3 is pushed up from the substrate.
By completely dividing the ceramic body through the notch 4, an electrically open state is created, which prevents damage to the multilayer ceramic capacitor and burnout of nearby electronic components and even the printed circuit board. .

Figures 4(a) and (b') are perspective views of shape memory alloys used in other embodiments of the present invention; Figure 4(a) is the shape at room temperature, and Figure 4(b) is the shape at 300°C. The shape shown above is shown. The construction method is generally the same as the first embodiment, but a shape memory alloy 51 that memorizes the torsion characteristics is inserted into the notch 4, which has the advantage of further increasing the displacement force due to heat and ensuring the effect is exerted. .

〔Effect of the invention〕

As explained above, according to the present invention, the shape memory alloy 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, heat generation due to overcurrent will occur. As a result, the ceramic body is heated, the shape memory alloy is deformed, the capacitor element is pushed up from the substrate, and the ceramic body is completely divided through the notch, creating an electrical open state and damaging the multilayer ceramic capacitor. It also has the effect of preventing nearby electronic components, especially 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. has been maintained without compromising the conventional advantages. There is.

[Brief explanation of the drawing]

1(a>.(b) is a diagram showing a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 1(a) is a perspective view, FIG. 1(b) is a sectional view, and FIG. 2(a) is a perspective view. a) to (d) are diagrams showing the manufacturing process of an embodiment of the present invention, and Fig. 2(a).(b)
are respectively a cross-sectional view and a perspective view of the process of cutting the laminate and forming the notches, FIG. 2(C) is a cross-sectional view of the capacitor element after cutting and forming the notches, and FIG. 3(a) and 9(b) are perspective views of a shape memory alloy, which is a part of a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 3(a) is a perspective view after forming electrodes. Figure 3 (b) is a diagram showing the shape at temperatures above about 300°C, and Figures 4 (a) and (b) are parts of a multilayer ceramic capacitor according to another embodiment of the present invention, a shape memory alloy. Figure 4 (a) is a perspective view of the shape at room temperature. Figure 4 (b) is approximately 30 mm.
5(a) and 5(b) are cross-sectional views showing the effects of the multilayer ceramic capacitor of the present invention, and FIG. 5(a) shows the state when it is normally mounted. (b) is a diagram showing a state when a short-circuit failure occurs, and FIG. 6 is a cross-sectional view of an example of a conventional multilayer ceramic capacitor. 1, 11...inner electrode, 2,12...external electrode, 3
... Capacitor element, 4 ... Notch, 5,51.
... Shape memory alloy, 6... Laminated body, 7... Sintered body,
8... Board, 21... Cutting blade, 22... Cutting position, 41... Notch 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 shape memory alloy that is fitted into the notch and has substantially the same shape as the notch at room temperature, and has a characteristic 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 shape memory alloy having a shape memory alloy.