JPH0513526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer ceramic capacitor and a method for manufacturing the same.

[Conventional technology]

Conventionally, multilayer ceramic capacitors have been composed of dielectric ceramic sheets, internal electrodes, and external electrodes.

FIG. 4 is a sectional view showing an example of a conventional multilayer ceramic capacitor.

A multilayer ceramic capacitor is manufactured by printing internal electrodes 11 on dielectric ceramic sheets, stacking the desired number of sheets, and bonding them under heat to form a laminate, which is then cut so that the internal electrodes 11 are exposed alternately on both end faces 15. Then, a capacitor element is formed by firing. Next, a paste made of a substance for improving the bond between metal powder mainly composed of silver or the like, glass frit, and ceramic is applied to the exposed end surface 15 of the internal electrode 11 and a part of its adjacent surface using a dip coating method or the like. A laminated ceramic capacitor was obtained by coating the capacitor with a polyester resin and firing it, and electrically connecting the end faces 15 with the internal electrodes 11 to form the external electrodes 12.

[Problem that the invention seeks to solve]

As described above, in conventional multilayer laminated capacitors, the external electrode 12 is generally made of a paste made of a substance that improves the bond between metal powder mainly composed of silver, glass frit, and ceramics. By firing both end surfaces 15 and a portion of the adjacent surfaces, the structure was miniaturized with good volumetric efficiency.

However, since a large number of recent chip-shaped electronic components such as multilayer ceramic capacitors are mounted on a printed circuit board, each electronic component is required to have high reliability. especially,
It is rare for short-circuit failures to occur in multilayer ceramic capacitors, but if they do occur, not only will the multilayer ceramic capacitor become defective, but the entire printed circuit board will also become defective, which could lead to a major accident such as equipment fire. There was a serious problem that could lead to this.

An object of the present invention is to maintain the volumetrically efficient structure of conventional multilayer ceramic capacitors, and even if a short circuit occurs, the low melting point metal melts and the internal electrodes 11 and external electrodes 12 are kept in an open state so that the device, etc. It is an object of the present invention to provide a multilayer ceramic capacitor having a structure that can avoid burning.

[Means for solving problems]

The multilayer ceramic capacitor of the present invention includes a capacitor element in which internal electrode layers facing each other are alternately laminated with dielectric ceramic sheets in between and buried so that the internal electrodes are not exposed at both ends, and both electrodes of the capacitor element. At least two through-holes are provided inside the end surface to pass through the capacitor element through each of the internal electrodes, and an end surface that becomes the electrode on both sides of the capacitor element, and a through-hole from the end surface to the end surface. an external electrode extending to and covering the surrounding area; and an external electrode provided in at least one of the through holes, made of a low melting point metal, and electrically connected to the external electrode near the entrance of the through hole. and an intermediate electrode.

The method for manufacturing a multilayer ceramic capacitor of the present invention includes a first step of printing internal electrodes on dielectric ceramic sheets, stacking a desired number of sheets, and forming a laminate by thermocompression bonding, and cutting the laminate. and a second step of forming a through hole penetrating the laminate through the internal electrodes corresponding to each electrode on the inside of the end face of the laminate that becomes both electrodes, and then firing to form a capacitor element. a third step of applying and firing a paste containing metal powder as a main component to the end face of the capacitor element and near the entrance of the through hole to form an external electrode; and melting a low melting point metal to the through hole. The method includes a fourth step of forming an intermediate electrode that electrically connects the internal electrode and the external electrode.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of the present invention.

A capacitor element 3 is formed by alternately stacking internal electrode layers facing each other with dielectric ceramic sheets in between and embedding the internal electrodes 1 so as not to expose them to both end faces 5. Inside the end surface 5 which becomes both electrodes of the capacitor element 3, there are respective internal electrodes 1.
A through hole 4 is provided through the capacitor element 3, and has end surfaces 5 serving as electrodes on both sides of the capacitor element 3, and extends from the end surface 5 to the periphery of the through hole 4 to be covered with an external electrode 2. The through hole 4 is provided with an intermediate electrode 6 made of a low melting point metal and electrically connected to the external electrode 2 near the entrance of the through hole 4 .

FIGS. 2a to 2d are cross-sectional views of a capacitor element shown in the order of steps for explaining one embodiment of the method for manufacturing a multilayer ceramic capacitor according to the present invention.

After kneading the finely divided ceramic powder and an organic binder, a green sheet is prepared using a doctor blade method. After providing internal electrodes 1 on the surface of the raw sheets by screen printing, a desired number of sheets are stacked and a laminate 7 is formed by thermocompression bonding. At this time, the internal electrode 1 is arranged at a position where it will not be exposed due to cutting in a later process. Next, the laminated body 7 is cut with a press die that integrates the cutting blade 8 and the hole punch 9, and at the same time, the through holes 4 are formed at predetermined positions 10 in the laminated body 7, and then fired. In this way, a capacitor element 3 is obtained in which the internal electrode 1 is exposed within the through hole 4 and is not exposed to the end surface 5.

A paste consisting of a substance for improving the bond between metal powder mainly composed of silver and glass frit and ceramic is applied to both end surfaces 5 of the capacitor element 3 and near the two entrances of the through hole 4 and baked to form the external electrode 2. form. Next, indium, tin,
A so-called fuse, which is a low melting point metal such as lead or an alloy thereof, is melted and injected into the through hole 4.
In this way, by forming the intermediate electrode 6 electrically connected to the internal electrode 1 inside the through hole 4 and the external electrode 2 near the entrance of the through hole 4,
While maintaining the volumetrically efficient structure of conventional multilayer ceramic capacitors, even if a short circuit occurs, the low melting point metal melts and the internal electrode 1 and external electrode 2
A multilayer ceramic capacitor having a structure in which it is possible to prevent the device from burning out by opening the capacitor can be obtained.

FIG. 3 is a sectional view showing a second embodiment of the multilayer ceramic capacitor of the present invention.

An intermediate electrode 6 made of a low melting point metal is provided only in one of the through holes 4 of the capacitor element, and the other through hole 14 is filled with the same material as the external electrode 2, which is a metal whose main component is silver.

When forming the external electrodes 2, a dipping method is used in which a paste made of a substance for improving the bond between metal powder containing silver as a main component, glass frit, and ceramic is applied by dipping. When forming the external electrode 2 by dipping, one of the through holes 4
The entrance of the through hole 4 is shielded so that the paste does not enter into the other through hole 14, and the entrance of the other through hole 14 is left open.After applying the paste and firing, a paste made of a single element such as indium, tin, or lead or an alloy thereof is coated. A multilayer ceramic capacitor having such a structure can be obtained by melting a low melting point metal and injecting it into the through hole 4. A laminated ceramic capacitor with this structure has the advantage that the manufacturing process is simpler and the cost can be reduced.

〔Effect of the invention〕

As explained above, by providing the intermediate electrode 6 in the multilayer ceramic capacitor, the present invention achieves
While maintaining the volumetrically efficient structure of conventional multilayer ceramic capacitors, even if a short circuit occurs, the low melting point metal melts and the internal electrode 1 and external electrode 2
This has the effect that it is possible to prevent equipment, etc. from catching fire by keeping it in an open state.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the multilayer ceramic capacitor of the present invention, and FIGS. 2 a to 2 d are sequential steps for explaining an embodiment of the method of manufacturing the multilayer ceramic capacitor of the present invention. FIG. 3 is a cross-sectional view showing a second embodiment of the multilayer ceramic capacitor of the present invention, and FIG.
The figure is a sectional view showing an example of a conventional multilayer ceramic capacitor. DESCRIPTION OF SYMBOLS 1...Internal electrode, 2...External electrode, 3...Capacitor element, 4...Through hole, 5...End surface, 6...
Intermediate electrode, 7... Laminated body, 8... Cutting blade, 9...
Punch, 10... Through hole position, 11... Internal electrode, 12... External electrode, 14... Through hole, 15...
…End face.

Claims (1)

[Scope of Claims] 1. A capacitor element in which internal electrode layers facing each other are alternately laminated with dielectric ceramic sheets in between and buried so that the internal electrodes are not exposed at both ends, and both electrodes of the capacitor element. At least two through-holes are provided inside the end surface to pass through the capacitor element through each of the internal electrodes, and an end surface that becomes the electrode on both sides of the capacitor element, and a through-hole from the end surface to the end surface. an external electrode extending to and covering the surrounding area; and an external electrode provided in at least one of the through holes, made of a low melting point metal, and electrically connected to the external electrode near the entrance of the through hole. 1. A multilayer ceramic capacitor characterized by having an intermediate electrode. 2. A first step of printing internal electrodes on dielectric ceramic sheets, stacking the desired number of sheets, and forming a laminate by thermocompression bonding, and cutting the laminate to form both electrodes of the laminate. a second step of forming a capacitor element by providing through holes penetrating the laminate through the internal electrodes corresponding to the respective electrodes on the inside of the end face, and then firing the paste; and a paste containing metal powder as a main component. a third step of applying and firing a metal on the end face of the capacitor element and near the entrance of the through hole to form an external electrode; and a third step of melting a low melting point metal and injecting it into the through hole to form the internal electrode and the external electrode. and a fourth step of forming an intermediate electrode for electrically connecting the multilayer ceramic capacitor and its manufacturing method.