JPS63305505A - Layered type capacitor - Google Patents

Abstract

PURPOSE:To fusion-cut only a fuse electrode formed on a deteriorated layer, and to prevent the damage of a function as the whole capacitor by connecting capacitance electrodes and leading-out electrodes shaped onto each dielectric layer by fuse electrodes and giving fuse functions at every unit capacitance layer. CONSTITUTION:An internal electrode 11 on the side connected to at least one external electrode consists of a capacitance electrode 16 constituting electrostatic capacitance, a leading-out electrode 17 connected to the external electrode, and a fuse electrode 18 being composed of a metallic material having an electric resistance higher than the capacitance electrode 16 and fusion-cut by Joule heat and connecting the capacitance electrode 16 and the leading-out electrode 17. That is, when unit capacitance electrodes are short-circuited by a void, etc., generated in a certain one layer in a dielectric sheet held by the capacitance electrode and large currents flow, the fuse electrode generates heat by the currents and is fusion-cut by Joule heat. Accordingly, a function as a capacitor is lost in a short-circuited unit capacitance layer, but functions as capacitors can be held in other normal layers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer capacitor in which dielectric sheets having internal electrodes provided on the surface thereof are stacked, and in particular to the structure of the electrode portion thereof.

Conventional technology and its problems Conventionally, multilayer capacitors require dielectric sheets 2 on which internal electrodes 1 are formed to be stacked so that the t-pole extraction portions are alternated, as shown in FIGS. 8 and 9. It has a structure in which external electrodes 3, 3 connected to the electrode 1 are attached to both ends of the laminated dielectric sheets 2.

In this multilayer capacitor 4, for example, if a void or the like occurs in a certain layer of the dielectric sheet 2 and the electrodes 1, 1 arranged on both sides of the void are short-circuited, a large current flows through that point and generates heat. The other dielectric sheets 2 are destroyed by the heat, and the electrodes 1 are short-circuited one after another. As a result, the entire capacitor 4 breaks down, resulting in a short-circuit mode, which ultimately causes the device itself to fail.

Therefore, in order to ensure a stable operation even in the event of the above-mentioned malfunction, a multilayer capacitor 6 is provided with a fuse 5 attached to the outside, as shown in FIG. 10.

However, this integrated type capacitor 6 requires a structure and labor for separately attaching the fuse 5, which not only increases the cost, but also causes the fuse 5 to melt and enter oven mode when a malfunction occurs, causing the capacitor to malfunction. The problem was that the function itself was also lost. Further, it is necessary to pay attention to the directionality when mounting on a printed wiring board, etc., and there is also a problem that the presence of the fuse 5 increases the equal series resistance more than necessary.

Means for Solving the Problems The multilayer capacitor according to the present invention has been developed in view of the above problems, and the internal electrode connected to at least one external electrode has the following characteristics: (i) an extraction electrode connected to an external electrode; and (i) a metal material that has a higher electrical resistance than the capacitance electrode and melts with Joule heat, and the capacitance electrode and the extraction electrode are and a fuse electrode to be connected.

In other words, when the unit capacitance electrodes are short-circuited due to voids generated in one layer of the dielectric sheet sandwiched between the capacitance electrodes and a large current flows, the fuse electrode generates heat due to the current Tt and melts due to Joule heat. I will do it. Therefore, the function as a capacitor is lost in the unit capacitance layer where the short circuit has occurred, but the function as a capacitor is maintained in other normal layers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a multilayer capacitor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor 10, in which a plurality of internal electrodes 11 are embedded in a dielectric 12 in a pattern, and the internal electrodes 11 are embedded in a dielectric 12. They are alternately connected to external electrodes 13 and 14, and if necessary, lead terminals (not shown) are connected to the external electrodes 13 and 14, and then molded with an appropriate resin.

This multilayer ceramic capacitor 10 is manufactured by the following method.

In FIG. 2, reference numeral 15 denotes a dielectric green sheet before sintering, which is formed into a sheet shape with a thickness of 15 to 60 μm using various ceramic raw materials. A metal paste made of a metal material with low electrical resistance is applied to one side of the green sheet 15 in a predetermined shape, and then dried to form a capacitor electrode 16 and an extraction electrode 17. The capacitor electrode 16 is an electrode for forming a capacitance, and the extraction electrode 17 is an electrode for forming a current extraction portion by being connected to the external electrodes 13 and 14. The main material of the metal paste is
For example, palladium, palladium-silver alloy, platinum, nickel, copper, etc. are used.

Next, as shown in FIG. 3, the capacitor electrode 16 completely formed on the green sheet 15 and the extraction electrode 17 are connected by a fuse electrode 18. The fuse electrode 18 is the capacitor electrode 16
A metal material having a higher electrical resistance than the green sheet 15 is used, for example, a nickel-chromium alloy, zinc, aluminum, etc., and these metal pastes are applied on the green sheet 15,
Fired. Here, the pattern shape (width, length), electrode thickness, metal material, etc. of the fuse electrode 18 are such that the fuse electrode 18 will melt due to Joule heat caused by the maximum allowable current flowing between the capacitor electrodes 16 in the event of a short circuit. is set to .

As described above, the capacitor electrode 16. Extraction electrode 17. and a green sheet 15.15. on which the fuse electrode 18 was formed. ,
.

However, as shown in FIG. 4, the extraction electrodes 17 are alternately stacked so as to face opposite directions, and green sheets 15a, 15a, 15a, 15a, 15a, 15a, 15a, 15a, 15a, 15a, 15a, 15b, 15b, 15a, 15b, 15b, 15b, 15b, 15a, 15b, 15b, 15a, 15b, 15b, 15b, 15a, 15a, 15a, 15a, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , have a
Or can be further stacked. After stacking a predetermined number of green sheets 15 according to the desired capacitance, they are pressed together using a press or the like to form one block.

This block is fired, and as shown in Figure 1,
External electrodes 13 and 14 are coated with thick film metal paste and baked to obtain a multilayer ceramic capacitor. After connecting further lead terminals to this capacitor as necessary,
Resin etc. are molded.

Here, the metal material forming the capacitor electrode 16 and the extraction electrode 7 and the metal material forming the fuse electrode 18 both have melting points higher than the sintering temperature of the ceramic forming the green sheet 15, In addition, it is necessary to select materials whose metal materials do not react with the ceramic during firing.

It is preferable that the metal material forming the capacitor electrode 16 and the extraction electrode 17 and the metal material forming the fuse electrode 18 are materials that alloy with each other, but they may be materials that do not alloy with each other. The capacitor electrode 16, the extraction electrode 17, and the fuse electrode 18 are embedded in ceramic in surface contact with each other and are pressed together using a press or the like, and since they are fired at the same time, there is no possibility of poor connection between the electrodes. Because it will never happen.

Specific examples of the combination of electrode materials include nickel with a resistance value of 10-6 Ω·cm for the capacitor electrode 16 and extraction electrode 17, and nickel with a resistance value of 101 Ω·ct as the fuse electrode 18.
Examples include nickel-chromium alloys of Il.

The multilayer ceramic capacitor manufactured as described above is represented by an electrical equivalent circuit as shown in FIG. In the same figure, the dielectric layer sandwiched between the capacitor electrodes 16.16 may deteriorate and the capacitor electrodes 16.16 located adjacent to the capacitor electrodes 16.16 may
When short-circuited and current flows between both electrodes, fuse electrode 1
8 will be melted down by Joule heat. Therefore,
The failed layer is electrically disconnected from other good layers and no longer functions as a capacitor. However, other normal layers retain their function as capacitors. In this case, only the defective layer is electrically separated from other normal layers, so the entire capacitor does not go into short mode, and the capacitance of the capacitor decreases slightly, but the entire capacitor Its function will be maintained.

Furthermore, the fuse electrode 18 does not significantly increase the equivalent series resistance as a capacitor, but rather has the effect of adjusting the equivalent series resistance as a capacitor.

Next, another embodiment of the present invention will be described based on FIG. In this embodiment, the capacitive electrode 16. A structure in which green sheets 15 on which extraction electrodes 17 and fuse electrodes 18 are formed, and green sheets 20 on which electrodes 19 (no fuse electrodes are formed), which are integrated with capacitor electrodes and extraction electrodes, are stacked one on top of the other. That is. In this case, the extraction electrode 17 is connected to one common external electrode, and the electrode 19 is connected to the other common external electrode. Therefore, the electrical equivalent circuit of this embodiment has a configuration in which a series circuit of capacitor A and fuse B is connected in parallel, as shown in FIG.

Note that the present invention is not limited to the above embodiments,
Various modifications can be made within the scope of the gist.

For example, the shape of the fuse electrode 18 is not limited to a rectangular shape, but can also be curved to match the maximum allowable current value that flows between the two electrodes due to a defect occurring in the dielectric layer sandwiched between the capacitive electrodes 16. be. Further, the fuse electrode 18 may be used to electrically connect the capacitor electrode 16 and the output voltage wA17, and the printing position of the fuse electrode 18 can be selected as appropriate. Furthermore, the capacitor electrode 16 and the extraction electrode 17 may be provided on the green sheet 15 by screen printing.

As is clear from the above explanation, according to the present invention, the capacitance electrode and the extraction electrode formed on each resonator layer are connected by a fuse electrode, and each unit capacitance layer is Because it has a fuse function, even if a large current flows between adjacent capacitor electrodes due to deterioration of the dielectric layer, only the fuse electrode formed on the deteriorated layer will melt and the current flow will be cut off. Therefore, the function of the capacitor as a whole is not impaired.Moreover, as shown in Figure 10, it is possible to omit the trouble of separately attaching a fuse externally, and the directionality can be adjusted when mounting on a printed wiring board, etc. There is no need to be careful, and the equivalent series resistance does not increase more than necessary.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor which is an embodiment of the present invention. 2 to 4 are diagrams for explaining the manufacturing method of the multilayer ceramic capacitor shown in FIG.
The figure is a plan view showing a state in which a capacitor electrode and an extraction electrode are formed on a green sheet, FIG. 3 is a plan view showing a state in which a capacitor electrode and an extraction electrode are connected by a fuse electrode, and FIG.
The figure is an exploded perspective view of the main parts. FIG. 5 is an electrical equivalent circuit diagram of the multilayer ceramic capacitor shown in FIG. 1. FIG. 6 is an exploded perspective view of essential parts of another embodiment of the present invention, and FIG. 7 is an electrical equivalent circuit diagram of the embodiment in FIG. 6. FIG. 8 is an exploded perspective view of the main parts for explaining the conventional method of manufacturing a multilayer ceramic capacitor, and FIG.
The figure is a sectional view of the conventional example in FIG. 8, and FIG. 10 is a sectional view showing another conventional example. DESCRIPTION OF SYMBOLS 10... Multilayer ceramic capacitor, 11... Internal electrode, 12... Dielectric material, 13.14... External electrode, 15.20... Green sheet, 16... Capacitive electrode, 17... Takeout electrode, 18... Fuse electrode,
19...electrode.

Claims (2)

[Claims] (1) In a multilayer capacitor in which dielectric sheets with internal electrodes provided on their surfaces are stacked and the internal electrodes are alternately connected to a pair of external electrodes to provide capacitance between the internal electrodes, at least one The internal electrode on the side connected to the external electrode is a capacitive electrode that forms a capacitance, an extraction electrode that is connected to the external electrode, and a metal material that has a higher electrical resistance than the capacitive electrode and melts with Joule heat. A multilayer capacitor comprising: a fuse electrode connecting a capacitor electrode and an extraction electrode; (2) The multilayer capacitor according to claim 1, wherein the capacitor electrode, the extraction electrode, and the fuse electrode are formed by coating a dielectric green sheet with metal paste.