JPH0831393B2 - Multilayer ceramic capacitor with fuse - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a multilayer capacitor to which a fuse element is added, and more particularly to an improved connection structure between a fuse element and an external electrode.

[Conventional technology]

An example of a conventional laminated capacitor with a fuse is shown in FIG. In the laminated capacitor with a fuse 1, a plurality of internal electrodes are arranged in a sintered body 2 made of a dielectric ceramic so as to overlap each other in the thickness direction via a ceramic layer.

Planar shapes of the internal electrodes are shown in FIGS. 3 (a) and 3 (b).
The internal electrode 3a is formed on the second side surface 2b of the sintered body by the internal electrode 3b.
Are drawn out to the first side surface 2a, and the internal electrodes 3a, 3
b are alternately laminated via ceramic layers. The internal electrodes 3a, 3b are electrically connected to the first and second external electrodes 4, 5 provided on the first and second side faces 2a, 2b of the sintered body 2.

A third external electrode 6 is provided on the third side surface 2c of the sintered body 2, while a fourth external electrode 7 is formed on the fourth side surface 2d. Then, the second external electrode 5 and the third
A fuse element 8 made of a fusible material such as a low melting point metal wire is electrically connected to the external electrode 6. The third external electrode 6 and the fourth external electrode 7 are electrically connected to each other by a connection electrode described later.

Therefore, the capacitor and the fuse element are connected in series between the first external electrode 4 and the fourth external electrode 7.

FIG. 3 (c) shows the plan-view shape of the connection electrodes in the above-mentioned laminated capacitor with fuse 1. The connecting electrode 9 is the sintered body 2
Inside, it is formed on the outer side in the thickness direction of the internal electrode group. The connection electrode 9 is formed so as to be exposed on the third side surface 2c and the fourth side surface 2d of the sintered body 2. This is the fourth
This is because the external electrode 7 can be used as a connection terminal with the outside. That is, in the laminated capacitor with fuse 1 of FIG. 2, the first and fourth external electrodes 4 and 7 arranged to face each other are used as the connection terminals to the outside, so that direction selection at the time of use is omitted. It is possible to do.

[Technical problem to be solved by the invention]

When an overvoltage is applied to the fused multilayer capacitor 1, a crack is usually generated between the internal electrodes 3a and 3b in the thickness direction. However, this crack may propagate further up and down in the thickness direction and may reach the portion where the connection electrode 9 is arranged. In such a case, the connection electrode 9 and the internal electrodes 3a and 3b may be short-circuited in some cases, and the fuse element 8 may not function.

In order to reduce the above accidents, the connection electrode 9
Needs to be narrowed. However, the connection electrode 9
When the width of is narrowed, the equivalent series resistance (ESR) of the capacitor
Will be higher. Therefore, in order to reduce the ESR, the connection electrode 9
It is necessary to increase the number of sheets, resulting in a problem that the dimension in the thickness direction becomes large and the cost becomes high.

Further, in order to manufacture the above-described fuse-containing multilayer capacitor, in addition to the ceramic green sheet on which the electrode paste for forming the internal electrodes 3a and 3b is applied and printed, the electrode for forming the connecting electrode 9 is formed. There is also a problem that a ceramic green sheet on which the paste is printed must be prepared, and therefore the manufacturing process becomes complicated.

An object of the present invention is to provide a laminated ceramic capacitor with a fuse that can surely function a fuse element even when a voltage breakdown occurs, can prevent an increase in ESR, and can simplify the manufacturing process. is there.

[Means for solving technical problems]

In the multilayer ceramic capacitor with the fuse of the present invention,
A plurality of internal electrodes are arranged in a sintered body made of dielectric ceramics so as to overlap each other in the thickness direction with a ceramic layer interposed therebetween. The plurality of internal electrodes are alternately drawn out to the first and second side surfaces of the sintered body in the thickness direction, and are electrically connected to the first and second external electrodes provided to the first and second side surfaces. Connected to each other.

In addition, a connection electrode is formed in the sintered body so as to be exposed at the third side surface and the fourth side surface, and the third and fourth side surfaces are provided on the third and fourth side surfaces of the sintered body. The external electrodes of are electrically connected. A fuse element is electrically connected between the second external electrode and the third external electrode.

The present invention is configured as described above, and has a structure in which a capacitor and a fuse are connected in series between the first and fourth external electrodes, wherein the connection electrode is the internal electrode in the sintered body. It is characterized in that it is formed separately from the internal electrode in the same plane.

[Action]

The connection electrode for connecting the fuse element to a desired external electrode is formed on the same plane as the internal electrode, that is, in a region where the internal electrode and the sintered body do not overlap in the thickness direction. Therefore, even if a crack extending in the thickness direction occurs between the internal electrodes due to voltage breakdown, the crack does not reach the connection electrode. Therefore, even if a crack occurs due to voltage breakdown, the fuse function is not hindered.

Further, since a short circuit with the internal electrode is unlikely to occur, it is possible to prevent an increase in ESR without having to narrow the width of the connection electrode.

Furthermore, since the connecting electrode is formed in the same plane as the internal electrode, the connecting electrode can be formed by printing the connecting electrode on the electrode paste on the ceramic green sheet for forming the internal electrode. It is not necessary to prepare a ceramic green sheet on which only the electrode paste for connecting electrodes for forming is printed.

[Explanation of Example]

FIG. 4 is a perspective view showing a laminated ceramic capacitor with a fuse according to an embodiment of the present invention. In a laminated ceramic capacitor 11 with a fuse, a plurality of internal electrodes are arranged in a sintered body 12 made of a dielectric ceramic so as to overlap each other in the thickness direction. That is, the internal electrodes 13 and 14 shown in the plan sectional views of FIGS. 1A and 1B are alternately laminated. The internal electrode 14 is the first side surface 12a of the sintered body 12.
Have been withdrawn. On the other hand, the internal electrode 13 is drawn out to the second side surface 12b of the sintered body 12.

On the first and second side surfaces 12a, 12b of the sintered body 12, respectively,
First and second external electrodes 15 and 16 are formed. Therefore, a capacitor is formed between the first external electrode 15 and the second external electrode 16.

On the other hand, as shown in FIG. 1A, the connection electrode 17 is formed on the same plane as the internal electrode 13 so as to be exposed at the third side surface 12c and the fourth side surface 12d of the sintered body 12. There is. Then, as shown in FIG. 4, the third and fourth external electrodes 18, 19 are formed on the third side surface 12c and the fourth side surface 12d of the sintered body 12, respectively.
Are formed. Third external electrode 18 and fourth external electrode
19 are electrically connected to each other by the connection electrode 17.

A fuse element 20 made of a fusible material is electrically connected between the second external electrode 16 and the third external electrode 18. Therefore, a configuration in which the capacitor and the fuse element are connected in series between the first external electrode 15 and the fourth external electrode 19 is realized.

Also in the multilayer capacitor with a fuse 11 of this embodiment,
Since the capacitor and the fuse element are connected in series between the first and fourth external electrodes 15 and 19 formed on 12a and 12d on the opposing first and fourth side surfaces, the sintered body 12 faces each other. The first and fourth external electrodes 15, 19 provided on the side surfaces 12a, 12d
Can be used as a connection terminal to the outside. Therefore, at the time of use, there is no inconvenience of selecting an external electrode to be a connection terminal with the outside.

Consider a case in which cracks are generated in the sintered body 12 by applying an overvoltage in the embodiment of FIG. The crack due to the application of the overvoltage is usually easily propagated in the thickness direction, and therefore, it is usually formed so as to extend in the thickness direction in the region where the internal electrodes 13 and 14 overlap each other. However, in this embodiment, since the connection electrode 17 is formed on the same plane as the internal electrode 13 with the gap 21 (see FIG. 1) being separated, the crack is less likely to reach the connection electrode 17, and the connection electrode 17 is Very unlikely to short circuit with the internal electrodes 13 or 14. Therefore, the function of the fuse element 20 is not hindered.

Since the gap 21 is formed by applying an electrode paste for forming the internal electrode 13 and the connection electrode 17 on the ceramic green sheet,
The width of the ceramic green sheets is unlikely to change due to a stacking deviation of the ceramic green sheets or a deviation when cutting the laminate. That is, a short circuit between the connection electrode 17 and the internal electrode 13 or 14 is extremely unlikely to occur.

Although the connection electrode 17 is formed to have a uniform width along the third side surface 12c of the sintered body 12 in FIG. 1 (a), it may be configured to have another planar shape.

For example, as shown in FIG. 5, the fourth side surface of the sintered body 12
L is exposed on the 2d side for a considerable distance.
The connection electrode 27 may be shaped like a letter. Thereby, the electrical connection with the fourth external electrode 19 (FIG. 4) can be made more reliable.

Further, as shown in FIGS. 6 (a) and 6 (b), the sintered body
Connection electrodes 37, 47 with a shape excluding the vicinity of the corner 12e of 12
By forming the above, it is possible to increase the adhesion strength between the upper and lower ceramic layers in the corner portion 12e and prevent layer peeling.

Further, in order to reduce the peeling on the third side surface 12c of the sintered body 12, as shown in FIG. 7, the connection electrode 57 having a shape in which the region exposed on the third side surface 12c is reduced may be formed. .

Further, in the embodiment of FIG. 1, the connection electrode 17 is formed on the same plane as the internal electrode 13, but the connection electrode may be formed on the same plane as the internal electrode 14, or both internal electrodes are formed on the same plane. You may form the connection electrode on it. Not only that, the connection electrodes may be formed only on the same plane as any one of the internal electrodes, and the number of connection electrodes is arbitrary.

〔The invention's effect〕

As described above, according to the present invention, the connection electrode for drawing out the third external electrode connected to the fuse element to the fourth external electrode is formed on the same plane as the internal electrode. Therefore, even if a crack extending in the thickness direction occurs in the sintered body, the function of the fuse element is not hindered.

Further, in the conventional example, it is necessary to narrow the width of the connection electrode in order to prevent the internal electrode and the connection electrode from being short-circuited due to the crack generated when the overvoltage is applied.
There is a problem that the R becomes high and the number of connecting electrodes must be increased in order to reduce the ESR, resulting in an increase in thickness and an increase in cost. On the other hand, in the present invention, since the connection electrode is formed on the same plane as the internal electrode, ES
No deterioration of R occurs, and even if the number of connecting electrodes is increased, the thickness of the sintered body does not increase.

Moreover, when forming the connection electrodes, the electrode paste for forming the connection electrodes may be printed together on the ceramic green sheet coated with the electrode paste for forming the internal electrodes. It is not necessary to prepare a separate ceramic green sheet coated with an electrode paste for forming electrodes. Therefore, the manufacturing process can be simplified, and the cost of the ceramic laminated capacitor with fuse can be greatly reduced.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional plan views for explaining the shapes of internal electrodes and connection electrodes in one embodiment of the present invention, and FIG. 2 shows an example of a conventional laminated capacitor with a fuse. FIG. 3 is a perspective view, and FIGS. 3 (a) to 3 (c) are plan sectional views for explaining the shapes of internal electrodes and connection electrodes in the conventional example of FIG. 2, and FIG. 4 is an embodiment of the present invention. FIG. 5 is a perspective view of a multilayer capacitor with a fuse of FIG. 5, FIG. 5 is a plan sectional view for explaining a first modification of the connecting electrode, and FIGS. 6 (a) and 6 (b) are second and third connecting electrodes. 7 is a plan sectional view showing a modified example of the connection electrode, and FIG. 7 is a plan sectional view showing a fourth modified example of the connection electrode. In the figure, 11 is a multilayer capacitor with a fuse, 12 is a sintered body, 12a to 12d are first to fourth side surfaces, 15 is a first external electrode, 16 is a second external electrode, 17 is a connecting electrode, 18 Is a third external electrode, 19 is a fourth external electrode, 13 and 14 are internal electrodes, and 20 is a fuse element.

Claims (1)

[Claims] 1. A sintered body made of a dielectric ceramic, and a first sintered body and a first sintered body which are arranged in the sintered body so as to overlap each other in the thickness direction with a ceramic layer interposed therebetween and which are alternately arranged in the thickness direction. A plurality of internal electrodes drawn out to the second side surface, and first and second external electrodes provided on the first and second side surfaces of the sintered body so as to be electrically connected to the internal electrodes. And at least 1 disposed in the sintered body and exposed to the third side surface and the fourth side surface of the sintered body.
Connection electrodes, and third and fourth external electrodes provided on the third and fourth side surfaces of the sintered body and electrically connected to the connection electrodes, and the second external electrode. A fuse-equipped multilayer capacitor, comprising: a fuse element electrically connected to a third external electrode; and a structure in which a capacitor and a fuse element are inserted in series between the first and fourth external electrodes. A fused ceramic capacitor with a fuse, wherein the connection electrode is formed in the sintered body in the same plane as the internal electrode and separated from the internal electrode.