JPH0658861B2 - Multilayer capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multilayer capacitor having an improved internal electrode shape.

[Conventional technology]

As is well known, in a multilayer capacitor, a plurality of internal electrodes that overlap with each other through a dielectric ceramic layer are arranged in a sintered body made of a dielectric ceramic, and the internal electrodes are alternately formed on the end faces of the sintered body. It is configured to connect to the first or second external electrode and to take out the capacitance between the internal electrodes.

FIGS. 2 (a) and 2 (b) are plan sectional views showing the upper part of the conventional multilayer capacitor in a cutaway manner. In the example of FIG. 2 (a), the extraction electrode 2 is formed on the one end surface 1a side of the sintered body 1, and the internal electrode 3 having a width narrower than this extraction electrode 2 is provided on the end surface 1b side of the sintered body. It has been postponed.

In the example of FIG. 2 (b), the one end surface 1a of the sintered body 1 is
The internal electrode 4 is formed so as to extend from the side toward the other end surface 1b of the sintered body with an equal width.

The internal electrodes 3 and 4 having the above-described shapes are alternately drawn out to the different end faces 1a and 1b of the sintered body 1 in the thickness direction and connected to the external electrodes 5 and 6.

[Technical problem to be solved by the invention]

The equivalent series resistance (hereinafter, referred to as ESR) -frequency characteristic of the conventional multilayer capacitor configured by using the internal electrodes 3 and 4 as described above is as shown in FIG. There was a tendency for the ESR value to increase as time passed.

On the other hand, the ESR-frequency characteristic greatly affects the Q value of the capacitor as shown by the following equation.

In the above equation, tan δ is tan δ of the dielectric ceramics, C is the capacitance, L is the inductance of the capacitor, and there is a relationship of ω = 2πf (f: frequency).

Therefore, in the conventional multilayer capacitor, the ESR value increases on the high frequency band side as shown in FIG.
There is a problem that the Q characteristic is deteriorated.

In the internal electrodes 3 and 4 of FIGS. 2 (a) and 2 (b), a current is caused to flow in the direction of the arrow indicated by the alternate long and short dash line A, in which case an eddy current indicated by the arrow B is generated. Then
It is considered that this is because the ESR value increases in the high frequency range due to the eddy current loss.

Therefore, an object of the present invention is to provide a multilayer capacitor which can reduce the eddy current loss induced by the current flowing through the internal electrodes as described above, and thus have an improved Q characteristic in the high frequency region.

[Means for solving technical problems]

According to the present invention, a plurality of internal electrodes are arranged in a sintered body made of a dielectric ceramic so as to overlap with each other with a dielectric ceramic layer interposed therebetween, and the internal electrodes are attached to a pair of external electrodes provided on the end faces of the sintered body. The alternately drawn out multilayer capacitor is characterized by having the following configuration.

That is, at least one internal electrode is a first electrode portion extending in a predetermined direction from an edge portion connected to the external electrode, and the edge portion is folded back from the tip of the first electrode portion. It is configured to have a folded shape including a second electrode portion extended to the side.

[Action]

Since at least one internal electrode has a first electrode portion and a second electrode and has a folded shape, the direction of the current flowing through the internal electrode is determined by the first electrode portion and the second electrode portion. And the directions are opposite to each other. Therefore, the directions of the eddy currents generated around the currents flowing through the first and second electrode portions are also opposite directions, so that they cancel each other, and as a result, the eddy current loss induced by the currents flowing through the internal electrodes is effective. Is reduced.

[Explanation of Examples]

FIG. 4 is a sectional view showing a multilayer capacitor according to an embodiment of the present invention. A plurality of internal electrodes 12 to 16 are arranged in a sintered body 11 made of a dielectric ceramic so as to overlap each other with a dielectric ceramic layer interposed therebetween. As will be described later, the feature of this embodiment is the planar shape of the internal electrodes 12 to 16.

External electrodes 17 and 18 are formed on opposite end surfaces of the sintered body 11. The internal electrodes 12 to 16 are alternately drawn out and electrically connected to the external electrodes 17 and 18.

Next, the features of this embodiment will be described with reference to FIG. 1, which is a plan sectional view taken along the line I-I of FIG. Internal electrode 12
Is the extraction electrode portion 12a on the one end surface 11a side of the sintered body 11.
The first electrode portion 1 which has a continuous line with the extraction electrode portion 12a and extends toward the other end surface 11b of the sintered body 11.
2b and the second electrode portion 12 folded back at the tip of the first electrode portion 12b and extended to the one end surface 11a side of the sintered body 11.
with c and.

Therefore, in the multilayer capacitor of FIG.
When a current is supplied from 8, the current flows in the internal electrode 12 in the direction indicated by the alternate long and short dash line A in FIG. In the first electrode portion 12b and the second electrode portion 12c, the flowing currents are in opposite directions, so that the induced eddy currents are also in opposite directions as indicated by arrows X and Y and cancel each other. Fit. Therefore, it is understood that the internal electrode 12 can effectively reduce the eddy current loss that occurs when a current is passed.

The other internal electrodes 13 to 16 are also configured to have the same planar shape as the internal electrode 12.

FIG. 5 shows the ESR-frequency characteristics of the multilayer capacitor of the above embodiment. As is clear from FIG. 5, according to the above-described embodiment, the ESR value decreases as the frequency becomes higher. Further, as shown in FIG. 6, it can be seen that the inductance-frequency characteristic also decreases as the frequency increases. For comparison, in FIG. 6, the inductance-frequency characteristic of the conventional multilayer capacitor is shown by a broken line.

From the results of FIG. 5 and FIG. 6, the eddy current loss is reduced by configuring the internal electrode shape as shown in FIG. 1, and as a result, the rise of the ESR value on the high frequency band side can be prevented. It can be seen that the Q characteristics of the multilayer capacitor can be improved.

If at least one internal electrode has the above-described first and second electrode portions, the effect of the present invention can be obtained. That is, it is not always necessary to configure all the internal electrodes 12 to 16 to have a folded shape as in the above embodiment.

Further, as shown in FIGS. 7A and 7B, the shapes of the internal electrodes that are adjacent to each other in the stacking direction, such as the internal electrodes 12 and 13, are the same as those of the first electrode portions 12b and 13b and the second electrode portions 12b and 13b. It is preferable that the electrode portions 12c and 13c of the above are overlapped with each other. This is because eddy currents can be canceled in the stacking direction as well.

Further, in the internal electrode 12 shown in FIG. 1, the linear first electrode portion 12b and the second electrode portion 12c are formed, but the shapes of the first electrode portion and the second electrode portion are It is not limited to that shown in FIG. For example, as shown in FIG.
Second electrode portion 22c extending toward the corner portion 11d of the sintered body, folded back in the vicinity of the corner portion 11d, and extending toward the other corner portion 11e located diagonally. The same effect can be obtained by forming.

Further, as shown in FIG. 9, the same effect can be obtained by forming a plurality of first and second electrode portions 32b and 32c from the extraction electrode portion 32a.

〔The invention's effect〕

As described above, according to the present invention, the currents flowing in the first and second electrode portions are in opposite directions, and the eddy currents generated in both electrode portions cancel each other out, so that the eddy current loss is effectively reduced. Therefore, the Q characteristic of the multilayer capacitor in the high frequency region can be effectively improved.

Also, regarding the inductance component of the multilayer capacitor,
Since it is reduced in the high frequency region, a capacitor having a high resonance point can be obtained.

In addition, in the folded internal electrode, the upper and lower ceramic layers are firmly adhered to each other in the gap between the first electrode portion and the second electrode portion, so that the mechanical strength of the multilayer capacitor is also improved. It

[Brief description of drawings]

FIG. 1 is a plan sectional view for explaining the shape of the internal electrode in one embodiment of the present invention, and FIGS. 2A and 2B are for explaining the shape of the internal electrode of the conventional multilayer capacitor. 3 is a sectional view of an ESR-frequency characteristic in a conventional example, FIG. 4 is a sectional view of a multilayer capacitor of one embodiment of the present invention, and FIG. 5 is a diagram showing an ESR-frequency characteristic of the embodiment. FIG. 6 is a diagram showing the inductance-frequency characteristics of the example and the conventional example, FIG. 7 is a plan view showing the shape of the internal electrodes in the example of the present invention, and FIGS. 8 and 9 are respectively, It is each plane sectional drawing for explaining the modification of the shape of an internal electrode. In the figure, 11 is a sintered body, 11a and 11b are end faces of the sintered body, 12 to 16 are internal electrodes, and 12b, 22b and 32b.
Is a first electrode portion, 12c, 22c and 32c are second electrode portions, and 17 and 18 are external electrodes.

Claims (1)

[Claims] 1. A plurality of internal electrodes are arranged in a sintered body made of a dielectric ceramic so as to overlap each other with a dielectric ceramic layer interposed therebetween, and are alternately drawn out to a pair of external electrodes provided on the end faces of the sintered body. In the multilayer capacitor described above, at least one internal electrode has a first electrode portion extended in a predetermined direction from an edge portion connected to the external electrode,
A multilayer capacitor configured to have a folded shape including a second electrode portion that is folded back from the tip of the first electrode portion and extended to the edge portion side.