JPH06283370A - Layered capacitor - Google Patents

Abstract

PURPOSE:To relax a field concentration between a capacitor electrode and an external electrode and restrict creeping discharge from a capacitor surface, by providing a floating electrode which is inherent in an insulator outer layer in an electrically non-contact state in either electrode. CONSTITUTION:A layered type capacitor 1 in which an external electrode 3 is installed to the end is layered with a capacitor 4 and an insulator outside layer 5 which protects the capacitor 4 in the thickness direction in structure. A frame-shaped floating electrode 20, which is not electrically connected to any electrode inside the insulator outside layer 5. The floating electrode 20 is installed virtually at a position between an end part 3a of the outside electrode 3 and an end part 22a of a capacitor electrode 22. The capacitor 4 is alternately layered with capacitor electrodes 22 to 24 and dielectric layers 7 to 9. Frame-shaped floating electrodes 27 and 28 are installed inside the dielectric layers 7 and 8. This construction makes it possible to relax a field concentration between the capacitor electrodes and the outside electrodes and provide a small-sized laminated type capacitor which is excellent in voltage resistant performance without increasing the thickness of the insulator outside layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated capacitor having excellent withstand voltage.

[0002]

2. Description of the Related Art Conventionally, various measures have been taken to improve the withstand voltage performance of multilayer capacitors. For example, it has been proposed to improve the withstand voltage performance by increasing the thickness of the dielectric layer between the capacitance electrodes. However, there has been a problem that the external dimensions are increased in order to obtain a high withstand voltage capacitor.

In addition to this, Japanese Patent Application No. 1-20442
The ones described in Japanese Patent Application No. 1 and Japanese Patent Application No. 1-220422 are known. This multilayer capacitor has floating electrodes that are not connected to any of the electrodes in the dielectric layer between the capacitance electrodes, and by relaxing the electric field concentration at the ends of the capacitance electrodes, Withstand voltage. However, since the creeping discharge voltage on the surface of the capacitor is lower than the dielectric breakdown voltage between the capacitance electrodes, there is a problem that the creeping discharge occurs first and the effect of the floating electrode cannot be fully exerted.

Therefore, an object of the present invention is to provide a small-sized multilayer capacitor having excellent withstand voltage performance.

[0005]

In order to solve the above-mentioned problems, a multilayer capacitor according to the present invention has (a) a plurality of capacitor electrodes and (b) alternately stacked capacitor electrodes. A dielectric layer that forms a capacitor part by (c)
An insulator outer layer for protecting a capacitor part in which the capacitance electrodes and the dielectric layers are alternately laminated, (d) a plurality of external electrodes electrically connected to the capacitance electrodes, and (e) any of the electrodes And a floating electrode that is internally provided in the outer layer of the insulator without being electrically connected.

With the above structure, the floating electrode provided in the outer layer of the insulator relieves the electric field concentration between the capacitor electrode and the external electrode disposed on the outermost side of the capacitor portion, and the creeping discharge on the surface of the capacitor hardly occurs. Become. In particular, since the electric field strength between the end of the capacitance electrode and the end of the external electrode is high, the floating electrode is provided at a position approximately between the end of the capacitance electrode and the end of the external electrode, The effect of alleviating the electric field concentration between the electrode and the external electrode is further improved.

Further, the multilayer capacitor according to the present invention is characterized in that it is provided with a floating electrode which is included in the dielectric layer between the capacitance electrodes in a state where it is not electrically connected to any of the electrodes. With the above configuration, the electric field concentration between the capacitance electrodes is alleviated, so that the dielectric breakdown of the capacitor is further unlikely to occur.

[0008]

Embodiments of the multilayer capacitor according to the present invention will be described below with reference to the accompanying drawings. [First Embodiment, FIGS. 1 to 10] In the multilayer capacitor of the first embodiment, one floating electrode is provided in each of the insulating outer layer and the dielectric layer.

As shown in FIGS. 1 to 3, a multilayer capacitor 1 is provided with external electrodes 2 and 3 at both ends thereof, and a capacitor portion 4 and insulating outer layers 5 and 6 for protecting the capacitor portion 4 are thick. It has an integrated structure that is stacked and fired in the same direction. As shown in FIG. 4, a frame-shaped floating electrode 20 that is not electrically connected to any of the electrodes is provided inside the outer insulator layer 5. Hereinafter, an electrode that is not electrically connected to any of the electrodes will be referred to as a floating electrode. Similarly, a frame-shaped floating electrode 21 is provided inside the outer insulator layer 6. The reason for forming the frame shape is that when the floating electrode and the outer layer of the insulator are joined to each other over a wide area, the adhesion strength of the joined portion becomes weak. In addition, the amount of electrode material used is smaller than that of the floating electrode having a large area, and the cost increase can be suppressed. As the material of the outer insulator layers 5 and 6, the same (or another) ceramic sheet as the capacitor portion 4 is used. The floating electrodes 20 and 21 are formed, for example, by applying paste-like Ag, Pd, Cu, Ni, Ag-Pd or the like to the surface of the ceramic sheet by printing or the like.

The capacitor section 4 includes capacitance electrodes 22, 23, 2
4, 25, 26 and dielectric layers 7, 8, 9, 10 are alternately laminated. One end of the capacitance electrode 22 is exposed on the left end surface of the capacitor unit 4 and is electrically connected to the external electrode 2 (see FIG. 5). Similarly, the capacitance electrodes 24 and 26 are exposed on the left end surface of the capacitor portion 4 and are electrically connected to the external electrode 2. One end of the capacitance electrode 23 is exposed on the right end surface of the capacitor unit 4 and is electrically connected to the external electrode 3 (see FIG. 7). Similarly, the capacitance electrode 25 is exposed on the right end surface of the capacitor portion 4 and is electrically connected to the external electrode 3. The material of the capacitor electrodes 22 to 26 is A
g, Pd, Cu, Ni, Ag-Pd, etc. are used.

Inside the dielectric layer 7, as shown in FIG. 6, a frame-shaped floating electrode 27 is provided. Similarly, frame-shaped floating electrodes 28, 29, 30 are provided inside the dielectric layers 8, 9, 10, respectively. Next, the floating electrodes 20, 21 and 27 to 30 will be described in detail. The floating electrodes 20, 21 and 27 to 30 are designed to have the same size, and are set to be slightly larger than the capacity effective surface portion formed by the capacity electrodes 22 to 26. The reason why the sizes of the floating electrodes 20, 21 and 27 to 30 are made larger than the capacitance effective surface portion formed by the capacitance electrodes 22 to 26 is that it is more effective in relaxing electric field concentration. As shown in FIG. 8, the floating electrode 20 is provided substantially between the end 3 a of the external electrode 3 and the end 22 a of the capacitor electrode 22. In the case of the first embodiment, the floating electrode 20 has the end portion 2 at a position half the electrode width X.
It is aligned with the position of 2a and is provided at a position of 1/2 of the thickness d of the outer insulator layer 5. Similarly, the floating electrode 21
Also, the position of 1/2 of the electrode width X is aligned with the position of the end of the capacitor electrode 26, and is provided at the position of 1/2 of the thickness d of the outer insulator layer 6. The floating electrodes 20 and 21 alleviate the electric field concentration between the capacitance electrode 22 and the external electrode 3 and between the capacitance electrode 26 and the external electrode 3, respectively, and suppress the creeping discharge on the surface of the capacitor 1.

The floating electrodes 27 to 30 are provided at positions half the thickness c of the dielectric layers 7, 8, 9 and 10, respectively. The floating electrodes 27 to 30 alleviate the electric field concentration between the capacitance electrodes 22 and 23, between the capacitance electrodes 23 and 24, between the capacitance electrodes 24 and 25, and between the capacitance electrodes 25 and 26, respectively. Dielectric breakdown is suppressed. Here, the electrode half width X / of the floating electrodes 20, 21 and 27 to 30
2 is an end portion of the capacitive electrodes 22, 24 and 26 and the external electrode 3
(Or, the ends of the capacitance electrodes 23 and 25 and the external electrode 2)
It is preferable to design g / 4 to 3g / 4, where g is the gap size.

Further, specific numerical values will be exemplified and described.
For example, the external dimensions of the multilayer capacitor 1 are 5.7 mm ×
5.0 mm, the gap dimension g between the ends of the capacitance electrodes 22, 24 and 26 and the external electrode 3 and the gap dimension g between the ends of the capacitance electrodes 23 and 25 and the external electrode 2 are 0.42 mm, the outer insulator layers 5 and 6 Has a thickness d of 0.2 mm and the dielectric layers 7 to 10 have a thickness c of 0.12 mm.
The electric field strength inside the capacitor 1 when the electrode width X of ˜30 was changed was evaluated. FIG. 9 is a graph displaying the evaluation result. The horizontal axis of the graph is the floating electrode width X, and the vertical axis is the maximum electric field intensity ratio defined by the following equation (1).

Maximum electric field strength ratio = E ₁ / E ₂ (1) E ₁ : Maximum electric field strength of the capacitor 1 having a floating electrode E ₂ : The same structure as the capacitor 1 except that there is no floating electrode The maximum electric field strength solid line 41 of the capacitor represents the maximum electric field strength ratio in the longitudinal direction of the capacitor 1, and the solid line 42 represents the maximum electric field strength ratio of the capacitor 1 in the width direction. If the maximum electric field strength ratio is smaller than 1.0, the floating electrodes 20, 21, 27 ...
It means that the electric field concentration is eased by 30, and the withstand voltage performance of the capacitor 1 is improved. On the contrary, if the maximum electric field strength ratio is larger than 1.0, the floating electrodes 20, 21, 27 ...
It means that the electric field concentration is increased by 30 and the withstand voltage performance of the capacitor 1 is lowered. According to the graph, when the floating electrode width X is set to about 0.3 mm or more, the electric field concentration is alleviated and the withstand voltage performance of the capacitor 1 can be improved.

Tables 1 and 2 show the test results of the dielectric breakdown test with a DC voltage and an AC voltage, respectively.
The test is performed with 100 V applied to the sample set in the air atmosphere.
A direct current voltage or an alternating current voltage was applied at a voltage increase of 1 second per second until a dielectric breakdown occurred in the sample.

[0016]

[Table 1]

[0017]

[Table 2]

From Tables 1 and 2, the floating electrodes 20, 21,
By providing 27 to 30, the dielectric breakdown voltage is about 10
You can see that it becomes higher. 10 and 11 are graphs in which the test results are displayed in frequency distribution. In the graph, the solid line shows the test result of the capacitor 1 provided with the floating electrode. For comparison, the test result of the capacitor having the same structure as the capacitor 1 except that there is no floating electrode is also shown by a dotted line.

[Second Embodiment, FIG. 12] The multilayer capacitor of the second embodiment has two floating electrodes inside the insulator outer layer and the dielectric layer. As shown in FIG. 12, the multilayer capacitor 51 has an external electrode 53 at the left end.
Is provided and has a structure in which a capacitor portion 54 and an outer insulator layer 55 for protecting the capacitor portion 54 are stacked in the thickness direction. Inside the outer insulator layer 55,
Frame-shaped floating electrodes 60 and 61 that are not electrically connected to any of the electrodes are provided.

The capacitor section 54 includes capacitance electrodes 70, 71,
72 and dielectric layers 57, 58 and 59 are alternately laminated. Inside the dielectric layers 57 and 58, frame-shaped floating electrodes 62, 63, 64, and 65 are provided, respectively. The floating electrodes 60 and 61 are the end portions 53 of the external electrode 53.
It is provided between a and the end portion 70a of the capacitance electrode 70. In the case of the second embodiment, the floating electrodes 60 and 61 have their ends located on the line connecting the ends 70a and the corners 53b of the external electrodes 53, and the thickness d of the outer insulator layer 55 is set to 3 mm.
It is provided at equal positions. This floating electrode 60, 6
By 1, the electric field concentration between the capacitance electrode 70 and the external electrode 53 is relaxed, and creeping discharge on the surface of the capacitor 51 is suppressed.

The floating electrodes 62 and 65 have the same size as the floating electrode 61, and the floating electrodes 63 and 64 are the floating electrodes 60.
Is the same size as. The floating electrodes 62 to 65 are provided at positions that divide the thickness c of the dielectric layers 57 and 58 into three equal parts. The floating electrodes 62 to 65 alleviate the electric field concentration between the capacitance electrodes 70 and 71 and between the capacitance electrodes 71 and 72, and suppress the dielectric breakdown between the capacitance electrodes. Therefore, it is possible to obtain a small-sized multilayer capacitor having excellent withstand voltage performance.

The multilayer capacitor according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of its gist. In particular, the shape and position of the floating electrode are arbitrary. Although the shape of the floating electrode in the above embodiment is a frame shape, it may be a shape without a hole in the central portion. Further, three or more floating electrodes may be incorporated in the outer layer of the insulator or the dielectric layer. Further, in the second embodiment, the floating electrodes 60 and 61, the floating electrodes 62 and 63 and the like have different sizes, but even if the floating electrodes 61 and 62 are increased in size to the same size as the floating electrodes 60 and 63, respectively. Good.

[0023]

As is apparent from the above description, according to the present invention, since the floating electrode which is not electrically connected to any of the electrodes is provided in the outer layer of the insulator, the space between the capacitor electrode and the external electrode is increased. Electric field concentration is relieved, and creeping discharge on the capacitor surface can be suppressed. In particular, if the floating electrode is provided at a position approximately between the end of the capacitance electrode and the end of the external electrode, the electric field concentration between the capacitance electrode and the external electrode can be alleviated more. As a result, it is possible to obtain a small multilayer capacitor excellent in withstand voltage performance without increasing the thickness of the outer layer of the insulator.

Further, by providing the floating electrodes between the capacitance electrodes, the electric field concentration between the capacitance electrodes can be alleviated, and the one having further excellent withstand voltage performance can be obtained.

[Brief description of drawings]

1 to 11 show a first embodiment of a multilayer capacitor according to the present invention.

FIG. 1 is a perspective view showing the appearance of a multilayer capacitor.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view showing the internal structure of the multilayer capacitor.

FIG. 5 is a plan view showing the internal structure of the multilayer capacitor.

FIG. 6 is a plan view showing the internal structure of the multilayer capacitor.

FIG. 7 is a plan view showing the internal structure of the multilayer capacitor.

FIG. 8 is a partially enlarged cross-sectional view for explaining a positional relationship between floating electrodes.

FIG. 9 is a graph showing the relationship between the floating electrode width and the maximum electric field strength ratio.

FIG. 10 is a graph showing the evaluation results of dielectric breakdown due to DC voltage.

FIG. 11 is a graph showing the evaluation results of dielectric breakdown due to an AC voltage.

FIG. 12 is a partially enlarged sectional view showing a second embodiment of the multilayer capacitor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer capacitor 2, 3 ... External electrode 3a ... End of external electrode 4 ... Capacitor part 5, 6 ... Insulator outer layer 7, 8, 9, 10 ... Dielectric layer 20, 21 ... Floating electrode 22, 23, 24, 25, 26 ... Capacitance electrode 22a ... Capacitance electrode end 27, 28, 29, 30 ... Floating electrode 51 ... Multilayer capacitor 53 ... External electrode 53a ... External electrode end 53b ... External electrode corner 54 ... Capacitor section 55 ... Insulator outer layer 57, 58, 59 ... Dielectric layer 60, 61, 62, 63, 64, 65 ... Floating electrode 70, 71, 72 ... Capacitance electrode 70a ... End of capacitance electrode

Claims (3)

[Claims] 1. A plurality of capacitance electrodes, a dielectric layer that is alternately laminated with each of the capacitance electrodes to form a capacitor section, and a capacitor section in which the capacitance electrodes and the dielectric layers are alternately laminated is protected. An outer layer of an insulating material, a plurality of outer electrodes electrically connected to the capacitance electrode, and a floating electrode that is internal to the outer layer of the insulating material without being electrically connected to any of the electrodes. Multilayer type capacitor. 2. The floating electrode, which is internal to the outer layer of the insulator, is provided at a position approximately between the end of the capacitive electrode and the end of the external electrode which form the capacitor section.
The multilayer capacitor described. 3. The multilayer capacitor according to claim 1, wherein the floating electrode is internally provided in the dielectric layer between the capacitance electrodes in a state where it is not electrically connected to any of the electrodes.