JPH0950935A - Laminated capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a leak initiation voltage caused by surface flash-over in air, by forming a most outer-layer inner electrode with a widthwise gap smaller than each gap on a first side and on a second side. SOLUTION: A widthwise gap 32 on a first side, at which the first outer electrode connected to an inner electrode 23 is located, is made smaller than a widthwise gap 33 on a second side, at which a second outer electrode not connected electrically is located. As to a second inner electrode 24, a widthwise gap 34 on the first side, at which the second outer electrode electrically connected to the inner electrode 24 is located, is made smaller than a widthwise gap 35 on the second side, at which the first electrode not connected electrically is located. In this way, a good shielding effect can be ensured with low intensity of magnetic field, and an initiation voltage of flash-over is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer capacitor, and more particularly to a multilayer capacitor suitable for medium and high voltage.

[0002]

2. Description of the Related Art A general cross-sectional structure of a multilayer capacitor such as a multilayer ceramic capacitor is shown in FIG. The multilayer capacitor 1 shown in FIG. 4 includes a capacitor body 5 in which a plurality of internal electrodes 2 and 3 and a plurality of dielectric layers 4 are alternately laminated. Capacitor body 5
First and second outer electrodes 8 and 9 are formed on the first and second end faces 6 and 7, respectively, in the longitudinal direction. The plurality of internal electrodes 2 and 3 are classified into a first internal electrode 2 and a second internal electrode 3 which are arranged alternately.

The first inner electrode 2 is electrically connected to the first outer electrode 8 at the first end face 6 in the longitudinal direction of the capacitor body 5, and the second end face in the longitudinal direction of the capacitor body 5. 7 and both end faces in the width direction (not shown)
A gap is formed for each. On the other hand, the second
Inner electrode 3 is electrically connected to the second outer electrode 9 at the second end face 7 in the longitudinal direction of the capacitor body 5, and the first end face 6 in the longitudinal direction of the capacitor body 5 is
And gaps are formed on both end faces (not shown) in the width direction.

According to the multilayer capacitor 1 having such a structure, the ratio of the effective area contributing to the capacitance formation to the area of each of the internal electrodes 2 and 3 can be made relatively high, and the efficiency of the internal electrodes 2 and 3 can be increased. There is an advantage that it can be utilized effectively and therefore can be designed in a small size. However, although this multilayer capacitor 1 is suitable as a capacitor having a relatively low withstand voltage rating, it is not necessarily suitable as a so-called medium-high voltage capacitor having a rated voltage of several hundreds V or higher. When designing a medium- and high-voltage capacitor, the breakdown value in the dielectric layer 4 can be increased by increasing the thickness of the dielectric layer 4, but it may still occur between the external electrodes 8 and 9. You cannot solve the flashover problem.

For the purpose of increasing the flashover start voltage value, measures as shown in FIGS. 5 and 6 have been proposed. In the multilayer capacitor 1a shown in FIG. 5, the longitudinal dimension of the inner electrodes 2a and 3a located in the outermost layer is made shorter than the longitudinal dimensions of the other internal electrodes 2 and 3, and the longitudinal dimension of the capacitor body 5 is reduced. Has been almost half of. Further, in the multilayer capacitor 1b shown in FIG. 6, in addition to the elements included in the multilayer capacitor 1a shown in FIG. 5, a dummy internal electrode 2b is formed on the same surface as the outermost internal electrode 2a via a gap 10. This dummy internal electrode 2b is electrically connected to the second external electrode 9, and a dummy internal electrode 3b is formed on the same surface as the outermost internal electrode 3a with a gap 11 therebetween. The inner electrode 3b is electrically connected to the first outer electrode 8.

In FIGS. 5 and 6, elements corresponding to those shown in FIG. 4 are designated by the same reference numerals,
Duplicate description will be omitted. Generally, the flashover on the surface of the capacitor body starts when the electric field strength formed in the external electrode portion reaches or exceeds the electric field strength that induces discharge in air. The electric field strength at the external electrode portion is (1) the potential difference applied between the opposing external electrodes,
And the distance between these external electrodes, and (2) the potential difference applied between one external electrode and the internal electrode connected to the external electrode opposite thereto, and the distance between these external electrodes and the internal electrode. The larger the potential difference or the shorter the distance, the higher the electric field strength and the lower the flashover start voltage.

In the multilayer capacitor 1 having the general structure as shown in FIG. 4, the distance between the external electrode 8 and the internal electrode 3 or the distance between the external electrode 8 and the internal electrode 3 is larger than the distance between the external electrodes 8 and 9. The distance from 2 is much shorter, and therefore, the electric field strength formed at the external electrodes 8 and 9 is determined by the factor (2). Based on this factor (2), it is attempted to suppress the electric field strength by separating one external electrode and the internal electrode connected to the external electrode opposite thereto as much as possible.
And the structure shown in FIG. That is, in FIGS. 5 and 6, the dimension of the inner electrodes 2a and 3a located in the outermost layer in the longitudinal direction is made shorter than the dimension of the other internal electrodes 2 and 3 in the longitudinal direction, and the dimension of the capacitor body 5 in the longitudinal direction is set. Of the internal electrode 3a connected to one external electrode 8 and the external electrode 9 facing the external electrode 8
And the other external electrode 9 and the internal electrode 2a connected to the external electrode 8 opposite to the other external electrode 9 as far as possible so as to suppress the electric field strength.

However, in the structure shown in FIGS. 5 and 6, the electric field strength at the upper and lower surfaces of the capacitor body 5 is weakened at the external electrodes 8 and 9, but the electric field at the side surface of the capacitor body 5 is reduced. It has no effect of weakening strength. This is because the distance between the internal electrodes 2 and 3 and both widthwise end faces of the capacitor body 5, that is, both side faces, is still relatively short.

In order to suppress the above-mentioned electric field strength, it is conceivable to increase the gaps formed between all the internal electrodes and one end face in the longitudinal direction of the capacitor body. However, the effective facing area of the internal electrodes that contributes to the formation of the above becomes small and the acquired capacitance also becomes small, which is not practical.

[0010]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a multilayer capacitor capable of increasing the starting voltage of leakage due to surface flashover in the air. That is.

[0011]

The present invention, like the multilayer capacitor 1 shown in FIG. 4 described above, includes a capacitor body in which a plurality of internal electrodes and a plurality of dielectric layers are alternately laminated, and this capacitor. The first and second external electrodes are respectively formed on the first and second end faces of the main body in the longitudinal direction, and the plurality of internal electrodes are arranged alternately.
The first internal electrode is electrically connected to the first external electrode at the first end face in the longitudinal direction of the capacitor body, and the first internal electrode is Gaps are formed on the second end face in the horizontal direction and both end faces in the width direction, and the second internal electrode is electrically connected to the second external electrode at the second end face in the longitudinal direction of the capacitor body. The present invention is directed to such a multilayer capacitor, which is connected and forms a gap with respect to the first end face in the longitudinal direction and both end faces in the width direction of the capacitor body, respectively. In order to solve the above, it is characterized by having the following configuration.

First, similarly to the multilayer capacitors 1a and 1b shown in FIGS. 5 and 6, the longitudinal dimension of the inner electrode located in the outermost layer is made shorter than the longitudinal dimension of the other inner electrodes. Furthermore, the size of the gap in the width direction of the other internal electrode is larger than that of the first side where the external electrode electrically connected to the internal electrode is located compared to the first side where the external electrode not electrically connected is located. It is made larger on the 2 side. At this time, the dimension of the widthwise gap of the internal electrode located in the outermost layer is equal to or smaller than the dimension of the gap on the first side and smaller than the dimension of the gap on the second side.

In the present invention, preferably, the difference between the size of the gap on the first side and the size of the gap on the second side is selected to be equal to or larger than the thickness of the dielectric layer between adjacent internal electrodes. Note that, in the present invention, as with the multilayer capacitor 1b shown in FIG. 6, an external electrode that is formed on the same surface as an internal electrode located in the outermost layer via a gap and to which the internal electrode is electrically connected is Dummy internal electrodes electrically connected to different external electrodes may be further provided.

[0014]

According to the present invention, first, similarly to the multilayer capacitors 1a and 1b shown in FIGS. 5 and 6, the lengthwise dimension of the inner electrode located in the outermost layer is the same as that of the other inner electrodes. Since it is shorter than the dimension of the capacitor body, the electric field strength of the external electrode portion on the surface defined by the longitudinal dimension and the width dimension of the capacitor body, that is, the upper and lower surfaces of the capacitor body can be suppressed.

Further, in the present invention, the size of the gap in the width direction of the other internal electrode is electrically connected as compared with the first side where the external electrode electrically connected to the internal electrode is located. Since it is made larger on the second side where the external electrode is not located, when viewed from the surface defined by the longitudinal dimension and the thickness dimension of the capacitor body, that is, both side surfaces of the capacitor body, an internal electrode is It can be covered by an internal electrode having a potential opposite to that, whereby the shield effect can be exerted. As a result, it is possible to suppress the electric field strength of the external electrode portions on both sides of the capacitor body.

In this way, the electric field strength can be reduced over the entire surface of the capacitor body, and therefore the flashover start voltage can be further increased. Therefore, according to the present invention, it is possible to obtain a multilayer capacitor suitable for medium and high voltages. According to the present invention, as described above, the dimension of the widthwise gap of the inner electrode located in the outermost layer is equal to or smaller than the dimension of the gap on the first side and smaller than the dimension of the gap on the second side. To be done. As a result, the inner electrode located in the outermost layer also acts to exert the shield effect.

As described above, when the difference between the size of the gap on the first side and the size of the gap on the second side is selected to be greater than or equal to the thickness of the dielectric layer between adjacent internal electrodes, It is more preferable because the shield effect is increased. The larger the gap size difference, the greater the shielding effect. However, if this dimensional difference becomes smaller than the thickness of the dielectric layer,
The shield effect becomes smaller.

In the present invention, it is preferable that the boundary portion between the first side and the second side is located at the central portion in the longitudinal direction of the capacitor main body because a higher effect can be obtained.
Also, the longitudinal dimension of the inner electrode located in the outermost layer is
If it is selected so as to cover the second side of the other internal electrode adjacent to this, the shield effect can be more perfectly exhibited.

[0019]

1 is a perspective view showing a multilayer capacitor 21 according to an embodiment of the present invention in a perspective manner.
FIG. 2 is a sectional view taken along line II-II in FIG. FIG.
Are dielectric layers 22a, 22b made of, for example, a dielectric ceramic included in the multilayer capacitor 21 shown in FIG.
22c is a perspective view showing the layers 22c, ... It should be noted that in FIG. 1, the illustration of the inner electrode located at the outermost layer is omitted, and in FIG. 3, the illustration of the dielectric layer laminated further outside each of the dielectric layers 22a and 22n is omitted.

This multilayer capacitor 21 is similar to the multilayer capacitors 1, 1a and 1b shown in FIGS. 4 to 6.
First, the capacitor main body 25 is provided, in which a plurality of internal electrodes 23 and 24 and a plurality of dielectric layers 22a, ..., 22n are alternately laminated. The first and second end faces 26 and 27 in the longitudinal direction of the capacitor body 25 are respectively
First and second outer electrodes 28 and 29 are formed. The plurality of internal electrodes 23 and 24 are classified into a first internal electrode 23 and a second internal electrode 24 which are arranged alternately. The first inner electrode 23 is electrically connected to the first outer electrode 28 at the first end face 26 in the longitudinal direction of the capacitor body 25, and the second end face 27 in the longitudinal direction of the capacitor body 25. In addition, gaps are formed on both end faces 30 and 31 in the width direction. On the other hand, the second inner electrode 24 is connected to the capacitor body 2
5 is electrically connected to the second external electrode 29 at the second end face 27 in the longitudinal direction of the capacitor 5, and the capacitor body 2
A gap is formed with respect to the first end face 26 in the longitudinal direction and the both end faces 30 and 31 in the width direction.

Further, in this multilayer capacitor 21,
Multilayer capacitors 1a and 1b shown in FIGS. 5 and 6
Similarly to the internal electrodes 23a and 24a located in the outermost layer,
Have their respective longitudinal dimensions shorter than those of the other inner electrodes 23 and 24. With this, first
Similar to the multilayer capacitor 1a shown in FIG. 5, the surface (LW surface) defined by the lengthwise dimension (L) and the widthwise dimension (W) of the capacitor body 25, that is, the capacitor body 2
It is possible to suppress the electric field strength on the upper and lower surfaces of No. 5.

The multilayer capacitor 21 is further characterized in relation to the shapes of the other internal electrodes 23 and 24 described above. That is, the widthwise dimensions of each of the internal electrodes 23 and 24 are not constant, and therefore the internal electrode 23
The size of the widthwise gap of each of Nos. 24 and 24 is not constant. More specifically, in terms of the first internal electrodes 23, compared with the size of the width-direction gap 32 on the first side where the first external electrodes 28 to which these internal electrodes 23 are electrically connected are located. Thus, the size of the gap 33 in the width direction on the second side where the opposite second electrically non-connected external electrode 29 is located is made larger. On the other hand, as for the second internal electrodes 24, the size of the gap 34 in the width direction on the first side where the second external electrodes 29 to which these internal electrodes 24 are electrically connected is located is opposite to the size of the gap. The size of the gap 35 in the width direction on the second side where the first external electrode 28 that is not electrically connected is located is made larger.

As a result, the capacitor body 2 is further
When viewed from the surface (LT surface) defined by the lengthwise dimension (L) and the thicknesswise dimension (T) of 5, ie, both side surfaces of the capacitor body, a certain internal electrode 23 or 24 has a potential opposite to this. It can be covered with the internal electrode 24 or 23, which has a shield effect. As a result, the electric field strength on both side surfaces (LT surface) of the capacitor body 25 can be suppressed.

As a result, the electric field strength can be reduced over the entire surface of the capacitor body 25, and therefore the flashover start voltage can be further increased.
Also, in order to ensure the above-mentioned shielding effect,
In the illustrated embodiment, the dimensions of the widthwise gaps 36 and 37 of the inner electrodes 23a and 24a located in the outermost layer are equal to the dimensions of the widthwise gaps 32 and 34 on the first side described above. To be elected. The size of the former is
It may be smaller than the latter size. Further, the respective dimensions of the widthwise gaps 36 and 37 of the inner electrodes 23a and 24a located in the outermost layer are selected to be smaller than the respective dimensions of the widthwise gaps 33 and 35 on the second side. As a result, the inner electrodes 23a and 24 located in the outermost layer are formed.
a also acts to exert the shield effect.

Also, the gaps 32 and 3 on the first side
The difference between the dimensions of 4 and the dimensions of the gaps 33 and 35 on the second side is preferably the dielectric layers 22a ,.
It is selected so as to be not less than each thickness of n. This dimensional difference
Even if the thickness of the dielectric layers 22a, ..., 22n is smaller than the thickness of the dielectric layers 22a ,.
The shield effect is larger when the thickness is larger than 22n. However, this dimensional difference cannot be so large. This is because the larger the size difference, the smaller the effective area of the internal electrodes 23 and 24 that contributes to the acquisition of the capacitance, which is not practical.

Further, in the illustrated embodiment, the boundary portion between the first side and the second side described above is located at the central portion in the longitudinal direction of the capacitor body 25. The position of such a boundary portion may be slightly deviated from the central portion, but if it is in the central portion as shown in the figure, a higher effect can be expected.
Further, the longitudinal dimension of the inner electrodes 23a and 24a located in the outermost layer is selected in this embodiment so as to cover the second sides of the other inner electrodes 23 and 24 adjacent thereto. With such a configuration, the shield effect can be exhibited more completely.

Although the present invention has been described above with reference to the illustrated embodiments, within the scope of the present invention, other
Various embodiments can be adopted. For example, in the illustrated embodiment, at the boundary between the first side and the second side of each of the internal electrodes 23 and 24,
Although taper-graded, it may be bounded by lines extending at right angles to the longitudinal direction.

The corners of the internal electrodes 23, 23a, 24 and 24a may be rounded. Further, in the multilayer capacitor 21 according to the illustrated embodiment, dummy internal electrodes corresponding to the dummy internal electrodes 2b and 3b shown in FIG. 6 are formed adjacent to the internal electrodes 23a and 24a located in the outermost layers, respectively. Good.

Further, the present invention is not limited to the monolithic ceramic capacitor using ceramic as the dielectric, but can be applied to the monolithic capacitor using other dielectrics.

[Brief description of drawings]

FIG. 1 is a multilayer capacitor 2 according to an embodiment of the present invention.
It is a schematic top view which shows 1 transparently.

FIG. 2 is a capacitor body 25 taken along line II-II in FIG.
FIG.

FIG. 3 is a view showing dielectric layers 22a, 22b forming a capacitor body 25 included in the multilayer capacitor 21 shown in FIG.
22c is a perspective view showing the layers 22c, ...

FIG. 4 is a sectional view schematically showing a conventional typical multilayer capacitor 1 which is of interest to the present invention.

5 is a cross-sectional view schematically showing a multilayer capacitor 1a in which a countermeasure against surface leak is applied to the multilayer capacitor 1 shown in FIG.

6 is a sectional view schematically showing a multilayer capacitor 1b in which another countermeasure against surface leak is applied to the multilayer capacitor 1 shown in FIG.

[Explanation of symbols]

21 multilayer capacitor 22a, ..., 22n dielectric layer 23,23a first internal electrode 24,24a second internal electrode 23a, 24a internal electrode located at the outermost layer 25 capacitor body 26 first end face in the longitudinal direction 27 longitudinal Direction second end surface 28 first outer electrode 29 second outer electrode 30,31 width direction end surface 32,34 width gap on first side 33,35 width direction on second side Gap 36, 37 Gap in the width direction of the inner electrode located on the outermost layer

Claims (5)

[Claims] 1. A capacitor body in which a plurality of internal electrodes and a plurality of dielectric layers are alternately laminated, and first and second capacitor bodies respectively formed on first and second end faces in the longitudinal direction of the capacitor body. Two external electrodes, wherein the plurality of internal electrodes are arranged alternately with a first internal electrode and a second internal electrode.
The first internal electrode is electrically connected to the first external electrode at the first end face in the longitudinal direction of the capacitor body, and the first internal electrode in the longitudinal direction of the capacitor body. A gap is formed on each of the second end face and both end faces in the width direction.
Is electrically connected to the second outer electrode at the second end face in the longitudinal direction of the capacitor body, and is formed on the first end face in the longitudinal direction and both end faces in the width direction of the capacitor body. In the multilayer capacitor having a gap formed therein, the dimension of the inner electrode located in the outermost layer in the longitudinal direction is shorter than the dimension of the other inner electrode in the longitudinal direction. The dimension of the gap in the width direction is made larger on the second side on which the external electrode that is not electrically connected is located, as compared to the first side on which the external electrode that is electrically connected to the internal electrode is located, The size of the gap in the width direction of the inner electrode located in the outermost layer is equal to or smaller than the size of the gap on the first side and smaller than the size of the gap on the second side. Characterized in that there, the multilayer capacitor. 2. The difference between the size of the gap on the first side and the size of the gap on the second side is selected to be greater than or equal to the thickness of the dielectric layer between the adjacent internal electrodes. Item 1. The multilayer capacitor according to Item 1. 3. The multilayer capacitor according to claim 1, wherein a boundary portion between the first side and the second side is located at a central portion in the longitudinal direction of the capacitor body. 4. The longitudinal dimension of the inner electrode located in the outermost layer is selected so as to cover the second side of the other inner electrode adjacent thereto.
The multilayer capacitor according to any one of 1. 5. A dummy which is formed on the same surface as an inner electrode located in the outermost layer through a gap and is electrically connected to an external electrode different from an external electrode to which the internal electrode is electrically connected. The multilayer capacitor according to claim 1, further comprising an internal electrode.