JP2002118028A - Laminated ceramic capacitor - Google Patents

Abstract

(57) [Problem] To provide a multilayer ceramic capacitor having a high withstand voltage by improving the starting voltage of creeping discharge generated on a ceramic surface. SOLUTION: An internal electrode 122 is composed of a capacitance forming electrode 122a and a discharge suppressing electrode 122b formed on the same surface, and the discharge suppressing electrode 122b is a capacitor forming electrode 1
22a, which are provided on both sides on the outer side of the capacitor 22a.
External electrode 140 facing external electrode 140a connected to
b. Thereby, the electric field concentration on the ceramic surface is reduced, and the multilayer ceramic capacitor element 1
It is possible to increase the voltage at which creeping discharge occurs on the side surface of the side plate 30, and thus to obtain a multilayer ceramic capacitor having a high withstand voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, a multilayer ceramic capacitor is formed by stacking and pressing a dielectric ceramic green sheet and a sheet obtained by printing an internal electrode paste on the dielectric ceramic green sheet, and cutting and separating the laminate into individual pieces. Next, the laminated ceramic capacitor element is fired to form a multilayer ceramic capacitor element, and external electrodes connected to internal electrodes are provided at both ends of the multilayer ceramic capacitor element.

In a conventional multilayer ceramic capacitor for medium and high pressures, creeping discharge easily occurs on the surface of the dielectric ceramic. Therefore, the length of the multilayer ceramic capacitor element in the longitudinal direction is increased and the distance between external electrodes is increased to increase the creeping surface. The discharge starting voltage was increased.

As a method for increasing the creeping discharge starting voltage without changing the length of the multilayer ceramic capacitor element, there is known a method described in Japanese Patent Application Laid-Open No. 57-176715.

FIGS. 7 and 8 are cross-sectional views of a conventional multilayer ceramic capacitor. FIG. 7 shows the shape of internal electrodes in upper and lower outermost layers, and FIG. 8 shows the shape of internal electrodes in an intermediate layer. is there. FIG. 9 is a longitudinal sectional view of a conventional multilayer ceramic capacitor.

As shown in FIG. 9, a conventional multilayer ceramic capacitor 300 includes internal electrodes 321 to 327 of a multilayer ceramic capacitor element 330 including a dielectric ceramic 310 and a plurality of internal electrodes 321 to 327 opposed to each other.
External electrodes 340a, 340b electrically connected to the
As shown in FIGS. 9 and 7, the length of the lowermost outermost internal electrode 321 and the uppermost outermost internal electrode 327 is reduced to about half the length of the multilayer ceramic capacitor element 330. As a result, the creeping discharge generation start voltage has been improved.

[0007]

However, in the above-described conventional structure, the multilayer ceramic capacitor element 330 is not provided.
Although the creeping discharge start voltage on the upper and lower surfaces of the multilayer ceramic capacitor element 330 can be improved, the creeping discharge start voltage on the side surface of the multilayer ceramic capacitor element 330 cannot be increased.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a multilayer ceramic capacitor having a high withstand voltage by increasing the starting voltage of creeping discharge on the upper and lower surfaces and side surfaces of the multilayer ceramic capacitor element. It is assumed that.

[0009]

In order to achieve the above object, the present invention has the following arrangement.

[0010] The invention described in claim 1 of the present invention is, in particular,
At least the inner electrodes except for the upper and lower outermost layers are composed of a capacitance forming electrode and a discharge suppressing electrode formed on the same surface, and the discharge suppressing electrodes are provided on both outer sides of the capacitance forming electrode. The external electrode connected to the external electrode is connected to the external electrode opposite to the external electrode. This makes it possible to increase the generation start voltage of the creeping discharge on the side surface of the multilayer ceramic capacitor element, and thus the multilayer ceramic having a high withstand voltage. The effect of being able to be a capacitor is obtained.

[0011] The invention described in claim 2 of the present invention is, in particular,
The length of the discharge suppressing electrode, that is, the distance between the tip of the discharge suppressing electrode and the external electrode connected thereto is set to be 0.25 to 0.75 times the total length of the multilayer ceramic capacitor element. Is specified, whereby the voltage at which creeping discharge starts on the side surface of the multilayer ceramic capacitor element can be stably increased, and therefore, the multilayer ceramic capacitor having a high withstand voltage can be surely obtained. The effect is obtained.

[0012] The invention described in claim 3 of the present invention particularly provides
The shape of the discharge suppressing electrode is such that the distance from the side surface of the multilayer ceramic capacitor element increases as the distance from the external electrode to be connected increases. Can be further increased, so that a multilayer ceramic capacitor having a higher withstand voltage can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described in detail with reference to Embodiment 1. FIG.

FIG. 1 is a cross-sectional view of the multilayer ceramic capacitor according to the first embodiment of the present invention, showing the shape of the internal electrodes of the multilayer ceramic capacitor according to the first embodiment of the present invention. FIG. 2 is also a cross-sectional view of the multilayer ceramic capacitor according to Embodiment 1 of the present invention, and shows a shape of an internal electrode facing the internal electrode of FIG. FIG. 3 is a longitudinal sectional view of the multilayer ceramic capacitor according to Embodiment 1 of the present invention.

As shown in FIG. 3, a multilayer ceramic capacitor 100 according to a first embodiment of the present invention has a plurality of internal electrodes 121 to 1 opposed to a dielectric ceramic 110.
27 and a pair of external electrodes 140a, 140b electrically connected to the internal electrodes 121 to 127 of the multilayer ceramic capacitor element 130, and as shown in FIGS. , The capacitance forming electrodes 122a and 123 formed on the same surface, respectively.
a and discharge suppressing electrodes 122b and 123b, and the discharge suppressing electrode 122b is
The electrodes 122 for capacitance formation are provided on both sides on the outer side of 2a.
external electrode 14 facing external electrode 140a connected to
0b, the discharge suppressing electrodes 123b are provided on both outer sides of the capacitance forming electrodes 123a, and are connected to the external electrodes 140a facing the external electrodes 140b connected to the capacitance forming electrodes 123a. In addition, the length of the lowermost outermost internal electrode 121 and the uppermost outermost internal electrode 127 is reduced to about half the length of the multilayer ceramic capacitor element 130.

Next, a method for manufacturing a multilayer ceramic capacitor according to the first embodiment of the present invention will be described in the order of steps.

First, a ceramic green sheet comprising a ceramic powder containing barium titanate as a main component and an organic binder was prepared and prepared. At this time, the thickness of the ceramic green sheet was about 90 μm.

Next, a plurality of the above ceramic green sheets were laminated to form a lower ineffective layer. Subsequently, a conductor layer serving as the lowermost outermost internal electrode 121 shown in FIG. 3 was formed on the ineffective layer by a screen printing method using a metal paste containing nickel as a main component. At this time, the lowermost outermost internal electrode 1
The shape of the conductor layer 21 was shortened so that its length was about half the length of the multilayer ceramic capacitor element 130, similarly to the conventional multilayer ceramic capacitor shown in FIG.

Further, the above-mentioned ceramic green sheet is laminated, on which a capacitor forming electrode 122a having the shape shown in FIG. A conductor layer to be used as the electrode 122b was formed. Subsequently, the ceramic green sheet is laminated, and a capacitor forming electrode 123 having the shape shown in FIG.
a and a conductor layer to be the discharge suppressing electrode 123b was formed. Printing of these conductor layers and lamination of the ceramic green sheets were alternately repeated a plurality of times. Then, a conductor layer to be the uppermost outermost internal electrode 127 was formed thereon. At this time, the shape of the conductor layer serving as the uppermost outermost internal electrode 127 is, like the lowermost outermost internal electrode 121, such that its length is about half the length of the multilayer ceramic capacitor element 130. Was shortened to Subsequently, a plurality of the ceramic green sheets were laminated to form an upper ineffective layer to obtain a laminate.

In the above description, the capacitance forming electrode 12
The length of 2a and 123a is fixed to be 0.85 times the total length of the multilayer ceramic capacitor element 130, and the length of the discharge suppressing electrodes 122b and 123b, ie, FIG.
In FIG. 2A, a laminate was prepared by variously changing the total length of the multilayer ceramic capacitor element to be 0.15 to 0.85 times the total length.

The thickness of the conductor layer was about 2.5 μm. The printed conductor layer pattern was a pattern shape in which a large number of the illustrated shapes were vertically and horizontally arranged so as to have the shapes shown in FIGS. 1, 2 and 7 after being laminated and cut.

Next, the laminate was cut and separated into desired dimensions to obtain individual raw chips. The green chip was heated in nitrogen gas to remove the binder, and then heated to 1300 ° C. in a mixed gas atmosphere of nitrogen and hydrogen in which nickel was not oxidized and fired to obtain a sintered body.

Next, the sintered body is chamfered to completely expose the internal electrodes on both end faces of the sintered body. Subsequently, an electrode paste containing copper as a main component is applied to both end faces and side faces of the sintered body. After the application, baking was performed in a nitrogen atmosphere at 800 ° C. to form the external electrodes 140a and 140b, and nickel and solder were plated thereon to produce the multilayer ceramic capacitor 100 according to the first embodiment.

The manufactured multilayer ceramic capacitor 100 in the first embodiment has a longitudinal dimension of 3.2 m.
m, width dimension: 1.6 mm, thickness dimension: 1.15
mm, the capacitance is 0.01 μF, and the Tan δ is 1.0
%, And the insulation resistance was 1 × 10 ¹¹ Ω.

As a comparative example, the conventional multilayer ceramic capacitor 300 shown in FIGS.
It was produced under the same conditions as described above.

The multilayer ceramic capacitor 3 of this comparative example
00 also has a longitudinal dimension of 3.2 mm, a width dimension of 1.6 mm, a thickness dimension of 1.15 mm, a capacitance of 0.01 μF, a Tan δ of 1.0%, and an insulation resistance of 1 × 10 ¹¹
Ω.

With respect to the multilayer ceramic capacitor 100 of the first embodiment and the multilayer ceramic capacitor 300 of the comparative example manufactured as described above, the results of measuring the creeping discharge starting voltage are shown in Table 1. The creeping discharge generation start voltage was obtained by increasing the DC voltage, indicating the voltage at which the creeping discharge occurred, and the number of tests was 30.

[0028]

[Table 1]

As shown in (Table 1), the first embodiment
In the multilayer ceramic capacitor 100 of the comparative example, the generation start voltage of the creeping discharge could be increased as compared with the conventional multilayer ceramic capacitor 300 of the comparative example. Further, by setting the length of the discharge suppressing electrodes 122b and 123b to be in a range of 0.25 to 0.75 times the total length of the multilayer ceramic capacitor element, it is possible to further increase the creeping discharge generation start voltage, and to withstand. A multilayer ceramic capacitor 100 having a high voltage was obtained.

As described above, in the multilayer ceramic capacitor 100 according to the first embodiment, the internal electrodes 122 to 126 except for the upper and lower outermost layers have the capacitance forming electrodes 122a to 126a (not shown) formed on the same surface. ) And discharge suppressing electrodes 122b to 126b (not shown). The discharge suppressing electrodes 122b to 126b are provided on both sides of the capacitance forming electrodes 122a to 126a on the outer side, respectively, and the capacitance forming electrodes 122a to 126a. External electrodes 140a opposite to the external electrodes 140a and 140b connected to
By providing the structure connected to the surface of the multilayer ceramic capacitor 140a, the electric field concentration on the ceramic surface is reduced, so that the starting voltage of the creeping discharge on the side surface of the multilayer ceramic capacitor element 130 can be increased. This has the effect of being 100.

The discharge suppressing electrodes 122b to 126b
Of the external electrode 140b, 1
The distance from the multilayer ceramic capacitor element 13
By setting the total length of 0 to 0.25 to 0.75 times, the generation start voltage of the creeping discharge on the side surface of the multilayer ceramic capacitor element 130 can be stably increased,
Therefore, the multilayer ceramic capacitor 1 having a high withstand voltage is surely provided.
This has the effect of becoming 00.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to Embodiment 2.

FIG. 4 is a cross-sectional view of the multilayer ceramic capacitor according to the second embodiment of the present invention, showing the shape of the internal electrodes of the multilayer ceramic capacitor according to the second embodiment of the present invention. FIG. 5 is also a cross-sectional view of the multilayer ceramic capacitor according to Embodiment 2 of the present invention, and shows a shape of an internal electrode facing the internal electrode of FIG. FIG. 6 is a longitudinal sectional view of the multilayer ceramic capacitor according to Embodiment 2 of the present invention.

The multilayer ceramic capacitor 200 according to the second embodiment of the present invention is different from the first embodiment in that a discharge suppressing electrode 222 is provided as shown in FIGS.
b and 223b, and the discharge suppressing electrode 222
b and 223b are about 0.5 times the total length of the multilayer ceramic capacitor element 230, and the discharge suppressing electrodes 22
The shapes of 2b and 223b increase the distance between the end of the discharge suppressing electrode and the side surface of the multilayer ceramic capacitor element 230 as the distance from the connected external electrodes 240b and 240a increases.
Is larger than C. Further, similarly to the first embodiment, the length of the lowermost outermost internal electrode 221 and the uppermost outermost internal electrode 227 is reduced to about half the length of the multilayer ceramic capacitor element 230. . 4 and 5, reference numeral 210 denotes a dielectric ceramic, 2
22a and 223a are capacitance forming electrodes.

The multilayer ceramic capacitor 200 according to the second embodiment manufactured by the same manufacturing method as in the first embodiment has a longitudinal dimension of 3.2 as in the first embodiment.
mm, width dimension 1.6 mm, thickness dimension 1.1
5 mm, capacitance 0.01 μF, Tan δ 1.0%,
The insulation resistance was 1 × 10 ¹¹ Ω.

With respect to the manufactured multilayer ceramic capacitor 200 according to the second embodiment, the results of measuring the creeping discharge onset voltage are shown in Table 1 together. The measurement method and the number of tests of the creeping discharge onset voltage were the same as those in the first embodiment.

As shown in (Table 1), the second embodiment
In the multilayer ceramic capacitor 200, the generation start voltage of the creeping discharge could be further increased as compared with the first embodiment.

As described above, the multilayer ceramic capacitor 200 according to the second embodiment has the discharge suppressing electrode 222
b, 223b are connected to external electrodes 240b, 2
By forming the shape such that the distance from the side surface of the multilayer ceramic capacitor element 230 increases as the distance from the side of the multilayer ceramic capacitor element 230 increases, the generation start voltage of the creeping discharge on the side surface of the multilayer ceramic capacitor element 230 can be further increased. The effect is that the multilayer ceramic capacitor 200 has a high performance.

In the multilayer ceramic capacitors according to the first and second embodiments, the lengths of the inner electrodes of the upper and lower outermost layers are shortened so as to be about half the length of the multilayer ceramic capacitor element. Therefore, the discharge suppressing electrodes were not provided on both sides of the outer side of the capacitance forming electrode, but when the length of the internal electrodes of the upper and lower outermost layers was long,
It is preferable to provide a discharge suppressing electrode.

In the first and second embodiments, a ceramic material containing barium titanate as a main component and nickel as an internal electrode are used as the dielectric.
Similar effects can be obtained when other materials are used.

[0041]

As described above, according to the present invention, at least the internal electrodes except for the upper and lower outermost layers are composed of the capacitance forming electrode and the discharge suppressing electrode formed on the same surface, and the discharge suppressing electrode is used for forming the capacitance. A multilayer ceramic capacitor that is provided on both sides of the outer side of the electrode and is connected to the external electrode facing the external electrode connected to the capacitance forming electrode, thereby reducing the electric field concentration on the ceramic surface. It is possible to increase the voltage at which creeping discharge occurs on the side surface of the multilayer ceramic capacitor element, and thus provide a multilayer ceramic capacitor having a high withstand voltage.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the same.

FIG. 3 is a longitudinal sectional view of the same.

FIG. 4 is a cross-sectional view of a multilayer ceramic capacitor according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of the same.

FIG. 6 is a longitudinal sectional view of the same.

FIG. 7 is a cross-sectional view of a conventional multilayer ceramic capacitor.

FIG. 8 is a transverse sectional view of the same.

FIG. 9 is a longitudinal sectional view of the same.

[Explanation of symbols]

100, 200 Multilayer ceramic capacitor 110, 210 Dielectric ceramic 121-127, 221-227 Internal electrode 122a, 123a, 222a, 223a Capacitor forming electrode 122b, 123b, 222b, 223b Discharge suppressing electrode 130, 230 Multilayer ceramic capacitor element 140a, 140b, 240a, 240b External electrode

Claims (3)

[Claims] 1. A multilayer ceramic capacitor element comprising a dielectric ceramic and a plurality of internal electrodes opposed to each other, and a pair of external electrodes electrically connected to the internal electrodes, wherein at least the upper and lower outermost layers are excluded. The electrodes include a capacity forming electrode and a discharge suppressing electrode formed on the same surface, and the discharge suppressing electrode is provided on both sides of the outer side of the capacity forming electrode and connected to the capacity forming electrode. A multilayer ceramic capacitor configured to be connected to an external electrode facing the electrode. 2. The multilayer ceramic capacitor according to claim 1, wherein the discharge suppressing electrode has a length of 0.25 to 0.75 times the entire length of the multilayer ceramic capacitor element. 3. The multilayer ceramic capacitor according to claim 1, wherein the discharge suppressing electrode has such a shape that the distance from the side surface of the multilayer ceramic capacitor element increases as the distance from the connected external electrode increases.