JPH09260193A - Multilayer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer capacitor which can reduce its stray capacitance and can suppress crack generation. SOLUTION: The multilayer capacitor comprises an element body 23 of a rectangular parallelopiped shape made up of dielectrid layers and internal electrodes 22 alternately stacked and also comprises a pair of external electrodes 24 provided to both ends of the element body 23 as connected alternately in parallel to the internal electrodes 22. Parts (leads 22a of the internal electrodes) of the internal electrodes 22 connected to the pair of external electrodes 24 in the vicinity of their connections with the external electrodes 24 are gradually bent toward the direction of its center layer as it goes to the external electrodes 24. Further, in formation sites of the external electrodes 24, a peripheral edge parts 23a of the element body 23 are curved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multilayer capacitor.

[0002]

2. Description of the Related Art FIGS. 2 to 4 show a conventional multilayer capacitor. 2 is an exploded perspective view, FIG. 3 is a plan view, and FIG.
3 is a sectional view taken along line AA of FIG.

[0003] In the drawing, reference numeral 10 denotes a multilayer capacitor in which a dielectric body 13 formed by alternately laminating dielectric layers 11 and internal electrodes 12 and internal electrodes are alternately connected in parallel at both ends of the dielectric body 13. And a pair of external electrodes 14.

The internal electrode 12 is composed of an internal electrode piece 12a provided near the central region of the dielectric layer 11 and an internal electrode lead portion 12b provided along the external electrode 14 and connected to the external electrode 14. The internal electrode piece 12a is connected to the external electrode 14 via the internal electrode lead-out portion 12b.

[0005] The dielectric layer 11 is formed of a ceramic sintered body on a rectangular sheet, and the ceramic sintered body is formed of a dielectric ceramic material containing, for example, barium titanate as a main component. The internal electrode 12 is formed of a metal thin film obtained by sintering a metal paste. As the metal paste, for example, an electrode mainly containing a noble metal material such as Pd or Ag-Pd is used. The external electrode 14 is also formed of the same material as the internal electrode 12, and the surface is plated with solder to improve solder wettability.

[0006]

However, in the above-mentioned conventional multilayer capacitor, stray capacitance is often generated between the internal electrode 12 and the external electrode 14, and the capacitance value is often out of the standard range. Sometimes caused a decrease. Further, when forming the external electrode, the element body may be cracked due to stress.

In view of the above problems, it is an object of the present invention to provide a multilayer capacitor which has reduced stray capacitance and reduced cracking.

[0008]

In order to achieve the above object, the present invention provides a rectangular parallelepiped shaped element body in which dielectric layers and internal electrode layers are alternately laminated, and the element body. A multilayer capacitor composed of a pair of external electrodes in which the internal electrodes formed in the internal electrode layers are alternately connected in parallel at both ends of the internal electrode of each internal electrode connected to the pair of external electrodes. A multilayer capacitor is proposed in which at least one of the upper layer portion and the lower layer portion is bent in the direction of the central layer in the vicinity of the connection portion with the external electrode.

According to the multilayer capacitor, since the vicinity of the connection portion of the internal electrode with the external electrode is bent in the direction of the center layer, the distance between the internal electrode of the outermost layer and the external electrode is increased, and the internal electrode is The capacitance generated between the external electrode and the external electrode is reduced.

According to a second aspect of the present invention, in the multilayer capacitor according to the first aspect, the internal electrode connected to one external electrode is connected to the other external electrode in the vicinity of the connecting portion with the external electrode. We propose a multilayer capacitor that has a portion facing the tip of the internal electrode.

According to the multilayer capacitor, the internal electrode connected to one of the external electrodes has a portion in the vicinity of the connection portion with the external electrode, the portion facing the tip of the internal electrode connected to the other external electrode. However, the capacitance can be obtained at the facing portion.

A third aspect of the present invention proposes the multilayer capacitor according to the first or second aspect, wherein at least the peripheral portion of the external electrode forming portion of the element body is formed into a curved surface.

According to the multilayer capacitor, since the peripheral portion of the external electrode forming portion of the element body is formed into a curved surface, the stress generated when the external electrode is formed is relaxed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view showing a multilayer capacitor according to a first embodiment of the present invention. In the figure,
Reference numeral 20 denotes a multilayer capacitor, which includes a dielectric layer 21 and internal electrodes 22.
The element body 23 is formed by alternately stacking and, and a pair of external electrodes 24 that alternately connect the internal electrodes 22 in parallel at both ends of the element body 23.

The dielectric layer 21 is made of a rectangular sheet-shaped ceramic sintered body, and the sintered body is made of a dielectric ceramic material formed by firing a green sheet containing barium titanate as a main component, for example.

Each of the pair of internal electrodes 22 adjacent to each other with the dielectric layer 21 in between has a rectangular shape.
The long side of is substantially perpendicular to the external electrode 24. The width of each internal electrode 22 is formed to be equal.

On the other hand, in the vicinity of the connecting portion between the internal electrode 22 and the external electrode 24 (internal electrode lead-out portion 22a) in the upper layer portion,
As it approaches the outer electrode 24, it gradually bends toward the center layer. This is formed by applying pressure from the upper layer portion toward the lower layer portion during manufacturing.

Further, at the formation portion of the external electrode 24, the peripheral edge portion 23a of the element body 23 is formed into a curved surface.

The above-mentioned internal electrode 22 is made of a metal thin film obtained by sintering a thin film of a conductive paste, and as the conductive paste, for example, one containing palladium powder as a main component is used. The external electrode 24 is also made of the same material as the internal electrode 22, and the surface thereof is plated with solder to improve solder wettability.

This multilayer capacitor was manufactured as follows. First, an organic binder was added to the dielectric raw material powder.
% By weight, and further 50% by weight of water, and these were put into a ball mill and mixed well to prepare a slurry of a dielectric ceramic raw material.

Next, after putting this slurry in a vacuum defoamer to defoam it, put it in a reverse roll coater to form a thin film of this slurry on the polyester film,
This thin film is dried by heating to 100 ° C. on a polyester film, punched out, and 10 cm square, about 2 mm thick.
A green sheet of 0 μm was obtained.

On the other hand, 10 g of palladium powder having an average particle diameter of 1.5 μm and 0.9 g of ethyl cellulose dissolved in 9.1 g of butyl carbitol were placed in a stirrer.
By stirring for 10 hours, a conductive paste for an internal electrode was obtained.

After this, the above-mentioned internal electrode pattern
Using each of the screens having zero, a pattern of the internal electrode made of the conductive paste was printed on one surface of the green sheet, and dried.

Next, a plurality of green sheets were laminated with the printed surface facing upward, and further, unprinted green sheets were laminated on the upper and lower surfaces of this laminate. Then
This laminate was pressed at a temperature of about 50 ° C. by applying a pressure of about 40 tons in the thickness direction. Thereafter, the laminate was cut into a lattice to obtain about 50 laminated chips.

Next, this laminated chip is put in a furnace capable of performing atmospheric firing, heated to 600 ° C. in the atmosphere to fire the organic binder, and then the atmosphere of the oven is set to the atmospheric atmosphere to heat the laminated chip. The temperature was maintained at 600 ° C. to 1150 ° C. (maximum temperature), which is the firing temperature, for 3 hours. After this, 1
The temperature was lowered to 600 ° C. at a rate of 00 ° C./hr and cooled to room temperature to obtain a sintered body chip.

Next, a conductive paste composed of silver, glass frit and vehicle is applied to the side surface of the sintered body chip where the internal electrodes are exposed and dried, and this is dried in air at 800 ° C.
Baking at a temperature of 15 minutes to form a silver electrode layer, further depositing copper thereon by electroless plating, and providing a Pb-Sn solder layer thereon by electroplating to form a pair of external electrodes did. As a result, a multilayer capacitor was obtained.

According to the multilayer capacitor 20 having the above-described structure, since the internal electrode lead-out portion 22a is bent toward the center layer, the distance L between the uppermost internal electrode lead-out portion 22a and the external electrode 24 is reduced. Since the stray capacitance spreading between the internal electrode lead-out portion 22a and the external electrode 24 is reduced, the capacitance value can be set within the standard range, and the yield can be improved.

Further, as shown in FIG. 5, the internal electrode 22 connected to one external electrode 24 faces the tip of the internal electrode 22 connected to the other external electrode 24 at the internal electrode lead-out portion 22a. Since the capacitor C has a portion to be provided, the electrostatic capacitance C can be obtained also in this facing portion, so that a multilayer capacitor having an equivalent capacitance can be formed smaller than the conventional one.

Further, since the internal electrode and the external electrode face each other on the inclined surface, it is difficult for cracks to occur at the boundary surface between the external electrode and the ceramic.

Further, since the peripheral edge portion 23a of the external electrode forming portion of the element body 23 is formed in a curved shape, the stress generated in the element body 23 at the time of forming the external electrode is relieved.
No structural defects such as cracks and delamination occur. Thereby, the yield can be further improved.

Next, a second embodiment of the present invention will be described. FIG. 6 is a side sectional view showing the multilayer capacitor of the second embodiment. In the figure, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. Further, the difference between the first embodiment and the second embodiment is that in the lower layer portion in addition to the upper layer portion, in the vicinity of the connection portion between the internal electrode 22 and the external electrode 24 (internal electrode lead-out portion 22a).
However, it is configured such that it gradually bends toward the center layer as it approaches the external electrode 24. This is formed by applying pressure from the upper layer portion and the lower layer portion toward the center layer using a hydrostatic press or the like during manufacturing.

The multilayer capacitor 20 of this second embodiment
According to the above, the internal electrode lead-out portions 2 in the upper layer portion and the lower layer portion are
Since 2a is bent in the direction of the central layer, the distance between the inner electrode lead-out portions 22a and the outer electrodes 24 of the uppermost layer and the lowermost layer is widened, and the floating that occurs between the inner electrode lead-out portions 22a and the outer electrode 24. Since the capacity is further reduced, the manufacturing accuracy of the capacity value can be further improved, and the yield can be further improved.

These embodiments are merely examples, and the present invention is not limited to these. For example, the internal electrode 22
The tip portion of may be bent. In this case, it is desirable that the deflection be provided in the innermost electrode of the outermost layer.

[0034]

As described above, according to claim 1 of the present invention, the vicinity of the connection portion of the internal electrode with the external electrode is
Since it is bent in the direction of the central layer, the distance between the inner and outer electrodes of the outermost layer is widened, and the electrostatic capacitance generated between the inner and outer electrodes is reduced. It can be set within the range, and the yield can be improved.

According to claim 2, in addition to the above effects, the internal electrode connected to one external electrode is connected to the other external electrode in the vicinity of the connection portion with the external electrode. Since it has a portion facing the tip of the electrode and the capacitance can be obtained at the facing portion, a multilayer capacitor having an equivalent capacitance can be formed smaller than the conventional one.

According to the third aspect, in addition to the above effects, since the peripheral portion of the external electrode forming portion of the element body is formed into a curved surface, the stress generated when the external electrode is formed is relaxed. No crack is generated in the element body. Thereby, the yield can be further improved.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a multilayer capacitor according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a conventional multilayer capacitor.

FIG. 3 is a cross-sectional plan view showing a conventional multilayer capacitor.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a diagram showing a main part of the multilayer capacitor according to the first embodiment of the present invention.

FIG. 6 is a side sectional view showing a multilayer capacitor according to a second embodiment of the present invention.

[Explanation of symbols]

20 ... Multilayer capacitor, 21 ... Dielectric layer, 22 ... Internal electrode, 22a ... Internal electrode lead-out part, 23 ... Element body, 23a ... Peripheral part, 24 ... External electrode.

Claims (3)

[Claims] 1. A rectangular parallelepiped element body in which dielectric layers and internal electrode layers are alternately laminated, and internal electrodes formed on the internal electrode layers at both ends of the element body are alternately connected in parallel. At least one of the upper layer portion or the lower layer portion of each internal electrode connected to the pair of external electrodes, in the vicinity of the connection portion with the external electrode, A multilayer capacitor characterized by being bent toward the center layer. 2. The internal electrode connected to one of the external electrodes has a portion near the tip of the internal electrode connected to the other external electrode in the vicinity of the connection portion with the external electrode. The multilayer capacitor according to claim 1, which is characterized in that. 3. The multilayer capacitor according to claim 1, wherein at least a peripheral portion of the external electrode forming portion of the element body is formed into a curved surface.