JPH04286107A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a laminated ceramic capacitor capable of adjusting its capacity without an outside shape in terms of a laminated ceramic capacitor used for various electronic equipment. CONSTITUTION:Out of internal electrodes 5, two and more layers on the upper side are formed as a capacity adjustable electrode 5a in such a fashion that they may be longer or wider than the other layers. In other words, the capacity of the internal electrodes 5 in the stage where no capacity adjustable electrode 5a is installed yet, is designed in such a fashion that its capacity may be slightly smaller that a target capacity value. The capacity under this condition is measured where the capacity, if insufficient, can be controlled by the capacity adjustable electrodes 5a of two layers and more.

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 used in various electronic devices.

0002

2. Description of the Related Art Multilayer ceramic capacitors are small in size and have a large capacity, so they are used in various electronic devices such as electronic tuners, video tape recorders, and video cameras, and their demand has been rapidly increasing recently.

The structure of a conventional multilayer ceramic capacitor is, as shown in FIGS. 6 and 7, in which a plurality of dielectric ceramics 1 and internal electrodes 2 reaching different ends are alternately laminated. It consists of external electrodes 3 provided at both ends to electrically connect. FIG. 6 is a sectional view in the length direction, and FIG. 7 is a sectional view in the width direction. The capacitance (hereinafter referred to as capacitance) of such a multilayer ceramic capacitor is determined by the dielectric constant of the dielectric ceramic 1, the thickness of the dielectric ceramic 1 between the opposing internal electrodes 2, and the electrodes of the opposing internal electrodes 2. It is determined by the area of the overlapping part and the number of layers. This capacity was determined at the time when the dielectric ceramic 1 and the internal electrode 2 were sintered together, and it was impossible to adjust the capacity thereafter.

As a method for adjusting the capacitance, a structure has been proposed in which the capacitance is designed to be slightly smaller than the target value, and after sintering, an electrode for capacitance adjustment with a variable area is provided on the surface of the laminate (for example, , Utility Model Application Publication No. 49-70448, Utility Model Application Publication No. 5
3-23535, Japanese Utility Model Application Publication No. 55-32027).

[0005]

[Problems to be Solved by the Invention] However, in the above-described structure, considering the actual usage conditions of the multilayer ceramic capacitor, it is necessary to cover the capacitance adjusting electrode on the surface of the multilayer body with an insulating material.

[0006] As described above, the conventionally proposed capacitance adjustment methods change the external shape of the multilayer ceramic capacitor, which poses problems in terms of mounting.

[0007] The present invention has been made to solve these problems, and it is an object of the present invention to provide a multilayer ceramic capacitor whose capacity can be adjusted without changing its external shape.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the multilayer ceramic capacitor of the present invention has a plurality of dielectric ceramics and internal electrodes that alternately reach different ends, and has the above-described structure at both ends. It is equipped with an external electrode that electrically connects the internal electrodes, and the upper two of the internal electrodes are provided with an external electrode that electrically connects the internal electrodes.
At least one layer is shorter in length or narrower in width than the other layers as a capacitance adjusting electrode.

[0009]

[Operation] According to the configuration of the present invention, it is possible to recognize the capacitance error at the design stage and perform the design. In other words,
The capacitance without the capacitance adjustment electrode of the internal electrodes is designed to be slightly smaller than the desired capacitance value, the actual capacitance value in this state is measured, and the insufficient capacitance is used to adjust the capacitance of several layers. This is because adjustment is possible by providing electrodes. Therefore, the target capacitance value can be easily obtained without changing the external shape.

0010

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal cross-sectional view of a multilayer ceramic capacitor according to the present invention, and FIG. 2 is a cross-sectional view of the same in the width direction. In FIGS. 1 and 2, 4 is a dielectric ceramic, and 5 is an internal electrode disposed between the dielectric ceramics 4. The internal electrodes 5 alternately reach different ends. In addition, 5a is an internal electrode on the upper layer side,
It functions as a capacitance adjusting electrode, and is provided with two or more layers. The internal electrode 5a on the upper layer side serving as the capacitance adjusting electrode is at least shorter in length or narrower in width than the internal electrodes 5 in other layers. Reference numeral 6 denotes external electrodes provided at both ends of a laminate in which the dielectric ceramic 4 and internal electrodes 5, 5a are alternately stacked;
The internal electrodes 5 and 5a are electrically connected.

Next, the capacity adjusting means according to the present invention will be explained with reference to specific examples. First, the capacity standard is 270±1
To manufacture a 3.5 pF multilayer ceramic capacitor, a 25 μm thick dielectric ceramic sheet is
Cut this sheet into a shape of 0 mm x width 140 mm, and
Three sheets are laminated and crimped, and on the topmost sheet, the internal electrode has a width of 1.0 mm and a length of 3.92 mm, and the print interval is 0.5 mm in the width direction and 0.56 mm in the length direction.
Using the printing pattern shown in FIG. 3, one layer of internal electrodes made of palladium paste was printed. In Figure 3, 5
7 indicates an internal electrode, 7 indicates a dielectric ceramic sheet, and broken line 8 indicates a cutting position. Also, the cutting pitch is 2.24 in the length direction.
mm, and the width direction is 1.50 mm. Next, one dielectric ceramic sheet with a thickness of 25 μm is laminated and pressed onto the 13-layer laminate on which the internal electrodes 5 are printed on top, and the printed pattern shown in FIG. 3 is printed on the sheet. 1 in direction
．． The internal electrodes 5 were printed with a 50 mm shift, and this operation was repeated four times, and the internal electrodes 5 were shifted in the length direction so as to reach different ends alternately, so that five layers were arranged in parallel. Thirty blocks of this laminate were produced, and in order to examine the capacity in this state, a layer of 25 mm thick was similarly placed on one block of the laminate.
18 μm dielectric ceramic sheets were laminated and pressure-bonded, the main pressure was applied to the total thickness of this laminate of 900 μm, and the sheet was cut into 2.24 mm long x 1.57 mm wide at a predetermined position.
It was fired at 50°C. Next, both ends were ground with abrasive paper, and an indium-gallium electrode was applied to form the external electrode, increasing the capacitance to 5.
Measured. The average value of the capacity at this time is 226.35p
It was F.

Based on this capacitance, one dielectric ceramic sheet having a thickness of 25 μm was laminated and pressure-bonded to the other 29 block stacks, and the capacitance was adjusted using a printed pattern as shown in FIG. Ta. In FIG. 4, 5a is an internal electrode for capacity adjustment. In this capacity adjustment, the area of the electrode overlap part of the first layer for capacity adjustment is 8% (that is, about 67% in the length direction) of the total electrode overlap area of the lower internal electrode 5 shown in FIG. 5(a). , about 75% in the width direction) was printed as shown in FIG. 3(b). Furthermore, the printing pattern in Figure 4 was added 1.50m in the width direction.
Fig. 5 shows the internal electrode 5a as a capacitance adjustment electrode shifted by
As shown in (c), the printing operation is repeated three times (at this time, the internal electrodes 5a are also shifted in the length direction so as to reach different ends alternately), and 4 of the internal electrodes 5a are used as capacitance adjustment electrodes. The total area of the overlapping parts of the layers is 20% of the total area of the overlapping parts of the lower internal electrodes 5. Next, a dielectric ceramic sheet with a thickness of 25 μm was placed on the laminate.
4 sheets were laminated and crimped, and the main pressure was applied to the total thickness of this laminate of 900 μm, and the length was 2.24 mm x width 1.57 mm at the predetermined position.
It was cut into mm pieces and fired at 1350°C. Next, both ends were shaved, silver paste was applied, and external electrodes were baked at 850°C. As a result of measuring the capacity of 5 pieces, the average value was 27
The target capacitance value was 5.83 pF.

As described above, FIG. 5 shows the shape of the overlapping portion of the internal electrodes 5 and 5a, in which (a) shows the overlapped state of the lower internal electrode 5, and (b) shows the overlap between the lower internal electrode 5 and the capacitance. Electrode overlap state with internal electrode 5a as an electrode for adjustment, (c) internal electrode 5a as an electrode for capacity adjustment
FIG. The dotted line indicates the shape of the lower internal electrode.

In this embodiment, the total area of the overlapping portion of the four layers due to the internal electrode 5a serving as the capacitance adjusting electrode is 20% of the total area of the overlapping portion of the lower internal electrode 5. By changing the shape of the internal electrode 5a as a capacitance adjusting electrode and the number of laminated layers, it is possible to adjust the capacitance in a wide range. Here, the internal electrode 5a serving as a capacitance adjusting electrode can achieve its original purpose if two or more layers are shorter in length or narrower than at least other layers for capacitance adjustment. Further, although this embodiment shows a case in which the capacitance forming portion formed by the lower internal electrode 5 has five layers, it is also possible to have one or more layers. Furthermore, in this embodiment, dielectric ceramic sheets having the same thickness were used between the opposing internal electrodes 5 and 5a, but even if sheets with different thicknesses are used, the overlapping area of the internal electrodes 5a as capacitance adjusting electrodes and the lamination Needless to say, the capacity can be adjusted by changing the number.

[0015]

[Effects of the Invention] As described above, according to the configuration of the present invention,
Capacity can be adjusted without changing the external shape. By recognizing capacity errors at the design stage,
The ability to adjust the capacitance over a wide range even when a large error occurs has great practical value in manufacturing multilayer ceramic capacitors.

[Brief explanation of the drawing]

[Fig. 1] A longitudinal cross-sectional view of a multilayer ceramic capacitor in an embodiment of the present invention.

[Figure 2] Cross-sectional view in the width direction of the same example

[Fig. 3] A diagram illustrating the printing pattern of the lower internal electrode in the same example.

FIG. 4 is a diagram illustrating the printing pattern of internal electrodes as capacitance adjustment electrodes in the same example.

FIG. 5(a) illustrates the overlapping state of the lower internal electrodes in one embodiment; FIG. 5(b) illustrates the overlapping state of the lower internal electrodes and the internal electrodes serving as capacitance adjustment electrodes; Figure (c) is also a diagram explaining the overlapping state of internal electrodes as capacitance adjustment electrodes.

[Figure 6] Longitudinal cross-sectional view of a conventional multilayer ceramic capacitor

[Figure 7] Similarly cross-sectional view in the width direction

[Explanation of symbols]

4 Dielectric ceramic 5 Internal electrode 5a Internal electrode 6 as a capacitance adjustment electrode External electrode 7 Dielectric ceramic sheet 8 Cutting position

Claims (1)

[Claims] Claim 1: A plurality of dielectric ceramics and internal electrodes reaching different ends are alternately laminated, and external electrodes are provided at both ends to electrically connect the internal electrodes, and the internal electrodes are connected to each other. A multilayer ceramic capacitor in which two or more of the upper layers serve as capacitance adjustment electrodes and are at least shorter in length or narrower in width than other layers.