JPH11251174A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a low cost of an inner electrode layer by reducing raw material mixing/adjustment. storage and management of a material composition of a dielectric layer by incorporating an Ag-based conductor material and a dielectric material of barium titanate zirconate which is different from the dielectric layer is Ti/Zr ratio. SOLUTION: A lamination body 1 is formed by laminating a dielectric layer 2 and an inner electrode layer 3 alternately and backing them integrally. The inner electrode layer 3 is led out to different edge faces of the lamination body 1 wherein inner electrode layers 3a, 3b which are arranged between the dielectric layers 2 and adjacent each other are opposite to each other. Here, a dielectric material whose composition is the same or similar composition as a dielectric material constituting the dielectric layer 2 is added to the inner electrode layers 3a, 3b arranged between the dielectric layers 2 excepting an Ag-based conductor. The dielectric material is formed of the same Ba(Zr, Ti)O3 as a dielectric material constituting the dielectric layer 2 and Ba(Zr, Ti)O3 which is different in Ti/Zr ratio (mole ratio) therefrom.

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.

[0002]

2. Description of the Related Art A multilayer ceramic capacitor forms a sintered laminate (hereinafter referred to as a laminate) in which dielectric layers made of a dielectric material and internal electrode layers are alternately laminated, and a pair of end faces of the laminate is formed. And formed on external electrodes.

[0003] The thickness, material and shape of the internal electrodes of the dielectric layer are designed to predetermined values in accordance with the specifications satisfying the rated voltage, electrical characteristics, temperature characteristics, reliability and the like of the multilayer ceramic capacitor. I have.

In particular, additives such as shifters and depressors are added to a dielectric material for a high dielectric constant material having a temperature characteristic, and the ratio of A site and B site of the dielectric material (A / B) is added.
Ratio) is changed to obtain a desired temperature characteristic.

[0005]

In the prior art multilayer ceramic capacitor, in order to satisfy a desired temperature characteristic, there are many restrictions on the thickness, the number of layers, and the shape of the dielectric layer.
As a result, it was necessary to change the composition of the dielectric material.

Therefore, according to the use of the multilayer ceramic capacitor and the demand from the user, a dielectric sheet for forming an extremely large number of dielectric layers is prepared in the manufacturing process.
In accordance with these applications and the needs of the user, the sheet to be used in the production had to be selected from a great variety of dielectric sheets.

That is, there has been a problem that the cost is extremely increased, including the preparation and adjustment of raw materials for the dielectric material, storage, and management.

The present invention has been devised in view of the above-mentioned problems, and has as its object to reduce the raw material preparation / adjustment, storage, management, etc. of the material composition of the dielectric layer, thereby achieving low cost lamination. A ceramic capacitor is provided.

[0009]

According to the present invention, there is provided a multilayer ceramic capacitor comprising a plurality of alternately laminated internal electrode layers and dielectric layers containing Ba (Ti, Zr) O ₃ , wherein the internal electrode layers are made of Ag. -Based conductor material and Ti / Z of the dielectric layer
and a dielectric material of Ba (Ti, Zr) O _{3 having} a different r ratio.

[0010] More specifically, Ba (Ti, Zr) O ₃ is used as a dielectric material constituting the multilayer ceramic capacitor.
The Ag-based internal electrode material fired integrally with the dielectric layer includes an Ag-based metal component internal electrode material, Ti / Z
10 wt% of a dielectric material having an r ratio of 85/15 to 80/20
% Or less.

[0011]

The multilayer ceramic capacitor of the present invention has a Ba
The dielectric layer made of (Ti, Zr) O ₃ and the internal electrode layer are integrally fired. Then, in addition to the Ag-based metal component, Ba (Ti, Zr) O _{3 of} the same material constituting the dielectric layer and having a different composition (Ti / Zr ratio) is added to the internal electrode layer as a solid component. ing.

Therefore, Ba (Ti, Z) added to the internal electrode layer by integrally firing the dielectric layer and the internal electrode layer.
r) Part of O ₃ diffuses to the dielectric layer side.

As a result, Ba (T
i, Zr) O ₃ allows the initial Ti / Z on the dielectric layer side
By changing the r ratio, the initial characteristics of the dielectric layer change.

That is, predetermined characteristics of the dielectric layer, particularly, temperature characteristics can be improved by standardizing the composition of the dielectric layer of the multilayer ceramic capacitor and changing the material constituting the internal electrode layer. .

Therefore, the preparation, adjustment, storage, and management of the raw materials of the dielectric layer are greatly simplified.

In the present invention, preparation, adjustment, preservation, management, etc. of the internal electrode material are forced, but the adjustment of the dielectric material to be added is not performed because the internal electrode layer is formed. Since it is only performed when the conductive paste to be printed on the dielectric layer in the state is homogeneously mixed, the manufacturing process is simplified by several steps compared to the adjustment of the composition of the dielectric layer.

As a prior art, the addition of a dielectric material to an internal electrode has been proposed in Japanese Patent Application Laid-Open Nos. 57-30308, 3-77647, 3-285314, etc. All add a dielectric material having the same composition as the dielectric layer in the internal electrode layer. These are used to approximate the sintering behavior of the dielectric layer and the internal electrode layer, prevent separation at the interface between them, and increase the density of the internal electrode layer. It does not improve the characteristics, especially the temperature characteristics, by adjusting the ratio of the body composition.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multilayer ceramic capacitor according to the present invention will be described below with reference to the drawings.

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

In FIG. 1, 1 is a laminate, 2 is a dielectric layer constituting the laminate 1, 3a and 3b are internal electrode layers constituting the laminate 1 (3a and 3b are combined together). 3
, 4 and 5 are external electrodes.

The laminate 1 is formed by alternately laminating dielectric layers 2 and internal electrode layers 3 and integrally firing them.

The dielectric layer 2 has a Y5V characteristic (temperature characteristic: +
(22 to -85%), and is made of barium titanate, barium zirconate titanate, or the like, and has a thickness of 15 μm after firing.

The internal electrode layer 3 is disposed between the dielectric layers 2 and is led to different end faces of the laminated body 1 in which the adjacent internal electrode layers 3a and 3b face each other.

The internal electrode layer 3 is made of an Ag-based conductor such as Ag
It is composed of an Ag-Pd alloy of / Pd = 30/70, and a dielectric material that is the same as or similar to the components of the dielectric layer 2.

The laminated body 1 in which the dielectric layers 2 and the internal electrode layers 3 are alternately laminated and fired has, for example, a length of 2.0 mm, a width of 1.25 mm, and a thickness of 1.00 mm. The number of dielectric layers is 20.

On the opposite end faces of the laminate 1,
External terminal electrodes 4 and 5 made of an Ag base conductor film, a Ni plating layer, and a metal surface plating layer containing Sn are formed. The external terminal electrode 4 is electrically connected to the internal electrode layer 3a extending to one end face of the laminate 1, and the external terminal electrode 5
It is electrically connected to the internal electrode layer 3b extending to the other end face of the multilayer body 1.

Next, a brief description will be given of a method of manufacturing the above-mentioned multilayer ceramic capacitor. First, a dielectric green sheet to be the dielectric layer 2 is formed. Specifically, a slurry of a dielectric material having a predetermined composition is formed, a tape is formed by a doctor blade method or the like, and then cut into a predetermined size to form a dielectric green sheet.

Next, a conductive paste to be the internal electrode layer 3 is prepared. Specifically, Ag-Pd alloy powder, a dielectric material powder having the same composition as the dielectric material constituting the dielectric layer, a different composition ratio, a dielectric material powder having a similar composition, and an organic vehicle are homogeneously mixed. Formed.

Next, on the above-mentioned dielectric green sheet,
A conductive film to be the internal electrode layer 3 is formed by printing the above-mentioned conductive paste on each element region.

Next, a plurality of dielectric green sheets on which a conductor film is formed are laminated and pressed, and cut in accordance with the size of the element to form an unfired laminated body.

Next, the unfired laminate is fired at a peak temperature of 1100 to 1350 ° C. in an oxidizing atmosphere.
Thereby, the internal electrode layer 3 is provided between the fired dielectric layers 2.
Will be arranged.

Thereafter, the baked laminate 1 is subjected to barrel polishing or the like to completely expose the exposed portion of the internal electrode layer 3, and external terminal electrodes 4 and 5 are formed on the end surfaces.

A feature of the present invention is that the internal electrode layers 3a and 3b disposed between the respective layers of the dielectric layer 2 have the same composition as the dielectric material constituting the dielectric layer 2 in addition to the Ag-based conductor. That is, a dielectric material having a similar composition is added.

As the dielectric material, Ba (Zr, T
i) O _3, such as substantially identical to the dielectric material constituting the dielectric layer 2 Ba of (Zr, Ti) a O _3, Ti / Zr
By controlling the ratio (molar ratio) to a predetermined ratio, Ba (Zr, Ti)
A predetermined amount of a composite oxide powder (0.5 to 1.0 μm) composed of O ₃ is added.

The present inventor examined the characteristics of the dielectric layer 2 by changing the amount of the same additive as the dielectric material constituting the dielectric layer 2.
First, barium zirconate titanate (Ti / Zr ratio = 75.5 / 24.5) is used as the dielectric layer 2, and a dielectric made of Ba (Zr, Ti) O ₃ added to the internal electrode layer 3 is used. The characteristics were examined by changing the amount of addition of the material (Ti / Zr ratio = 80/20). The results are shown in Table 1. In the table, the capacity variation is a percentage using the average of the number of samples as the denominator and the standard deviation 分子 as the numerator, and the temperature characteristic is a rate of change based on the capacity at 25 ° C. This is the value at the Curie point.

[0036]

[Table 1]

As shown in Table 1, for a multilayer ceramic capacitor in which Ba (Ti, Zr) O ₃ was not added to the conductive paste serving as the internal electrode layer 3 which is the sample 1, as shown in samples 2 to 4, It can be understood that, even when added within 10% by weight of the components, each item of capacitance, dielectric loss, capacitance variation, and MLD (application amount of conductive paste) is comparable to that of sample No. 1. .

As for the temperature characteristic, the Curie point can be changed particularly at a value satisfying the Y5V characteristic. This means that Ba (T
It shows that the capacity-temperature characteristics can be arbitrarily adjusted by controlling the amount of (i, Zr) O ₃ added.

However, as shown in Sample Nos. 5 and 6, the amount of Ba (Ti, Zr) O ₃ added to the internal electrode layer 3 was 1
If the content exceeds 0% by weight, a capacity variation due to a capacity loss in the internal electrode layer 3 occurs. This is because Ba (Ti, Z
r) It is considered that the addition of O ₃ lowers the conductivity of the internal electrode.

The MLD also tends to decrease. This is because if the amount of addition is increased, abnormal grain growth of the internal electrode layer is suppressed, and the generation of vacancies is reduced,
This is because the conductivity of the internal electrode layer 3 does not decrease.

Therefore, the dielectric material added to the internal electrode layer for adjusting the characteristics of the multilayer ceramic capacitor, particularly the temperature characteristics, is less than the metal component of the internal electrode.
It is important that the content be 10 to 10% by weight (including 10% by weight excluding 0).

Next, the addition amount of Ba (Ti, Zr) O ₃ was fixed at 10 wt%, and the composition of the dielectric material added to the internal electrode layer 3 was examined. That is, the Ti / Zr ratio of Ba (Ti, Zr) O ₃ constituting the dielectric layer 2 is 87.5.
/12.5.

When the Ti / Zr ratio of the dielectric material added to the internal electrode layer 3 disposed between the dielectric layers 2 is 95
/ 5, 90/10, 85/15, 80/20, 70/3
It was changed to 0.

The results are shown in Table 2.

[0045]

[Table 2]

As can be understood from Table 2, the capacitance and the dielectric loss tend to increase as the ratio of Zr in the added dielectric material decreases.

However, Zr of the dielectric material which is extremely added
Is large, for example, in the case of Sample Nos. 7 and 8, the temperature characteristic due to the Curie point temperature is deteriorated, and the Y5V characteristic is not satisfied. If the proportion of Zr in the dielectric material to be added is extremely reduced, the temperature characteristics at + 85 ° C. are deteriorated and the Y5V characteristics are not satisfied, for example, as in Sample No. 11.

As described above, the value of the Ti / Zr ratio is set in an appropriate range, for example, in the case of the above-described dielectric layer 2, Ti / Zr
It is desirable that the ratio be in the range of 85/15 to 80/20.

This tendency is due to the fact that the component of the dielectric material added to the internal electrode layer is deposited on the dielectric layer side by integral sintering of the conductor film serving as the internal electrode layer and the sheet serving as the dielectric layer. This is caused by diffusion.

Therefore, it is possible to reduce the management of the characteristics of the multilayer ceramic capacitor on the sheet side of the dielectric layer formed by complicated steps such as formation of a slurry and formation of a sheet. That is, the adjustment of the characteristics can be replaced by the adjustment of the dielectric material on the side of the conductive paste that becomes the internal electrode layer 3 which is relatively easy to prepare.

That is, when the conductive paste is prepared, the characteristics of the multilayer ceramic capacitor can be easily adjusted by controlling the dielectric material to be added and the composition ratio thereof according to the characteristics to be adjusted.

[0052]

As described above, in the present invention, since the dielectric material that can diffuse into the dielectric layer is added to the internal electrode layer, the characteristics of the multilayer ceramic capacitor are adjusted by the amount and the added component. be able to.

In adjusting the characteristics of the multilayer ceramic capacitor, the very difficult control of selecting the dielectric material of the dielectric layer is eliminated, the versatility of the dielectric layer is improved, the control of the manufacturing process is simplified, and A low cost multilayer ceramic capacitor can be achieved.

Further, by adding a dielectric material to the conductive paste, the internal electrode coating amount (MLD) can be reduced.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Dielectric layer 3, 3a, 3b ... Internal electrode layer 4, 5 ...... External terminal electrode

Claims (1)

[Claims] 1. An internal electrode layer and Ba (Ti, Zr) O ₃
And a dielectric layer including a plurality of alternately stacked dielectric layers, wherein the internal electrode layer includes an Ag-based conductor material and a T of the dielectric layer.
A multilayer ceramic capacitor comprising a dielectric material of Ba (Ti, Zr) O ₃ different from the i / Zr ratio.