JP3481740B2 - Multilayer ceramic capacitor for temperature compensation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-compensating monolithic ceramic capacitor, and more particularly to a temperature-compensating monolithic ceramic capacitor whose temperature coefficient is easily corrected.

[0002]

2. Description of the Related Art A monolithic ceramic capacitor has a structure in which a plurality of green sheets of a dielectric material whose surface is coated with a conductive paste are laminated and integrally fired to form an internal electrode between dielectric layers to form a capacitor body. The structure is such that a pair of external electrodes is formed on the side surface of the main body and the internal electrodes are alternately connected in parallel, and the external electrodes are directly soldered to the circuit board for mounting.

Such monolithic ceramic capacitors are roughly classified into two types according to their characteristics, and those used in resonance circuits of electronic equipment and circuits generally having high Q and stability of capacitance with respect to temperature are important. , Called a temperature compensation multilayer ceramic capacitor.

The temperature compensation monolithic ceramic capacitor is
The capacitance changes linearly with temperature and has reproducibility, and is widely used in various electronic circuits and electronic devices as a small-sized and large-capacity capacitor.

The rate of change of capacitance with respect to the temperature of the temperature-compensated multilayer ceramic capacitor, that is, the temperature coefficient, differs mainly depending on the characteristics of the dielectric material used for the dielectric layer. It was done like.

First, in the case of correcting the temperature coefficient within a relatively large range of ± 20 ppm / ° C. or more, a method of changing the composition ratio of the dielectric material used for the dielectric layer has been adopted.

When the temperature coefficient is corrected within a relatively small range of ± 20 ppm / ° C., the composition ratio of the dielectric material used is not changed, and the firing conditions for firing the capacitor body are changed. The method was adopted.

[0008]

However, in the above correction method, the following problems are likely to occur.

That is, when the composition ratio of the dielectric material is changed in order to correct the temperature coefficient, there is a problem that the green sheet of the dielectric material having a different temperature coefficient cannot be adjusted and recycled. , There was a problem that such green sheets had to be discarded.

The temperature coefficient is set to the N (negative) side or P
By changing the composition ratio of the dielectric material when adjusting to the (positive) side, it is inevitable to change the firing conditions, which changes the dielectric constant of the dielectric material and changes the capacitance when a capacitor is formed. There is also a problem that it tends to occur.

Further, by changing the composition ratio of the dielectric material and the firing conditions, it is easy to cause confusion in the manufacturing process,
This also causes a problem that the same defects as described above are likely to occur.

On the other hand, for example, in Japanese Unexamined Patent Publication No. 5-36569, a plurality of dielectric porcelain green sheets are used as a method for easily forming a monolithic ceramic capacitor having a small temperature change rate (temperature coefficient) of capacitance. Part or all of the plurality of conductive paste coating layers disposed between the layers,
It is disclosed that a substance for changing the Curie point of the dielectric ceramic layer is mixed.

According to this, one or a plurality of rare earth elements such as CeO ₂ (cerium oxide) is used as a substance for changing the Curie point for the dielectric porcelain layer composed mainly of barium titanate porcelain. By adding an oxide to the internal electrode layer, the Curie point of the dielectric porcelain layer shifts to the negative side or the positive side, so that the content or type of the substance for changing the Curie point may be different,
Desired temperature characteristics can be obtained by forming dielectric ceramic layers with different Curie points by combining different dielectric ceramic materials, making it easy to obtain multilayer ceramic capacitors with a small temperature coefficient of capacitance. It can be formed.

However, even with such a method, there is a problem that it is difficult to correct the temperature coefficient by adding such a rare earth oxide in the temperature compensating material which does not cause the Curie point variation.

The present invention has been completed in view of the above circumstances to solve the problems, and an object thereof is to easily correct the temperature coefficient without changing the composition ratio of the dielectric material or the firing conditions. An object of the present invention is to provide a temperature-compensated multilayer ceramic capacitor.

Another object of the present invention is to make it possible to easily correct the temperature coefficient without changing the composition ratio of the dielectric material or the firing conditions, and to use the green material of the dielectric material, which has been unavoidable until now. It is an object of the present invention to provide a temperature-compensated monolithic ceramic capacitor that can reuse a sheet and does not cause various defects because it does not require changing firing conditions.

[0017]

In the laminated ceramic capacitor for temperature compensation according to the present invention, one dielectric material is used between a plurality of dielectric layers for 100% by volume of metal powder.
What is claimed is: 1. A multilayer ceramic capacitor for temperature compensation, comprising a capacitor main body formed by alternately laminating a plurality of internal electrode layers containing 3% by volume or less (excluding 0% by volume). The composition or the content of the dielectric material to be contained is different for each internal electrode layer.

Further, the temperature compensating laminated ceramic capacitor of the present invention is characterized in that the dielectric material contained in the metal powder has a spherical shape.

[0019]

According to the laminated ceramic capacitor for temperature compensation of the present invention, the dielectric material contained in the internal electrode portion is formed by including a predetermined amount of the dielectric material forming the dielectric layer in the internal electrode layer. The material is combined with the original dielectric material (green sheet part) at the time of sintering, and as a result, the temperature coefficient of the capacitor is corrected without changing the composition ratio of the dielectric material of the dielectric layer or the firing conditions of the capacitor body. can do.

At this time, the degree of correction of the temperature coefficient can be adjusted on the P side and the N side by selecting the dielectric material to be used or the addition amount thereof, and thereby, for temperature compensation having a desired temperature coefficient. A monolithic ceramic capacitor can be easily obtained.

Further, according to the temperature-compensated multilayer ceramic capacitor of the present invention, a predetermined amount of the same dielectric material as the dielectric layer is contained in the conductive paste layer to adjust the dielectric material and the addition amount thereof. It is possible to obtain a temperature-compensating multilayer ceramic capacitor in which the temperature coefficient is corrected to a desired value without changing the composition ratio of the dielectric layer or the firing conditions.

Therefore, according to the temperature-compensated monolithic ceramic capacitor of the present invention, it is not necessary to change the composition ratio of the dielectric material in order to correct the temperature coefficient of the capacitor. The green sheets that had to be disposed of can now be reused. Furthermore, since it is not necessary to change the firing conditions, various defects and confusion in the manufacturing process associated with such changes will not occur.

The temperature compensating multilayer ceramic capacitor of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following examples, and various modifications and improvements may be added without departing from the spirit of the present invention.

FIG. 1 is a sectional view showing the structure of a temperature compensating multilayer ceramic capacitor of the present invention. The multilayer ceramic capacitor 1 for temperature compensation according to the present invention includes a plurality of dielectric layers 2.
A plurality of internal electrode layers 3 containing the dielectric material of the dielectric layer 2 are alternately laminated in between, and a capacitor body 4 is provided.
A pair of external electrodes 5 that are alternately connected to the internal electrode layers 3 are formed.

The dielectric layer 2 is formed by firing a plurality of green sheets made of a dielectric material, and the internal electrode layer 3 is formed by firing a conductive paste layer applied on the surface of the green sheets. . Therefore, by firing a green laminated body in which a plurality of green sheets whose surfaces are coated with a conductive paste are fired, a plurality of internal electrode layers 3 are alternately laminated between a plurality of dielectric layers 2. The body portion 4 is formed.

The external electrodes 5 are alternately formed with the internal electrode layers 3 by applying a conductive paste for external electrodes to the side surfaces of the capacitor body 4 where the end surfaces of the internal electrode layers 3 are exposed and baking it. Is formed to connect to.

As the dielectric material of the dielectric layer 2, a normal temperature compensating dielectric material can be used. For example, barium titanate (BaTiO ₃ ) or lanthanum titanate (La) can be used.
₂ Ti ₂ O ₇ ) ・ Magnesium titanate (MgTi
O ₃ ), calcium titanate (CaTiO ₃ ), neodymium titanate (Nd ₂ Ti ₂ O ₇ ) and other main components, titanium oxide (TiO ₂ ), manganese oxide (MnO ₂ ), alumina (Al ₂ O ₃ ).・ Silicon (SiO ₂ ) and clay (Frog eye clay, etc.) are added.

As the conductive material of the internal electrode layer 3, a usual material for the internal electrode layer 3 can be used. For example, palladium (Pd), silver (Ag), gold (Au), platinum (P).
t) -Noble metals such as Ag-Pd and base metals such as nickel (Ni) -copper (Cu) -zinc (Zn). Above all,
As will be described later, when a dielectric material is contained, it is preferable to use a material having a small specific surface area and a spherical shape, because aggregation is less likely to occur and higher dispersion can be achieved.

Then, these metal powders are prepared as a conductive paste by kneading with an organic binder and an organic vehicle or various additives as required, and are applied to the surface of the green sheet and baked to give an internal The electrode layer 3 is obtained.

The temperature compensating laminated ceramic capacitor 1 of the present invention is characterized in that the internal electrode layer 3 contains the dielectric material of the dielectric layer 2. The dielectric material to be contained is as described above, and its content is appropriately set according to the type of the dielectric material of the dielectric layer 2 and the degree of correction of the desired temperature coefficient. The content of the dielectric material of the dielectric layer 2 may be 13% by volume or less (excluding 0% by volume) with respect to 100% by volume of the metal powder used for the internal electrode layer 3.

When the above content exceeds 13% by volume, the capacitance value of the capacitor is lowered so that the desired capacitance characteristic cannot be obtained, or the temperature coefficient is corrected so much that the desired temperature coefficient cannot be obtained. There is.

In containing the dielectric material in the internal electrode layer 3 as described above, in addition to the dielectric material of the dielectric layer 2, other dielectric materials can be used together. In that case, It is desirable that the total content does not exceed the above range.

Examples of main dielectric materials contained in the internal electrode layer 3 are as follows. For example, as a dielectric material, lanthanum titanate (La ₂ Ti ₂
When O ₇ ) is used, the metal powder of the internal electrode layer 3 is 100
It is preferable to set the volume ratio within the range of 13% by volume or less (excluding 0% by volume). This content is 0% by volume
With, the temperature coefficient cannot be corrected, and when the capacitance exceeds 13% by volume, the capacitance value of the capacitor tends to decrease.

Also, when magnesium titanate (MgTiO ₃ ) is used as the dielectric material, the internal electrode layer 3
It is advisable to set it within the range of 13% by volume or less (excluding 0% by volume) with respect to 100% by volume of the metal powder. When the content is 0% by volume, the temperature coefficient cannot be corrected, and when it exceeds 13% by volume, the temperature coefficient becomes large on the P side and cannot be corrected, and the capacitance value of the capacitor becomes small. There is a tendency to end up.

Also, when calcium titanate (CaTiO ₃ ) is used as the dielectric material, 13 vol% or less (however, 0 vol% is used with respect to 100 vol% of the metal powder of the internal electrode layer 3).
It is recommended to set it within the range of (excluding capacity%). If this content is 0% by volume, the temperature coefficient cannot be corrected, and
If it exceeds 13% by volume, the temperature coefficient tends to increase toward the N side, making it impossible to correct, and the capacitance value of the capacitor tends to decrease.

As described above, when the content of the dielectric material increases beyond the preferable range, the capacitance value of the capacitor becomes small because the content of the dielectric material increases. It is considered that this is because the amount of metal powder in the internal electrode layer 3 is reduced and the effective printing area of the internal electrode is reduced.

When setting the above range of content and the range of content when other dielectric materials are used, the temperature coefficient is 0 ± 30 ppm /
It is preferable from the viewpoint of practical commercialization in accordance with the standards such as JIS and EIA that the change in the capacitance value and the capacitance value are kept within ± 10% with respect to the original capacitance value.

Furthermore, it is desirable to take the resistance value of the internal electrode layer 3 into consideration as a criterion for judging the content of the dielectric material. The resistance value is also appropriately selected according to the required characteristics of the capacitor. For example, it is necessary to set the resistance value of the internal electrode layer 3 containing the dielectric material so that it does not become much higher than about 300 mΩ at 470 MHz. This is preferable in that the power consumption of the capacitor body 4 does not become too large.

In addition, the material composition or content of the dielectric material in the internal electrode layers 3 may be changed for each internal electrode layer 3 in order to correct it to a desired temperature coefficient. For example, the temperature coefficient can be corrected within a finer range by changing the type and the amount of the dielectric material added for each laminated green sheet.

If the dielectric material contained in the internal electrode layer 3 is spherical and the specific surface area is smaller,
It is preferable in that the dispersibility is further increased in the internal electrode material.

The size (particle size, etc.) of the metal powder used in the internal electrode layer is preferably the same as that of the metal powder in terms of dispersibility. There is a tendency that the printing cannot be performed, and if the size of the metal powder exceeds the size, uniform printing cannot be performed due to the large dielectric powder.

In forming the capacitor body 4 as described above, the green sheet to be the dielectric layer 2 has a green thickness of about 10 to 80 μm, and the conductive paste layer to be the internal electrode layer 3 has a thickness of 10 to 80 μm. The green thickness is preferably about 1 to 5 μm. The thickness, the number of laminated layers, etc. are appropriately set according to the specifications of the capacitor.

As the conductive material of the external electrode 5, a material for the normal external electrode 5 can be used, for example, silver (Ag).
Palladium (Pd), Ag-Pd, gold (Au), nickel (Ni), copper (Cu), cobalt (Co), tin (S)
n) and antimony (Sb).

Then, these metal powders are kneaded with an organic binder, an organic vehicle, a glass frit or various additives as necessary to prepare a conductive paste for an external electrode, which is used as a conductive paste for a laminated body or a capacitor body 4. The external electrode 5 is formed by being applied on the side surface and baked.

[0045]

EXAMPLES Specific examples of the temperature compensating multilayer ceramic capacitor of the present invention will be described below.

First, as a dielectric material of the dielectric layer 2, lanthanum titanate (La ₂ Ti ₂ O ₇ ), calcium titanate (CaTiO ₃ ), magnesium titanate (MgTi).
A raw material powder containing O ₃ ) as a main component is prepared, and an emulsion binder of 30 to 50% by weight is added as an organic binder to form a slurry, and a slurry having a thickness of 20 to 30 μm is prepared by a doctor blade method. A ceramic green sheet was produced.

On the other hand, a highly dispersed Pd powder was prepared as a conductive material for the internal electrode layer 3, and an ethyl cellulose resin was prepared as an organic vehicle. In addition, lanthanum titanate, magnesium titanate, and calcium titanate were prepared as dielectric materials to be contained therein for temperature correction.

Next, as a conductive paste containing one kind of each dielectric material, its content was 100% by weight of Pd.
To 0% by weight and 2% by weight, 5% by weight, 8% by weight, 11% by weight and 14% by weight, and an appropriate amount of organic vehicle was added to each to prepare a conductive paste.

Then, lanthanum titanate (La ₂ Ti ₂
O ₇₎ and a total of 30 layers, the result of printing an internal electrode layer pattern having a thickness 3~4μm laminated on the ceramic green sheet using a conductive paste containing, by thermocompression bonding and cutting
After making a chip of 2.0mm x 1.25mm, 1,330 ~ 1,35
Firing was performed at 0 ° C. under the condition of keeping the peak for 2 to 3 hours to obtain a capacitor body 4. After that, after applying Ag, N
The external electrodes 5 were formed by i / Sn plating to prepare capacitor samples 1 to 6 shown in Table 1.

Further, magnesium titanate (MgTiO 3
₃ ) A ceramic green sheet containing an internal electrode layer pattern with a thickness of 3 to 4 μm printed on the above ceramic green sheet using a conductive paste containing 20 layers is laminated in the same manner, and thermocompression bonding, cutting and firing are performed in the same manner to obtain the capacitor body. Part 4 is obtained. afterwards,
External electrodes 5 were formed in the same manner as above, and capacitor samples 7 to 12 shown in Table 2 were produced.

Calcium titanate (CaTi
O ₃ ) -containing conductive paste is printed on the above-mentioned ceramic green sheet with an internal electrode layer pattern having a thickness of 3 to 4 μm, and a total of 20 layers are laminated, and thermocompression bonding, cutting and firing are performed in the same manner to obtain a capacitor. The body 4 was obtained. Then, the external electrodes 5 were formed in the same manner as above, and capacitor samples 13 to 18 shown in Table 3 were produced.

Capacitor sample 1 produced in this way
For Nos. 18 to 18, the capacitance value, the temperature coefficient of the capacitance value, the internal and external defects, and the surface resistance value of the internal electrode layer were evaluated as follows.

The capacitance value was evaluated under the conditions of a frequency of 1 MHz, a voltage of 1 Vrms, and a temperature of room temperature.

The temperature coefficient of the capacitance value is evaluated by measuring the frequency at 1M.
It was measured under the conditions of Hz, voltage of 1 Vrms, and temperature of −55 ° C. to + 125 ° C., and those having a temperature coefficient of 0 ± 30 ppm / ° C. were regarded as good.

Regarding internal and external defects, external defects are those in which 500 to 600 finished porcelains are observed under a microscope at a magnification of 10 times, and there are no defects such as chipping or line delamination on the surface, side faces or end faces. Was good. For internal defects, 50 to 100 finished porcelains were polished and observed under a microscope at a magnification of 10 times, and those having no defects such as delamination and poor adhesion inside were regarded as good.

The sheet resistance of the internal electrode layer was evaluated by measuring the internal electrode paste prepared as described above by applying it on an alumina substrate and baking it.
Those with a resistance of 300 mΩ or less were considered good.

These results are summarized in Tables 1 to 3 together with the content of the dielectric material contained in each internal electrode layer 3. It should be noted that those marked with * in the sample number are outside the scope of the present invention.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

From these results, in the temperature-compensated laminated ceramic capacitors of Samples 2 to 5, 8 to 11 and 14 to 17, the capacitance value was within ± 10% of the set value, which was good. Also, it can be seen that the temperature coefficient of the capacitance value is as small as 0 ± 30 ppm / ° C. and the capacitor has good capacitance characteristics for temperature compensation. Moreover, neither internal nor external defects were observed, and the resistance value of the internal electrode layers was 300 mΩ or less, which indicates that all of them are good temperature compensating multilayer ceramic capacitors.

On the other hand, as in Samples 1, 7, and 13, lanthanum titanate (La ₂ T), which is a dielectric material, is used for the internal electrode layers.
i ₂ O ₇ ) or magnesium titanate (MgTi
When O ₃ ) / calcium titanate (CaTiO ₃ ) is not contained, the temperature coefficient becomes larger than 0 ± 30 ppm / ° C. and becomes larger than those in the range of the present invention, and the temperature characteristics may deteriorate. I understand.

Further, in samples 6.12.18, lanthanum titanate (La ₂ Ti ₂ O ₇ ) or magnesium titanate (MgTiO ₃ ) .calcium titanate (CaTi
Since the content of O ₃ ) exceeds 13% by volume, the content of O ₃ ) is less than the set capacity value in comparison with those within the range of the present invention.
It can be seen that the capacity falls below 10% and the capacity characteristics are inferior.

From the above results, according to the temperature-compensating laminated ceramic capacitor of the present invention, the temperature-temperature coefficient could be easily corrected without changing the composition ratio of the dielectric material or the firing conditions.

Further, since the temperature coefficient could be easily corrected without changing the composition ratio of the dielectric material and the firing conditions, the green sheet of the dielectric material, which had been unavoidable until now, was recycled. We were able to.

Furthermore, since it was not necessary to change the firing conditions, various defects due to the change in conditions did not occur.

As described in detail above, according to the temperature-compensated multilayer ceramic capacitor of the present invention, the temperature coefficient can be easily corrected without changing the composition ratio of the dielectric material or the firing conditions. A multilayer ceramic capacitor for use in the electric field.

Further, according to the present invention, the temperature coefficient can be easily corrected without changing the composition ratio of the dielectric material and the firing conditions. Was able to reuse the green sheets of dielectric material that had to be discarded.

Further, since it was not necessary to change the firing conditions when manufacturing the temperature-compensated laminated ceramic capacitor having the corrected temperature coefficient, various defects due to the changes in the conditions did not occur and the manufacturing process was confused. It never happened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a temperature-compensating laminated ceramic capacitor of the present invention.

[Explanation of symbols]

1 Temperature compensation multilayer ceramic capacitors 2 Dielectric layer 3 Internal electrode layer 4 Capacitor body 5 external electrodes

Claims (2)

(57) [Claims] 1. A plurality of internal electrode layers containing a dielectric material of 13% by volume or less (excluding 0% by volume) of the dielectric layer with respect to 100% by volume of metal powder between the plurality of dielectric layers. the a temperature compensating multilayer ceramic capacitor formed by including a capacitor main body formed by laminating alternately, the composition of the dielectric material to be contained in the metal powder walking
Is characterized in that the content is different for each of the internal electrode layers.
A temperature-compensated monolithic ceramic capacitor. 2. The shape of the dielectric material contained in the metal powder.
The temperature according to claim 1, wherein the shape is spherical.
Compensation multilayer ceramic capacitor.