JPH06318404A - Dielectric ceramic composition powder and multilayered ceramic capacitor using same - Google Patents

Abstract

PURPOSE:To provide dielectric ceramic composition powder capable of obtaining a large dielectric constant and a multilayered ceramic capacitor at a low cost having high reliability, a small size, and a large capacit-ance and made of this powder by using perovskite type oxide powder expressed by a specific formula. CONSTITUTION:At least one or more kinds of perovskite type oxide powders are used as main components, which include 0.03wt.% or less of alkaline metal oxide as impurity, are expressed by a formula ABO3, and are produced by utilizing a hydrothermal reaction, thus obtaining dielectric ceramic composition powder which satisfies a formula {(Ba1-xCax)O}m(Ti1-o-pZroNbp)O2+p/2, wherein 0 <= (x) <=0.20, 0< (o) <= 0.25, 0 <= (p) <= 0.015, and 1<= (m) (-) 1.03. An A group element is selected from Ba and Ca, and a B group element is selected from Ti, Zr and Nb. As auxiliary components 0.02-2.0 mols of at least one or more kinds of oxides of Mn, Fe, Cr, Co and Ni are added to be included into 100 mols of the main components, where a specific surface is set to 8.0m<2>/g or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition and a laminated ceramic capacitor using the same, and particularly to a dielectric ceramic composition powder used for a laminated ceramic capacitor including internal electrodes made of Ni or Ni alloy, and The present invention relates to a laminated ceramic capacitor using the same.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of a monolithic ceramic capacitor, first, a sheet-shaped dielectric material having an electrode material applied to the surface thereof as an internal electrode is prepared. As the dielectric material, for example, a material containing BaTiO ₃ as a main component is used. A sheet-shaped dielectric material coated with this electrode material is laminated, thermocompressed, and integrated to be fired at 1250 to 1350 ° C. in a natural atmosphere to obtain a dielectric ceramic having internal electrodes. Then, an external electrode that is electrically connected to the internal electrode is printed on the end surface of the dielectric ceramic to obtain a monolithic ceramic capacitor.

[0003]

The materials for the internal electrodes used in such a monolithic ceramic capacitor are as follows:
The following conditions must be met.

(A) Since the dielectric porcelain and the internal electrodes are fired at the same time, the dielectric porcelain must have a melting point higher than the firing temperature.

(B) It should not be oxidized even in an oxidizing high temperature atmosphere and should not react with the dielectric.

Noble metals such as platinum, gold, palladium or alloys thereof have been used as the electrode material satisfying such conditions.

However, while these electrode materials have excellent characteristics, they are expensive. Therefore, the ratio of the electrode material cost to the monolithic ceramic capacitor is 30 to 7
It reached 0%, which was the biggest factor in raising the manufacturing cost.

N having a high melting point other than precious metals
Although there are base metals such as i, Fe, Co, W, and Mo, these base metals are easily oxidized in a high-temperature oxidizing atmosphere and cannot serve as an electrode. Therefore, in order to use these base metals as the internal electrodes of the monolithic ceramic capacitor, it is necessary to fire them together with the dielectric ceramic in a neutral or reducing atmosphere. However, the conventional dielectric ceramic material has a drawback that it is remarkably reduced when it is fired in such a reducing atmosphere and becomes a semiconductor.

In order to overcome these drawbacks, for example, as shown in Japanese Patent Publication No. 57-42588, a barium titanate solid solution having a barium site / titanium site ratio in excess of the stoichiometric ratio should be used. Body materials are known.

By using such a dielectric material, it is possible to obtain a dielectric ceramic which does not become a semiconductor even when fired in a reducing atmosphere, and it is possible to manufacture a monolithic ceramic capacitor using a base metal such as Ni as an internal electrode. Became.

However, a monolithic ceramic capacitor using a base metal such as Ni as an internal electrode is a monolithic ceramic whose internal electrode is a precious metal such as platinum, gold, palladium or silver-palladium alloy which is fired in a natural atmosphere. As compared with a capacitor, it has a problem that the insulation resistance has a shorter life under a high temperature load and a humidity load, and the reliability is low.

On the other hand, with the recent development of electronics, miniaturization of electronic parts has rapidly progressed, and the trend toward miniaturization of monolithic ceramic capacitors has become remarkable. Further, as a method of miniaturizing the monolithic ceramic capacitor, it is generally known to use a material having a large dielectric constant or to thin the dielectric layer. However, a material having a large dielectric constant has large crystal grains, and if the film is a thin film having a thickness of 15 μm or less, the number of crystal grains present in one layer decreases, resulting in a significant decrease in reliability.

Therefore, a main object of the present invention is to obtain a dielectric ceramic composition powder which does not become a semiconductor even when fired in a reducing atmosphere and has a large dielectric constant despite its small crystal grain size. Another object of the present invention is to provide a small-sized and large-capacity multilayer ceramic capacitor that is low in cost and highly reliable.

[0014]

According to a first aspect of the present invention, the content of an alkali metal oxide contained as an impurity produced by utilizing a hydrothermal reaction is 0.03% by weight or less, and the content of halogen is 0. 0.03% by weight or less of the perovskite type oxide powder represented by the general formula ABO ₃ (however, the group A element is Ba
Alternatively, it is Ca, and the B group element is Ti, Zr, or Nb. ) Of at least one of the following general formulas: {(Ba _1-x Ca _x ) O} _m (Ti _1-op Zr _o
Nb _p ) O _{2 + p / 2} , where x, o, p and m are 0
≦ x ≦ 0.20, 0 <o ≦ 0.25, 0 ≦ p ≦ 0.01
5, Mn, Fe, C as auxiliary components with respect to 100 mol of the main component satisfying the relationship of 1.000 ≦ m ≦ 1.03
The oxides of r, Co and Ni were replaced by MnO ₂ , Fe.
When expressed as ₂ O ₃ , Cr ₂ O ₃ , CoO and NiO, at least one kind of each oxide is 0.02 to 2.
It is a dielectric ceramic composition powder containing 0 mol added and having a specific surface area of 8.0 m ² / g or less.

A second aspect of the present invention is a dielectric ceramic sintered body laminated with a plurality of internal electrodes interposed therebetween, and an external body provided so as to be electrically connected to the internal electrodes in the dielectric ceramic sintered body. A multilayer ceramic capacitor including an electrode, wherein the internal electrode is made of one of Ni and a Ni alloy, and the dielectric ceramic sintered body is formed by using the dielectric ceramic composition powder. .

[0016]

The perovskite type oxide represented by the general formula ABO ₃ is often used as the raw material powder of the laminated ceramic capacitor. As a method for producing this perovskite type oxide, a conventional group A element (A = Ba, C
A mixture of the carbonate of a) and the oxide of the group B element (B = Ti, Zr, Nb) is calcined at 1000 ° C. or higher, and then pulverized to obtain a raw material powder. In order to reduce the crystal grain size of the porcelain sintered body, it is desired to make these raw material powders finer, but in the conventional manufacturing method, sintering proceeds during calcination, and since a large amount of coarse particles is contained, It was difficult to obtain a powder having a fine and uniform particle size. As an attempt to solve this problem, raw material powders have been synthesized by a coprecipitation method, an alkoxide method, a hydrolysis method, a hydrothermal synthesis method, or the like. Among them, the powder synthesized by the hydrothermal reaction has not only fine particles but also a uniform composition, and is compared with a dielectric ceramic sintered body using a raw material powder manufactured by a conventional manufacturing method. It is known that the crystal grain size is small and a large dielectric constant can be obtained. However, the powder synthesized by the hydrothermal reaction has a large specific surface area because the particles are fine.

On the other hand, in perovskite type oxide powder synthesized by hydrothermal reaction, chloride is often used as a starting material. Further, in order to promote crystallization, it has been common to use various alkali metal solutions such as NaOH and KOH as a mineralizer. for that reason,
Alkali metal oxides such as Na ₂ O and K ₂ O and halogens such as Cl are taken in as impurities.

When a monolithic ceramic capacitor is manufactured using a dielectric ceramic composition powder having a large specific surface area, the state of dispersion with the binder becomes poor when mixed with the binder.
As a result, pinholes are created in the green sheet, and many pores are generated after firing, or the density of the green sheet decreases, and the shrinkage rate during firing increases, causing delamination and other defects. It was

The present inventors have also proposed that as a raw material powder for a dielectric ceramic sintered body of a laminated ceramic capacitor having an internal electrode made of Ni or Ni alloy, a perovskite type oxide powder synthesized by a hydrothermal synthesis method. When using
It found present as an impurity Na ₂ O, the content of halogens, such as alkali metal oxides and Cl such as K ₂ O, temperature load of the dielectric ceramic, that greatly affects the middle of the load of the insulation resistance lifetime humidity It was

That is, the dielectric ceramic composition powder according to the present invention can be fired even in a reducing atmosphere without deteriorating its characteristics, and as an internal electrode,
It is possible to obtain a highly reliable laminated ceramic capacitor using Ni or a Ni alloy which is a base metal and having no pores or delamination.

Further, since the dielectric ceramic composition powder according to the present invention uses the raw material powder synthesized by the hydrothermal reaction, the crystal grain size is small and a large dielectric constant can be obtained. Therefore, the number of crystal grains existing in one dielectric layer can be increased, and even if the thickness of the dielectric layer is reduced, deterioration of reliability can be prevented. Therefore, a monolithic ceramic capacitor having a large capacitance is provided. Can be obtained.

[0022]

According to the present invention, it is possible to obtain a dielectric ceramic composition powder which is not reduced even if it is fired in a reducing atmosphere and whose insulation resistance does not deteriorate under high temperature load and wet load. Therefore, by using this dielectric ceramic composition powder, a highly reliable laminated ceramic capacitor can be obtained even if a base metal is used as the electrode material. Furthermore, since this dielectric ceramic composition powder can be fired at a relatively low temperature, it is possible to reduce the cost of the monolithic ceramic capacitor.

Further, in the monolithic ceramic capacitor using this dielectric ceramic composition, the crystal grain size is small despite the high dielectric constant. Therefore, even if the dielectric layer is thinned, the amount of crystal grains existing in the layer does not decrease unlike the conventional multilayer ceramic capacitor. For this reason,
It is possible to obtain a monolithic ceramic capacitor that has high reliability, is small, and has a large capacity.

The above and other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below.

[0025]

EXAMPLES First, titanium isopropoxide (Ti (OC
₃ H ₇ ) ₄ ) and zirconium isobutoxide (Zr (O
C ₄ H ₉ ) ₄ ) and niobium isobutoxide (Nb (OC ₄
An appropriate amount of H ₉ ) ₅ ) is weighed so that the total amount becomes 0.1 mol, and about 300 ml of isopropyl alcohol (IPA) is added.
Several kinds of solutions dissolved in were prepared. After sufficiently stirring these solutions, 120 cc of an aqueous solution containing 0.2 mol to 0.6 mol of NaOH was added to each of them to cause hydrolysis.

Next, BaCl ₂ .2H ₂ O and CaCl ₂ .2H ₂ O were added and mixed into each of these hydrolyzed solutions while blowing N ₂ gas so that the total amount became 0.1 mol. , A mixed solution was obtained. After that, each of these mixed solutions was placed in an autoclave of 500 ml and hydrothermally treated at 200 ° C. for 6 hours to 10 hours. After that, the slurry obtained by cooling is filtered and washed and filtered several times by a usual method.
Eight kinds of perovskite type oxide powders shown in Table 1 were obtained by drying at 0 ° C.

[0027]

[Table 1]

Next, the above eight types of perovskite type oxides and BaCO ₃ , CaC having a purity of 99.8% or more are used.
O ₃ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , MnO ₂ , F
_{e 2 O 3, Cr 2 O} 3, CoO, were prepared and NiO.
Using these raw materials as {(Ba _1-x Ca _x ) O} _m (Ti
_1-op Zr _o Nb _p ) O _{2 + p / 2} is represented by the composition formula, x,
Blending was carried out so that o, p and m were in the ratios shown in Table 2 to obtain blended raw materials. The blended raw materials are wet mixed in a ball mill, pulverized, and then dried, and the mixture is dried in the air at 1000 ° C.
It was calcined at 1180 ° C. for 2 hours to obtain a calcined product. This calcined product was crushed by a dry crusher to obtain a raw material powder having a specific surface area shown in Table 2.

[0029]

[Table 2]

A polyvinyl butyral binder and an organic solvent such as ethanol were added to this raw material powder and wet-mixed by a ball mill to prepare a ceramic slurry. After that, the ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular green sheet having a thickness of 26 μm. Next, a conductive paste containing Ni as a main component was printed on this ceramic green sheet to form a conductive paste layer for forming internal electrodes. A plurality of ceramic green sheets having a conductive paste layer formed thereon were laminated so that the sides from which the conductive paste was drawn out were staggered to obtain a laminate. The obtained laminated body was heated to a temperature of 350 ° C. in an N ₂ atmosphere to burn the binder, and then the H 2 of which oxygen partial pressure was 10 ⁻⁹ to 10 ⁻¹² MPa.
₂ -N ₂ - calcined for 2 hours at a temperature shown in Table 3 in a reducing atmosphere consisting of air gas, to obtain a ceramic sintered body. The surface of the obtained ceramic sintered body was observed with a scanning electron microscope at a magnification of 1500 times to measure the grain size.

[0031]

[Table 3]

After firing, an Ag paste was applied to both end faces of the obtained sintered body and baked at a temperature of 600 ° C. in an N ₂ atmosphere to form external electrodes electrically connected to the internal electrodes. The external dimensions of the thus-obtained monolithic ceramic capacitor are 1.6 mm in width, 3.2 mm in length,
The thickness is 1.2 mm, and the thickness of the dielectric ceramic layer interposed between the internal electrodes is 15 μm. The total number of effective dielectric ceramic layers is 19, and the area of the counter electrode per layer is 2.1 mm ² .

Capacitance (C) and dielectric loss (tan)
δ) is a frequency of 1 kHz using an automatic bridge type measuring instrument
The measurement was performed at z, 1 V _rms , and temperature of 25 ° C., and the dielectric constant (ε) was calculated from the capacitance. Next, in order to measure the insulation resistance (R), a DC voltage of 25 V was applied for 2 minutes to measure the insulation resistance (R) at 25 ° C. and 85 ° C. using an insulation resistance meter, and the capacitance was measured. The product of (C) and insulation resistance (R), that is, the CR product was obtained. In addition, the rate of change of capacitance with respect to temperature change was measured. Furthermore, the DC breakdown voltage value (BDV) and a voltage of 1 kHz and 1 V _rms were applied, and the rate of change in capacitance was measured when the DC voltage was superimposed at 13 V. The rate of change of capacitance with respect to temperature change is 2
The rate of change (ΔC / C ₂₀ ) at −25 ° C. and 85 ° C. based on the capacitance at 0 ° C. is shown. As a high temperature load test,
100 samples of each sample, DC voltage of 50V at a temperature of 85 ℃
The voltage was applied and the insulation resistance after 1000 hours was measured.
In addition, as a wet and medium load test, 100 pieces of each sample,
Applying 25V DC voltage at humidity 95% and temperature 70 ℃,
The insulation resistance after 1000 hours was measured. In the high temperature load test and the humidity and medium load test, the product of the insulation resistance (R) and the capacitance (C) after 1000 hours, that is, C
The number of samples whose R product was 50 MΩ · μF or less was regarded as defective and the number thereof was shown.

Further, as a comparative example for sample No. 8,
BaCO ₃ , CaCO ₃ , TiO with a purity of 99.8% or more
₂ , ZrO ₂ , and MnO ₂ were prepared and blended so as to have the composition of Sample No. 8 in Table 2 to obtain a blended raw material. This blended raw material is wet mixed in a ball mill, crushed and then dried,
It was calcined in air at 1100 ° C. for 2 hours to obtain a calcined product. This calcined product was pulverized by a dry pulverizer to obtain a raw material powder having a specific surface area of 3.0 m ² . Using this raw material powder, a multilayer capacitor was produced by the method described above.
Then, also in this comparative example, the above-mentioned respective characteristics were measured.

The results of the above tests are also shown in Table 3.

Next, the reasons for limiting each composition will be described.

{(Ba _1-x Ca _x ) O} _m (Ti _1-op
In the dielectric ceramic composition powder represented by Zr _o Nb _p ) O _{2 + p / 2} , when the Zr amount o is 0 as in Sample No. 1, the dielectric constant ε becomes less than 11000 and the dielectric loss tan
δ exceeds 5.0%, which is not preferable. On the other hand, sample number 1
When the Zr amount o exceeds 0.25 as in No. 4, the sinterability is lowered and the dielectric constant is lowered, which is not preferable.

In addition, as in sample number 2, {(Ba _1-x
When the molar ratio m of Ca _x ) O} _m (Ti _1-op Zr _o Nb _p ) O _{2 + p / 2} is less than 1.000, the porcelain is reduced when fired in a reducing atmosphere to become a semiconductor. Insulation resistance decreases, which is not preferable. On the other hand, when the molar ratio m exceeds 1.03 as in Sample No. 16, the sinterability is extremely deteriorated, which is not preferable.

As in sample No. 3, MnO ₂ , Fe ₂ O
_When the content of ₃ , Cr ₂ O ₃ , CoO, and NiO is less than 0.02 mol, the insulation resistance at 85 ° C. or higher is lowered, and defects in the high temperature load test and the humidity and medium load test occur, which is not preferable. On the other hand, like sample No. 20, MnO ₂ , Fe ₂ O
_{Even if} the content of ₃ , Cr ₂ O ₃ , CoO, and NiO exceeds 2.0 mol, the insulation resistance at 85 ° C. or higher will decrease, and defects will occur in the high temperature load test and the humidity and medium load test, which is not preferable. .

Further, as in Sample No. 13, the Ca amount x
Is more than 0.20, the sinterability is lowered and the dielectric constant is lowered, which is not preferable.

As in the sample No. 15, the Nb amount p is 0.0
When it exceeds 2, the porcelain is reduced when it is fired in a reducing atmosphere to become a semiconductor, and the insulation resistance is significantly reduced, which is not preferable.

When the content of the alkali metal produced by utilizing the hydrothermal reaction exceeds 0.03% by weight, as in sample No. 17, the number of defects in the high temperature load test increases, which is not preferable.

When the content of halogen produced by utilizing the hydrothermal reaction exceeds 0.03% by weight like sample No. 18, the number of defects in the high temperature load test and the humidity and medium load test increases, which is not preferable. .

Further, when the specific surface area exceeds 8.0 m ² / g as in sample No. 19, delamination occurs, which is not preferable.

As in the comparative example, the dielectric ceramic composition powder produced without using the perovskite type oxide powder is not preferable because the dielectric constant and the breakdown voltage value are lowered and the crystal grain size is increased.

On the other hand, the monolithic ceramic capacitor according to the present invention has a high dielectric constant of 13,000 or more,
To obtain a dielectric porcelain having a dielectric loss tan δ of 5.0% or less and a rate of change of capacitance with respect to temperature satisfying E characteristic or F characteristic standard defined in JIS standard in a range of -25 ° C to 85 ° C. You can Moreover, in this multilayer ceramic capacitor, the insulation resistance at 25 ° C and 85 ° C is
The product of capacitance (C) and insulation resistance (R), that is, CR
When expressed as a product, 5000 MΩ · μF or more,
It shows a high value of 1000 MΩ · μF or more. Further, the insulation resistance has a long life under a high temperature load and a wet and medium load, and exhibits excellent reliability. Further, the dielectric constant and the breakdown voltage value are high and the voltage dependence is small as compared with the conventional multilayer ceramic capacitor using the dielectric ceramic composition powder produced without using the perovskite type oxide powder. The dielectric ceramic composition powder according to the present invention also has a firing temperature of 1250.
It can be sintered at a low temperature of ℃ or less, and the particle size after sintering is as small as 3 µm or less.

In the dielectric ceramic composition powder according to the present invention, the addition of a slight amount of a sintering aid such as silica and oxide glass does not impair the characteristics of the obtained monolithic ceramic capacitor. .

Claims (2)

[Claims] 1. A general formula ABO ₃ produced by utilizing a hydrothermal reaction, wherein the content of alkali metal oxides contained as impurities is 0.03% by weight or less and the content of halogen is 0.03% by weight or less. A perovskite oxide powder represented by the formula (wherein the group A element is Ba or Ca, and the group B element is Ti, Zr or Nb), and the following general formula: (Ba _1-x Ca _x ) O} _m (Ti _1-op Zr _O N
b _p ) O _{2 + p / 2} , where x, o, p and m are 0 ≦ x ≦ 0.20 0 <o ≦ 0.25 0 ≦ p ≦ 0.015 1.000 ≦ m ≦ 1 With respect to 100 moles of the main component satisfying the relationship of 0.03, Mn, Fe, Cr, Co, and Ni oxides are added as sub-components to MnO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , CoO, and Ni.
When expressed as O, 0.02 to 2.0 mol of at least one kind of each oxide is added and contained, and the specific surface area is 8.0 m.
Dielectric ceramic composition powder having a content of ² / g or less. 2. A dielectric ceramic sintered body laminated with a plurality of internal electrodes interposed, and an external electrode provided so as to be electrically connected to the internal electrode in the dielectric ceramic sintered body. In the monolithic ceramic capacitor, the internal electrodes are made of one of Ni and a Ni alloy, and the dielectric ceramic sintered body is formed by using the dielectric ceramic composition powder according to claim 1. , Monolithic ceramic capacitors.