JP3146966B2 - Non-reducing dielectric ceramic and multilayer ceramic electronic component using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reducing dielectric ceramic and a multilayer ceramic electronic component using the same, such as a multilayer ceramic capacitor or a multilayer ceramic substrate.

[0002]

2. Description of the Related Art Multilayer ceramic electronic components have been reduced in size and cost, and ceramic layers have been made thinner and internal electrodes have been made base metal. For example,
In a multilayer ceramic capacitor which is one of the multilayer ceramic electronic components, the thickness of the ceramic layer has been reduced to near 5 μm, and at present, Cu, Ni or the like is used for the internal electrodes.

However, when the ceramic layer becomes thinner as described above, the electric field applied to the ceramic layer increases, and a problem arises in the use of a dielectric whose dielectric constant is largely changed by the electric field. Ceramics having a core-shell structure have been proposed and used as dielectrics to solve this problem. The core-shell structure is a material having a different crystal structure and composition between the core at the center and the shell at the periphery in one sintered body particle, and is excellent in electric field characteristics of dielectric constant and temperature characteristics. The core-shell structure is obtained by diffusing necessary components from the particle surface into the particles in the course of sintering the ceramic.

When Cu or Ni is used for the internal electrode,
When firing is performed under conditions where the electrode metal is not oxidized, the ceramic itself is generally reduced and the insulating property cannot be maintained. Therefore, for example, in the case of barium titanate as a non-reduced dielectric material, the composition is determined from the stoichiometric ratio by the general formula
A non-reducing material is used which is shifted to the A site side in ₃ , or an acceptor element is added.

[0005]

As described above, a conventional dielectric having a core-shell structure is obtained by diffusing certain components from the particle surface in the sintering process and sintering them. Therefore, when the particle diameter of the raw material is reduced, the components forming the shell diffuse to the center of the particle, so that the core-shell structure is not exhibited, and the characteristics of the core-shell structure are lost. At present, the particle size of the sintered body from which a core-shell structure is obtained is at least about 1 μm.

Therefore, when a dielectric having such a core-shell structure is used as a ceramic layer of a multilayer ceramic electronic component, if the thickness of the ceramic layer becomes as thin as 5 μm or less, it is present in the thickness direction in the layer. However, there is a problem that the number of particles to be reduced is reduced and the reliability of the multilayer ceramic electronic component is reduced. For this reason, there has been a limit in making the ceramic layer of the multilayer ceramic electronic component thinner.

Accordingly, an object of the present invention is to provide a non-reducing dielectric ceramic having a sintered body having a small particle size, a structure other than a core-shell structure, and having excellent temperature characteristics and electric field characteristics of a dielectric constant. An object of the present invention is to provide a multilayer ceramic electronic component comprising a thin ceramic layer having a thickness of 3 μm or less.

[0008]

In order to achieve the above object, the non-reducing dielectric ceramic of the present invention has a maximum particle diameter of 0.5 μm or less and an average particle diameter of 0.1 to 0.3 μm. A plurality of particles, wherein the plurality of particles have a uniform composition and crystal system in each particle, and have the same composition and crystal system among each other. It is characterized by the following.

[0009] The non-reducing dielectric ceramic of the present invention is characterized in that a grain boundary phase having a thickness of 5 nm or less having a different component from that of the particles is present at the grain boundaries of the particles.

Further, the multilayer ceramic electronic component of the present invention comprises:
The non-reducible dielectric ceramic is a laminate of ceramic layers, and a conductor made of a base metal is formed between the ceramic layers of the laminate.

Further, the multilayer ceramic electronic component of the present invention comprises:
The non-reducing dielectric ceramic is a laminate of ceramic layers, and an internal conductor made of a base metal is formed between the ceramic layers of the laminate, and the surface of the laminate is electrically connected to the internal conductor. An outer conductor made of a base metal is formed.

As described above, in the non-reducing dielectric ceramic of the present invention, the average particle diameter of the sintered body is as small as 0.1 to 0.3 μm, so that the thickness of the ceramic layer is 5 μm or less. However, many particles are stacked in the thickness direction in the layer, and the reliability of the ceramic layer is improved.

In addition, since the individual particles of the sintered body have a uniform composition and crystal system, the structure of the ceramic does not change during the firing process and is stable. Further, since the particle diameter is small, the dielectric properties of the ceramic are suppressed, and excellent electric field characteristics and temperature characteristics similar to those of a ceramic having a core-shell structure are exhibited.

Further, when there is a grain boundary phase having a thickness of 5.0 nm or less having a different component from the particles at the grain boundary of the particles of the sintered body, an electric field is concentrated on the grain boundary phase, and Since the electric field applied to itself is suppressed, the reliability of the particles is improved.
Since the diffusion speed of oxygen is high at the grain boundary, oxygen diffusion to oxygen defects, which is a cause of poor reliability, also occurs sufficiently, and reliability does not decrease even if electric field concentration occurs at the grain boundary. However, when the grain boundary phase is 5 nm or more, the influence of the grain boundary phase having a lower dielectric constant than that of the particles becomes large, and the dielectric constant of the ceramic is greatly reduced.

Further, even if there is a phase having a component different from the grain boundary phase at the so-called triple point existing between three or more particles, there is little probability that the particles exist in series in the electric field direction. There is no effect on the dielectric properties and there is no problem.

By using the non-reducing dielectric ceramic as a ceramic layer and using a base metal for the inner conductor and the outer conductor, an inexpensive multilayer ceramic electronic component with low conductor cost can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The non-reducing dielectric ceramic of the present invention and a multilayer ceramic electronic component using the same are described below.
Description will be made by taking a multilayer ceramic capacitor as an example.

As shown in FIG. 1, the multilayer ceramic capacitor has both ends of a laminated body 1 obtained by laminating a plurality of dielectric ceramics 2 as ceramic layers via an internal electrode 3 as an internal conductor. An external electrode 5 as an external conductor, a plating film 6 of nickel, copper, or the like, and a plating film 7 of solder, tin, or the like are formed thereon, thereby obtaining a chip having a rectangular parallelepiped shape.

Next, a method of manufacturing the multilayer ceramic capacitor will be described below. First, a main component such as barium titanate and an additive for the purpose of property modification are used as starting materials, and a predetermined amount thereof is weighed and wet-mixed to obtain a mixed powder. Thereafter, an organic binder and a solvent are added to the powder to form a slurry, and a ceramic green sheet is produced using the slurry. Thereafter, an internal electrode layer made of a base metal such as nickel or copper is formed on the ceramic green sheet. In addition, as a method of forming the internal electrode layer, there are a screen printing method, an evaporation method, a plating method, and the like.

Next, a required number of ceramic green sheets having internal electrode layers formed thereon are laminated, sandwiched by ceramic green sheets having no internal electrode layers, and pressed to form a laminate. Thereafter, firing is performed at a predetermined temperature in a reducing atmosphere to form the laminate 1.

Next, external electrodes 5 are formed on both end faces of the laminate 1 so as to be connected to the internal electrodes 3. As the material of the external electrode 5, the same material as that of the internal electrode 3 can be used. Also, silver, palladium, silver - palladium alloys, copper, copper alloy is available and also these metal powders into B ₂ O ₃ -SiO ₂ -BaO-based glass, Li ₂
Although a glass frit such as an O—SiO ₂ —BaO-based glass is also used, an appropriate material is selected in consideration of a use application, a use place, and the like of the multilayer ceramic capacitor.

The external electrode 5 is usually obtained by applying a metal powder paste as a material to the fired laminate 1 and baking it. However, the external electrode 5 is applied to the fired laminate before firing. They may be formed simultaneously.

Thereafter, plating of nickel, copper or the like is performed on the external electrode 5 to form a plating film 6. Finally, a plating film 7 such as solder or tin is formed on the plating film 6 to obtain a chip-type multilayer ceramic capacitor.

(Example) First, an appropriate amount of an organic solvent was added to the starting materials having the types and ratios (molar parts) shown in Table 1 to obtain a starting material.
The mixture was pulverized in a resin pot having a zirconia pulverization medium of mmφ. In Table 1, sample number 1
7 are examples of the present invention. Details of the starting material for each sample number are as follows.

[0025]

[Table 1]

That is, in sample No. 1, barium titanate (BaTi) having an average particle diameter of 0.1 μm manufactured by a hydrothermal synthesis method was used.
O ₃ ) and a Mn compound soluble in an organic solvent during mixing and pulverization were used as starting materials.

In sample No. 2, barium titanate (BaTiO ₃ ) having an average particle size of 0.2 μm prepared by hydrolysis and calcined was mixed with an organic solvent soluble in an organic solvent at the time of mixing and pulverization.
The n compound and the Mg compound were used as starting materials.

In sample No. 3, barium titanate (BaTiO 3) having an average particle diameter of 0.3 μm manufactured by a hydrothermal synthesis method was used.
₃ ) and pulverized manganese carbonate was used as a starting material.

In sample No. 4, barium titanate (BaTiO ₃ ) and calcium titanate (CaTiO ₃ ) prepared by a hydrolysis method were mixed at a molar ratio of 9/1 and calcined at 950 ° C. The obtained powder having an average particle size of 0.2 μm and a Mn compound soluble in an organic solvent at the time of mixing and pulverization were used as starting materials.

In sample No. 5, barium titanate (BaTiO) having an average particle size of 0.2 μm produced by a hydrothermal synthesis method was used.
₃ ), finely ground manganese carbonate, and finely ground Li-
Ba-Si glass powder was used as a starting material.

In sample No. 6, barium carbonate, titanium oxide and zirconium oxide were mixed so that the molar ratio of Ba / (Ti + Zr) was 1 and the molar ratio of Ti / Zr was 7/3, and 1100 ° C. And calcined and then crushed.
Barium zirconate titanate {Ba (Zr, Ti) O ₃ } having an average particle size of 0.25 μm by solid phase method, finely pulverized manganese carbonate, and Li−
A Ba-Si compound was used as a starting material.

In sample No. 7, barium carbonate and titanium oxide were mixed so that the molar ratio of Ba / Ti became 1, calcined, and then pulverized.
3 μm of barium titanate (BaTiO ₃ ), a Mn compound soluble in an organic solvent during mixing and pulverization, and B-Ba-Si
Compound was used as starting material.

The compound soluble in the organic solvent is
These are metal alkoxides, acetylacetonates or metal soaps, respectively.

Next, a predetermined amount of an organic binder was added to the mixed and pulverized product to prepare a slurry, and a thin ceramic green sheet having a thickness of 2 μm after firing on an organic film by a doctor blade was obtained.

Next, a conductive layer mainly composed of Ni was formed on the obtained ceramic green sheet by a printing method. Thereafter, six ceramic green sheets on which the conductive layers were formed were stacked such that the sides from which the conductive layers were drawn out were alternated, and sandwiched between ceramic green sheets having no internal electrodes to form a laminate.

Thereafter, the laminate was heated in an N ₂ atmosphere to remove the binder, and then fired at a firing temperature shown in Table 1 in a reducing atmosphere to obtain a ceramic sintered body.

Finally, an Ag paste to which glass frit is added is applied and baked to form an external electrode electrically connected to the internal electrode, thereby forming a multilayer ceramic using a non-reducible dielectric ceramic as a ceramic layer. The capacitor was completed.

(Comparative Example) First, an appropriate amount of an organic solvent was added to the starting materials having the types and ratios (molar parts) shown in Table 1,
The mixture was pulverized in a resin pot containing a zirconia pulverization medium of mmφ. In Table 1, sample numbers 8 to 1
0 is a comparative example. Details of the starting material for each sample number are as follows.

That is, in Sample No. 8, the same starting material as Sample No. 1 was used. In sample number 9, the same starting material as sample number 5 was used. Further, in Sample No. 10, the same starting material as Sample No. 7 was used, but B-Ba-Si
The amount of compound was different from sample no.

Thereafter, a multilayer ceramic capacitor using a non-reducing dielectric ceramic as a ceramic layer was completed at the firing temperatures shown in Table 1 and otherwise in the same manner as in the example.

Next, with respect to each of the obtained multilayer ceramic capacitors of Examples and Comparative Examples, the particles and grain boundaries of the ceramic layers were observed. That is, the surface of the multilayer ceramic capacitor that had been broken and thermally etched was observed with a scanning electron microscope, and the particle size was determined from the photograph. Further, the grain boundaries were observed with a transmission electron microscope to determine the presence or absence of a grain boundary phase and its thickness. Table 1 shows the above results.

When the composition of the particles and the grain boundaries of the ceramic layer was analyzed by a transmission analysis electron microscope, it was found that the composition had a uniform composition within each particle and the same composition among the particles. It was also confirmed that the constituent components differed between the particles and the grain boundary phase. Also, when the structure of the ceramic particles is observed with a transmission electron microscope, the individual particles have a uniform crystal structure without showing a core-shell structure or the like, and have the same crystal structure among the particles. It was confirmed that.

Next, the electrical characteristics of the obtained multilayer ceramic capacitor were determined. That is, the capacitance and the dielectric loss were measured at a frequency of 1 kHz, a voltage of 1 Vrms, and a temperature of 25 ° C., and the dielectric constant was calculated from the capacitance. Also, at 25 ° C, 10
A DC voltage of V was applied, the insulation resistance was measured, and the specific resistance was determined. Also, capacitance against temperature change (ie, dielectric constant)
Was determined as the rate of change at 85 ° C. and 125 ° C. based on 25 ° C. Further, the rate of change of the capacitance (that is, the dielectric constant) when a DC bias of 3 kV / mm was applied was determined on the basis of no bias application. Table 2 shows the results.

[0044]

[Table 2]

As is clear from the above observation and analysis results, the ceramic dielectric of the example of the present invention has a maximum particle diameter of 0.5 μm or less , an average particle diameter of 0.1 to 0.3 μm, It shows a uniform composition and crystal system within the individual particles. Further, Sample Nos. 5 to 7 have a grain boundary phase having a thickness of 0.5 to 5.0 nm which is different from the constituent components of the particles.

When the non-reducing dielectric ceramic of the present invention having such a structure is used as a multilayer ceramic capacitor, the change rate of the dielectric constant at 125 ° C. is 15%.
When the value is less than the above, the dielectric constant-temperature characteristic satisfying the X7R characteristic is exhibited.
The change in dielectric constant when a DC bias is applied is 20%.
Less than and good.

On the other hand, as shown in sample 8,
When the maximum particle size exceeds 0.5 μm, the dielectric loss is 5
%, And the rate of change of the dielectric constant with temperature is 1
The dielectric constant becomes larger than 5%, and the change rate of the dielectric constant when a DC bias is applied becomes larger than 20%, which is not preferable. Further, as shown in Sample No. 9, when the average particle diameter exceeds 0.3 μm and the maximum particle diameter exceeds 0.5 μm, the dielectric loss increases beyond 5%, and the rate of change of the dielectric constant with temperature increases. This is undesirably larger than 15%, and the rate of change of the dielectric constant when a DC bias is applied is larger than 20%. Further, as shown in Sample No. 10, when the thickness of the grain boundary phase exceeds 5.0 nm, there is no problem in the rate of change of the dielectric constant with temperature and the rate of change of the dielectric constant when a DC bias is applied. This is not preferable because the dielectric constant decreases.

When a reliability test was conducted on each of the above-mentioned samples by continuously applying a DC voltage of 18 V at a temperature of 150 ° C. for 1000 hours, no deterioration in characteristics such as insulation resistance was observed in the products of the examples of the present invention. . On the other hand, in the samples of Comparative Examples 8 and 9, the insulation resistance was deteriorated due to the large particle diameter, and there was a problem in reliability. In the above example, since an organic solvent is used during mixing and pulverization, alkoxide, acetylacetonate or metal soap of each metal is used as a compound soluble in the organic solvent. When is used, water-soluble compounds such as nitrates, acetates, borates, and chlorides can be used as appropriate.

In the above embodiment, firing is performed in a reducing atmosphere. However, firing in an air atmosphere promotes ceramic particle growth. In particular, the rate of change of the dielectric constant with temperature and the dielectric constant when a DC bias is applied are increased. Is large, which is not preferable.

In the above embodiment, Ag was used as the external electrode.
However, it is more preferable to use a base metal for the external electrode, since the electrical connection with the internal electrode, which is a base metal, is excellent.

In the above examples, samples Nos. 1 to 3 were also confirmed to have a composition in which the molar ratio of Ba: Ti of BaTiO ₃ was shifted from the stoichiometric ratio. No significant difference was observed in the characteristics.

Further, in the above-described embodiment, the case where the multilayer ceramic component is a multilayer ceramic capacitor has been described, but it has been confirmed that good characteristics can be exhibited also in the case of another multilayer ceramic component such as a multilayer ceramic substrate. .

[0053]

As is clear from the above description, the non-reducing dielectric ceramic having the structure shown in the present invention is excellent in the temperature characteristic and the electric field characteristic of the dielectric constant.

Therefore, the non-reducing dielectric ceramic is used as a dielectric, and a conductor made of a base metal is formed between the dielectric ceramics and on the surface of the dielectric ceramic to form a multilayer ceramic electronic component such as a multilayer ceramic capacitor or a multilayer substrate. The size and cost can be reduced.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated body 2, 4 Dielectric ceramic 3 Internal electrode 5 External electrode 6, 7 Plating film

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI H05K 3/46 H05K 3/46 H T ( 56) references Patent Rights 7-69634 (JP, a) Patent Rights 7-37749 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35 H01B 3/00 H01G 4/12, 4/30 H05K 3/46

Claims (4)

(57) [Claims] 1. A sintered body comprising a plurality of particles having a maximum particle diameter of 0.5 μm or less and an average particle diameter of 0.1 to 0.3 μm, wherein the plurality of particles are individual particles. A non-reducible dielectric ceramic characterized by exhibiting a uniform composition and crystal system within the same, and exhibiting the same composition and crystal system between particles of each other. 2. The non-reducible dielectric ceramic according to claim 1, wherein a grain boundary phase having a thickness of 5 nm or less having a different component from that of the particles is present at the grain boundaries of the particles. 3. A non-reducing dielectric ceramic according to claim 1 or 2, wherein the non-reducing dielectric ceramic is a laminate of ceramic layers, and a conductor made of a base metal is formed between the ceramic layers of the laminate. A multilayer ceramic electronic component. 4. The non-reducing dielectric ceramic according to claim 1 or 2 is a laminate of ceramic layers, and an internal conductor made of a base metal is formed between the ceramic layers of the laminate. An outer conductor made of a base metal which is electrically connected to the inner conductor is formed on a surface of the multilayer body, wherein the multilayer ceramic electronic component is provided.