JP2001307940A - Laminated ceramic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which an electric field is increased in intensity per layer when dielectric layers are each lessened in thickness and increased in number of layers so as to enhance a laminated ceramic capacitor in capacitance and to lessen it in size at the same time, and a dielectric breakdown is liable to occur between inner electrodes, so that the laminated ceramic capacitor is shortened in service life and deteriorated in reliability of electrical properties. SOLUTION: Dielectric layers and inner electrode layers are laminated into a laminated ceramic capacitor of integral structure, where the dielectric layer is made of dielectric porcelain composition formed of sintered bodies that contain main component particles and these of a secondary phase formed at their grain boundaries. The component particles of a secondary phase are set higher in insulation resistance than the main component particles. At this point, a component contained as a solid solution in the main component particles may serve as a main component of the main particles of a secondary phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic ceramic capacitor having improved life characteristics and capable of achieving further miniaturization and large capacity by thinning and multilayering, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 2 is an explanatory view of a multilayer ceramic capacitor. As shown in the figure, the multilayer ceramic capacitor includes a chip-shaped element body 18 and a pair of external electrodes 20 formed on both ends of the element body 18. The element body 18 is generally formed of a laminate in which a large number of dielectric layers 22 and internal electrodes 24 are alternately laminated. Of the internal electrodes 24, the adjacent internal electrodes 24, 24 face each other via the dielectric layer 22,
It is electrically connected to separate external electrodes 20 and 20.

Here, as a material of the dielectric layer 22, for example, a reduction-resistant dielectric porcelain composition containing barium titanate as a main component and an oxide of a rare earth element added thereto is used. As shown in FIG. 3, the dielectric porcelain composition is composed of ceramic particles 10 and a sintering aid 26. The ceramic particles 10 are composed of a core portion 12 at the center and a shell portion 14 surrounding the core portion 12. Become. In addition, the internal electrodes 24
For example, a material obtained by sintering a conductive paste containing Ni metal powder as a main component is used.

The element body 18 is obtained by removing a chip-like laminate in which ceramic green sheets and internal electrode patterns are alternately and integrally laminated, and then subjecting the laminate to a high temperature of about 1200 to 1300 ° C. in a non-oxidizing atmosphere. It is manufactured by firing and then reoxidizing in an oxidizing atmosphere.

[0005]

With the recent trend of miniaturization and high density of electronic circuits, multilayer ceramic capacitors are also required to have a small size and a large capacity.
To increase the size and the capacity, the number of stacked dielectric layers is further increased, and the thickness of each dielectric layer is further reduced.

However, when the thickness of the dielectric layer is reduced, the electric field strength per one layer increases, and the life of the multilayer ceramic capacitor is shortened, so that a multilayer ceramic capacitor having a desired life cannot be obtained. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multilayer ceramic capacitor which has a desired life even when the dielectric layers are multilayered and thinned, and which can be reduced in size and capacity, and a method of manufacturing the same.

[0008]

A multilayer ceramic capacitor according to the present invention is formed by integrally laminating a plurality of dielectric layers and a plurality of internal electrodes, and the dielectric layers are made of a dielectric ceramic composition. A sintered body including a main component particle and a secondary phase (a portion other than the main component particle) formed at a grain boundary (a portion between the particles) of the main component particle; Wherein the secondary phase has a higher insulation resistance than the main component particles.

[0009] Here, a component that is dissolved in the main component particles may be a main component of the secondary phase. Also,
The secondary phase may be formed from a crystal.

The main component particles include a core portion forming a central portion, and a shell portion surrounding the core portion.
The core may be made of a crystalline material, the shell may be made of a solid solution, and the insulation resistance of the secondary phase may be higher than the insulation resistance of the shell.

The dielectric porcelain composition may be formed of, for example, a barium titanate-based dielectric porcelain composition, a strontium titanate-based dielectric porcelain composition, or a lead-based dielectric porcelain composition. However, you may form with a dielectric ceramic composition other than these.

The dielectric ceramic composition may be either a dielectric ceramic composition having a JIS temperature characteristic of B characteristic or a dielectric ceramic composition having an F characteristic. Here, the F characteristic is-
Capacitance change rate of + 20% to 25-85 ° C
Within the range of −80%, the B characteristic is −25 to +
Capacitance change rate is -10 to + 10% in 85 ° C temperature range
Is within the range.

In the secondary phase, Sc, Y, Gd, D
One, two or more rare earth elements selected from y, Ho, Er, Yb, Tm, and Lu may be contained. In this case, the rare earth element is preferably contained at a ratio of 2 to 18 atm% with respect to 100 mol% of the dielectric ceramic composition. If the rare earth element is less than 2 atm%, the desired life (lif
e) is not obtained, and if it exceeds 18 atm%, the desired dielectric constant
This is because (ε) cannot be obtained.

Further, Mg may be contained in the secondary phase. In this case, it is preferable that Mg is contained in a ratio of 0.8 to 5.0 atm% based on 100 mol% of the dielectric ceramic composition. Desired life if Mg is less than 0.8 atm%
(life) cannot be obtained, and even if it exceeds 5 atm%, the extension of the life cannot be expected any longer.

Further, Mn, V, Cr, C is contained in the secondary phase.
One, two or more elements selected from o, Fe, Ni, Cu, Mo, P, Nb and Ta may be included. Further, the sintering aid is not limited to BaSiO ₃ used in the examples, and may include Li or B.

Further, the method of manufacturing a multilayer ceramic capacitor according to the present invention includes a raw material step of preparing a ceramic raw material including a main component material forming a main component compound and an auxiliary component material forming a solid solution with the main component compound. A sheet forming step of forming a ceramic green sheet using the ceramic raw material, a printing step of printing an internal electrode pattern on the ceramic green sheet, and a stacking step of forming a laminate by stacking the ceramic green sheets after the printing step A step of cutting the laminate into internal electrode patterns to obtain a chip-shaped laminate, and a firing step of firing the chip-shaped laminate obtained in the cutting step. The amount of the raw material is set to be equal to or larger than the limit at which the raw material is dissolved in the main component compound.

Here, as the ceramic raw material, for example, a barium titanate-based ceramic raw material, a strontium titanate-based ceramic raw material, or a lead-based ceramic raw material can be used. May be used.

Further, Sc, Y,
A compound of one or more rare earth elements selected from Gd, Dy, Ho, Er, Yb, Tm, and Lu may be included. Here, it is preferable that the rare earth element is contained in a ratio of 2 to 18 atm% with respect to 100 mol% of the ceramic raw material. Life is less than 2atm% rare earth element
This is because the extension of (life) cannot be expected, and if it exceeds 18 atm%, the desired dielectric constant (ε) cannot be obtained.

Further, Mg may be contained in the subcomponent. Here, it is preferable that Mg is contained at a ratio of 0.8 to 5.0 atm% with respect to 100 mol% of the ceramic raw material. If the Mg content is less than 0.8 atm%, the desired life (lif
This is because e) cannot be obtained, and even if it exceeds 5 atm%, a longer life can not be expected.

Further, Mn, V, Cr and C are contained in the secondary phase.
One, two or more elements selected from o, Fe, Ni, Cu, Mo, P, Nb and Ta may be included. Further, the sintering aid is not limited to BaSiO ₃ used in the examples, and may include Li or B.

Further, the firing step may include a re-oxidation step of firing the chip-shaped laminate in a non-oxidizing atmosphere and then firing in an oxidizing atmosphere.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, BaCO ₃ , MgO, SrO, TiO
₂ and oxides of rare earth elements (Ho, Dy, Er, Sm) were weighed, and these compounds were put into a pot mill together with alumina balls and water, and sufficiently stirred and mixed to obtain a raw material mixture.

Next, the raw material mixture is placed in a stainless steel pot, dried at 150 ° C. using a hot air drier, coarsely pulverized, and the coarsely ground raw material mixture is subjected to a tunnel furnace. About 1200 ° C in air
For 2 hours to obtain a powder of the first basic component.

Further, BaCO ₃ and ZrO ₂ were weighed so as to be equimolar, mixed, dried and pulverized, and calcined in the atmosphere at about 1250 ° C. for 2 hours. A powder of the second basic component was obtained.

Then, 98 mole parts (976.28 g) of the powder of the first basic component and 2 mole parts (23.85 g) of the powder of the second basic component were mixed to obtain 1000 g of the basic component.

Next, with respect to 100 mole parts of the basic component,
1.5 mol% of BaSiO ₃ (sintering aid), MnO
(Reduction inhibitor) is added in an amount of 0.05 mol%, and an organic binder composed of an aqueous solution of an acrylate polymer, glycerin and a condensed phosphate is added in an amount of 15% by weight.
Add 50% by weight of water, put them in a ball mill,
The mixture was pulverized and mixed to prepare a porcelain raw material slurry.

Next, the ceramic slurry is placed in a vacuum defoaming machine to remove bubbles, and the ceramic slurry is placed in a reverse roll coater, and the thin film obtained therefrom is continuously received on a long polyester film. At the same time, the film was heated to 100 ° C. and dried on the same film to obtain a square ceramic green sheet having a thickness of about 5 μm and a square of 10 cm.

On the other hand, 10 g of nickel powder having an average particle size of 1.5 μm and 0.9 g of ethyl cellulose dissolved in 9.1 g of butyl carbitol were placed in a stirrer.
By stirring for a time, a conductive paste for an internal electrode was obtained. Then, using this conductive paste, a length of 14 m
An internal electrode pattern was printed on one side of the ceramic green sheet through a screen having 50 m and 7 mm wide patterns, and this was dried.

Next, eleven ceramic green sheets on which the internal electrode patterns were printed were laminated with the internal electrode patterns facing upward. At this time, the printed surfaces of the adjacent upper and lower ceramic green sheets were arranged so as to be shifted by about half in the longitudinal direction of the internal electrode pattern. Furthermore,
On the upper and lower surfaces of the laminate, ceramic green sheets for a protective layer on which no internal electrode pattern was printed were laminated with a thickness of 200 μm.

Next, the laminate is pressed at a temperature of about 50 ° C. by applying a load of about 40 tons in a thickness direction, and thereafter,
This laminate is cut into a lattice shape for each internal electrode pattern,
Fifty 3.2 × 1.6 mm chip-shaped laminates were obtained.

Next, this chip-shaped laminate is placed in a furnace capable of firing in an atmosphere, and is heated at 100 ° C./h in an air atmosphere.
The temperature was raised to 600 ° C. at a rate of to burn off the organic binder.

After that, the atmosphere of the furnace was changed from the air atmosphere to H _2.
The atmosphere was changed to a reducing atmosphere of (2% by volume) + N ₂ (98% by volume). Then, while keeping the furnace in the reducing atmosphere, the heating temperature of the laminated chip was raised from 600 ° C. to the sintering temperature of 1130 ° C. at a rate of 100 ° C./h, and 11
30 ° C. (maximum temperature) was maintained for 3 hours.

Then, the temperature was lowered to 600 ° C. at a rate of 100 ° C./h, the atmosphere was changed to the air atmosphere (oxidizing atmosphere), and the oxidation treatment was carried out at 600 ° C. for 30 minutes.
Thereafter, the resultant was cooled to room temperature to obtain a body of a multilayer ceramic capacitor.

Next, zinc, glass frit and vehicle (v) are applied to the side surfaces of the element where the ends of the internal electrodes are exposed.
ehicle) and dried.
This is baked in the air at a temperature of 550 ° C. for 15 minutes to form a zinc electrode layer, a copper layer is further formed thereon by an electroless plating method, and a Pb—Sn solder layer is further formed thereon by an electroplating method. To form a pair of external electrodes.

The life of the multilayer ceramic capacitor thus manufactured and the dielectric constant of the dielectric layer
When (ε) was examined, it was as shown in Table 1.

Here, the life is as follows:
A voltage of 70 V was applied to the multilayer ceramic capacitor, and the breakdown time was measured and determined. In addition, the numerical value of the life in Table 1 shows the sample No. It is represented by the magnification when the value of 1 is set to 1.

The dielectric constant (ε) is obtained by measuring the capacitance of a multilayer ceramic capacitor under the conditions of a temperature of 20 ° C., a frequency of 1 kHz, and a voltage of 1.0 V. It was calculated from the thickness of the dielectric layer.

[0038]

[Table 1]

From the above results, at least a 20% life (L
up of ife) was recognized. However, no. It was also found that when the added amount of the rare earth element exceeded 20 atm% as in the sample No. 6, the dielectric constant (ε) was greatly reduced.

When the cross section of the dielectric layer of the multilayer ceramic capacitor was observed with a microscope, it was found that a secondary phase 16 was formed at the grain boundaries of the ceramic particles 10 as shown in FIG. When the components of the secondary phase 16 were analyzed, it was found that they were substantially the same as the additive components dissolved in the ceramic particles 10.

[0041]

According to the present invention, the secondary phase having a high insulating property is present in a dispersed state in the dielectric ceramic composition forming the dielectric layer, so that the voltage applied to the dielectric layer can be reduced. Partially shared by the secondary phase, the electrical load on the ceramic particles is reduced, and the life characteristics of the multilayer ceramic capacitor, especially when the dielectric layer is made thinner, are improved. The multilayer ceramic capacitor has an effect that the multilayer ceramic capacitor can be reduced in size and increased in capacity.

Further, according to the present invention, when the secondary phase is made of a crystalline material, a decrease in the dielectric constant of the dielectric layer can be suppressed,
This has the effect of contributing to the miniaturization and large capacity of the multilayer ceramic capacitor.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a fine structure of a porcelain composition forming a dielectric layer of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is an explanatory diagram of a multilayer ceramic capacitor.

FIG. 3 is an explanatory view of a fine structure of a porcelain composition forming a dielectric layer of a conventional multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ceramic particle 12 Core part 14 Shell part 16 Secondary phase 18 Element body 20 External electrode 22 Dielectric layer 24 Internal electrode 26 Sintering aid

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Kishi 6-16-20 Ueno, Taito-ku, Tokyo F-term within Taiyo Denki Co., Ltd. (reference) 5E001 AB03 AD00 AE00 AE01 AE02 AE03 AE04 AF06 AH01 AH06 AH08 AH09 AJ01 AJ02 5E082 AA01 AB03 BC39 EE04 EE35 FG06 FG26 FG54 LL01 LL02 LL03 MM24 PP03

Claims (18)

[Claims] 1. A plurality of dielectric layers and a plurality of internal electrodes are integrally laminated, wherein the dielectric layers are made of a dielectric ceramic composition, wherein the dielectric ceramic composition comprises main component particles, A multilayer ceramic capacitor comprising a sintered body including a secondary phase formed at a grain boundary of the main component particles, wherein the secondary phase has a higher insulation resistance than the main component particles. 2. The multilayer ceramic capacitor according to claim 1, wherein a component dissolved in the main component particles is a main component of the secondary phase. 3. The main component particles include a core forming a central portion and a shell surrounding the core, wherein the core is formed of a crystalline material and the shell is formed of a solid solution. 3. The multilayer ceramic capacitor according to claim 1, wherein the insulation resistance of the secondary phase is higher than the insulation resistance of the shell portion. 4. 4. The multilayer ceramic capacitor according to claim 1, wherein the secondary phase is made of a crystalline material. 5. The dielectric ceramic composition according to claim 1, comprising a barium titanate-based dielectric ceramic composition, a strontium titanate-based dielectric ceramic composition, or a lead-based dielectric ceramic composition. Item 5. The multilayer ceramic capacitor according to any one of Items 1 to 4. 6. In the secondary phase, Sc, Y, Gd, Dy,
The multilayer ceramic capacitor according to any one of claims 1 to 5, further comprising one or more rare earth elements selected from Ho, Er, Yb, Tm, and Lu. 7. The multilayer ceramic capacitor according to claim 6, wherein the rare earth element is contained in an amount of 2 to 18 atm% based on 100 mol% of the dielectric ceramic composition. 8. The multilayer ceramic capacitor according to claim 1, wherein Mg is contained in the secondary phase. 9. The multilayer ceramic capacitor according to claim 8, wherein Mg is contained in an amount of 0.8 to 5.0 atm% based on 100 mol% of the dielectric ceramic composition. 10. Mn, V, Cr, C in the secondary phase
The multilayer ceramic according to any one of claims 1 to 9, wherein one or more elements selected from the group consisting of o, Fe, Ni, Cu, Mo, P, Nb, and Ta are contained. Capacitors. 11. A raw material process for preparing a ceramic raw material including a main component material for forming a main component compound and a subcomponent material for forming a solid solution in the main component compound, and forming a ceramic green sheet using the ceramic material. A sheet forming step, a printing step of printing an internal electrode pattern on the ceramic green sheet, and a laminating step of forming a laminate by laminating the ceramic green sheets after the printing step,
A cutting step of cutting the laminated body for each internal electrode pattern to obtain a chip-shaped laminated body; and a firing step of firing the chip-shaped laminated body obtained in the cutting step. Is more than the limit of solid solution in the main component compound. 12. The method according to claim 11, wherein the ceramic material comprises a barium titanate-based ceramic material, a strontium titanate-based ceramic material, or a lead-based ceramic material. 13. Sc, Y, G in the ceramic raw material
13. The multilayer ceramic capacitor according to claim 11, wherein the multilayer ceramic capacitor according to claim 11, further comprising one or more compounds of a rare earth element selected from d, Dy, Ho, Er, Yb, Tm, and Lu. Production method. 14. The method according to claim 13, wherein the rare earth element is contained in an amount of 2 to 18 atm% based on 100 mol% of the ceramic raw material. 15. The method of manufacturing a multilayer ceramic capacitor according to claim 11, wherein Mg is contained in said subcomponent. 16. The method according to claim 15, wherein Mg is contained in an amount of 0.8 to 5.0 atm% based on 100 mol% of the ceramic raw material. 17. Mn, V, Cr, C in the secondary phase
The multilayer ceramic according to any one of claims 11 to 16, wherein the multilayer ceramic includes one or more elements selected from o, Fe, Ni, Cu, Mo, P, Nb, and Ta. Manufacturing method of capacitor. 18. The method according to claim 11, wherein the firing step includes a re-oxidation step of firing the chip-shaped laminate in a non-oxidizing atmosphere and then firing in an oxidizing atmosphere. 18. The method for manufacturing a multilayer ceramic capacitor according to any one of claims 17 to 17.