JP2001230150A - Laminated ceramic capacitor and method of manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor which does not raise such a problem that the electric field intensity of each dielectric layer increases and dielectric breakdowns are apt to occur between internal electrodes and, accordingly, the service life of the capacitor becomes shorter even when the number of laminated dielectric layers is increased by reducing the thicknesses of the layers with the purpose of reducing the size of the capacitor and increasing the capacitance of the capacitor. SOLUTION: In this laminated ceramic capacitor which is constituted by integrally laminating a plurality of dielectric layers, made of sintered bodies of ceramic particles, each of which is composed of a crystalline core section and a shell section surrounding the core section, and internal electrodes upon another, one, two, or more kinds of additive elements selected from among Mn, V, Cr, Mo, Fe, Ni, Cu, and Co are mixed in the core sections with concentration gradients (concentration distributions).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to improve the life characteristics by increasing the electric resistance of ceramic particles forming a dielectric layer, and to further advance the miniaturization and large capacity by thinning and multilayering. And a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, a multilayer ceramic capacitor comprises a chip-shaped body and a pair of external electrodes formed at both ends of the body. The element body generally comprises a laminate in which a large number of dielectric layers and internal electrodes are alternately laminated. Among the internal electrodes, adjacent internal electrodes face each other via a dielectric layer and are electrically connected to different external electrodes.

Here, when the temperature characteristic of the multilayer ceramic capacitor is the B characteristic of the JIS standard, the dielectric layer contains, for example, barium titanate as a main component and a rare earth element oxide, Mn, V, Cr, Mo, Fe, N
A reduction-resistant ceramic composition to which a compound of an acceptor element such as i, Cu, or Co is added is used. As the internal electrode, for example, a material obtained by sintering a conductive paste containing Ni metal powder as a main component is used.

[0004] After removing a chip-shaped laminate in which ceramic green sheets and internal electrode patterns are alternately and integrally laminated, the element body is heated at 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 the dielectric layers is further reduced.

However, when the thickness of the dielectric layer is reduced, the electric field strength per layer is increased, dielectric breakdown is likely to occur between the internal electrodes, and the life of the multilayer ceramic capacitor is shortened.

An object of the present invention is to provide a multilayer ceramic capacitor capable of achieving a small size and a large capacity without a decrease in life due to dielectric breakdown or the like even when the dielectric layers are multilayered and thinned, and a method of manufacturing the same. Aim.

[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 layer is made of a sintered body of ceramic particles. The ceramic particles comprise a crystalline core portion and a shell portion surrounding the core portion, wherein the core portion contains an additive element with a concentration gradient (concentration distribution). It is.

Here, the concentration of the additive element contained in the core part increases from the center of the core part toward the shell part.

The ceramic particles may be any of a barium titanate-based ceramic composition, a strontium titanate-based ceramic composition, and a lead-based ceramic composition. In addition, as for this ceramic composition, particularly, the capacitance-temperature characteristic of the multilayer ceramic capacitor is JIS.
A ceramic composition that satisfies standard B characteristics is preferred.

Further, Mn, V,
One or more elements selected from Cr, Mo, Fe, Ni, Cu and Co are preferred. Preferably, the additive element is contained in the core portion in a range of 10 to 1000 ppm. If the amount of the additive element is less than 10 ppm, an increase in the life cannot be expected, and if it exceeds 1000 ppm, a desired dielectric constant cannot be obtained.

The material of the internal electrode is not limited to a material containing Ni as a main component, but may be a material containing Pd, Ag-Pd or the like as a main component. In addition, Ho,
Sc, Y, Gd, Dy, Er, Yb, Tb, Tm and L
one or more rare earth elements selected from u, Mg
And BaSiO ₃ may be included. Further, Mn, V, Cr, Mo, Fe, Ni, Cu, Co,
A small amount of P, Nb, Ta may be contained. Further, the grain boundaries of the ceramic particles may be filled with a glass component.

Further, the method for manufacturing a multilayer ceramic capacitor according to the present invention includes a raw material preparing step of preparing a ceramic raw material, and a sheet forming step of forming a ceramic green sheet using the ceramic raw material obtained in the raw material preparing step. A printing step of printing an internal electrode pattern on the ceramic green sheet obtained in the sheet forming step, a laminating step of laminating the ceramic green sheets having undergone the printing step to obtain a laminate, and a laminating step obtained by the laminating step. The method includes a cutting step of cutting the laminate for each internal electrode pattern to obtain a chip-shaped laminate, and a firing step of firing the chip-shaped laminate obtained in the cutting step.

The raw material preparation step includes a step of adding an additive element to the crystal structure of the main component compound of the ceramic raw material. The step of allowing the additive element to be contained in the crystal structure of the main component compound of the ceramic raw material is also a step of mixing the additive element compound with the raw material compound of the main component compound of the ceramic raw material to synthesize the main component compound. Alternatively, a step of mixing the compound of the additive element with the main component compound of the ceramic raw material and calcining the mixture may be used.

The ceramic raw material may be any of a barium titanate-based material, a strontium titanate-based material, and a lead-based material. The additive element is M
One or more elements selected from n, V, Cr, Mo, Fe, Ni, Cu and Co are preferred.

It is preferable that the additive element is contained in the main component compound of the ceramic raw material in an amount of 10 to 1000 ppm. If the amount of the additive element is less than 10 ppm, an increase in the life cannot be expected, and if it exceeds 1000 ppm, a desired dielectric constant cannot be obtained.

In the raw material preparation step, Ho, Sc, Y, Gd, Dy, Er, Y
A compound of one or more rare earth elements selected from b, Tb, Tm and Lu and MgO may be added. Further, Mn, V, Cr, Mo, F
A small amount of a compound of e, Ni, Cu, Co, P, Nb, and Ta may be added. Further, a glass component (Li, B, Si, etc.) may be added to the ceramic raw material as a sintering aid.

Further, the firing step may include a reoxidation step of firing the chip-shaped laminate in a non-oxidizing atmosphere and thereafter firing in an oxidizing atmosphere. Also,
The conductive paste for forming the internal electrodes is not limited to one containing Ni as a main component, and may be one containing Pd, Ag-Pd, or the like as a main component.

[0019]

EXAMPLE First, equimolar amounts of BaCO ₃ and TiO ₃ were each weighed, and any one of Mn, V, Cr, and Mo was added thereto in the range of 10 to 2000 ppm, and mixed well. Calcination was performed at 200 ° C. for 2 hours. BaCO ₃ and TiO ₃ react by this calcination, and 10 to 2000 pp
BaTiO containing any of Mn, V, Cr and Mo
₃ was formed.

Next, 100 mole parts of the BaTiO
₃ (containing a trace amount of Mn), a rare earth element (H
o, Sc, Y, Gd, Dy, Er, Yb, Tb, Tm,
Lu) oxide, MgO and BaSiO ₃ were prepared according to sample Nos. 1 to 11, were mixed well, and calcined at 1000 ° C. for 2 hours.

Next, 15% by weight of an organic binder composed of an aqueous solution of an acrylate polymer, glycerin and a condensed phosphate, and 50% by weight of water are added thereto, and these are put into a ball mill and mixed well to obtain a ceramic. Got a rally.

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 0.2 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 is lowered to 600 ° C. at a rate of 100 ° C./h, the atmosphere is changed to the air atmosphere (oxidizing atmosphere), and the oxidation treatment is performed by maintaining the temperature 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 were examined. The results are as shown in Table 1. Here, the life is 17
It was obtained under the conditions of 0 ° C. and 70 V. 1
Was expressed as a magnification when the value of was set to 1. In addition, No. 1,
No. 9 is a comparative example. 1 is an example not containing Mn,
No. 9 is an example in which Mn was excessively added.

[0031]

[Table 1]

Then, the ceramic particles forming the dielectric layer of the multilayer ceramic capacitor thus produced were analyzed by STEM (analytical electron microscope).
As shown in FIG. 1, it was confirmed that Mn was present in the core. In addition, in FIG. 1, 10 is a ceramic particle, 1
2 is a core part and 14 is a shell part.

[0033]

As described above, according to the present invention, Mn, V, Cr, Mo, Fe,
Since acceptor-type additive elements such as Ni, Cu, and Co are contained with a concentration gradient, the reoxidation property of the core part is improved, the electric resistance of the core part is increased, and the life characteristics, particularly, the dielectric properties are improved. The life characteristics when the body layer is thinned are improved, the thinning and the multi-layering become possible, and the multilayer ceramic capacitor can be reduced in size and capacity.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a concentration distribution of an acceptor element contained in ceramic particles forming a dielectric layer of a multilayer ceramic capacitor according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 ceramic particles 12 core part 14 shell part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Kishi 6-16-20 Ueno, Taito-ku, Tokyo F-term in Taiyo Denki Co., Ltd. (reference) 5E001 AB03 AC04 AC09 AD03 AE00 AE01 AE02 AE03 AE04 AF00 AF06 AH01 AH05 AH06 AH09 AJ01 AJ02

Claims (16)

[Claims] 1. A plurality of dielectric layers and a plurality of internal electrodes are integrally laminated, wherein the dielectric layers are made of a sintered body of ceramic particles, and the ceramic particles are formed of a crystalline core portion. And a shell portion surrounding the core portion, wherein the core portion contains an additive element with a concentration gradient (concentration distribution). 2. The multilayer ceramic capacitor according to claim 1, wherein the concentration of the additive element contained in the core increases from the center of the core toward the shell. 3. The multilayer ceramic capacitor according to claim 1, wherein the ceramic particles are made of a barium titanate-based material, a strontium titanate-based material, or a lead-based material. 4. The method according to claim 1, wherein the additive element is Mn, V, Cr, M.
4. It is composed of one or more elements selected from o, Fe, Ni, Cu and Co.
The multilayer ceramic capacitor according to any one of the above. 5. The method according to claim 1, wherein the additive element is present in the core portion in an amount of 10 to 10.
The multilayer ceramic capacitor according to any one of claims 1 to 4, wherein the content is in a range of 1000 ppm. 6. Ho, Sc, Y, G
The lamination according to any one of claims 1 to 5, further comprising one or more rare earth elements selected from d, Dy, Er, Yb, Tb, Tm, and Lu, and Mg. Ceramic capacitors. 7. The multilayer ceramic capacitor according to claim 1, wherein a glass component fills a grain boundary of the ceramic particles. 8. A raw material preparing step for preparing a ceramic raw material, a sheet forming step for forming a ceramic green sheet using the ceramic raw material obtained in the raw material preparing step, and a ceramic green sheet obtained in the sheet forming step A printing step of printing an internal electrode pattern on the substrate, a laminating step of laminating the ceramic green sheets having undergone the printing step to obtain a laminated body, and cutting the laminated body obtained in the laminating step for each internal electrode pattern into chips. Cutting step of obtaining a chip-shaped laminate, and a firing step of firing the chip-shaped laminate obtained in the cutting step, wherein the raw material preparation step includes adding an additive element in a main component compound of the ceramic raw material. A method for producing a multilayer ceramic capacitor, characterized by comprising a step of containing. 9. The step of causing the additive element to be contained in the main component compound of the ceramic raw material, wherein the compound of the additive element is mixed with the raw material compound of the main component compound of the ceramic raw material to synthesize the main component compound. 9. The method for manufacturing a multilayer ceramic capacitor according to claim 8, comprising a step. 10. The method according to claim 1, wherein the step of adding an additive element to the main component compound of the ceramic raw material comprises a step of mixing a compound of the additive element with the main component compound of the ceramic raw material and calcining. The method for manufacturing a multilayer ceramic capacitor according to claim 8. 11. The multilayer ceramic capacitor according to claim 8, wherein the ceramic raw material is made of a barium titanate-based material, a strontium titanate-based material, or a lead-based material. Method. 12. The method according to claim 12, wherein the additive element is Mn, V, Cr, M.
2. The semiconductor device according to claim 1, wherein the material is at least one element selected from the group consisting of o, Fe, Ni, Cu, and Co.
2. The method for manufacturing a multilayer ceramic capacitor according to any one of 1. 13. The multilayer ceramic capacitor according to claim 8, wherein the additive element is contained in the main component compound of the ceramic raw material in a range of 10 to 1000 ppm. Method. 14. Ho, S is contained in the ceramic raw material.
c, Y, Gd, Dy, Er, Yb, Tb, Tm and Lu
9. A compound comprising one or more rare earth elements selected from the group consisting of MgO and MgO.
14. The method for manufacturing a multilayer ceramic capacitor according to any one of 13. 15. The method according to claim 1, wherein the firing step includes a re-oxidation step in which the chip-shaped laminate is fired in a non-oxidizing atmosphere and then fired in an oxidizing atmosphere. 15. The method for manufacturing a multilayer ceramic capacitor according to any one of 8 to 14. 16. The method according to claim 8, wherein the ceramic raw material contains a glass component.