JP2003007562A - Multilayer ceramic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the contribution of an electric barrier caused by a grain boundary of dielectric layers becomes small, and field intensity applied to one layer out of the dielectric layers becomes large when the layer is thinned, so that the insulation property of the dielectric layers is apt to be deteriorated in a high temperature load life test, and therefor it is difficult to make the dielectric layers thinner than or equal to 3 μm or further 2 μm in the conventional technique. SOLUTION: Metal powder or organic metal compound is contained in a ceramic material for forming the dielectric layers. In the case of baking, metal is driven out from the dielectric layers, thereby forming a thin film metal layer that is an electric barrier between the dielectric layers and an internal electrode layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-layer large-capacity type monolithic ceramic capacitor having a dielectric layer having a thickness of, for example, 5 μm or less, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a monolithic ceramic capacitor is
A large number of layers of ceramic green sheets and internal electrode patterns are alternately laminated, and the internal electrode patterns are cut, external electrode paste is added to the ends of the obtained chip-shaped laminated body, and firing is performed at a high temperature of about 1200 ° C. It is manufactured by

Here, the ceramic green sheet is formed by connecting ceramic raw material powders with an organic binder to form a sheet, and becomes a dielectric layer by firing. The internal electrode pattern and the external electrode paste are made of a conductive paste containing metal powder as a main component, and this conductive paste becomes an internal electrode layer or an external electrode by firing.

By the way, the monolithic ceramic capacitor is
Material composition of dielectric layer, physical properties of raw material powder for forming dielectric layer, physical properties of ceramic green sheet for forming dielectric layer, simultaneous firing of internal electrode layer and dielectric layer, reoxidation technology of dielectric layer Now, the thickness of the dielectric layer is 3μ.
m, the number of laminated layers exceeds 600 layers is mass-produced.

[0005]

By the way, when the dielectric layer is made thin, the contribution of the electrical barrier due to the grain boundary of the dielectric layer is reduced, and moreover, it is applied to one layer of the dielectric layer. Since the electric field strength increases, the dielectric layer is easily deteriorated in insulation in the high temperature load life test. Therefore, it is difficult to reduce the thickness of the dielectric layer to 3 μm, further to 2 μm or less, as an extension of the conventional technique.

It is an object of the present invention to provide a highly reliable multilayer ceramic capacitor which has a long life as much as possible and is highly resistant to insulation deterioration even if the dielectric layer is made thin, and a method for manufacturing the same.

[0007]

A monolithic ceramic capacitor according to the present invention comprises one or more dielectric layers made of a dielectric ceramic composition and at least two internal electrodes sandwiching the dielectric layer. A layer, an external electrode electrically connected to the internal electrode layer, and a metal thin film layer formed between the dielectric layer and the internal electrode layer. Is.

The method for manufacturing a monolithic 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 subjected to the printing step to obtain a laminate; The raw material preparing step includes 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. The ceramic raw material is characterized by containing a metal powder or an organometallic compound.

The present invention is particularly effective when the dielectric layer has a thickness of 0.5 to 5 μm or the ceramic green sheet has a thickness of 0.7 to 10 μm. When the thickness of the dielectric layer is less than 0.5 μm or the thickness of the ceramic green sheet is less than 0.7 μm, the electric field strength applied to one layer of the dielectric layer becomes too large and the dielectric layer is loaded with high temperature. This is because the insulation deterioration is likely to occur in the life test.

Further, as the metal or alloy forming the metal thin film layer, or the metal powder or metal in the organometallic compound contained in the ceramic raw material, an internal electrode layer is formed on the dielectric ceramic composition. A metal or an alloy having a wettability lower than that of the metal, specifically, a metal or an alloy having a contact angle of 110 to 180 degrees with respect to the dielectric ceramic composition is preferable.

When the dielectric ceramic composition is a barium titanate system and the internal electrode layer is made of Ni or an alloy containing Ni as a main component, examples of the metal or alloy having a lower wettability than the internal electrode layer include: , One or more metals selected from Au, Pt, Pd, Ag and Cu, or A
An alloy of Ni and one or more metals selected from u, Pt, Pd, Ag and Cu can be mentioned.
When the firing temperature of the chip-shaped laminate is high, Pt, P
d is preferred.

The metal thin film layer has a thickness of 10Å-5.
0 nm is preferred. If the thickness of the metal thin film layer is less than 10Å, it is insufficient as an electrical barrier, and the thickness of the metal thin film layer is 5
This is because if the thickness exceeds 0 nm, the material cost of the metal thin film layer becomes too high, and the raw material cost of the monolithic ceramic capacitor becomes too high.

The metal contained in the ceramic raw material is not limited to the metal powder / sol state, but may be the metal state such as an organometallic compound as long as the binder removal property is not impaired.

The metal powder or the organometallic compound contained in the ceramic raw material is preferably 0.04 to 5 parts by weight with respect to 100 parts by weight of the ceramic raw material. If the amount of the metal powder or the organometallic compound is less than 0.04 parts by weight, it is insufficient as an electric barrier, and if the amount of the metal powder or the organometallic compound exceeds 5 parts by weight, the raw material cost of the monolithic ceramic capacitor becomes too high. .

The average particle size of the metal powder is 0.00
5 to 0.1 μm is preferable. This is because when the average particle size of the metal powder is in this range, the metal powder is well dispersed in the ceramic raw material. Further, the metal thin film layer does not necessarily have to form a perfect film as long as it exhibits the intended effect.

[0016]

EXAMPLES First, BaTiO ₃ , Ho ₂ O ₃ , MgO,
Powders of each compound of MnO and BaSiO ₃ and Pt powder were weighed at the ratios shown in Table 1, and these compounds were treated with PS.
Put it in a ball mill containing Z, add water, and wet about 15
Mixed for hours. Then, the obtained sludge is dehydrated to 150
It was heated at ℃ for 15 hours and dried.

[0017]

[Table 1]

Next, the dried slurry is crushed and calcined in the atmosphere at about 800 ° C. for 2 hours, the calcined product is put into a ball mill, ethanol is added, and a wet process of about 8 is performed.
Crushed on time. Then, the obtained slurry was heated at 120 ° C. for 5 hours and dried to obtain a calcined powder.

Next, 1000 g (10
1 part by weight of an organic binder composed of an aqueous solution of acrylic acid ester polymer, glycerin and condensed phosphate.
5% by weight was added, and further 50% by weight of water was added, and these were placed in a ball mill, pulverized and mixed to prepare a slurry. Although Pt powder is added to the raw material powder and mixed in this embodiment, Pt powder may be added at the stage of preparing the slurry.

Next, this slurry was put in a vacuum defoaming machine to defoam, and then put in a reverse roll coater to form a thin film of this slurry on the polyester film.
Then, this thin film is placed on a polyester film at 100 ° C.
It was heated to dryness and punched out to obtain a 10 cm × 10 cm square green sheet.

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, and 1
After stirring for 0 hour, a conductive paste for internal electrode layers was obtained. Then, a conductive pattern made of this conductive paste was printed on the green sheet and dried.

Next, ten green sheets were laminated with the printed surface of the conductive pattern facing up. At this time, the adjacent upper and lower sheets were arranged such that their printing surfaces were displaced by about half in the longitudinal direction of the pattern. Further, green sheets on which conductive patterns were not printed were laminated on the upper and lower surfaces of this laminate.

Next, the laminate is pressed at a temperature of about 50 ° C. by applying a pressure of about 40 tons in the thickness direction, and then the laminate is cut into a lattice shape, and the length is 3.2 mm × width 1 .6m
m laminated chips were obtained.

Next, a Ni external electrode is formed by dipping on the end face of the laminated chip from which the internal electrode layer is exposed, and the laminated chip is placed in a furnace capable of atmospheric firing and heated in an N ₂ atmosphere to form an organic binder. And then the oxygen partial pressure is reduced to 10
^It was fired at 1200 ° C. under the condition of ⁻⁵ to 10 ⁻¹⁰ atm, and then reoxidized at 600 to 1000 ° C. in an N ₂ atmosphere to obtain a laminated ceramic capacitor.

Next, the obtained laminated ceramic capacitor was cut along a plane orthogonal to the internal electrode layers and the cross section thereof was observed with an electron microscope. As shown in FIG. 1, the internal electrode layers 10 and the dielectric layers 12 were obtained. The metal thin film layer 14 was formed between them.
This is because the metal powder added to the ceramic raw material has poor wettability with respect to the dielectric layer, so that the metal powder is removed from the dielectric layer 12 during firing, and the internal electrode layer 10 and the dielectric layer 12 are removed.
It is thought that they were formed by gathering at the interface of.

Next, in the same manner, the cross section of the laminated ceramic capacitor was observed, and the thickness (μm) of the dielectric layer 12 and the thickness (μm) of the metal thin film layer 14 were measured. It was on the street.

Next, various electric characteristics of the obtained laminated ceramic capacitor were measured, and the results were as shown in Table 2.

The electrical characteristics were measured as follows.

(A) The relative permittivity ε s is measured by measuring the electrostatic capacity under the conditions of a temperature of 20 ° C., a frequency of 1 kHz, and a voltage (effective value) of 1.0 V. It was calculated from the area and the thickness of the dielectric ceramic layer between the pair of internal electrode layers.

(B) Dielectric loss tan δ (%) was measured under the same conditions as in the above-mentioned measurement of relative permittivity.

(C) The specific resistance (Ωcm) was obtained by applying DC 25 V for 60 seconds at a temperature of 20 ° C. and then measuring the resistance value between a pair of external electrodes.

(D) Accelerated life (sec) is 150 ° C / 1
It was obtained by measuring the time until the leakage current became 10 times the minimum leakage current under a DC electric field of 8 V / μm.

(E) The rate of change in capacity (%) was determined by placing the sample in a constant temperature bath, and at a temperature of -25 ° C. and + 85 ° C., at a frequency of 1 kHz and a voltage (effective value) of 1.0 V. It was obtained by measuring the capacitance and determining the rate of change of the capacitance with respect to the capacitance of 20 ° C.

[0034]

[Table 2]

As is clear from Tables 1 and 2, according to the present invention, the dielectric layer has a layer thickness of 5 μm or less, desired electrical characteristics, and an accelerated life of Sample No. 1, No.
7, No. It was possible to obtain a highly reliable laminated porcelain capacitor which was remarkably improved as compared with the case of No. 9 with no added metal (comparative example), that is, the case of forming the internal electrode with Ni alone.

[0036]

According to the present invention, since the metal thin film layer having a wettability with respect to the dielectric layer lower than that of the internal electrode layer is provided between the internal electrode layer and the dielectric layer, even if the dielectric layer is thinned. There is an effect that it is possible to obtain a monolithic ceramic capacitor that does not easily cause insulation deterioration and has good life characteristics.

The reason why the life characteristics are improved is considered to be as follows. That is, between the internal electrode layers of the monolithic ceramic capacitor, there are electrical barriers at the grain boundaries between the ceramic particles of the dielectric layer and at the interface between the internal electrode layer and the dielectric layer. The number of grain boundaries between particles is reduced, the electrical barrier between the internal electrode layers is reduced, and insulation deterioration occurs.

However, when a metal thin film layer having a wettability with respect to the dielectric layer lower than that of the internal electrode layer is provided between the dielectric layer and the internal electrode layer, the electrical barrier at the interface between the dielectric layer and the metal thin film layer is The internal electrode layer is higher than when it is in direct contact with the dielectric layer, which compensates for the lowering of the electrical barrier due to the reduction of grain boundaries, and insulation deterioration is less likely to occur. For this reason, it is considered that the life has been extended.

[Brief description of drawings]

FIG. 1 is a partially enlarged explanatory view of a cross section of a monolithic ceramic capacitor according to the present invention.

[Explanation of symbols]

10 Internal electrode layer 12 Dielectric layer 14 Metal thin film layer

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E001 AB03 AC04 AC09 AC10 AH01                       AH06 AH09 AJ01 AJ02                 5E082 AB03 BC35 BC39 EE04 EE18                       EE19 EE23 EE26 EE35 FG06                       FG26 FG54 LL01 LL02 LL03                       MM24 PP03 PP09 PP10

Claims (15)

[Claims] 1. One or more dielectric layers made of a dielectric ceramic composition, at least two internal electrode layers sandwiching the dielectric layers, and electrically connected to the internal electrode layers. And a metal thin film layer formed between the dielectric layer and the internal electrode layer. 2. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layer has a thickness of 0.5 to 5 μm. 3. The wettability of the metal forming the metal thin film layer to the dielectric ceramic composition is worse than the wettability of the metal forming the internal electrode layer to the dielectric ceramic composition. The multilayer ceramic capacitor according to claim 1 or 2. 4. The laminated ceramic according to claim 1, wherein a contact angle of a metal forming the metal thin film layer with respect to the dielectric ceramic composition is 110 to 180 degrees. Capacitors. 5. The multilayer ceramic capacitor according to claim 1, wherein the internal electrode layers are made of Ni or an alloy containing Ni as a main component. 6. The metal thin film layer comprises Au, Pt, Pd,
One or more metals selected from Ag and Cu,
Or 1 selected from Au, Pt, Pd, Ag and Cu
6. The multilayer ceramic capacitor according to claim 1, wherein the multilayer ceramic capacitor is made of one kind or an alloy of two or more kinds of metals and Ni. 7. The metal thin film layer has a thickness of 10Å to 50 n.
The multilayer ceramic capacitor according to any one of claims 1 to 6, wherein m is m. 8. A raw material preparing step of preparing a ceramic raw material, a sheet forming step of 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 ceramic green sheets that have undergone the printing step to obtain a laminated body, and cutting the laminated body obtained in the laminating step into internal electrode patterns And a firing step of firing the chip-shaped laminate obtained in the cutting step, wherein the ceramic raw material contains a metal powder or an organometallic compound. Method for manufacturing laminated ceramic capacitor. 9. The method according to claim 8, wherein the ceramic green sheet has a thickness of 0.7 to 10 μm. 10. The wettability of the metal powder or the metal in the organometallic compound contained in the ceramic raw material with respect to the dielectric ceramic composition obtained by firing the ceramic green sheet is the internal electrode pattern. 10. The method for producing a monolithic ceramic capacitor according to claim 8, wherein the wettability of the metal powder, which is the main component of the above, with respect to the dielectric ceramic composition is worse. 11. The contact angle of the metal contained in the ceramic raw material or the metal in the organometallic compound with respect to the dielectric ceramic composition obtained by firing the ceramic green sheet is 110 to 180 degrees. The method for manufacturing a monolithic ceramic capacitor according to any one of claims 8 to 10, wherein: 12. The multilayer ceramic capacitor according to claim 8, wherein the metal powder which is the main component of the internal electrode pattern is made of Ni or an alloy whose main component is Ni. Production method. 13. The metal in the metal powder or the organometallic compound contained in the ceramic raw material is Au, Pt,
13. The method for producing a multilayer ceramic capacitor according to claim 8, wherein the metal is one or more metals selected from Pd, Ag and Cu. 14. The monolithic ceramic capacitor according to claim 8, wherein an average particle diameter of the metal powder contained in the ceramic raw material is 0.005 to 0.1 μm. Manufacturing method. 15. The method for manufacturing a monolithic ceramic capacitor according to claim 8, wherein the metal powder is 5 parts by weight or less with respect to 100 parts by weight of the ceramic raw material.