KR100951319B1 - Manufacturing method of dielectric ceramic material, green sheet, sintered body and multi layered ceramic condenser using dielectric material manufactured thereby - Google Patents

Abstract

Provided are a method for producing a dielectric ceramic material in which a main component powder and a subcomponent powder are uniformly dispersed. A plasticity process for plasticizing a mixture of plural kinds of subcomponent powders, a pulverization process for pulverizing the plasticized subcomponent powders, a plasma treatment process for atomizing the pulverized subcomponent powders with plasma, and a subcomponent powder atomized with plasma The particle size distribution of the subcomponent powder after grinding | pulverization in the grinding | pulverization process was provided so that it might be set to D90 / D50 <3.0.

Dielectric, Plasticity, Plasma, Particle Size Distribution

Description

Manufacturing method of dielectric ceramic material, green sheet, sintered body and multi layered ceramic condenser using dielectric material manufactured}

The present invention provides a method for producing a dielectric ceramic material in which the main component powder and the subcomponent powder are uniformly dispersed, which can produce a green ceramic sheet having a low surface roughness and a high stability of the firing temperature and a low short ratio. It relates to a green sheet, a sintered body and a ceramic capacitor manufactured using.

Conventional multilayer ceramic capacitors use a barium titanate (BaTiO ₃ ) -based ceramic dielectric material as a main component and a metal compound for characteristic composition as a secondary component to form a molded green sheet in the form of a sheet, and laminate an electrode printed on the green sheet. It is produced by repeating the process of making.

In recent years, along with the miniaturization of electronic device products, high-density electronic circuits have progressed, and as a result, there is a strong demand for miniaturization of multilayer ceramic capacitors. Therefore, in order to realize this demand, attempts have been made to increase the thickness of the internal electrode layer and the dielectric layer and increase the number of stacked layers.

With the thinning of the dielectric layer, smaller particle diameters are used as the main component and the subcomponent, but the subcomponent powder having the small particle diameter tends to aggregate and deteriorate dispersibility with the main component. As a result, the surface roughness (unevenness) of the green sheet becomes large, and variations in the thickness of the dielectric layer after firing occur, resulting in uneven electric field strength of the multilayer ceramic capacitor, deterioration of electrical characteristics, and high short rate.

Therefore, there is a need for a method for producing a dielectric ceramic material in which powders of the main component and the subcomponent are uniformly dispersed.

Although Patent Document 1 and Patent Document 2 disclose that the subcomponent is subjected to a plasma treatment to ultrafine particles, it is aggregated as described above simply by ultrafine particles.

[Patent Document 1] Japanese Patent Laid-Open No. 10-255549

[Patent Document 2] Japanese Patent Laid-Open No. 10-270284

SUMMARY OF THE INVENTION In view of the above-described phenomenon, an object of the present invention is to provide a method for producing a dielectric ceramic material in which the main component powder and the subcomponent powder are uniformly dispersed, and a green sheet, a sintered body, and a ceramic capacitor manufactured using the same.

The method for producing a dielectric ceramic material according to the present invention includes a plasticizing step of plasticizing a mixture of plural kinds of subcomponent powders, a pulverizing step of pulverizing the plasticized subcomponent powders, and a plasma processing step of atomizing the pulverized subcomponent powders by plasma; The subcomponent powder finely divided by plasma is added to the main component powder, and the particle size distribution of the subcomponent powder after pulverizing in the pulverizing step is D90 / D50 <3.0.

In such a case, the subsidiary powder after plasticity is pulverized to have a particle size distribution of D90 / D50 <3.0, and then the aggregated subsidiary powder is pulverized, followed by plasma treatment to finely granulate the subsidiary powder and at the same time dispersibility of the subsidiary powder. Therefore, the dielectric ceramic material in which the main component powder and the subcomponent powder are uniformly dispersed can be obtained.

It is preferable that the maximum particle diameter of the said subcomponent powder after micronization in the said plasma processing process is 3/4 or less of the average particle diameter of the said main component powder.

The subcomponent powder is preferably a powder made of a compound containing at least one element selected from the group consisting of Mg, Ba, Ca, Si, Mn, Al, V, Dy, Y, Ho and Yb.

The main component powder is preferably a barium titanate-based dielectric powder.

The average particle diameter of the barium titanate-based dielectric powder is preferably 0.3 μm or less.

The green sheet manufactured using the dielectric ceramic material obtained by the manufacturing method which concerns on this invention is also one of this invention.

The sintered compact manufactured by baking the green sheet which concerns on this invention is also one of this invention.

The ceramic capacitor provided with the dielectric layer which consists of a some electrode and the sintered compact which concerns on this invention provided between the said electrodes is also one of this invention.

It is preferable that the said electrode contains Ni or Ni alloy.

According to the present invention, it is possible to obtain a dielectric ceramic material in which the subcomponent powder does not aggregate and the main component powder and the main component powder are uniformly dispersed. Since the green sheet manufactured using the dielectric ceramic material has high dispersibility of the main powder and the subcomponent powder, the surface roughness is small, so that even if the dielectric layer after sintering is a thin layer having a thickness of 2 µm or less, the thickness of the multilayer ceramic capacitor is reduced. . In addition, the green sheet fabricated using such a dielectric ceramic material is dense in structure and uniform in particle size, so that the particle size after firing is stable, the electrical characteristics are stable, and the effective temperature range of the firing temperature is also widened.

EMBODIMENT OF THE INVENTION Hereinafter, the multilayer ceramic capacitor 1 which concerns on one Embodiment of this invention is demonstrated with reference to drawings.

As shown in Fig. 1, the multilayer ceramic capacitor 1 according to the present embodiment is provided on the capacitor chip body 2 and the surface of the capacitor chip body 2 in which the dielectric layers 3 and the internal electrodes 4 are alternately stacked. An external electrode 5 conducting with the internal electrode 4 is provided. The internal electrodes 4 are laminated so that their ends are alternately exposed on two opposing surfaces of the capacitor chip body 2 and are formed on the corresponding surface of the capacitor chip body 2 to constitute the predetermined capacitor circuit. It is electrically connected with.

The dielectric layer 3 is composed of a sintered body of a dielectric ceramic material, and the dielectric ceramic material can be obtained by adding the main component powder to the subcomponent powder that has been granulated through a plasticity process, a crushing process, and a plasma treatment process.

In the plasticizing step, a mixture of plural kinds of subcomponent powders is calcined.

Examples of the subcomponent powders include compound powders such as oxides and carbonates containing one or a plurality of elements of Mg, Ba, Ca, Si, Mn, Al, V, Dy, Y, Ho and Yb. Two or more types of these subcomponent powders are mixed and plasticized at about 800-1000 degreeC, for example.

In the grinding step, the calcined subcomponent powder is ground using, for example, a ball mill, a bead mill, a dry jet mill, a wet jet mill, or the like.

In the grinding step, the subcomponent powder is crushed and dispersed so that the particle size distribution is D90 / D50 <3.0, preferably D90 / D50 <2.0. If D90 / D50 is 3.0 or more, the maximum particle diameter of the subcomponent powder after plasma processing will become larger than 3/4 of the average particle diameter of a main component powder, and it is unpreferable.

It is not particularly limited as a grinding method or media material for grinding the subsidiary powder so as to have such a particle size distribution. For example, when using a batch bead mill, a circumferential speed of 4 m / s or more and a ZrO ₂ media filling rate of 20 vol% In the above, grinding processing is performed in processing time 1 hour or more.

In the plasma processing step, the pulverized subcomponent powder is atomized by plasma. Plasma treatment is, for example, heated and melted in a plasma salt at 2000 to 20000 ° C. using a high frequency induction heat plasma apparatus.

In the plasma processing step, it is preferable to make the subcomponent powder into fine particles so that the maximum particle size of the subcomponent powder is 3/4 or less of the average particle diameter of the main component powder added after the plasma processing step. If the average particle diameter of the subcomponent powder exceeds this range, the sintering reaction of the main component powder and the subcomponent powder hardly occurs uniformly during firing.

The powder as a main component is, for example, but are not particularly limited, and a barium titanate-based dielectric powder consisting of _{Ba X Ca 1 -X TiO 3 (} 0 <X≤1) or the like is used suitably.

The average particle diameter of the barium titanate-based dielectric powder is preferably 0.3 μm or less. If the thickness exceeds 0.3 占 퐉, a green sheet having low surface smoothness and nonuniformity in thickness is obtained.

It is preferable to add a dispersant together when the main component powder is added to the subcomponent powder.

Although it does not specifically limit as said dispersing agent, For example, a polyvinyl butyral type dispersing agent, a polyvinyl acetal type dispersing agent, a polycarboxylic acid type dispersing agent, a maleic acid type dispersing agent, a polyethyleneglycol type dispersing agent, an allyl ether copolymer type dispersing agent, etc. are mentioned. .

A dielectric ceramic material can be obtained by adding a main component powder and a dispersing agent to the said subcomponent powder, for example, mixing it with a homogenizer, and then grinding and dispersing with a bead mill. The slurry for green sheet formation can be obtained by adding a solvent and a binder to the dielectric ceramic material obtained in this way, and mixing using a ball mill etc.

The solvent is not particularly limited, but for example, glycols such as ethyl carbitol, butanediol and 2-butoxyethanol: alcohols such as methanol, ethanol, propanol and butanol: acetone, methyl ethyl ketone, diacetone alcohol and the like Ketones; esters such as methyl acetate and ethyl acetate; aromatics such as toluene, xylene and benzyl acetate; and the like. These solvents may be used independently or two or more types may be used together.

Although it does not specifically limit as said binder, For example, acrylic resin, polyvinyl butyral resin, polyvinyl acetal resin, ethyl cellulose resin, etc. are mentioned.

The binder is preferably dissolved in the solvent beforehand, filtered to make a solution, and the dielectric ceramic material is added to the solution. Binder resins of high degree of polymerization do not dissolve well in solvents and tend to deteriorate the dispersibility of the slurry by conventional methods. By dissolving the binder resin of high polymerization degree in a solvent and adding other components to this solution, the dispersibility of each component in the slurry for green sheet formation can be improved, and generation | occurrence | production of undissolved binder resin can also be suppressed. In addition, solvents other than the above-mentioned solvents may not increase the solid content concentration, and may tend to increase with time the lacquer viscosity.

The green sheet is formed by applying the thus prepared green sheet forming slurry on a substrate made of polyethylene terephthalate or the like in a sheet form. The dielectric layer 3 consists of a sintered compact obtained by baking the obtained green sheet. It is preferable that the thickness per layer of the dielectric agent layer 3 is 2 micrometers or less.

Although it does not specifically limit as the internal electrode 4, For example, metals, such as Cu, Ni, W, Mo, Ag, these alloys, etc. are mentioned.

Although it does not specifically limit as the external electrode 5, For example, Metal, such as Cu, Ni, W, Mo, Ag, or alloys thereof; Alloy, such as In-Ga, Ag-10Pd; Carbon, graphite, the mixture which consists of carbon and graphite, etc. are mentioned.

Although it does not specifically limit as a manufacturing method of the multilayer ceramic capacitor which concerns on this embodiment, For example, it manufactures as follows. First, a conductive paste film for the internal electrode 4 is formed by printing a conductive paste for the internal electrode 4 containing the various metals and the like into a predetermined shape on the green sheet.

Next, as described above, a plurality of green sheets on which the conductive paste film for the internal electrode 4 is formed are laminated, and the green sheets on which the conductive paste film is not formed are laminated and crimped with these green sheets interposed therebetween. By cutting, a laminated body (green chip) is obtained.

After the de-binder treatment is performed on the obtained green chip, the green chip is fired in, for example, a reducing component crisis to obtain a capacitor chip body (2). In the capacitor chip body 2, the dielectric layer 3 and the internal electrode 4 which consist of the sintered compact which bakes a green sheet are alternately laminated | stacked.

It is preferable to anneal the obtained capacitor chip body 2 in order to reoxidize the dielectric layer 3.

Next, an electrode made of the above-described various metals or the like on the cross section of the capacitor chip body 2 such that the external electrode 5 is electrically connected to each edge of each end of the internal electrode 4 exposed at the cross section of the capacitor chip body 2. The external electrode 5 is formed by applying. If necessary, a coating layer is formed on the surface of the external electrode 5 by plating or the like.

Although an Example is given to the following and this invention is demonstrated to it in more detail, this invention is not limited only to these Examples.

BaCO ₃ , MgO, SiO _{2 ,} Mn ₃ O _4, and Y ₂ O ₃ were prepared as _{secondary components} . The amount of Ba element added was 0.95 mol%, the amount of Si element added 1.55 mol%, the amount of Y element added 0.65 mol%, and the amount of Mg element added to the main component barium titanate (BaTiO ₃ ) to be added to the subcomponent thereafter. Is 1.2 mol%, and the amount of Mn element added is 0.13 mol%.

Next, the above-mentioned various subcomponents were put into the ball mill, water was added, and it mixed. The resulting mixture of subcomponents was then dried and the dried subcomponent was calcined at 900 ° C. In addition, the plastic subcomponent was placed in a batch bead mill and water was added to fill the ZrO ₂ media with a particle diameter of 0.1 mm to 45 vol%, and ground at 7 m / s for 6 hours at a circumferential speed, and then the crushed subcomponent was dried.

Next, the pulverized subcomponent was atomized by plasma treatment. The plasma treatment was performed under conditions of an output of 140 kW, an Ar gas supply amount of 100 L / min, an O ₂ gas supply amount of 50 L / min, and a sample supply amount of 5.0 g / min using a high frequency induction heat plasma apparatus.

Next, the subcomponent refined by plasma treatment with respect to 100 weight part of barium titanate powders whose average particle diameter is 0.3 micrometer was added so that each element might add the above-mentioned addition amount. After grinding, the D90 / D50 of the subcomponent powder, the presence or absence of plasma treatment, and the maximum particle diameter of the subcomponent powder after the plasma treatment with respect to the main component powder are as shown in Table 1, respectively. Among the values shown in Table 1, D90 / D50 of the subcomponent powder after the pulverization treatment was calculated by the particle size distribution measured using LA-920 manufactured by Horiba, and the maximum particle diameter of the subcomponent powder after the plasma treatment with respect to the main component powder was Each powder was observed with a sand-type electron microscope, and the particle size of 300 particles was measured, and the average particle diameter of the main component powder was compared with the maximum particle diameter of the subcomponent powder.

D90 / D50 after grinding Plasma Treatment Maximum Particle Size of Subsidiary Powders after Plasma Treatment Comparative Example 1 3.0 radish - Comparative Example 2 3.0 U Over 3/4 Example 1 2.5 U 3/4 or less Example 2 2.0 U 3/4 or less Example 3 1.6 U 3/4 or less Example 4 1.4 U 3/4 or less

* Comparative Example 1 Mixes the subcomponent powder with the main component powder without plasma treatment

As a powder, 1.0 wt% of a polyvinyl butyral dispersant (BL-1 manufactured by Sekisui Chemical Co., Ltd.) was added to 100 parts by weight of the barium titanate powder, and mixed with a homogenizer. Next, these mixtures were charged with a vertical bead mill having a function of separating beads and slurries by centrifugal force such that the ZrO ₂ media filling rate of 0.05 mm in diameter was 64 vol%, and the flow rate was 12 m / s at a sample feed rate of 100 ml / min. Dispersion and crushing gave a slurry of dielectric ceramic material.

Next, the obtained slurry was placed in a ball mill and mixed together with a toluene ethanol mixed solvent, a polyvinyl butyral binder and a plasticizer until a suitable viscosity was obtained, and a slurry for forming a green sheet was prepared. And the slurry was apply | coated on the polyethylene terephthalate film by the doctor blade method, and the green sheet was produced.

Next, after screen-printing the conductive paste for internal electrodes made of Ni powder on each green sheet in a predetermined shape, a plurality of green sheets on which the conductive paste film was formed were laminated, thermocompression-bonded and integrated to prepare a laminate.

The laminate was heated at 300 ° C. for 10 hours in air to remove the organic binder, and then calcined for 2 hours in a reducing atmosphere at 1100 ° C., and then reoxidized and sintered for 2 hours in an N ₂ gas atmosphere at 1000 ° C. to obtain a condenser chip body. . Next, the cross section of the obtained capacitor chip body was polished by sandblasting, and then an In-Ga electrode was applied to the cross section to form an external electrode, and a multilayer ceramic capacitor having the structure illustrated in FIG. 1 was produced.

Various characteristics were evaluated for the green sheet and the multilayer ceramic capacitor as follows and the results are shown in Table 2.

<Evaluation of Green Sheet>

The surface roughness (Rz) of the green sheet was measured by a scanning probe microscope (SPM-9500J3 manufactured by Shimadzu Corporation). The sample whose Rz exceeded 0.4 µm was evaluated by NG.

<Evaluation of Multilayer Ceramic Capacitor>

The resistance value of 100 samples per laminated ceramic capacitor was measured with an insulation ohmmeter, and the sample whose resistance value is 100 kΩ or less was judged to be a defective product, and the short ratio was calculated | required. Samples with a short rate exceeding 10% were evaluated by NG.

Surface Roughness Rz (㎛) of Sheet Short rate (%) Comparative Example 1 0.49 20 Comparative Example 2 0.42 12 Example 1 0.39 9 Example 2 0.38 8 Example 3 0.37 6 Example 4 0.36 5

<Manufacturing Method and Measurement Conditions of Single-Plate Samples>

The evaluation sample of the single plate was produced as follows. The green sheets were cut at an angle of 1 cm and stacked to have a thickness of 1 mm. Next, this was molded at a pressure of 1000 kg / cm 3. Next, in order to incinerate the resin component, it was calcined at 300 ° C. for 10 hours in the air, and then calcined for 2 hours in the firing temperature and the reducing atmosphere shown in Table 3. Thereafter, the mixture was stabilized at 1000 ° C. in nitrogen gas and subjected to reoxidation for 2 hours.

The obtained single plate sample was evaluated as follows in density, particle size, and effective firing temperature range, and the results are shown in Table 3.

Density (g / cm <3>) was measured using the Archimedes method.

The presence or absence of the particle | grains of particle size 0.5 micrometer or more was measured by measuring the particle diameter of a sintered compact with the scanning electron microscope, and was determined.

The effective firing temperature range represents the effective range of the firing temperature on the condition that there are no particles having a density of 5.8 g / cm 3 or more and a particle diameter of 0.5 µm or more.

When the density was 5.8 g / cm 3 or more, the particle size after sintering was less than 0.5 μm, and the effective firing temperature range did not satisfy at least one within each condition of 30 ° C. or more, the desired characteristic was not obtained. .

evaluation Firing temperature (℃) Density (g / cm 3) 0.5μm or more particles Effective firing temperature range (℃) NG Comparative Example 1 1155 5.76 Insufficient plasticity 1160 5.82 radish 5 ℃ (1125 ~ 1140 ℃) 1165 5.89 radish 1170 5.89 U NG Comparative Example 2 1120 5.76 Insufficient plasticity 1125 5.82 radish 20 ℃ (1125 ~ 1140 ℃) 1130 5.83 radish 1145 5.84 radish 1145 5.85 U NG Example 1 1125 5.76 Insufficient plasticity 1130 5.83 radish  30 ℃ (1130 ~ 1160 ℃) 1143 5.87 radish 1155 5.93 radish 1160 5.90 radish NG 1165 5.91 U NG Example 2 1125 5.77 Insufficient plasticity 1130 5.82 radish  40 ℃ (1130 ~ 1160 ℃) 1145 5.86 radish 1150 5.91 radish 1170 5.90 radish NG 1185 5.91 U NG Example 3 1120 5.76 Insufficient plasticity 1125 5.82 radish  60 ℃ (1130 ~ 1160 ℃) 1140 5.86 radish 1150 5.88 radish 1185 5.89 radish NG 1195 5.89 U NG Example 4 1120 5.76 Insufficient plasticity 1125 5.82 radish  70 ℃ (1130 ~ 1160 ℃) 1140 5.86 radish 1150 5.88 radish 1195 5.89 radish NG 1200 5.89 U

1 is a schematic sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1 multilayer ceramic capacitor

2 condenser chip

3 laminate layer

4 internal electrode

5 External Electrode

Claims (9)

Plasticizing step of plasticizing a mixture of plural kinds of subcomponent powders; A grinding step of grinding the plasticized subcomponent powder; A plasma processing step of atomizing the pulverized subcomponent powder by plasma; And Adding the subcomponent powder atomized by plasma to the main component powder, The particle size distribution of the subsidiary powder after milling in the milling step is D90 / D50 <3.0. The method of claim 1, The maximum particle diameter of the said subcomponent powder after micronization in the said plasma processing process is the manufacturing method of the dielectric ceramic material which is 3/4 or less of the average particle diameter of the said main component powder. The method according to claim 1 or 2, Said subcomponent powder is a powder comprising a compound containing at least one element selected from the group consisting of Mg, Ba, Ca, Si, Mn, Al, V, Dy, Y, Ho and Yb. The method according to claim 1 or 2, The main component powder is a method for producing a dielectric ceramic material is a barium titanate-based dielectric powder. The method of claim 4, wherein A method for producing a dielectric ceramic material, wherein the average particle diameter of the barium titanate-based dielectric powder is 0.3 μm or less. delete delete delete delete

Images