KR20000037541A - Reduction-resistant dielectric composition and preparation method of multi-layered ceramic capacitor using the composition - Google Patents

Abstract

PURPOSE: A reduction-resistant dielectric composition for a multi-layered ceramic capacitor and a preparation method of multi-layered ceramic capacitor using the composition are provided, to lower the sintering temperature and reduce the shrinkage between a dielectric layer and a Ni internal electrode. CONSTITUTION: A reduction-resistant dielectric composition comprises BaTiO3, MgCO3, Y2O3, Cr2O3, Nb2O5 and BaxCa(1-x)SiO3, and the composition is represented by the formula a BaTiO3 - b MgCO3 - c Y2O3 - d Cr2O3 - e Nb2O5 - f BaxCa(1-x)SiO3, wherein a is 100, b is between 0.2-6.0, c is between 0.05 and 1.5, d is between 0.1 and 1.5, e is between 0.05 and 0.40, and f is between 0.2 and 3.0. A multi-layered ceramic capacitor is prepared by mixing BaTiO3, MgCO3, Y2O3, Cr2O3 and Nb2O5 with BaCO3, CaCO3 and SiO3 and drying the mixture; adding a binder and a solvent to the mixture to prepare slurry; forming the slurry in the shape of a sheet; printing a Ni internal electrode on the sheet, layering the printed sheets and pressing it; cutting the layered one in regular size and baking it out to remove the inner binder; sintering it at 1200-1250°C; and forming an external electrode at the both terminal of the sintered body.

Description

Reduction-resistant dielectric composition and manufacturing method of multilayer ceramic capacitor using same

The present invention relates to a multilayer ceramic capacitor, and more particularly, to a ceramic dielectric composition and a method of manufacturing a multilayer ceramic capacitor using Ni as an internal electrode.

In general, a multilayer ceramic capacitor is made of three materials: a dielectric, an internal electrode paste, and an external electrode paste. Conventionally, expensive Pd noble metals have been mainly used as internal electrode materials for multilayer ceramic capacitors. In order to cope with the cost rise due to the price increase of Pd and to cope with the demand for high lamination and high capacity products, Ni has recently been relatively inexpensive. Is applied to the internal electrode.

However, when Ni is used as an internal electrode in a conventional dielectric composition, the dielectric is semiconductorized by free electrons generated with oxygen vacancies, and thus it is difficult to apply it to a multilayer ceramic capacitor as it is. Therefore, in order to use Ni as the internal electrode, the dielectric material needs to be fired in a reducing atmosphere in order to prevent oxidation of the dielectric. In addition, in the case of the reduction-resistant dielectric, it is known that the degradation of reliability due to the oxygen vacancy present therein is severe compared to the dielectric using the conventional Pd as an internal electrode.

On the other hand, as a representative example of the dielectric composition using the Ni internal electrode, as disclosed in Japanese Patent Laid-Open No. 6-215979, a reduction-resistant ceramic dielectric composition of BaTiO ₃ -Y ₂ O ₃ -V ₂ O ₅ system is known. Specifically, the composition is composed of 86.32 to 97.64 mol% BaTiO ₃ , 0.01 to 10.00 mol% Y ₂ O ₃ , 0.01 to 10.00 mol% MgO, 0.001 to 0.200 mol% V ₂ O ₅ , or as an additive thereto. 0.01-1.0 mol% of MnO, Cr ₂ O ₃ , Co ₂ O ₃ and at least one and / or 0.5-10.0 mol% of (Ba _α , Ca _(1-α) ) SiO ₃ (0 ≦ _α ≦ 1 ), Which satisfies the X7R characteristic (B characteristic in Japanese standard) according to the EIA (Electric Industry Association) standard. However, the dielectric composition disclosed in Japanese Unexamined Patent Publication No. 6-215979 greatly improves the accelerated life of the dielectric when V ₂ O ₅ is added in a small amount, but above all, V ₂ O ₅ is toxic and causes environmental pollution. There are disadvantages.

In addition, there is a problem that the sintering temperature should be increased to 1300 ℃ or more when producing a capacitor using this composition. Usually, when firing a multilayer ceramic capacitor in which Ni is intersected with an internal electrode layer and a ceramic dielectric layer, the internal electrode layer shrinks at a lower temperature than the ceramic dielectric layer, and delamination is likely to occur. Therefore, in the case of manufacturing the multilayer ceramic capacitor, as the firing temperature is increased, the aggregation of the electrode layers becomes more prominent, and thus, the incidence rate of short defects between internal electrodes is increased.

The present invention has been proposed to solve the above-mentioned problems, and when manufacturing a multilayer ceramic capacitor, low-temperature firing is possible without using toxic additives, so that the difference in shrinkage between the Ni internal electrode layers and the dielectric is reduced. It is an object to provide a multilayer ceramic capacitor composition having reliability.

In addition, another object of the present invention is to provide a novel manufacturing method for producing a multilayer ceramic capacitor having excellent reliability while firing at a lower temperature than the conventional composition using the above-described composition.

In the present invention for achieving the above object, in the dielectric composition used in the multilayer ceramic capacitor,

Barium titanate (BaTiO ₃ ), magnesium carbonate (MgCO ₃ ), yttrium oxide (Y ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), and Ba _x Ca _(1-x) SiO ₃ , the composition of which is represented by the general formula of a BaTiO ₃ -b MgCO ₃ -c Y ₂ O ₃ -d Cr ₂ O ₃ -e Nb ₂ O ₅ -f Ba _x Ca _(1-x) SiO ₃ When molar ratio, a = 100, 0.2≤b≤6.0, 0.05≤c≤1.5, 0.1≤d≤1.5, 0.05≤e≤0.40, 0.2≤f≤3.0. .

In addition, the present invention is a method of manufacturing a multilayer ceramic capacitor using Ni as an internal electrode,

BaTiO ₃ , MgCO ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ powder and BaCO ₃ , CaCO ₃ and SiO ₂ powder as a sintering aid so as to have the above composition by wet mixing and drying;

Preparing a slurry by adding a binder and a solvent to the dried powder;

Molding into a sheet having a predetermined shape using the slurry;

Printing the Ni internal electrodes on the molded sheet, and stacking and pressing a plurality of printed sheets;

Cutting the laminated stack to a predetermined size and baking to remove the binder therein;

Sintering the debindered molded body at a temperature of 1200 to 1250 ° C; And

Forming external electrodes at both ends of the sintered body; It relates to a method of manufacturing a multilayer ceramic capacitor comprising a.

Hereinafter, the composition of the present invention will be described in detail.

The ceramic dielectric composition of the present invention is barium titanate (BaTiO ₃ ), magnesium carbonate (MgCO ₃ ), yttrium oxide (Y ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ) and Ba _x Ca _(1-x) BaTiO consisting including _{SiO 3 3 - MgCO 3 - Y} 2 O 3 - Cr 2 O 3 - Nb 2 O 5 - Ba x Ca (1-x) SiO 3 is a dielectric composition.

The ceramic dielectric composition of the present invention is a titanic acid when expressed as a BaTiO ₃ -b MgCO ₃ -c Y ₂ O ₃ -d Cr ₂ O ₃ -e Nb ₂ O ₅ -f Ba _x Ca _(1-x) SiO ₃ The composition of each component is as follows based on 100 mol ratio of barium.

First, the magnesium carbonate serves to improve the reduction resistance of the dielectric, the composition is preferably in the molar ratio of 0.2≤b≤6.0. If b is less than 0.2, the loss coefficient is increased, the temperature characteristic is deteriorated, and if it is more than 6.0, the acceleration life is reduced.

In addition, the yttrium oxide is substituted in the Ba ²⁺ ion site to improve the life, it is preferable that the yttrium oxide is formed in the range of 0.05≤c≤1.5 in molar ratio. If c is less than 0.05, the accelerated lifetime is reduced, and if it is greater than 1.5, it is semiconductorized.

In addition, the chromium oxide serves to strengthen the reduction resistance, the content is preferably in the range of 0.1≤d≤1.5 in molar ratio. If d is less than 0.1, it is semiconductorized and if it is more than 1.5, the insulation resistance is lowered.

In addition, the niobium oxide serves to improve the reliability, the content is preferably in the range of 0.05≤e≤0.40 in molar ratio. If e is less than 0.05, the acceleration lifetime is lowered, and if it exceeds 0.40, the dielectric constant and insulation resistance are reduced.

The Ba _x Ca _(1-x) SiO ₃ is preferably in a molar ratio as a sintering aid and has a range of 0.2 ≦ f ≦ 3.0. If f is less than 0.2, the sinterability deteriorates, the temperature characteristic is out of specification, and if it exceeds 3.0, the dielectric constant decreases. Preferably, Ba _x Ca _(1-x) SiO ₃ is used that consists of 0.2≤x≤0.7.

Since the ceramic dielectric composition of the present invention configured as described above is a reducing-resistant composition, it can be made of a dielectric of a multilayer ceramic capacitor of X7R standard (B characteristic) using Ni as an internal electrode.

Hereinafter, a method of manufacturing a multilayer ceramic capacitor using the dielectric composition of the present invention will be described in detail.

The present invention is very useful for the production of multilayer ceramic capacitors using Ni as the internal electrode. First, BaTiO ₃ , MgCO ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ powder and BaCO ₃ , CaCO ₃ and SiO ₂ powder as a sintering aid so as to have the composition described above are wet mixed and dried. In the present invention, the Ba-Ca-Si-O is calcined by calcination of BaCO ₃ , CaCO ₃ and SiO ₂ powder in advance as a sintering aid, it is possible to eliminate the pressing treatment before calcination, the production process more There is an advantage to simplify. It is preferable that calcination of the said sintering aid powder is performed at least 1000 degreeC or more for 2 hours. The calcined sintering aid is preferably pulverized using a planetary mill or the like so that the particle size thereof is about 0.85 μm or less, and then dried.

Next, a binder and a solvent are added to the dried powder to prepare a slurry. As a binder, any conventional binder can be used, for example, polyvinyl butyl-type or acryl-type.

Then, this slurry is used to form a sheet into a certain form in the same manner as in the usual method, and Ni internal electrodes are printed on the formed sheet. Then, a plurality of printed sheets are laminated and pressed to cut the press-formed body into a predetermined size, and baking out to remove the binder therein.

The binder removed in this way is sintered at a temperature of 1200 to 1250 ° C. Since the dielectric composition of the present invention can be sintered at a temperature of 1200 to 1250 ° C., cost can be reduced and high reliability can be obtained by decreasing the dielectric grain size.

Subsequently, when external electrodes are formed at both ends of the sintered body, a multilayer ceramic capacitor having Ni as an internal electrode is obtained. As described above, the capacitor manufactured by the present invention is capable of low temperature firing without using a toxic substance and exhibits X7R characteristics with a dielectric constant of 2200 or more.

Hereinafter, the present invention will be described in detail in the following examples, but the composition and manufacturing conditions of the present invention are not limited to the following examples.

EXAMPLE

BaTiO ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , Ba _x Ca _(1-x) SiO ₃ powder having a purity of 99.5% or more as a starting material were weighed to have each composition of Table 1 below. At this time, the Ba _x Ca _(1-x) SiO ₃ powder was applied after calcining and grinding BaCO ₃ , CaCO ₃ and SiO ₂ powder in advance.

Sample Number BaTiO ₃ (molar ratio) MgCO ₃ (molar ratio) Y ₂ O ₃ (molar ratio) Cr ₂ O ₃ (molar ratio) Nb ₂ O ₅ (molar ratio) Ba _x Ca _(1-x) SiO ₃ (molar ratio) x Comparative Material 1 100 1.8 1.1 0.2 0.01 2.0 0.58 Invention 1 100 1.8 1.1 0.2 0.05 2.0 0.58 Invention 2 100 1.8 1.1 0.2 0.2 2.0 0.58 Invention 3 100 1.8 1.1 0.2 0.4 2.0 0.58 Comparative Material 2 100 1.8 1.1 0.2 0.6 2.0 0.58 Invention 4 100 1.1 1.1 0.2 0.2 2.0 0.50 Invention 5 100 2.5 1.1 0.15 0.2 2.0 0.50 Invention 6 100 1.8 0.6 0.15 0.2 2.0 0.42 Invention 7 100 1.8 1.5 0.2 0.3 2.0 0.40 Invention Material 8 100 1.8 1.1 0.1 0.4 2.0 0.58 Invention Material 9 100 1.8 1.1 0.3 0.2 2.0 0.58 Comparative Material 3 100 1.8 1.1 0.2 0.2 0.1 0.58 Invention 10 100 1.8 1.1 0.2 0.2 2.0 0.25 Comparative Material 4 100 1.8 1.1 0.2 0.2 5.0 0.58 Comparative Material 5 100 0.1 1.1 0.2 0.2 2.0 0.58 Comparative Material 6 100 7.0 1.1 0.2 0.3 2.0 0.58 Comparative Material7 100 1.8 3.0 0.2 0.3 2.0 0.58 Comparative Material 8 100 1.8 1.1 0.03 0.2 2.0 0.58 Comparative Material 9 100 1.8 1.1 3.0 0.2 2.0 0.58

A polyvinyl butyl (PVB) -based binder and a solvent were added to the composition powder thus weighted to prepare a slurry, and then molded into a tape having a thickness of 20 μm. After the Ni internal electrode was printed on the molded body, five layers of the tape molded body were laminated and cut to prepare a multilayer capacitor having a standard size of 3216.

Then, the binder was sintered at an appropriate temperature as shown in Table 2 for 2 hours. In-Ga electrode treatment was performed on both ends of the sintered chip to measure capacitance and dielectric loss with an LCR meter at a temperature of −55 to 125 ° C., and the dielectric constants thereof were shown in Table 2 below.

Sample Number Dielectric constant (K) 25 ℃ Dielectric Loss (%) 25 ℃ Dielectric constant temperature coefficient -55 ℃ (%) Dielectric constant temperature coefficient + 125 ℃ (%) Insulation Resistance x10 ¹¹ (Ω) Chip life expectancy μ (HR) Firing temperature (℃) Comparative Material 1 2530 1.5 -14.3 +3.4 23 2 1250 Invention 1 2480 1.3 -13.1 +2.7 18 56 1250 Invention 2 2370 1.1 -11.1 +1.8 8 86 1240 Invention 3 2310 0.8 -9.3 +1.5 3 69 1235 Comparative Material 2 Semiconductor 1220 Invention 4 2603 1.1 -14.1 +6.9 11 83 1215 Invention 5 2350 1.0 -9.9 +6.0 3 98 1245 Invention 6 2640 1.1 -14.2 +5.5 6 54 1250 Invention 7 2260 1.0 -10.2 +8.5 One 112 1220 Invention Material 8 2330 1.0 -9.9 +7.0 4 57 1240 Invention Material 9 2340 1.1 -9.6 +5.9 3 61 1240 Comparative Material 3 2610 1.9 -18.2 -2.3 2 17 1250 Invention 10 2430 1.1 -11.0 +5.4 7 61 1230 Comparative Material 4 2070 0.7 -5.3 +4.2 16 87 1200 Comparative Material 5 2450 2.4 -17.3 -1.5 8 48 1210 Comparative Material 6 2230 1.2 -12.7 +3.8 4 7 1260 Comparative Material7 Semiconductor 1210 Comparative Material 8 Semiconductor 1230 Comparative Material 9 2270 1.1 -13.9 +4.8 0.3 35 1240

As shown in Table 2, in Comparative Material 1 using a dielectric composition containing less niobium oxide, the capacity change was severe according to the temperature change, and in the case of Comparative Material 2 which was added a lot, the characteristics of the dielectric material were lost.

In addition, low-temperature firing was not possible in the case of the comparative material 3 containing less Ba-Ca-Si-O-based sintering aid, and in the case of the comparative material 4 added more, the dielectric constant was greatly decreased, which is not preferable.

In the case of the comparative material (5-9) in which the main additive MgCO ₃ , Y ₂ O _3, or Cr ₂ O ₃ does not satisfy the condition range, it can be seen that the capacity according to temperature falls or becomes semiconductor.

On the other hand, in the case of the inventive material (1-10) using the dielectric composition of the present invention, the shrinkage between the dielectric layer and the Ni internal electrode is reduced by low temperature sintering, but the X7R characteristic has a dielectric constant of more than 2200 or more, thereby reducing the reliability. It can be seen that a multilayer ceramic capacitor is obtained.

As described above, the dielectric composition of the present invention does not contain toxic additives once, and when the multilayer ceramic capacitor is manufactured using the dielectric composition, low-temperature firing is possible, thereby reducing the difference in shrinkage between the Ni internal electrode layers and the dielectric, As a result, it has a high reliability and is useful for multilayer ceramic capacitors which are very suitable for X7R characteristics.

Claims (7)

In the dielectric composition used for the multilayer ceramic capacitor, Barium titanate (BaTiO ₃ ), magnesium carbonate (MgCO ₃ ), yttrium oxide (Y ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), and Ba _x Ca _(1-x) SiO ₃ , the composition of which is represented by the general formula of a BaTiO ₃ -b MgCO ₃ -c Y ₂ O ₃ -d Cr ₂ O ₃ -e Nb ₂ O ₅ -f Ba _x Ca _(1-x) SiO ₃ When the molar ratio, a = 100, 0.2≤b≤6.0, 0.05≤c≤1.5, 0.1≤d≤1.5, 0.05≤e≤0.40, 0.2≤f≤3.0 Composition. The dielectric composition of claim 1, wherein Ba _x Ca _(1-x) SiO ₃ is in a range of 0.2 ≦ _x ≦ 0.7. In the method of manufacturing a multilayer ceramic capacitor using Ni as the internal electrode, a BaTiO ₃ -b MgCO ₃ -c Y ₂ O ₃ -d Cr ₂ O ₃ -e Nb ₂ O ₅ -f Ba _x Ca _(1-x) Molar ratio expressed by the general formula of SiO ₃ , a = 100, BaTiO ₃ , MgCO ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , so as to have a composition of 0.2 ≦ b ≦ 6.0, 0.05 ≦ c ≦ 1.5, 0.1 ≦ d ≦ 1.5, 0.05 ≦ e ≦ 0.40, and 0.2 ≦ f ≦ _3.0 . Weighing BaCO ₃ , CaCO ₃ and SiO ₂ powders as Nb ₂ O ₅ powder and sintering aid, followed by wet mixing to dry; Preparing a slurry by adding a binder and a solvent to the dried powder; Molding into a sheet having a predetermined shape using the slurry; Printing the Ni internal electrodes on the molded sheet, and stacking and pressing a plurality of printed sheets; Cutting the laminated stack to a predetermined size and baking to remove the binder therein; Sintering the debindered molded body at a temperature of 1200 to 1250 ° C; And Forming external electrodes at both ends of the sintered body; Method for manufacturing a multilayer ceramic capacitor, characterized in that configured to include The method of claim 3, wherein Ba _x Ca _(1-x) SiO ₃ is in a range of 0.2 ≦ _x ≦ 0.7. The method according to claim 3, wherein the sintering aid BaCO ₃ , CaCO ₃ and SiO ₂ powder is calcined and ground in advance. 6. A method according to claim 5, wherein said calcination is carried out at least 1000 [deg.] C. for at least 2 hours. The method of claim 5, wherein the sintering aid powder is characterized in that the particle size of about 0.85㎛ or less.