KR20060110603A - Dielectric ceramic composition and multilayer ceramic capacitor using the same - Google Patents

Abstract

Dielectric ceramic composition for forming multi-layered ceramic capacitor is provided to improve temperature stability and DC-bias property, and form uniform core-shell structure and particle system because of preparing microfine particles by comprising barium-carbon titanate as (Ba1-xCax)TiO3 as well as barium titanate BaTiO3 to improve dielectricity and electrical reliability. The ceramic composition comprises 25-75wt.% of (Ba1-xCax)TiO3(wherein x ranges from 0.01-0.15) and the balance of BaTiO3, and additional ingredient with less than 0.2 micrometers of particle size D_50and more than 20m^2/g of specific surface area. The additional ingredient includes: 0.1-2mol% of first ingredient selected from Ba compounds and Mg compounds; 0.1-1.5mol% of second ingredient selected from Y compounds and Re compounds, wherein Re is rare earth element; 0.01-3.0mol% of Mn compounds, Cr compounds and V compounds; and 1.0-3.0mol% of Si compounds.

Description

DIELECTRIC CERAMIC COMPOSITION AND MULTILAYER CERAMIC CAPACITOR USING THE SAME}

1 is a shape schematic view of a core cell structure of a dielectric material;

Figure 1 (a) is a dielectric using a subsidiary component of the assembly,

Fig. 1 (b) is a dielectric using fine particles.

2 is an example of a manufacturing process of a multilayer ceramic capacitor.

Japanese Laid-Open Patent Publication 2003-277136

Japanese Laid-Open Patent Publication 2004-079686

The present invention relates to a dielectric ceramic composition composed of BaTiO ₃ crystal grains and (Ba _1-x Ca _x ) TiO ₃ crystal grains, and a multilayer ceramic capacitor using the same.

In recent years, with the miniaturization and high performance of electronic devices, multilayer ceramic capacitors have also undergone high capacity thinning. Accordingly, reliability characteristics such as DC-bias according to the high electric field and capacity change due to temperature have become a problem.

As a dielectric constant of high dielectric constant, BaTiO ₃ (simply referred to as BT) powder having a perovskite structure is often used. BT dielectric materials have the drawback that the reduction of the relative dielectric constant (DC-bias) by applying a DC voltage is large. In order to solve this problem, the BT crystal particles are micronized, but there are adverse effects on the reduction of dielectric constant and the characteristics of capacity change with temperature. In addition, the BT dielectric material has a large dielectric constant of 4000 or more due to atomic fluctuations caused by phase transition for each temperature. However, this atomic fluctuation has a characteristic that the relative dielectric constant due to DC bias is greatly changed.

On the other hand, the insulation resistance to enhance the reducing resistance of BaTiO _3, in the steel in a reducing atmosphere in accordance with an A position and sub-component to B position of BaTiO ₃ Sikkim separately employed at the time of the firing of the acceptor and the donor element of the semiconductor screen of the BaTiO ₃ Research is underway to reduce degradation.

In order to improve the DC bias characteristics of the BaTiO ₃ was employed in some of the Ca A place of BaTiO ₃ (Ba _1-x Ca _x) TiO ₃ has been developed (also called simply denoted BCT) the dielectric material (Japanese Unexamined Patent Application Publication No. 2003- 277136 and Japanese Laid-Open Patent Publication 2004-079686).

The BCT dielectric material has little change in the phase transition temperature near the high temperature, but improves the DC bias characteristics by moving the two phase transition temperatures near the low temperature to the lower temperature side. In addition, since Ca can be employed in both A and B sites, when employed in some B sites, the octahedral of the crystal structure causes distortion, which makes it difficult to form oxygen vacancies in a reducing atmosphere. There is a structural advantage of improved reliability. Of course, playing the role of acceptor is also an important reason to promote reduction resistance.

However, as the Ca-dissolution in BCT increases, atomic fluctuations are reduced due to the decrease of the overall volume (quantum mechanics, Phonon's movement distance). In addition, as Ca is dissolved in BaTiO ₃ , the material movement of Ca is good in chip firing, and abnormal grain growth is generated, thereby deteriorating electrical characteristics. Therefore, to solve this problem, the plastic profile and the atmosphere are used, which requires a lot of equipment investment.

As such, the BT dielectric material has an advantage of high dielectric constant, but a DC-bias has a big disadvantage. In addition, the BCT dielectric material is improved in the bias characteristics of DC, but has a disadvantage in that the relative dielectric constant is greatly reduced.

In the present invention, BaTiO ₃ and (Ba _1-x Ca _x ) TiO ₃ are mixed as main components of the dielectric material. It is an object of the present invention to provide a dielectric ceramic composition and a multilayer ceramic capacitor capable of improving dielectric constant and electrical reliability. Furthermore, the purpose is to improve the capacity and electrical properties by forming a uniform core cell structure and grain boundaries according to the atomization of subcomponents.

In the dielectric ceramic composition of the present invention for achieving the above object, the main component is composed of (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15): 25 to 75% by weight and the remaining BaTiO ₃ .

In the present invention, the (Ba _1-x Ca _x ) TiO ₃ , wherein x is 0.

01 to 0.15) is preferably 45 to 55% by weight. The magnetic composition further includes a subcomponent, and the particle size of the subcomponent is preferably D50 of 0.2 µm or less and a specific surface area of 20 M ² / g or more. The subcomponent is at least one selected from Mg compound and Ba compound as a first subcomponent: 0.01 to 2 mol%. At least one selected from Y compound and Re compound (Re: rare earth element) as the second sub ingredient: 0.1-1.5 mol%, and at least one kind of Mn compound, Cr compound, and V compound as the third sub ingredient: 0.01-3.0 mol%, As a 4th component, Si compound: 1.0-3.0 mol% is preferable. Most preferably, as a minor component, BaCO ₃ : 0.01 to 2.0 mol%, MgO: 0.01 to 1.5 mol%, Y ₂ O ₃ : 0.1 to 1.5 mol%, MnO ₂ : 0.01 to 0.3 mol%, Cr ₂ O ₃ : 0.01 0.10 mol%, SiO _2: will be included with 1.0 to 3.0 mol% is added.

In addition, in the multilayer ceramic capacitor of the present invention, a laminate including a dielectric ceramic layer formed between internal electrodes and external electrodes electrically connected to internal electrodes are formed at both ends of the laminate, and the dielectric ceramic layer is The above-described dielectric self composition of the present invention.

Hereinafter, the present invention will be described in detail.

In the present invention, by mixing BaTiO ₃ having a high dielectric constant and (Ba _1-x Ca _x ) TiO ₃ having excellent temperature stability, DC-bias characteristics, and reduction resistance, high dielectric constant is ensured and high electrical reliability is achieved. .

BT particles and BCT particles in the present invention is preferably 0.2 ~ 0.6㎛, preferably 0.2 ~ 0.3㎛. BT particles and BCT particles are prepared by a hydrothermal synthesis method, a solid phase method, a coprecipitation method, a sol-gel method and the like, but is not limited thereto. In the present invention, the BCT preferably has a modification amount x of Ca in the range of 0.01 to 0.15.

According to the present invention, BT and BCT satisfy 100 wt% as the main components of the dielectric material, and the content of BCT is 25 to 75%, and the remaining BT is BT. Preferably the content of BCT is 25-55%, more preferably 45-55%, most preferably 50%. The higher the content of BCT, the better the temperature stability of the capacity on the high temperature side and the lower the DC-bias value.

Subsidiary components are added to the BT dielectric material and the BCT dielectric material, and such subcomponents may also be added to the present invention.

As the secondary component, components that act as acceptors and donors and sintering accelerators are added. As the acceptor, Mg, Ba, Mn, Cr, V and the like are known, and as the donor, rare earth elements (Dy, Er, Yb) and Y elements are known. In addition, sintering accelerators include glass frit and SiO ₂ .

In the present invention, there is a great feature in using the subcomponent as a particulate. In terms of atomization of the minor components, the sintering accelerator is preferably SiO ₂ rather than glass frit. This is because glass frit is difficult to be differentiated due to its high strength. Figure 1 (a) is a case of a sub-component of the assembly using the glass frit, and Fig. 1 (b) is a case of a sub-component of the particulate with the SiO _2.

As can be seen in Figure 1 (a) after the sintered glass rich (glass rich) phase (3) is present, the uniform core (1) and the cell (2) can not be formed locally by using the subsidiary components of the granulation separately, separately There is a tendency to exist. As a result of the thinning of the dielectric material due to this phenomenon, a large electric field is locally applied, which causes a problem in reliability such as a low breakdown voltage (BDV) and a high DC bias.

In Figure 1 (b) it is possible to form a uniform cell phase around the core. This is because all the subcomponents including the sintering aid are formed into one phase by using the particulate subcomponents, so that uniform dispersion is possible. Accordingly, it can be seen that the breakdown voltage (BDV) and the DC-bias characteristics are improved by the temperature characteristics of the capacitance and the formation of uniform grain boundaries.

As described above, in the present invention, the particle diameters of the subcomponents are made smaller to form more uniform core cells and grain boundaries, thereby improving electrical characteristics. Particle size conditions of the ^secondary component for this purpose is preferably D50 is 0.2㎛ or less (more than 50% of the particle size means 0.2㎛ or less), the specific surface area is more than 20m ² / g. More preferably, D50 is 0.1 micrometer or less and specific surface area is 40 m <^2> / g or more.

The addition of the preferable subcomponent in this invention is as follows.

At least 1 sort (s) chosen from Mg compound and Ba compound as a 1st component: 0.01-2 mol%. At least one selected from Y compound and Re compound (Re: rare earth element) as the second sub ingredient: 0.1-1.5 mol%, and at least one kind of Mn compound, Cr compound, and V compound as the third sub ingredient: 0.01-3.0 mol%, Si compound: 1.0-3.0 mol% as a 4th component. More specifically, BaCO ₃ : 0.01 to 2.0 mol%, MgO: 0.01 to 1.5 mol%, Y ₂ O ₃ : 0.1 to 1.5 mol%, MnO ₂ : 0.01 to 0.3 mol%, Cr ₂ O ₃ : 0.01 to 0.10 mol%, SiO _2: 1.0 ~ is preferably set to 3.0 mol%. The reason for these limitations is explained concretely.

BaCO ₃ : 0.01 ~ 2.0 mol%

The effect of suppressing grain growth by the reaction of grains is effectively carried out. If the content is less than 0.01 mol%, the desired additive effect cannot be exerted. In addition, the dielectric constant of the chip may be lowered.

MgO: 0.01-1.5 mol%

In order to control grain growth and control core and cell fraction by acceptor composition, it is not enough to suppress grain growth in case of less than 0.01 mol% and increase the fraction of shell in case of more than 1.5 mol%. It is the cause of decreasing the dielectric constant.

Y ₂ O ₃ : 0.1 ~ 1.5 mol%

In order to increase the reduction resistance and reliability by the donor composition, the reduction resistance and the insulation resistance of the dielectric layer are deteriorated in the case of less than 0.1 mol%, and the cell fraction of the grain constituting the dielectric layer is increased in the case of exceeding 1.5 mol%. The dielectric constant may be lowered.

MnO ₂ : 0.01 to 0.3 mol%

In order to suppress grain growth of grain and improve reliability by acceptor composition, it is not possible to improve sufficient reliability in case of less than 0.01 mol%, and inversely by lowering initial reliability and increasing shell fraction in case of more than 0.3 mol% The dielectric constant may be lowered.

Cr ₂ O ₃ : 0.01 ~ 0.1 mol%

In order to increase the dielectric constant with the accept composition and improve the reliability, it is not possible to increase the sufficient permittivity and the reliability improvement in case of less than 0.01 mol%, and in the case of more than 0.1 mol%, the dielectric constant due to the decrease of reliability and the increase of the shell fraction Causes a decrease in

SiO ₂ : 1.0 ~ 3.0 mol%

In order to act as a sintering accelerator, more than 1.0 mol% should be added. In case of more than 3.0 mol%, the firing temperature is lowered, but local abnormal grain growth occurs, which causes a decrease in reliability.

Next, a multilayer ceramic capacitor using the dielectric magnetic composition of the present invention will be described.

The multilayer ceramic capacitor includes a laminate including a dielectric ceramic layer formed between internal electrodes, and external electrodes electrically connected to the internal electrodes at both ends of the laminate, wherein the dielectric ceramic layer is the dielectric of the present invention. It is a self-composition. The stacked state of the internal electrode and the dielectric ceramic layer in the multilayer ceramic capacitor may be described as a laminate including a plurality of dielectric ceramic layers and internal electrodes formed between the ceramic layers.

The dielectric ceramic composition of the multilayer ceramic capacitor of the present invention is composed of (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15): 25 to 75% by weight and the remaining BaTiO ₃ . In the present invention, the content of (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15) is preferably 45 to 55% by weight. The magnetic composition further includes a subcomponent, and the particle size of the subcomponent is preferably D50 of 0.2 µm or less and a specific surface area of 20 m ² / g or more. More preferably, D50 is 0.1 micrometer or less and specific surface area is 40 m <^2> / g or more. The subcomponent is at least one selected from Mg compound and Ba compound as a first subcomponent: 0.01 to 2 mol%. At least one selected from Y compound and Re compound (Re: rare earth element) as the second sub ingredient: 0.1-1.5 mol%, and at least one kind of Mn compound, Cr compound, and V compound as the third sub ingredient: 0.01-3.0 mol%, As a 4th component, Si compound: 1.0-3.0 mol% is preferable. Most preferably, as a minor component, BaCO ₃ : 0.01 to 2.0 mol%, MgO: 0.01 to 1.5 mol%, Y ₂ O ₃ : 0.1 to 1.5 mol%, MnO ₂ : 0.01 to 0.3 mol%, Cr ₂ O ₃ : 0.01 0.10 mol%, SiO _2: will be included with 1.0 to 3.0 mol% is added.

The multilayer ceramic capacitor of the present invention can be manufactured according to the illustrated method of FIG.

The main component is weighed so as to satisfy the composition of the dielectric ceramic composition of the present invention, and the dielectric sheet is formed by molding methods such as a doctor blade method from a raw material powder containing fine particles. An internal electrode pattern is formed on the dielectric sheet by screen printing or the like. In this case, the internal electrode used is preferably a non-metal Ni metal. A dielectric sheet printed with internal electrodes is laminated and pressed. After firing the laminate, external electrodes electrically connected to the internal electrodes are formed at both ends of the laminate. In this case, it is preferable to use a paste made of Cu metal or Ni metal.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

BaTiO ₃ powder and (Ba _1-x Ca _x ) TiO ₃ powder (x is 0.06, Ca modification amount: 6 mol%) prepared by hydrothermal synthesis were used. As the secondary component, a milled product manufactured by a bead mill, a ball mill, an Attrition mill, or the like was used. Table 1 shows the molar ratios of the subcomponents, and Table 2 shows the powder characteristics of the subcomponents.

Molar ratio (mol%) BT + BCT BaCO ₃ MgO Y ₂ O ₃ MnO ₂ Cr ₂ O ₃ SiO ₂ 100 0.5 1.0 1.0 0.2 0.05 2.0

 division A1 A2 D10 0.10 0.05 D50 0.20 0.10 Dmax 0.40 0.20 Specific surface area (SSA, m ² / g) 20 40

The main components and subcomponents prepared as described above were weighed under the conditions shown in Table 3.

division B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 BCT (wt%) 0 0 25 25 50 50 75 75 100 100 BT (wt%) 100 100 75 75 50 50 25 25 0 0 Type of subcomponent A1 A2 A1 A2 A1 A2 A1 A2 A1 A2

Weighing was carried out as in Table 3, and an organic solvent and a dispersant were added thereto, and the slurry was dispersed using a bead mill. The binder dispersion was performed by adding polyvinyl butyral to the slurry thus dispersed. Thereafter, molding was performed at a thickness of 2.5 µm or less by the doctor blade method.

The internal electrodes were printed on a 2.0 mm x 1.2 mm pattern on the sheet thus formed. At this time, the thickness of the internal electrode was adjusted to be 2㎛ or less after drying. The printed sheets were laminated in 100 layers, and the binder was burned at 350 ° C., followed by 2 hours at an optimum temperature of H ₂ -N ₂ -H ₂ O in a reducing atmosphere of 10 ^-9 to 10 ^-12 MPa at an oxygen partial pressure. The chips were fired by holding.

The chips fired at each optimum temperature were evaluated for capacity, loss and short rate at 1Vrms of AC field at 1khz frequency. Capacity change rate with temperature was carried out at 85 ℃. BDV was evaluated based on the moment when the chip was broken while raising the DC electric field. DC-bias evaluation measured the capacity change rate in the environment of AC 1Vrms, frequency 1kHz to 6.3V DC electric field.

The evaluation results are shown in Table 4 below.

division Firing temperature (℃) Capacity Loss (%) Short rate (%) BDV (V) TCC (85 ℃) DC bias at 6.3V (%) B1 1180 5.10 6.2 2 151 -12.6 -68.2 B2 1180 5.21 5.9 3 163 -10 -67.5 B3 1175 4.88 6.6 2 140 -11.4 -58.5 B4 1175 5.04 6.4 2 144 -9.35 -54.3 B5 1170 4.67 7.0 3 136 -10.47 -42.3 B6 1170 4.86 6.9 2 140 -8.23 -41.2 B7 1160 4.41 7.7 34 65 -14.8 -66.8 B8 1160 4.47 7.5 24 74 -14.5 -66.4 B9 1155 4.09 7.9 42 64 -14.6 -72.8 B10 1155 4.32 7.6 38 68 -14.52 -71.8

As shown in Table 4, in the case of B1 and B2, when BT was used at 100%, the capacity was 5uF or more, the short rate was 2-3%, and the BDV was 150V or more. However, at 85 ° C, the capacity change rate was within -10 ~ -13% and the bias characteristic was -67% at DC 6.3V, which did not satisfy the X5R characteristics.

As a result of the particle size characteristics of the subcomponents in B1 and B2, in the case of B2 using the subcomponent as a fine particle, the capacity and the overall electrical characteristics were improved. This resulted in the formation of a uniform core cell structure by using particulate subcomponents to improve capacity reduction and temperature characteristics, and to form uniform grain boundaries, thereby improving insulation resistance and BDV. This tendency was judged that the case where the particle size of the subcomponent was small and the specific surface area was larger formed a more uniform core cell and grain boundaries.

In the case of B3 and B4, the BCT content was 25% and the dose and BDV were slightly decreased compared to B1 and B2. However, results have been obtained in which the temperature stability of the capacity and the DC-bias characteristics are improved.

In the case of B5 and B6, the BCT content was 50%. As the BCT content increased, the dose and BDV decreased. However, the temperature stability and DC-bias characteristics of the capacity were improved, and it was found that the X5R specification was satisfied.

The DC-bias characteristics were improved until the BCT content was 75%, but the short rate increased rapidly at 75% of the BCT content. This is thought to be a result of the occurrence of spleen growth during firing due to the higher BCT content than BT.

In addition, as shown in Table 4, it was confirmed that the working range of the firing temperature is widened as the firing temperature is lowered according to the mixing of BT and BCT.

Table 4 shows that optimum electrical properties can be obtained by properly mixing BT and BCT and further atomizing minor components.

As described above, in the present invention, by mixing BaTiO ₃ and (Ba _1-x Ca _x ) TiO ₃ as a main component of the dielectric material, it is possible to improve the high temperature stability and DC-bias characteristics at high temperatures with high dielectric constant. Could know. In addition, by further minimizing the subcomponents, as a result of forming a uniform core cell structure and grain boundaries, capacities and electrical characteristics were improved.

Claims (10)

A dielectric ceramic composition whose main component is (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15): 25 to 75% by weight and the remaining BaTiO ₃ . The dielectric ceramic composition according to claim 1, wherein the content of (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15) is 45 to 55% by weight. The dielectric ceramic composition according to claim 1, further comprising a minor component, the particle size of the minor component having a D50 of 0.2 µm or less and a specific surface area of 20 m ² / g or more. The dielectric ceramic composition according to claim 1, wherein the subcomponent has a particle size of D50 of 0.1 µm or less and a specific surface area of 40 m ² / g or more. The said subcomponent is at least 1 sort (s) chosen from Ba compound and Mg compound as a 1st component: 0.01-2 mol%. At least one selected from Y compound and Re compound (Re: rare earth element) as the second sub ingredient: 0.1-1.5 mol%, at least one of Mn compound, Cr compound, and V compound as the third sub ingredient: 0.01-3.0 mol% Si compound as a fourth component: a dielectric ceramic composition, characterized in that 1.0 ~ 3.0 mol%. The method according to any one of claims 1 to 4, wherein the minor components are BaCO ₃ : 0.01 to 2.0 mol%, MgO: 0.01 to 1.5 mol%, Y ₂ O ₃ : 0.1 to 1.5 mol%, MnO ₂ : 0.01 to 0.3 Mole%, Cr ₂ O ₃ : 0.01 ~ 0.10 mol%, SiO ₂ : 1.0 ~ 3.0 mol% dielectric ceramic composition, characterized in that. Including a laminate including a dielectric ceramic layer formed between the internal electrode and an external electrode electrically connected to the internal electrode at both ends of the laminate, the dielectric ceramic layer is the dielectric magnetic composition of claim 1 Multilayer ceramic capacitors. The multilayer ceramic capacitor according to claim 7, wherein the content of (Ba _1-x Ca _x ) TiO ₃ (where x is 0.01 to 0.15) is 45 to 55% by weight. The method of claim 7 or 8, wherein at least one selected from Ba compound and Mg compound is 0.01 to 2 mol% as the first accessory ingredient. At least one selected from Y compound and Re compound (Re: rare earth element) as the second sub ingredient: 0.1-1.5 mol%, and at least one kind of Mn compound, Cr compound, and V compound as the third sub ingredient: 0.01-3.0 mol%, Si compound: 1.0 to 3.0 mol% as a fourth component multilayer ceramic capacitor, characterized in that it further comprises. The method according to claim 7 or 8, wherein BaCO ₃ : 0.01 to 2.0 mol%, MgO: 0.01 to 1.5 mol%, Y ₂ O ₃ : 0.1 to 1.5 mol%, MnO ₂ : 0.01 to 0.3 mol%, Cr ₂ O ₃ : 0.01 ~ 0.10mol%, SiO ₂ : 1.0 ~ 3.0mol% of the additive is a multilayer ceramic capacitor characterized in that it further comprises.

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