KR100639018B1 - Non-reducing dielectric ceramic compositions for compensation of temperature and laminated ceramic capacitors having the same - Google Patents

Abstract

Provided are a reduction-resistant ceramic dielectric composition for temperature compensation which can be applied to a layered chip ceramic capacitor as a dielectric having a small thickness, and a layered chip ceramic capacitor using the composition. The ceramic dielectric composition comprises a main component represented by (1-x)CaZrO3-xBa5Nb4O15; and a side component which comprises at least one selected from the group consisting of calcium titanate, strontium zirconate and CaO-B2O3-SiO2-Li2O-MnO2-MoO3-based glass frit, wherein 0.07<=x<=0.20; and the amounts of calcium titanate, strontium zirconate and the glass frit to the main component are 5 wt% or less, 10 wt% or less and 3 wt% or less, respectively.

Description

Non-Reducing Dielectric Ceramic Compositions for Compensation of Temperature and Laminated Ceramic Capacitors having the Same}

1 is a view showing a multilayer ceramic capacitor made of the ceramic dielectric composition of the present invention.

The present invention relates to a dielectric composition that can be sintered in a reducing atmosphere and a multilayer chip ceramic capacitor using the same. More specifically, by applying a Cu or Ni internal electrode, a multilayer chip ceramic for temperature compensation having excellent dielectric and sintering characteristics as well as insulation characteristics The present invention relates to a dielectric composition applicable to a capacitor.

Multilayer chip ceramic capacitors play a role of signal blocking, coupling, and by-pass in an electronic circuit. A dielectric ceramic layer is formed between a plurality of internal electrodes facing each other to form capacitance. In general, ceramic dielectrics can be classified into temperature compensation and high permittivity meters according to temperature characteristics and dielectric constant. In the case of temperature compensation, the dielectric constant is 10 to 100. The high dielectric constant is BaTiO ₃ and the dielectric constant is about 2,000 to 20,000.

Typical compositions for temperature compensation dielectrics include MgTiO ₃ -CaTiO ₃ based on 20 dielectric constants that can be sintered only in the air, BaTi ₄ O ₉ based on dielectric constants between 30 and 40, and BaZ (Zr, Sn) TiO ₄ based on dielectric constants of 60 to 100 -Nd-Ti oxide type. These compositions show excellent properties in the air, but in a reducing atmosphere that is oxygen deficient, some of the oxides are reduced during sintering, resulting in reduced insulation resistance and poor dielectric properties, so Ni or Cu cannot be applied as internal electrodes.

However, in recent years, multilayer chip ceramic capacitors use inexpensive non-metals such as Ni and Cu as internal electrodes in precious metals such as Ag-Pd and Pd, which occupy more than 30% of the capacitor manufacturing cost due to the demand for low cost. The share is increasing. When a metal such as Ni or Cu is applied to a laminated chip capacitor, it is necessary to sinter in a reducing atmosphere in order to prevent oxidation of Ni or Cu, and thus a dielectric material having reduction resistance is required.

Currently, representative examples of temperature compensation dielectric compositions using nickel (Ni) internal electrodes are reported in US Pat. No. 6,118,648 and Japanese Patent Application Laid-open No. Hei 10-90751. A.sato et al. 157-158 (1999) published a paper entitled "Low Frequency Dielectric Dispersion in (CaSr) (TiZr) O3 Compositions Fired in a Reducing Atmosphere". The patent is an additive to the main component [(Ca _X Sr _1-X ) _m (Ti _Y Zr _1-Y ) O ₃ ] based manganese oxide (MnO ₂ ), alumina (or aluminum oxide, Al ₂ O ₃ , ( It is a dielectric composition containing BaCa) SiO ₃ -glass and shows excellent dielectric properties, but has a low dielectric constant of about 30 to 40 and has a problem of increasing dielectric thickness when fabricating a high capacity multilayer chip capacitor or a high voltage multilayer chip capacitor. have.

For this reason, there is still a need for the development of a dielectric composition that can be applied to a multilayer chip ceramic capacitor having a very high dielectric constant of 40 or more and excellent dielectric properties such as temperature coefficient and quality factor of dielectric constant.

Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is not only to use a low-cost metal such as Ni or Cu as an internal electrode, but also to provide excellent dielectric properties that can reduce the thickness of a dielectric when manufacturing a laminated chip capacitor. It is to provide a temperature-compensating, reduction-resistant ceramic dielectric composition exhibiting sintering characteristics and a multilayer chip ceramic capacitor using the same.

In order to achieve the above object, according to the present invention, as a temperature-compensation-resistant ceramic dielectric composition composed of a main component and a subcomponent, the main component, when the mole fraction of Ba ₅ Nb ₄ O ₁₅ is x, -x) is expressed as CaZrO ₃ -x Ba ₅ Nb ₄ O ₁₅ , wherein x has a value in the range 0.07≤x≤0.20, the minor components are calcium titanate, strontium zirconate, and CaO-B ₂ O ₃ -SiO At least one of ₂ -Li ₂ O-MnO ₂ -MoO _3- based glass frit, the addition amount of calcium titanate, strontium zirconate and the glass frit to the main components, respectively, 5wt% or less, 10wt% or less And a 3 wt% or less temperature-compensating, reduction resistant ceramic dielectric composition is provided.

Further, according to the present invention, there is provided a laminated chip ceramic capacitor having the temperature compensation ceramic dielectric composition as a dielectric material.

In the present invention, while CaZrO ₃ , which has been known as a temperature compensating ceramic dielectric composition, has been studied for a material satisfying a temperature characteristic suitable for the temperature compensation standard, Ba ₅ Nb ₄ O ₁₅ has a dielectric constant of 39 and a dielectric constant of- It was reported that it shows excellent dielectric properties in the air at 100 ppm / ° C and was selected.

On the other hand, in the present invention, it is possible to adjust the dielectric constant and the temperature coefficient of the dielectric constant by adding Ba ₅ Nb ₄ O ₁₅ to CaZrO ₃ as a main component by changing the molar ratio. Specifically, based on the (1-x) CaZrO ₃ -x Ba ₅ Nb ₄ O _15- based composition, in particular, when the mole fraction x of Ba ₅ Nb ₄ O ₁₅ is 0.07 ~ 0.20 dielectric properties and insulation resistance properties for temperature compensation When Ba ₅ Nb ₄ O ₁₅ is added below 0.07, the dielectric constant decreases, but the insulation resistance and the quality factor (inverse of the dielectric loss) are deteriorated, which is not suitable for the use of the multilayer chip capacitor. On the other hand, when the mole fraction x of Ba ₅ Nb ₄ O ₁₅ exceeds 0.20, the quality factor and dielectric constant are rather lowered, which does not meet the object of the present invention.

On the other hand, by adding calcium titanate (CaTiO ₃ ), strontium zirconate (SrZrO ₃ ) as an additional ingredient added to the composition of the present invention, the dielectric constant was improved and the temperature coefficient of the dielectric constant could be adjusted. Specifically, calcium titanate (CaTiO ₃₎ ) Is added to 5wt% can improve the dielectric constant, and when strontium zirconate (SrZrO ₃ ) is added to 10wt% can improve the temperature coefficient and quality factor of the dielectric constant.

In addition, the addition of glass frit, which is added as another minor component, lowers the firing temperature, and adds manganese oxide (MnO ₂ ) and molybdenum oxide (MoO ₃ ) to the glass frit composition to compensate for valence during firing in a reducing atmosphere. The high temperature insulation resistance characteristic by the change with time is improved, and the insulation resistance (IR) characteristic at normal temperature is improved by forming a liquid insulation layer between grain boundaries. In the case of the addition of glass frit, the room temperature IR (insulation resistance at 25 ° C) and the high temperature IR (insulation resistance at 125 ° C) increase simultaneously up to 3wt%, but at higher temperatures, the room temperature IR tends to increase. Seems. Therefore, in general, the IR value is known to be related to the reliability, and it is not preferable to considerably reduce the high temperature IR, in view of the fact that the deterioration of the characteristic occurs especially when the high temperature IR value decreases.

In the present invention, it can be seen that the glass frit content up to 3wt% increases the quality coefficient and insulation resistance. Such a result is included in the glass frit rather than the loss of grain boundaries due to the glass frit. It is expected by the addition of manganese oxide (MnO ₂ ) and molybdenum oxide (MoO ₃ ). In addition, in the manufacture of glass frit, manganese oxide (MnO ₂ ), molybdenum oxide (MoO ₃ ), etc. are used as additives alone in the conventional case, but in the present invention, manganese oxide and molybdenum oxide are added when glass frit is added. Simultaneous addition and mixing were intended to increase the uniformity of the additives.

In the composition of glass frit, the main composition mainly consists of calcium oxide (CaO) -boron oxide (B ₂ O ₃ ) -silicon oxide (SiO ₂ ) -lithium oxide (Li ₂ O). In the present invention, however, in addition to the above composition, manganese oxide (MnO ₂ ) and molybdenum oxide (MoO ₃ ) were added simultaneously, and showed excellent dielectric and sintering characteristics.

In order to lower the sintering temperature, liquid phase sintering is generally performed. The addition of glass frit allows liquid formation to be possible at 900 degrees or less.

To this end, in the glass frit of the present invention, when MnO ₂ and MoO ₃ are fixed at 8 mol% and 4 mol%, respectively, 20 mol% ≦ CaO ≦ 35 mol%, and B ₂ O ₃ is 30 mol% or less and 35 mol The melting point of the glass frit was adjusted to a range of 1300 to 1500 ° C. using a composition having% ≦ SiO ₂ ≦ 55 mol% and Li ₂ O of 15 mol% or less. This limited component has a difficulty in the glass manufacturing process because the liquid formation temperature is more than 900 degrees or flowability when manufacturing the glass frit outside the limited range.

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

The glass frit used in the present invention includes manganese oxide (MnO ₂ ), molybdenum oxide (MoO ₃ ), calcium oxide (CaO), boron oxide (B ₂ O ₃ ), and silicon oxide (SiO ₂ ) as shown in Table 1 below. After the basis weight in a ratio and dry mixing for 6 hours using an alumina (Al ₂ O ₃ ) ball, using a platinum crucible according to the composition was melted for 0.5 to 10 hours in the range of 1300 ~ 1500 ℃ and prepared by quenching. The prepared glass frit was added to 3 wt% or less in castability after adjusting the powder size (D ₅₀ ) to 0.5-1.0 μm using a ball mill or a dyno mill.

Table 1 shows the composition of each dielectric composition, where * in Table 1 is a composition range outside the scope of the present invention. That is, CaZrO ₃ , Ba ₅ Nb ₄ O ₁₅ , CaTiO _3, SrZrO ₃ and the glass frit were weighed to a desired composition, and then the raw materials were wet mixed for 24 hours using pure water (DI water) as a solvent. The wet mixed raw materials were dried, calcined at 600 to 900 ° C., and then ground again to prepare a powder size (D ₅₀ ) of 0.3 to 0.8 μm.

The prepared powder was ball milled using a zirconia (ZrO ₂ ) ball with PVB (Poly Vinyl Butyral) and toluene / ethanol solvent to prepare a slurry. The slurry formed a ceramic green sheet having a thickness of 3 to 50 µm using a predetermined coating method (doctor blade or die-coating). Several sheets of green sheet were laminated to a thickness of 1 mm and pressed to prepare disk-shaped specimens, and the dielectric properties were confirmed by forming electrodes after sintering in a reducing resistance atmosphere.

1 is a cross-sectional view showing a multilayer ceramic capacitor made of the dielectric composition of the present invention, respectively, and as shown in FIG. 1, a capacitor includes a ceramic body 1 in which a plurality of internal electrodes 2 are stacked, and both sides of the ceramic body. It consists of an external electrode (3) formed and connected to the inner electrode slightly protruding to the outside. In the manufacture of multilayer chip capacitors, an internal electrode was formed by printing a nickel paste using 0.1 to 0.3 μm of CaZrO ₃ as a ceramic additive on a ceramic green sheet having a thickness of ₃ to 50 μm. The laminate was pressed after lamination according to the desired electrical properties, and the pressed bars were cut. In order to remove organic matter from the cut products, the binder was burned out at a temperature in the range of 250 to 350 ° C., and then sintered in the range of 1260 to 1320 ° C. in a reducing atmosphere.

The sintered chip was polished to form an external electrode on the sintered product, and after polishing, copper (Cu) paste having a composition ratio of 60 to 100% spherical type and 0 to 40% flake type was applied. After the external electrode was formed, the external electrode was calcined in the range of 800 to 900 ° C. in a reducing atmosphere.

After forming the external electrode 3 (Cu), nickel plating was performed for solderability and corrosion resistance, and tin plating was performed on the outside thereof.

The dielectric constant and quality factor, which are the dielectric properties of the multilayer chip capacitor, were measured under the conditions of 1 MHz, 1 V _rms and 25 ° C., and the capacity change rate was calculated by measuring in the range of −55 to 125 ° C. Insulated resistance is 100V at two temperatures of 25 ° C (referred to as room temperature insulation resistance) and 125 ° C (referred to as high temperature insulation resistance) after charging for 1 minute. "High resistance meter (HP, 4329A, High Resistance Meter) Was measured using ".

The above result is shown in Table 2.

As shown in Table 2, the dielectric composition according to the present invention exhibits a high dielectric constant of about 40 to 70, a quality factor of about 500, and shows excellent dielectric properties. 25 ° C) is 1.00E + 12 or higher, the high temperature insulation resistance (125 ° C) exceeds approximately 1.00E + 10, and the temperature coefficient of dielectric constant is also changed within a range of ± 300 ppm / ° C. From these facts, it can be seen that the dielectric composition of the present invention exhibits dielectric and insulating properties that can replace conventional dielectric materials applied to multilayer chip ceramic capacitors.

As described above, according to the present invention, a low-cost metal such as Cu or Ni, etc. can be used for internal firing, as well as excellent dielectric and electrical insulation properties, such as dielectric constant and dielectric constant temperature coefficient, multilayer chip ceramic capacitors. It can be a temperature-compensating, reducing-resistant dielectric ceramic composition that can reduce the thickness of the dielectric when applied in.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and the general knowledge in the technical field to which the present invention pertains without departing from the spirit of the present invention. Various changes and modifications will be made by those who possess.

Claims (3)

A temperature compensation reduction ceramic dielectric composition composed of a main component and a subcomponent, The main component, Ba ₅ Nb ₄ O ₁₅ when referred to the mole fraction of x, formula _{(1-x) CaZrO 3 -} x Ba 5 Nb 4 O 15 is shown, the x value is in the range 0.07≤x≤0.20 Has, The minor component includes at least one of calcium titanate, strontium zirconate, and CaO-B ₂ O ₃ -SiO ₂ -Li ₂ O-MnO ₂ -MoO ₃ -based glass frit, with respect to the main component, calcium titanate and zircon The amount of the strontium acid and the glass frit added is 5 wt% or less, 10 wt% or less, and 3 wt% or less, respectively. The method of claim 1, When the composition of the glass frit is fixed to MnO ₂ and MoO ₃ , 8 mol% and 4 mol%, respectively, 20 mol% ≤ CaO ≤ 35 mol%, B ₂ O ₃ is 30 mol% or less, 35 mol% ≤ SiO ₂ ≤ 55 mol%, Li ₂ O is 15 mol% or less, A temperature-compensating, reduction-resistant ceramic dielectric composition, characterized in that. A multilayer chip ceramic capacitor, comprising using the ceramic dielectric composition of claim 1 as a dielectric material.

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