JP5407592B2 - Dielectric ceramic, manufacturing method thereof, and multilayer ceramic capacitor - Google Patents

Description

  The present invention relates to a dielectric ceramic, a manufacturing method thereof, and a multilayer ceramic capacitor formed using the dielectric ceramic, and more particularly to an improvement for improving the reliability of the multilayer ceramic capacitor.

  One effective means for satisfying the demand for a smaller and larger capacity multilayer ceramic capacitor is to reduce the thickness of the dielectric ceramic layer provided in the multilayer ceramic capacitor. However, as the dielectric ceramic layer becomes thinner, the electric field strength per layer of the dielectric ceramic layer becomes higher. Therefore, the dielectric ceramic used is required to have higher reliability, in particular, higher life characteristics in a load test.

  For example, in order to improve the reliability of a dielectric ceramic whose main component is a barium titanate series, a technique of adding V (vanadium) as a subcomponent is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-2151979 (Patent Document 1). Japanese Laid-Open Patent Publication No. 2000-31828 (Patent Document 2) and Japanese Unexamined Patent Application Publication No. 2004-35388 (Patent Document 3).

Patent Document 1 proposes a composition composed of BaTiO ₃ —Y ₂ O ₃ —MgO—V ₂ O ₅ — [MnO or Cr ₂ O ₃ or Co ₂ O ₃ ] —BaCaSiO ₃ . Here it is noted that V is added as V ₂ O ₅ .

Patent Document 2 proposes a composition composed of BaTiO ₃ —Y ₂ O ₃ — [CaO or MgO] —V ₂ O ₅ —MnO—BaCaSiO ₃ . Again, it is noted that V is added as V ₂ O ₅ .

In Patent Document 3, a composition comprising BaTiO ₃ — [Y ₂ O ₃ or Ho ₂ O ₃ or Dy ₂ O ₃ or Yb ₂ O ₃ ] —MgCO ₃ —Mn ₂ V ₂ O ₇ —Cr ₂ O ₃ —BaCaSiO _3. Has been proposed. Here, it is noted that V is added as a Mn ₂ V ₂ O ₇ compound together with Mn.

However, even when the dielectric ceramics described in Patent Documents 1 to 3 described above are used, the following problems may be encountered. That is, when the dielectric ceramic layer is thinned to, for example, 1 μm or less, the particle size of the dielectric ceramic raw material powder must be reduced to 1 μm or less, for example, the average particle size of the BaTiO ₃ powder is 150 nm or less. Then, the reactivity of the dielectric ceramic raw material at the time of firing increases, and grain growth is promoted, resulting in a decrease in reliability. In particular, it is considered that grain growth is caused by the reaction of V with BaTiO ₃ .

Japanese Patent Application Laid-Open No. 6-215979 JP 2000-31828 A JP 2004-35388 A

  Accordingly, an object of the present invention is to provide a dielectric ceramic, a method for manufacturing the dielectric ceramic, and a multilayer ceramic capacitor configured using the dielectric ceramic, which can solve the above-described problems.

In the present invention, ABO ₃ (A necessarily contains Ba and may further contain at least one of Ca and Sr. B necessarily contains Ti and may further contain at least one of Zr and Hf.) As a main component and R as a subcomponent (R is at least one selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y), The present invention is first directed to a method for producing a dielectric ceramic containing M (M is at least one selected from Mn, Cu, Ni, Cr, Al, Mg), V, and Si.

The dielectric ceramic manufacturing method according to the present invention includes a step of producing a dielectric ceramic raw material and a step of firing the dielectric ceramic raw material, and the step of producing the dielectric ceramic raw material includes Ba and V. The method includes a step of preparing a Ba-V compound and a step of adding the Ba-V compound powder to the ABO ₃ powder.

The Ba-V compound is preferably at least one selected from Ba ₃ V ₂ O ₈ , BaVO ₃ and Ba ₂ VO ₄ .

The present invention is also directed to a dielectric ceramic containing ABO ₃ as a main component and the R, M, V, and Si as subcomponents.

The dielectric ceramic according to the present invention is characterized in that Ba-V crystalline oxide particles containing Ba and V are present in addition to main phase particles having a composition of ABO ₃ .

The composition of the Ba-V crystalline oxide particles is, for example, at least one selected from Ba ₃ V ₂ O ₈ , BaVO ₃ and Ba ₂ VO ₄ .

  The present invention further includes a capacitor body including a plurality of laminated dielectric ceramic layers and a plurality of internal electrodes formed along a specific interface between the dielectric ceramic layers, and an outer surface of the capacitor body. And a plurality of external electrodes that are formed at different positions and are electrically connected to a specific one of the internal electrodes.

  The multilayer ceramic capacitor according to the present invention is characterized in that the dielectric ceramic layer is made of the dielectric ceramic according to the present invention described above.

  According to the present invention, a dielectric ceramic excellent in reliability under a high electric field strength can be obtained. The dielectric ceramic according to the present invention exhibits a remarkable effect particularly when applied to a multilayer ceramic capacitor having a dielectric ceramic layer having a thickness of 1 μm or less. The reason is estimated as follows.

When V reacts alone with BaTiO ₃ , BaTiO ₃ tends to grow and reliability decreases. In contrast, as in this invention, by adding V in the form of compounds with Ba, even when V is reacted with BaTiO _3, BaTiO ₃ is speculated that this is because it is difficult to grain growth Yes. The reason why BaTiO ₃ becomes difficult to grow has not been elucidated.

  Therefore, according to the multilayer ceramic capacitor in which the dielectric ceramic layer is formed using the dielectric ceramic according to the present invention, the reliability can be improved.

1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 configured using a dielectric ceramic according to the present invention.

  With reference to FIG. 1, first, a multilayer ceramic capacitor 1 to which a dielectric ceramic according to the present invention is applied will be described.

  A multilayer ceramic capacitor 1 includes a capacitor body 5 including a plurality of laminated dielectric ceramic layers 2 and a plurality of internal electrodes 3 and 4 formed along a specific interface between the dielectric ceramic layers 2. I have. The internal electrodes 3 and 4 are mainly composed of Ni, for example.

  First and second external electrodes 6 and 7 are formed at different positions on the outer surface of the capacitor body 5. The external electrodes 6 and 7 are mainly composed of Ag or Cu, for example. In the monolithic ceramic capacitor 1 shown in FIG. 1, the first and second external electrodes 6 and 7 are formed on the end surfaces of the capacitor body 5 facing each other. The internal electrodes 3 and 4 are a plurality of first internal electrodes 3 electrically connected to the first external electrode 6 and a plurality of second internal electrodes 4 electrically connected to the second external electrode 7. The first and second internal electrodes 3 and 4 are alternately arranged in the stacking direction.

  The multilayer ceramic capacitor 1 may be a two-terminal type including two external electrodes 6 and 7 or a multi-terminal type including a large number of external electrodes.

In such a multilayer ceramic capacitor 1, the dielectric ceramic layer 2 includes ABO ₃ (A necessarily includes Ba and may further include at least one of Ca and Sr. B necessarily includes Ti and further includes Zr. And Hf as a main component, and R (R is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). , Lu and Y), M (M is at least one selected from Mn, Cu, Ni, Cr, Al, Mg), V and Si.

As described above, the dielectric ceramic contains V as a subcomponent. In the raw material production process for the dielectric ceramic, ABO ₃ powder is prepared and Ba ₃ V ₂ containing Ba and V is prepared. A blending procedure in which a Ba-V compound such as O ₈ , BaVO ₃ or Ba ₂ VO ₄ is prepared in advance and the Ba-V compound powder is added to the ABO ₃ powder is employed.

More specifically, ABO ₃ is produced by, for example, a solid phase synthesis method, a hydrothermal synthesis method, a hydrolysis method, or the like, and is heat-treated at a temperature at which a desired particle size is obtained. The material form for ABO ₃ and the compound form of the additive component may be any of oxide, carbonate, chloride, or metal organic compound.

  On the other hand, a Ba compound and a V compound are weighed so as to have a predetermined molar ratio, and then mixed and heat-treated to produce a Ba-V compound.

Next, a dielectric ceramic raw material is obtained by adding and mixing the ABO ₃ and Ba-V compound with other subcomponents and, if necessary, a composition correcting Ba compound.

  In order to manufacture the multilayer ceramic capacitor 1, a ceramic slurry is produced using the dielectric ceramic raw material obtained as described above, a ceramic green sheet is formed from the ceramic slurry, and the plurality of ceramic green sheets are laminated. By doing this, the raw laminated body which should become the capacitor | condenser main body 5 is obtained, and the process of baking this raw laminated body is implemented. In the step of firing this raw laminated body, the dielectric ceramic material blended as described above is fired to obtain the dielectric ceramic layer 2 made of sintered dielectric ceramic.

In the sintered dielectric ceramic constituting the dielectric ceramic layer 2, there may be Ba-V crystalline oxide particles containing Ba and V in addition to the main phase particles having the composition of ABO ₃ . The composition of the Ba-V crystalline oxide particles is at least one selected from, for example, Ba ₃ V ₂ O ₈ , BaVO _3, and Ba ₂ VO ₄ .

In the dielectric ceramic according to the present invention, the molar ratio of A and B of ABO _{3 as} the main component may deviate from 1: 1. When the main component is represented by A _m BO ₃ , m can preferably be changed in the range of 0.96 to 1.03. m can be adjusted by adding AO or BO ₂ or adjusting the Ba amount of the Ba-V compound.

Further, in the dielectric ceramic according to the present invention, the content of the subcomponent is not particularly limited, but preferably, when the main component ABO ₃ is 100 mole parts, R is 0.4-3. 0.0 mole part, M is 0.5-3.5 mole part, V is 0.05-0.5 mole part, and Si is 0.1-3.5 mole part.

  Below, the experiment example implemented based on this invention is demonstrated.

[Experimental Example 1]
(A) Production of ceramic raw material First, each powder of BaCO ₃ and TiO ₂ was weighed so as to have a composition of BaTiO ₃ , then mixed by a ball mill, heat-treated at a temperature of 1150 ° C., and BaTiO ₃ as a main component. Got. The average particle diameter of this BaTiO ₃ was 0.15 μm, and the Ba / Ti ratio was 1.004.

On the other hand, each powder of BaCO ₃ and V ₂ O ₅ was weighed so as to have a molar ratio of 3: 1, 2: 1, and 4: 1, mixed by a ball mill, and heat-treated at a temperature of 1100 ° C. As shown in Table 1, the crystalline oxide of Ba ₃ V ₂ O ₈ is used in Example 1, the crystalline oxide of BaVO ₃ is used in Example 2, and the crystalline oxide of Ba ₂ VO ₄ is used in Example 3. I got each. In the comparative example, V ₂ O ₅ powder was used as it was. Both of these average particle diameters were 0.05 μm.

Next, in addition to the BaTiO ₃ and the Ba ₃ V ₂ O ₈ , BaVO ₃ or Ba ₂ VO ₄ or V ₂ O ₅ , Dy ₂ O ₃ , MgO, MnO ₂ and SiO ₂ , and if necessary Then, BaCO ₃ for correcting m value (= Ba / Ti ratio) was weighed so as to have the following composition for each of Examples 1 to 3 and Comparative Example, and then mixed by a ball mill to obtain a dielectric ceramic raw material. Obtained.

(1) Example 1
_{100 (Ba 1.004 TiO 3) -0.6Dy} 2 O 3 -0.9MgO-0.05MnO 2 -1.4SiO 2 -0.1Ba 3 V 2 O 8 -0.1BaCO 3
(2) Example 2
_{100 (Ba 1.004 TiO 3) -0.6Dy} 2 O 3 -0.9MgO-0.05MnO 2 -1.4SiO 2 -0.2BaVO 3 -0.2BaCO 3
(3) Example 3
_{100 (Ba 1.004 TiO 3) -0.6Dy} 2 O 3 -0.9MgO-0.05MnO 2 -1.4SiO 2 -0.2Ba 2 VO 4
(4) Comparative Example 100 (Ba _1.004 TiO ₃ ) -0.6Dy ₂ O ₃ -0.9MgO-0.05MnO ₂ -1.4SiO ₂ -0.1V ₂ O ₅ -0.4BaCO ₃
The above comparative example particularly corresponds to Example 1. V was added as Ba ₃ V ₂ O _{8 in} Example 1, but was added as BaCO ₃ and V ₂ O _{5 in the} comparative example. Thus, Example 1 and the comparative example differ only in the addition method of V, and all the constituent composition ratios are the same.

(B) Production of Multilayer Ceramic Capacitor A ceramic slurry was produced by adding a polyvinyl butyral binder and ethanol to the ceramic raw material and wet-mixing them with a ball mill.

  Next, this ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular ceramic green sheet.

  Next, a conductive paste mainly composed of Ni was screen-printed on the ceramic green sheet to form a conductive paste film to be an internal electrode.

  Next, a plurality of ceramic green sheets on which the conductive paste film was formed were stacked so that the side from which the conductive paste film was drawn was staggered to obtain a raw laminate that would become the capacitor body.

Next, the raw laminate is heated to a temperature of 300 ° C. in an N ₂ atmosphere to burn the binder, and then from an H ₂ —N ₂ —H ₂ O gas having an oxygen partial pressure of 10 ⁻¹⁰ MPa. The sintered capacitor body was obtained by firing for 2 hours at a temperature of 1200 ° C. in a reducing atmosphere.

Next, a Cu paste containing B ₂ O ₃ —Li ₂ O—SiO ₂ —BaO glass frit is applied to both end faces of the sintered capacitor body, and baked at a temperature of 800 ° C. in an N ₂ atmosphere. An external electrode electrically connected to the internal electrode was formed to obtain a multilayer ceramic capacitor as a sample.

The outer dimensions of the multilayer ceramic capacitor thus obtained are 1.2 mm wide, 2.0 mm long and 1.0 mm thick, and the thickness of the dielectric ceramic layer interposed between the internal electrodes is 0.8 μm. Met. The number of effective dielectric ceramic layers was 100, and the opposing area of the internal electrodes per ceramic layer was 1.6 mm ² .

(C) Evaluation of characteristics Next, with respect to the obtained multilayer ceramic capacitor, as shown in Table 2, dielectric constant ε, DF (tan δ), withstand voltage (DC breakdown electric field strength), and high temperature load life at room temperature Evaluated.

  The dielectric constant ε and DF (tan δ) calculated from the capacitance were measured under conditions of a temperature of 25 ° C., 1 kHz, and 0.5 Vrms.

  With respect to the withstand voltage (DC breakdown electric field strength), the withstand voltage with respect to the DC voltage was measured at a boosting rate of 100 V / sec.

  As for the high temperature load life, a high temperature load life test in which a voltage of 8 V (electric field strength of 10 kV / mm) is applied at a temperature of 150 ° C. is performed on 100 samples, and the insulation resistance is increased by 1000 hours. A sample having a value of 200 kΩ or less was determined to be defective, and the number of defects was determined.

  As can be seen from Table 2, according to Examples 1 to 3, even when the thickness of the dielectric ceramic layer is reduced to 0.8 μm, the dielectric constant is high while maintaining a high dielectric constant ε of 3500 or more. It had a withstand voltage and showed excellent reliability even under severe conditions of 150 ° C. and 10 kV / mm.

  On the other hand, the comparative example was inferior in the withstand voltage and reliability compared with Examples 1-3.

[Experiment 2]
In Experimental Example 2, the types and contents of subcomponents were changed.

(A) Preparation of ceramic raw material In the composition formula: [100Ba _m TiO ₃ ] + aRO _3/2 + bMO + cVO _5/2 + dSiO ₂ , the breakdown of R and M, and the values of m, a, b, c and d A dielectric ceramic raw material was obtained in the same manner as in Example 1 in Experimental Example 1 except that the conditions shown in FIG. Sample 1 in Table 3 is the same as Example 1 in Experimental Example 1.

(B) Production of Multilayer Ceramic Capacitor A multilayer ceramic capacitor according to each sample was produced in the same manner as in Experimental Example 1 using the dielectric ceramic raw material.

(C) Evaluation of characteristics The characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 4.

  As can be seen from Table 4, in all samples, while maintaining a high dielectric constant ε of 3500 or more, at the same time, it had a high withstand voltage and showed excellent reliability even under severe conditions of 150 ° C. and 10 kV / mm. .

[Experiment 3]
In Experimental Example 3, the main component ABO ₃ was evaluated for the case where Ca and / or Sr was included in addition to Ba at the A site, and the case where Zr and / or Hf was included in addition to Ti at the B site.

(A) Production of Ceramic Raw Material A dielectric ceramic raw material was prepared in the same manner as in Example 1 in Experimental Example 1 except that the “A site substitution component” and “B site substitution component” shown in Table 5 were applied. Got. Sample 1 in Table 5 is the same as Example 1 in Experimental Example 1.

(B) Production of Multilayer Ceramic Capacitor A multilayer ceramic capacitor according to each sample was produced in the same manner as in Experimental Example 1 using the dielectric ceramic raw material.

(C) Evaluation of characteristics The characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 6.

  As can be seen from Table 6, even if the main component raw material is changed as shown in Table 5, all the samples have high withstand voltage while maintaining a high dielectric constant ε of 3500 or more, and at 150 ° C. and 10 kV at the same time. Excellent reliability was exhibited even under severe conditions of / mm.

[Experimental Example 4]
In Experimental Example 4, various sintering aids other than those containing only Si were evaluated as the sintering aid containing Si.

(A) Production of ceramic raw material A dielectric ceramic raw material was obtained in the same manner as in Example 1 in Experimental Example 1 except that the sintering aid component was changed to the composition and content shown in Table 7. It was. Sample 1 in Table 7 is the same as Example 1 in Experimental Example 1.

(B) Production of Multilayer Ceramic Capacitor A multilayer ceramic capacitor according to each sample was produced in the same manner as in Experimental Example 1 using the dielectric ceramic raw material.

(C) Evaluation of characteristics The characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 8.

  As can be seen from Table 8, even when the sintering aid is changed as shown in Table 7, all samples have a high dielectric strength ε while maintaining a high dielectric constant ε of 3500 or more. Excellent reliability was exhibited even under severe conditions of 10 kV / mm.

[Experimental Example 5]
In Experimental Example 5, the influence of impurities was evaluated.

  There is a possibility that Zr, Zn, Ag, Hf, Co, Ni, Na, Cu, W, Fe, Mo, Pd, Y, etc. may be mixed in the dielectric ceramic as impurities during the manufacturing process of the multilayer ceramic capacitor such as raw material production. There is a possibility that these exist in the crystal grain boundaries that occupy the crystal grains and between the crystal grains. In addition, in the firing process of the multilayer ceramic capacitor, the internal electrode component may be diffused and present in the crystal grain boundaries occupying the crystal grains in the dielectric ceramic and between the crystal grains. Experimental Example 5 is intended to evaluate the influence of these impurities.

  In addition, although Y of the above impurities is scheduled to be included as a normal subcomponent, in Experimental Example 5, there is a possibility that Y may be included as an impurity even in a composition not including Y. Therefore, as a precaution, Y as an impurity is also considered.

(A) Production of Ceramic Raw Material A dielectric ceramic was prepared in the same manner as in Example 1 in Experimental Example 1 except that the impurity components shown in Table 9 were added to the composition of Example 1 in Experimental Example 1. The raw material was obtained. Sample 1 in Table 9 is the same as Example 1 in Experimental Example 1.

(B) Production of Multilayer Ceramic Capacitor A multilayer ceramic capacitor according to each sample was produced in the same manner as in Experimental Example 1 using the dielectric ceramic raw material.

(C) Evaluation of characteristics The characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 10.

  As can be seen from Table 10, even if impurities as shown in Table 9 are mixed, all samples have a high dielectric constant ε while maintaining a high dielectric constant ε of 3500 or more, and at the same time, 150 ° C., 10 kV / mm. Excellent reliability even under severe conditions.

1 Multilayer Ceramic Capacitor 2 Dielectric Ceramic Layer 3, 4 Internal Electrode 5 Capacitor Body 6, 7 External Electrode

Claims (5)

ABO ₃ (A necessarily contains Ba and may further contain at least one of Ca and Sr. B necessarily contains Ti and may further contain at least one of Zr and Hf). As subcomponents, R (R is at least one selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y), M (M is A method for producing a dielectric ceramic comprising at least one selected from Mn, Cu, Ni, Cr, Al, Mg), V and Si,
Producing a dielectric ceramic raw material;
And firing the dielectric ceramic raw material,
The step of producing the dielectric ceramic raw material includes a step of preparing a Ba-V compound containing Ba and V, and a step of adding the Ba-V compound powder to the ABO ₃ powder.
A method for producing a dielectric ceramic. _{2. The} method for producing a dielectric ceramic according to claim 1, wherein the Ba—V compound is at least one selected from Ba ₃ V ₂ O ₈ , BaVO _3, and Ba ₂ VO ₄ . ABO ₃ (A necessarily contains Ba and may further contain at least one of Ca and Sr. B necessarily contains Ti and may further contain at least one of Zr and Hf). As subcomponents, R (R is at least one selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y), M (M is A dielectric ceramic containing at least one selected from Mn, Cu, Ni, Cr, Al, Mg), V and Si,
A dielectric ceramic in which Ba-V crystalline oxide particles containing Ba and V are present in addition to main phase particles having a composition of ABO ₃ . The dielectric ceramic according to claim 3, wherein the composition of the Ba—V crystalline oxide particles is at least one selected from Ba ₃ V ₂ O ₈ , BaVO _3, and Ba ₂ VO ₄ . A capacitor body comprising a plurality of laminated dielectric ceramic layers and a plurality of internal electrodes formed along a specific interface between the dielectric ceramic layers;
A plurality of external electrodes formed at different positions on the outer surface of the capacitor body and electrically connected to a specific one of the internal electrodes;
The dielectric ceramic layer is made of the dielectric ceramic according to claim 3 or 4.
Multilayer ceramic capacitor.

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