JP2010208905A - Method for manufacturing dielectric ceramic, dielectric ceramic, method for manufacturing laminated ceramic capacitor and the laminated ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability while ensuring desired dielectric and temperature characteristics, even in the case of a thin dielectric ceramic layer having a thickness of ≤1.0 μm. <P>SOLUTION: A method for manufacturing a dielectric ceramic comprises: preparing a BaTiO<SB>3</SB>powder serving as an essential component, a Li compound that can be converted into Li<SB>2</SB>O by firing and a Ti compound that can be converted into TiO<SB>2</SB>by firing; weighing and mixing prescribed amounts thereof so as to prepare a ceramic raw material powder; molding the ceramic raw material powder; and firing the same. The Li compound is added in an amount corresponding to 0.2-6.0 pts.mol in terms of Li<SB>2</SB>O after firing, based on 100 pts.mol essential component after firing. The Ti compound is added in an amount corresponding to 0.05-4.0 pts.mol in terms of TiO<SB>2</SB>after firing, based on 100 pts.mol essential component after firing. As subsidiary components, a specific rare earth element oxide, a Mg compound, a Mn compound, a V compound, a Ba compound, a Ca compound and a Si compound may be optionally added in appropriate amounts. A portion of Ba may be optionally replaced by Ca and/or Sr, and a portion of Ti may be optionally replaced by Zr and/or Hf. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a dielectric ceramic manufacturing method and a dielectric ceramic, and a multilayer ceramic capacitor manufacturing method and a multilayer ceramic capacitor. More specifically, the present invention relates to a method for manufacturing a low-temperature fireable dielectric ceramic based on a BaTiO ₃ material. And a dielectric ceramic manufactured by the manufacturing method, a manufacturing method of a multilayer ceramic capacitor to which the manufacturing method of the dielectric ceramic is applied, and a multilayer having a small size, a large capacity and good reliability using the manufacturing method It relates to ceramic capacitors.

  Today, multilayer ceramic capacitors are widely used in various electronic devices such as mobile phones. With the progress of high performance and miniaturization in recent years, there is a demand for the realization of a further smaller and larger capacity multilayer ceramic capacitor.

  This type of monolithic ceramic capacitor usually produces a ceramic sintered body by co-firing ceramic laminates in which ceramic green sheets to be dielectric ceramic layers and conductive films to be internal electrode layers are alternately laminated. Then, it is manufactured by forming external electrodes on both end faces of the ceramic sintered body.

  Therefore, in order to reduce the size and increase the capacity of the multilayer ceramic capacitor, it is necessary to reduce the thickness of the dielectric ceramic layer and the internal electrode layer. Recently, the thickness of the dielectric ceramic layer is 1 μm or less. Is required.

  However, when the dielectric ceramic layer and the internal electrode layer are thinned in this way, the thickness of the dielectric ceramic layer and the internal electrode layer becomes close to each other. There is a risk of lack of reliability.

  When the ceramic laminate is fired at a high temperature, the conductive particles constituting the internal electrode are spheroidized and the smoothness of the internal electrode layer is impaired. Therefore, it is desirable to fire at the lowest possible temperature using a sintering aid. .

Therefore, for example, in Patent Document 1, the dielectric ceramic layer includes a barium titanate having an alkali metal oxide content of 0.03% by weight or less, yttrium oxide, zinc oxide, and nickel oxide. The following composition formula: (1-α-β) (BaO) _m TiO ₂ + αY ₂ O ₃ + β (Zn _1-x Ni _x ) O where 0.0025 ≦ α ≦ 0.030.0025 ≦ In terms of 100 mol of the main component represented by β ≦ 0.080 <β / α ≦ 80 <x <11.000 ≦ m ≦ 1.035, magnesium oxide is converted to MgO as an accessory component to 0.2. -2.5 mol, manganese oxide in terms of MnO is contained in an amount of 0.05-2.0 mol, and the total of the main component and subcomponents is 100 parts by weight, and Li ₂ O-RO- (Ti , Si) _{O 2} (where, R represents Ba, Sr A multilayer ceramic capacitor is proposed which is composed of a material containing 0.2 to 3.0 parts by weight of an oxide glass of at least one of Ca and Mg), and wherein the internal electrode is composed of nickel or a nickel alloy. ing.

The oxide glass is composed of Li ₂ O of ₂ to 45 mol%, MO of 0 to 40 mol%, RO of 5 to 40 mol%, (Ti, Si) O ₂ of 35 to 70 mol% {provided that (Ti, Si) O ₂ has a composition range of SiO ₂ component of 15 mol% or more}, and the above component is 100 parts by weight, and at least one of Al ₂ O ₃ and ZrO ₂ is 20 parts by weight in total. It is contained below (however, ZrO ₂ is 10 parts by weight or less), and this synthesized Li-based oxide glass is mixed with barium titanate or the like.

  In Patent Document 1, it is possible to perform low-temperature firing by adding Li-based oxide glass, thereby suppressing Ni particles in the internal electrode from coarsening. And it can avoid that a dielectric ceramic layer becomes thin locally by this, insulation can be improved and reliability can be aimed at.

Japanese Patent Laid-Open No. 08-191032 (Claims 1 and 2, paragraph numbers [0028] to [0031])

  However, in Patent Document 1, when the thickness of the dielectric ceramic layer exceeds 10 μm, the reliability can be improved, but when the thickness of the dielectric ceramic layer becomes a thin layer of 1.0 μm or less, the conductive particles As a result, the smoothness of the internal electrode layer cannot be secured sufficiently, and the dielectric ceramic layer may be locally thinned. As a result, there is a problem that the life is shortened due to the early decrease of the insulation resistance at the time of high temperature load, and sufficient reliability cannot be secured.

  The present invention has been made in view of such circumstances. Even when the dielectric ceramic layer is thinned to 1.0 μm or less, reliability is ensured while ensuring desired dielectric characteristics and temperature characteristics. It is an object of the present invention to provide a dielectric ceramic manufacturing method and dielectric ceramic that can be improved, and a multilayer ceramic capacitor manufacturing method and a multilayer ceramic capacitor.

In order to obtain good reliability even when the dielectric ceramic layer is thinned to 1.0 μm or less, the present inventors have conducted earnest research using a BaTiO ₃ based ceramic material. Rather than mixing the synthesized oxide glass with the main component powder, the Li compound powder that becomes Li oxide by firing and the Ti compound powder that becomes Ti oxide by firing are mixed individually with the main component powder to produce ceramic. Raw material powder was prepared. And when this ceramic raw material powder was molded and fired, it was found that further low-temperature firing was possible, and even when the dielectric ceramic layer was thinned to 1.0 μm or less, We have obtained the knowledge that the reliability can be improved without impairing the dielectric characteristics and the temperature characteristics.

The present invention has been made based on such knowledge, and a dielectric ceramic manufacturing method according to the present invention includes a main component powder made of a BaTiO ₃ -based compound, a Li compound that becomes Li oxide by firing, and firing. Preparing a plurality of subcomponent powders containing at least a Ti compound to be a Ti oxide, weighing each of the subcomponent powders in a predetermined amount, and mixing with the main component powder to produce a ceramic raw material powder, The ceramic raw material powder is formed and then fired.

In the dielectric ceramic manufacturing method of the present invention, the predetermined amount of the Li compound is 0.2 to 6.0 in terms of Li ₂ O after firing with respect to 100 mol parts of the fired main component. The predetermined amount of the Ti compound is 0.05 to 4.0 mole parts in terms of TiO ₂ after firing with respect to 100 mole parts of the main component after firing. .

Further, in the method for producing a dielectric ceramic according to the present invention, in the BaTiO ₃ -based compound, a part of Ba is replaced with at least one of Ca and Sr, and a part of Ti is replaced with at least one of Zr and Hf. One of the features is that either one is replaced.

  As a result of further diligent research by the present inventors, if a predetermined amount of Li compound and Ti compound are each mixed with the main component powder alone, a rare earth element oxide or a specific material can be specified as necessary within a predetermined range. It was found that the desired reliability can be secured without impairing the dielectric characteristics and temperature characteristics even when the metal oxide and silicon oxide are added.

That is, the dielectric ceramic manufacturing method according to the present invention is (Ba _1-x Ca _x ) _m TiO ₃ (x is 0 ≦ x ≦ 0.2, m is 0.960 ≦ m ≦ 1.030). ), And as sub-component powders, Li compound, Ti compound, R compound (R is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Prepare at least one selected from Er, Tm, Yb, Lu, and Y.), M compound (M represents at least one of Mn and V), and Si compound and the composition after firing, with respect to 100 parts by mol of the main ingredient, 0.2 to 6.0 molar parts in terms of Li ₂ O, 0.05 to 4.0 molar parts in terms of TiO _2, RO 0.2-5.0 molar parts in terms of _{3/2, MO} n (n is uniquely by the valence of M It determined the number of positive. 0.2 to 1.0 molar parts in terms of), so that a 0.5 to 4.0 molar parts in terms of SiO _2, weighing each subcomponent powder respectively The ceramic raw material powder is prepared by mixing with the main component powder, and the ceramic raw material powder is molded and then fired.

  Further, the dielectric ceramic manufacturing method of the present invention weighs the Mg compound so that the composition after firing is 2.0 mol parts or less in terms of MgO with respect to 100 mol parts of the main component, A ceramic raw material powder is produced by mixing with the main component powder.

  The dielectric ceramic manufacturing method of the present invention is characterized in that a part of the Ba is replaced with Ca in a range of 0.20 mol part or less.

Furthermore, in the method for producing a dielectric ceramic according to the present invention, the addition amount of the Ba compound with respect to 100 mole parts of the main component is converted to BaO, and the addition amount of the Ca compound is converted to CaO to be the β mole part. When the addition amount of the Ti compound with respect to 100 mole parts of the main component is f mole parts in terms of TiO ₂ , m, α, β, and f after firing are 0.960 ≦ m + (α + β) / 100 In order to satisfy ≦ 1.030 and α + β <f, Ba compound and Ca compound are respectively weighed and mixed with the main component powder to produce a ceramic raw material powder.

  The dielectric ceramic according to the present invention is manufactured by any one of the above-described manufacturing methods.

  Also, the method for producing a multilayer ceramic capacitor according to the present invention should form a ceramic raw material powder produced in the production process of any one of the above dielectric ceramic production methods into a sheet shape to form a dielectric ceramic layer. After producing the ceramic green sheet, a conductive paste is applied to the surface of the ceramic green sheet to form a conductive pattern to be an internal electrode layer, and then the ceramic green sheets on which the conductive pattern is formed are laminated and laminated. The laminated body is fired to produce a ceramic sintered body, and external electrodes are formed on the ceramic sintered body.

  Furthermore, the method for manufacturing a multilayer ceramic capacitor according to the present invention is characterized in that the conductive paste has a conductive material containing Ni as a main component.

  The multilayer ceramic capacitor according to the present invention is manufactured by the above manufacturing method.

According to the above dielectric ceramic manufacturing method, a main component powder composed of a BaTiO ₃ -based compound, a Li compound that becomes Li oxide by firing, and a plurality of subcomponent powders that contain at least a Ti compound that becomes Ti oxide by firing, A plurality of sub-component powders are weighed in predetermined amounts, mixed with the main component powders to produce ceramic raw material powders, and after the ceramic raw material powders are molded and fired, the Li compound and the Ti compound Are not added as a single composite, but are added individually to the main component powder, which enables further low-temperature firing. Therefore, even when manufacturing a multilayer ceramic capacitor having a dielectric ceramic layer thinned to 1.0 μm or less, it becomes difficult to spheroidize Ni or Cu conductive particles as an internal electrode material. Particle coarsening can be suppressed. As a result, local thinning of the dielectric ceramic layer can be suppressed, and even if the dielectric ceramic layer is left for a long time at a high temperature, a decrease in insulation resistance can be suppressed as much as possible, and reliability can be improved.

Further, the predetermined amount of the Li compound is 0.2 to 6.0 mole parts in terms of Li ₂ O after firing with respect to 100 mole parts of the main component after firing, Since the fixed amount is 0.05 to 4.0 mole parts in terms of TiO ₂ after firing with respect to 100 mole parts of the main component after firing, the above-described effects can be easily achieved.

The BaTiO ₃ -based compound has the same effect even when a part of Ba is substituted with at least one of Ca and Sr and a part of Ti is substituted with at least one of Zr and Hf. Can be obtained.

Furthermore, the composition after firing is 0.2 to 6.0 mol parts in terms of Li ₂ O, 0.05 to 4.0 mol parts in terms of TiO ₂ with respect to 100 mol parts of the main component, RO 0.2 to 5.0 mol parts in terms of _3/2 , 0.2 to 1.0 mol in terms of MO _n (n represents a positive number uniquely determined by the valence of M) Parts, each subcomponent powder is weighed so as to be 0.5 to 4.0 mol parts in terms of SiO ₂ , and mixed with the main component powder to produce a ceramic raw material powder. Since the powder is formed and fired, desired reliability can be ensured without impairing the dielectric characteristics and temperature characteristics.

  Furthermore, the Mg compound is weighed so that the composition after firing is 2.0 mol parts or less in terms of MgO with respect to 100 mol parts of the main component, and mixed with the main component powder to produce ceramic raw material powder. Even when a part of Ba is replaced with Ca in the range of 0.2 mol part or less, desired reliability can be ensured without impairing dielectric characteristics and temperature characteristics.

Furthermore, the addition amount of the Ba compound with respect to 100 mol parts of the main component is converted to BaO and α mol parts, and the addition amount of the Ca compound is converted to CaO with β mol parts. When the addition amount is converted to TiO ₂ to be f mole part, m, α, β, and f after firing satisfy 0.960 ≦ m + (α + β) /100≦1.030 and α + β <f As described above, each of the Ba compound and the Ca compound is weighed and mixed with the main component powder to produce a ceramic raw material powder, so that desired reliability can be ensured without impairing dielectric characteristics and temperature characteristics. .

  And according to the dielectric ceramic of this invention, since it is manufactured with the said manufacturing method, desired reliability can be ensured, without impairing a dielectric characteristic and a temperature characteristic.

  Further, according to the method for manufacturing a multilayer ceramic capacitor and the multilayer ceramic capacitor, since the internal electrode material such as Ni can be fired at a low temperature so as to sufficiently suppress the coarsening, the dielectric ceramic layer has the following characteristics. Even when the thickness is reduced to 0 μm or less, since the internal electrode layer has good smoothness, the dielectric ceramic layer can be suppressed from being locally thinned, and the dielectric ceramic layer can ensure desired smoothness. As a result, a small and large capacity multilayer ceramic capacitor having desired reliability can be obtained without impairing dielectric characteristics and temperature characteristics.

  Specifically, it can be co-fired at a low temperature of 1000 ° C. to 1050 ° C., so that even if the dielectric ceramic layer is a thin layer of 1.0 μm or less, a direct current of 12.5 V can be obtained at a high temperature of 150 ° C. When a voltage is applied, it has an average lifetime of 180 hours or more, a dielectric constant εr of 1300 or more, a dielectric loss tanδ of less than 5%, and a good dielectric property of EIA standard X5R characteristic (− A multilayer ceramic capacitor having a good temperature characteristic satisfying a temperature change rate of capacitance within ± 15% with reference to + 25 ° C in a temperature range of 55 ° C to + 85 ° C can be obtained.

1 is a cross-sectional view schematically showing an embodiment of a multilayer ceramic capacitor according to the present invention.

  Next, an embodiment of the present invention will be described in detail.

  One embodiment (first embodiment) of a dielectric ceramic manufactured by the manufacturing method according to the present invention can be represented by the following general formula (A).

100 (Ba _1-x Ca _x ) _m TiO ₃ + eLi ₂ O + fTiO ₂ (A)
Here, x, m, e, and f satisfy Expressions (1) to (4).

0 ≦ x ≦ 0.20 (1)
0.960 ≦ m ≦ 1.030 (2)
0.2 ≦ e ≦ 6.0 (3)
0.05 ≦ f ≦ 4.0 (4)
That is, the dielectric ceramic is composed of a barium titanate-based composite oxide whose main component has a perovskite structure (general formula ABO ₃ ), and Li ₂ O is 0.2 to 6.0 with respect to at least 100 mol parts of the main component. molar parts, TiO ₂ is contained 0.05 to 4.0 parts by mol.

  Next, the reason why x, m, e, and f are limited to the above ranges (1) to (4) will be described.

(1) x
By substituting a part of Ba in the main component with Ca as necessary, it is possible to obtain characteristics according to the application. However, if the substitution molar amount x of Ca exceeds 0.21, there is a possibility that when left at high temperature for a long time, the insulation resistance deteriorates early and sufficient reliability cannot be obtained.

  Therefore, when a part of Ba is substituted with Ca, the substitution molar amount x is prepared to be 0.20 or less.

(2) m
The molar ratio m of the Ba site (A site) to the Ti site (B site) in the main component is 1.000 stoichiometrically, but it may be made Ba site rich or Ti site rich as necessary. preferable.

  However, when the molar ratio m of the Ba site and Ti site is less than 0.960 or more than 1.030, the insulation resistance deteriorates early when left at high temperature for a long time, and sufficient reliability can be obtained. There is a risk that it will not be possible. In addition, when the molar ratio m is less than 0.960, the relative dielectric constant εr also decreases, making it difficult to obtain desired dielectric properties.

  Therefore, the molar ratio m after firing is adjusted to satisfy 0.960 ≦ m ≦ 1.030.

(3) e, f
By adding appropriate amounts of the Li compound that becomes Li ₂ O by firing and the Ti compound that becomes TiO ₂ by firing to the main component powder, firing at a low temperature of about 1000 ° C. to 1050 ° C. becomes possible. Therefore, when a multilayer ceramic capacitor to be described later is manufactured, even if the dielectric ceramic layer is thinned to 1.0 μm or less, it becomes difficult to spheroidize Ni or Cu conductive particles as an internal electrode material. Particle coarsening is suppressed. As a result, the smoothness of the internal electrode layer is improved, and the local thinning of the dielectric ceramic layer can be suppressed. As a result, even when left at high temperatures for a long time, a decrease in insulation resistance can be suppressed as much as possible, and reliability can be improved.

However, when the molar amount of Li ₂ O is less than 0.2 mol part or more than 6.0 mol part with respect to 100 mol parts of the main component, it is insulated relatively early when left at high temperature for a long time. There is a possibility that the resistance is lowered, and sufficient reliability cannot be improved.

Similarly, the molar content of TiO ₂ is relatively early when it is left at a high temperature for a long time if it is less than 0.05 mol part or exceeds 4.0 mol part relative to 100 mol parts of the main component. Insulation resistance may be reduced, and sufficient reliability cannot be improved.

Therefore, the molar content of Li ₂ O and TiO ₂ is adjusted to be 0.2 to 6.0 mol parts and 0.05 to 4.0 mol parts with respect to 100 mol parts of the main component, respectively. .

  And this dielectric ceramic is manufactured as follows.

That is, a Ba compound such as BaCO ₃ as a ceramic raw material, a Ti compound such as TiO ₂ , and a Ca compound such as CaCO _{3 as} necessary, and (Ba _1-x Ca _x ) _m TiO ₃ after firing are prepared. These ceramic raw materials are weighed so as to satisfy the above formulas (1) and (2).

  Next, this weighed product is put into a ball mill together with cobblestones such as PSZ (Partially Stabilized Zirconia) balls and pure water, and after sufficiently mixed and pulverized in a wet manner, calcined at a temperature of 1000 ° C. or higher, Ingredient powder is prepared.

Next, a Li compound that becomes Li ₂ O by firing and a Ti compound that becomes TiO ₂ by firing are prepared, and the above formulas (3) and (4) are satisfied after firing with respect to 100 mol parts of the main component after firing. Thus, these Li compounds and Ti compounds are weighed.

  Then, the weighed main component powder, Li compound, and Ti compound are put into a ball mill together with cobblestone and pure water, and after sufficiently mixed and pulverized in a wet manner, calcined at a temperature of 1000 ° C. or higher, whereby the ceramic raw material powder is obtained. Make it.

Thereafter, the ceramic raw material powder is put into a ball mill together with an organic binder and an organic solvent and wet-mixed, thereby producing a ceramic slurry. Then, after forming the ceramic slurry, the binder removal treatment was performed at a temperature of 300 ° C. to 500 ° C., and the oxygen partial pressure was controlled to be 10 ⁻⁹ to 10 ⁻¹² MPa. H ₂ —N ₂ —H ₂ In a reducing atmosphere composed of O gas, firing is performed at a temperature of 1000 to 1050 ° C. for about 2 hours, thereby producing the above-described dielectric ceramic (ceramic sintered body).

Thus, in the first embodiment, with respect to 100 mole parts of the main component after firing, 0.2 to 6.0 mole parts in terms of Li ₂ O and TiO ₂ after firing, in terms of Li ₂ O. Since the Li compound and Ti compound are individually added to the main component powder so as to be 0.05 to 4.0 mol parts, firing at a lower temperature of about 1000 ° C. to 1050 ° C. becomes possible. . Therefore, even when a multilayer ceramic capacitor having a dielectric ceramic layer thinned to 1.0 μm or less is manufactured, it becomes difficult to spheroidize Ni or Cu conductive particles as an internal electrode material. Particle coarsening can be suppressed. As a result, the dielectric ceramic layer can be suppressed from being locally thinned, and a decrease in insulation resistance can be suppressed as much as possible even when left at a high temperature for a long time, thereby improving reliability. .

Furthermore, in the present invention, desired reliability can be ensured by adding an appropriate amount of subcomponents in addition to the above Li ₂ O and TiO ₂ .

  Next, a dielectric ceramic manufacturing method according to the second embodiment will be described in detail.

  The dielectric ceramic manufactured by the manufacturing method of the second embodiment is represented by the general formula (B).

100 (Ba _1-x Ca _x ) _m TiO ₃ + αBaO + βCaO + aRO _3/2 + bMgO
+ CMO _n + dSiO ₂ + eLi ₂ O + fTiO ₂ (B)
That is, in the second embodiment, as a subcomponent, in addition to the Li compound and the Ti compound, a Ba compound that becomes BaO after firing, a Ca compound that becomes Ca after firing, a specific rare earth element oxide RO _{3 / 2} become R compound, Mg compound serving as MgO after the firing, M compound serving as MO _n after firing, Si compound serving as SiO ₂ is added after sintering.

  In the composition formula (B), M represents at least one of Mn and V, and n is a positive number that is uniquely determined by the valence of M. Therefore, when M is Mn, n is 1, and when M is V, n is 5/2.

  Further, as the specific rare earth element R, at least one selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y is used. Can be used.

  Here, a, b, c, and d satisfy Expressions (5) to (8).

0.2 ≦ a ≦ 5.0 (5)
0 ≦ b ≦ 2.0 (6)
0.2 ≦ c ≦ 1.0 (7)
0.5 ≦ d ≦ 4.0 (8)
Further, m, α, β, and f satisfy Expressions (9) and (10).

0.960 ≦ m + (α + β) /100≦1.030 (9)
α + β <f (10)
The reason why the various subcomponents in the general formula (B) are set in the range of the mathematical formulas (5) to (10) is as follows.

By adding a predetermined amount of Li ₂ O and TiO ₂ to the main component, as described above, further low-temperature firing at about 1000 ° C. to 1050 ° C. is possible, and the dielectric ceramic layer is 1.0 μm or less. Therefore, it is possible to improve the reliability when the thickness is reduced. As the subcomponent materials is shown in the above formula (B), an appropriate amount of _{BaO, CaO, RO 3/2, MgO} , MO n (M is Mn and / or V), and the SiO ₂ was added However, the effect of adding Li ₂ O and TiO ₂ is not impaired, and desired reliability can be ensured.

However, if these subcomponents are out of the range of the mathematical formulas (5) to (10), if they are left for a long time at a high temperature, the insulation resistance may be reduced in a short time, and sufficient reliability may not be ensured. is there. Moreover, when the rare earth element oxide RO _3/2 after firing exceeds 5.0 parts by mole with _respect to 100 parts by mole of the main component or the SiO ₂ exceeds 4.0 parts by mole, the temperature characteristics of the capacitance deteriorate. There is a risk.

  Furthermore, when {m + (α + β) / 100} exceeds 1.030, the relative dielectric constant εr is lowered, and there are cases where desired dielectric properties cannot be secured.

Therefore, in the present embodiment, when adding the subcomponent shown in the composition formula (B) in addition to the predetermined amount of Li ₂ O and TiO ₂ , it is added within the range of the formulas (5) to (10). Has been prepared.

  The dielectric ceramic can be manufactured by the following method.

First, as in the first embodiment, a main component powder is produced. Next, in addition to predetermined amounts of Li ₂ O and TiO ₂ , subcomponent powders that become BaO, CaO, RO _3/2 , MgO, MnO, V ₂ O ₅ , and SiO ₂ by firing are prepared, and predetermined amounts are weighed. .

  Then, the main component powder and each sub component powder are put into a ball mill together with cobblestone and pure water, and after sufficiently mixed and pulverized in a wet manner, calcined at a temperature of 1000 ° C. or higher, thereby producing a ceramic raw material powder.

  Thereafter, as in the first embodiment, a dielectric ceramic is produced through the steps of production of ceramic slurry → production of ceramic laminate → fired.

  Next, a multilayer ceramic capacitor using the dielectric ceramic will be described.

  FIG. 1 is a cross-sectional view schematically showing an embodiment of the multilayer ceramic capacitor.

  In the multilayer ceramic capacitor, internal electrode layers 2a to 2f are embedded in a ceramic sintered body 1, and external electrodes 3a and 3b are formed at both ends of the ceramic sintered body 1, and the external electrodes 3a, First plating films 4a and 4b and second plating films 5a and 5b are formed on the surface of 3b.

  That is, the ceramic sintered body 1 is formed by alternately laminating and firing the dielectric ceramic layers 6a to 6g and the internal electrode layers 2a to 2f formed of the dielectric ceramic, and the internal electrode layers 2a, 2c, 2e is electrically connected to the external electrode 3a, and the internal electrode layers 2b, 2d, and 2f are electrically connected to the external electrode 3b. A capacitance is formed between the opposing surfaces of the internal electrode layers 2a, 2c, and 2e and the internal electrode layers 2b, 2d, and 2f.

  Next, the manufacturing method of the manufacturing method of the said multilayer ceramic capacitor is demonstrated.

  First, a ceramic raw material powder is produced by a method similar to that of the first or second embodiment relating to a dielectric ceramic manufacturing method.

  Next, this ceramic raw material powder is put into a ball mill together with an organic binder and an organic solvent and wet-mixed, thereby producing a ceramic slurry. Thereafter, the ceramic slurry is formed using a doctor blade method or the like to produce a ceramic green sheet.

  Next, screen printing is performed on the ceramic green sheet using the internal electrode conductive paste, and a conductive film (conductive pattern) having a predetermined pattern is formed on the surface of the ceramic green sheet.

  The conductive material contained in the internal electrode conductive paste is preferably a base metal material mainly composed of Ni, Cu or an alloy thereof, more preferably Ni or Cu, from the viewpoint of cost reduction. Ni alloy is used.

Next, a plurality of ceramic green sheets on which a conductive film is formed are laminated in a predetermined direction, sandwiched between ceramic green sheets on which a conductive film is not formed, pressure-bonded, and cut into predetermined dimensions to produce a ceramic laminate. Thereafter, the binder removal treatment is performed at a temperature of 300 ° C. to 500 ° C., and the reducing property is made of H ₂ —N ₂ —H ₂ O gas whose oxygen partial pressure is controlled to 10 ⁻⁹ to 10 ⁻¹² MPa. Baking treatment is performed at a temperature of 1000 to 1100 ° C. for about 2 hours in an atmosphere. As a result, the conductive film and the ceramic green sheet are co-fired to obtain a ceramic sintered body 1 in which the internal electrodes 2a to 2f and the dielectric ceramic layers 6a to 6g are alternately laminated.

  Next, a conductive paste for external electrodes is applied to both end faces of the ceramic sintered body 1 and subjected to a baking treatment, whereby external electrodes 3a and 3b are formed.

  In addition, it is preferable to use base metal materials, such as Cu, also about the electroconductive material contained in the electroconductive paste for external electrodes from a viewpoint of cost reduction.

  Further, as a method of forming the external electrodes 3a and 3b, an external electrode conductive paste may be applied to both end faces of the ceramic laminate, and then a firing process may be performed simultaneously with the ceramic laminate.

  Finally, electrolytic plating is performed to form first plating films 4a and 4b made of Ni or the like on the surfaces of the external electrodes 3a and 3b, and solder or tin or the like is further formed on the surfaces of the first plating films 4a and 4b. The second plating films 5a and 5b made of are formed, whereby a multilayer ceramic capacitor is manufactured.

  Thus, according to the said multilayer ceramic capacitor, since it can bake at a low temperature of 1000-1050 degreeC, it can suppress that internal electrode materials, such as Ni, become coarse. Therefore, even when the dielectric ceramic layer is thinned to 1.0 μm or less, local thinning can be suppressed, and the dielectric ceramic layer can ensure desired flatness. As a result, a small and large capacity multilayer ceramic capacitor having desired reliability can be obtained without impairing dielectric characteristics and temperature characteristics.

  Specifically, even if the dielectric ceramic layer is a thin layer of 1.0 μm or less, it has an average life of 180 hours or more when a DC voltage of 12.5 V is applied at a high temperature of 150 ° C. The dielectric constant εr is 1300 or more, the dielectric loss tanδ is less than 5%, and the dielectric properties are less than 5%. Also, the X5R characteristic of EIA standard It is possible to obtain a monolithic ceramic capacitor with good temperature characteristics satisfying a temperature change rate of capacitance within ± 15%.

  The present invention is not limited to the above embodiment. The above subcomponents are merely examples, and it is also preferable to add various subcomponents within a range that does not impair the effects of adding the Li compound and the Ti compound.

  In the above embodiment, a part of Ba is allowed to be replaced with Ca. However, even if Sr is substituted in place of Ca or in addition to Ca, the intended effect of the present invention is obtained. Even if a part of Ti is substituted with at least one of Hf and Zr, the desired effects of the present invention can be achieved.

  Next, examples of the present invention will be specifically described.

[Sample preparation]
BaCO ₃ , CaCO ₃ and TiO ₂ were prepared as ceramic raw materials, and these ceramic raw materials were weighed so as to have the compositions shown in Tables 1 and 2.

These weighed materials were mixed, put into a ball mill, wet-mixed, and the agglomerates were pulverized to obtain a main component powder represented by a composition formula (Ba _1-x Ca _x ) _m TiO ₃ .

Next, BaCO ₃ , CaCO ₃ , R ₂ O ₃ (R is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), MgCO ₃ , MnCO ₃ , V ₂ O ₅ , SiO ₂ , Li ₂ CO ₃ , TiO ₂ were prepared.

  Then, the main component powder and the subcomponent powder were weighed so that the composition formula satisfied the following chemical formula (B).

100 (Ba _1-x Ca _x ) _m TiO ₃ + αBaO + βCaO + aRO _3/2 + bMgO
+ CMO _n + dSiO ₂ + eLi ₂ O + fTiO ₂ (B)
Here, M is at least one of Mn and V. When M is Mn, n is 1, and when M is V, n is 5/2.

  Next, these weighed materials were mixed, put into a ball mill, wet mixed, and evaporated to dryness to obtain a ceramic raw material powder.

  Next, a polyvinyl butyral binder and ethanol were added to the ceramic raw material powder, and the mixture was sufficiently wet-mixed by a ball mill to prepare a ceramic slurry. This ceramic slurry was formed into a sheet by a lip method to obtain a ceramic green sheet.

Next, a conductive paste containing Ni as a main component was screen-printed on the ceramic green sheet to form a conductive film to be an internal electrode layer. Then, a plurality of ceramic green sheets on which the conductive film was formed were laminated so that the side from which the conductive film was drawn was alternated to obtain a ceramic laminate. Next, this ceramic laminate is heated to a temperature of 300 ° C. in an N ₂ atmosphere to burn and remove the binder, and then a reducing atmosphere composed of H ₂ —N ₂ —H ₂ O gas having an oxygen partial pressure of 10 ⁻¹⁰ MPa. Inside, it baked for 2 hours at the temperature of 1025 degreeC, and the ceramic sintered compact was obtained.

After that, a conductive paste mainly composed of Cu containing B ₂ O ₃ —Li ₂ O—SiO ₂ —BaO glass frit is applied to both end faces of the ceramic sintered body, and 800 N in an N ₂ atmosphere. An external electrode electrically connected to the internal electrode was formed by baking at a temperature of ° C., and each sample (multilayer ceramic capacitor) of Example Samples 1 to 27 and Comparative Samples 31 to 51 was obtained.

The external dimensions of each of the prepared samples are 2.0 mm in length L, 1.2 mm in width W, 1.0 mm in thickness T, and the thickness of the dielectric ceramic layer interposed between the internal electrodes is 0.89 μm. there were. The total number of effective dielectric ceramic layers was 100, and the counter electrode area per layer was 1.4 mm ² .

(Characteristic evaluation)
For each of the sample samples 1 to 27 and the comparative sample samples 31 to 51, the relative dielectric constant εr, the dielectric loss tan δ, and the temperature change rate ΔC / C ₂₅ of the capacitance were determined.

  That is, using an automatic bridge type measuring device, the capacitance C and the dielectric loss tan δ are measured under the conditions of a frequency of 1 kHz, an effective voltage of 0.5 Vms, and a temperature of 25 ° C., and the relative dielectric constant is calculated from the capacitance C and the sample size. εr was determined. A non-defective product having a relative dielectric constant εr of 1300 or more and a dielectric loss tanδ of less than 5% was determined.

The temperature change rate ΔC / C ₂₅ of the capacitance was measured in the range of −55 ° C. to + 85 ° C., and the maximum rate of change based on the capacitance at + 25 ° C. was obtained. When the temperature change rate ΔC / C _{25 of the} capacitance was within ± 15%, the X5R characteristic of the EIA standard was satisfied and the product was judged to be a good product.

Moreover, the acceleration reliability test was done about each 11 samples of Example samples 1-27 and Comparative example samples 31-51. That is, when a DC voltage of 12.5 V was applied at a temperature of 150 ° C. and the insulation resistance value was 10 ⁵ Ω or less, it was regarded as a failure, an average value was obtained for 11 samples, and an average failure life was obtained. . The average failure life of 180 hours or more was judged as a good product.

  Tables 1 and 2 show the component compositions of Example Samples 1 to 27 and Comparative Example Samples 31 to 51, respectively. Tables 3 and 4 show the measurement results, respectively.

  As is clear from Tables 2 and 4, since the comparative sample 31 has {m + (α + β) / 100} of 0.959 and less than 0.960, the average failure life may be as short as 160 hours. I understood.

  Since Comparative Samples 32-35 had {m + (α + β) / 100} of 1.031 and exceeded 1.030, the average failure life was shortened to 150-160 hours. In addition, in this case, it was found that the relative dielectric constant εr was 1100 to 1200, and was reduced to less than 1300.

In Comparative Samples 36 to 38, (α + β) is 0.500, which is the same value as the molar amount f of TiO ₂ with respect to 100 mol of the main component, so that the average failure life is shortened to 150 hours to 160 hours. I understood.

  Comparative Example Sample 39 was found to have an average failure time of 170 hours and a decrease to less than 180 hours because the Ca content molar amount x at the A site in the main component was excessive at 0.21.

In Comparative Example Sample 40, since the mole part a of DyO _3/2 as a rare earth oxide is as small as 0.1 mole part with respect to 100 mole parts of the main component, the average failure time is 150 hours, which is reduced to less than 180 hours. I understood that.

In Comparative Sample 41, since the mole part a of YbO _3/2 as the rare earth oxide is excessive as 5.1 mole part with respect to 100 mole parts of the main component, the average failure time is 160 hours, which is less than 180 hours. Declined. In addition, in this case, it was found that the temperature change rate ΔC / C _{25 of the} capacitance was also −17%, the temperature characteristics were deteriorated, and the X5R characteristics of the EIA standard were not satisfied.

  Comparative Example Sample 42 was found to have an average failure time of 160 hours and a decrease to less than 180 hours because the molar part b of MgO is excessive at 2.1 parts by mole with respect to 100 parts by mole of the main component.

In Comparative Sample 43, since the total molar part c of MnO and VO _5/2 was as small as 0.10 mole part with respect to 100 mole parts of the main component, the average failure time was 140 hours and decreased to less than 180 hours.

In Comparative Sample 44, the total mole part c of MnO and VO _5/2 was as small as 1.10 mole parts with respect to 100 mole parts of the main component, so that the average failure time was 160 hours and decreased to less than 180 hours.

In Comparative Sample 45, since the mole part d of SiO ₂ was as small as 0.4 mole part with respect to 100 mole parts of the main component, the average failure time was 150 hours, which was reduced to less than 180 hours.

In Comparative Sample 46, the total mole part d of SiO ₂ was as large as 4.1 mole parts with respect to 100 mole parts of the main component, so the average failure time was 150 hours, which was reduced to less than 180 hours. In addition, in this case, it was found that the temperature change rate ΔC / C _{25 of the} capacitance was also −16%, the temperature characteristics were deteriorated, and the X5R characteristics of the EIA standard were not satisfied.

In Comparative Sample 47, since the mole part e of Li ₂ O was as small as 0.1 mole part relative to 100 mole parts of the main component, the average failure time was 170 hours, which was reduced to less than 180 hours.

In Comparative Sample 48, the molar part e of Li ₂ O was as large as 6.1 parts by mole with respect to 100 parts by mole of the main component, so the average failure time was 160 hours, which was reduced to less than 180 hours.

In Comparative Sample 49, since the mole part f of TiO ₂ was as small as 0.04 mole part with respect to 100 mole parts of the main component, the average failure time was 160 hours, which was reduced to less than 180 hours.

In Comparative Example Sample 50, since the mole part f of TiO ₂ was as large as 4.1 mole parts with respect to 100 mole parts of the main component, the average failure time was 150 hours, which decreased to less than 180 hours.

In the comparative sample 51, {m + (α + β) / 100} is excessive as 1.057, and (α + β) is 5.000, significantly exceeding 4.1 which is a molar part of TiO ₂ . Therefore, the average failure time was greatly reduced to 130 hours.

  On the other hand, as is clear from Tables 1 and 3, Example Samples 1 to 27 have 0.960 ≦ {m + (α + β) / 100} ≦ 1.030, α + β <f, 0 ≦ x ≦ 0.20. 0.2 ≦ a ≦ 0.9, 0 ≦ b ≦ 2.0, 0.2 ≦ c ≦ 1.0, 0.5 ≦ d ≦ 4.0, 0.2 ≦ e ≦ 6.0, 0 .05 ≦ f ≦ 4.0 was satisfied, and since the rare earth element and metal element M within the scope of the present invention were used, the average failure life was found to have good reliability of 180 hours or more. . In addition, it was possible to obtain a multilayer ceramic capacitor having good dielectric characteristics with a relative dielectric constant εr of 1300 or more and a dielectric loss tanδ of 5% or less, and good temperature characteristics satisfying the X5R characteristics of the EIA standard.

  Even if the dielectric ceramic layer becomes a thin layer of 1.0 μm or less, the reliability can be improved without impairing the dielectric characteristics and the temperature characteristics, and a high-quality small and large capacity multilayer ceramic capacitor can be realized. .

DESCRIPTION OF SYMBOLS 1 Ceramic sintered compact 2a-2f Internal electrode layer 4a, 4b External electrode 6a-6g Dielectric ceramic layer

Claims (11)

A main component powder made of a BaTiO ₃ -based compound, a Li compound that becomes Li oxide by firing, and a plurality of subcomponent powders that contain at least a Ti compound that becomes Ti oxide by firing, are prepared. A method for producing a dielectric ceramic, characterized by weighing each of a predetermined amount, mixing with the main component powder to produce a ceramic raw material powder, forming the ceramic raw material powder, and firing it. The predetermined amount of the Li compound is 0.2 to 6.0 mol parts in terms of Li ₂ O after baking with respect to 100 mol parts of the main component after baking, and the predetermined amount of the Ti compound is _{2. The} method for producing a dielectric ceramic according to claim 1, wherein the amount is 0.05 to 4.0 mole parts in terms of TiO ₂ after firing with respect to 100 mole parts of the fired main component. The BaTiO ₃ -based compound is characterized in that a part of Ba is substituted with at least one of Ca and Sr and a part of Ti is substituted with at least one of Zr and Hf. The method for producing a dielectric ceramic according to claim 1. While preparing a main component powder represented by (Ba _1-x Ca _x ) _m TiO ₃ (x is 0 ≦ x ≦ 0.20, m is 0.960 ≦ m ≦ 1.030), As component powder, Li compound, Ti compound, R compound (R is selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y At least one selected from the group consisting of M and M (wherein M represents at least one of Mn and V), and a Si compound.
The composition after firing is 0.2 to 6.0 mol parts in terms of Li ₂ O, 0.05 to 4.0 mol parts in terms of TiO ₂ with respect to 100 mol parts of the main component, RO _{3 /} 0.2-5.0 molar parts in terms of _2, 0.2 to 1.0 molar parts in terms of _MO n (n denotes a positive number determined by the valence of M.), Each subcomponent powder is weighed so as to be 0.5 to 4.0 mol parts in terms of SiO ₂ and mixed with the main component powder to prepare a ceramic raw material powder. A method for producing a dielectric ceramic, comprising firing after molding.   The Mg compound is weighed so that the composition after firing is 2.0 mol parts or less in terms of MgO with respect to 100 mol parts of the main component, and mixed with the main component powder to produce a ceramic raw material powder. The method for producing a dielectric ceramic according to claim 4, wherein:   6. The method for producing a dielectric ceramic according to claim 4, wherein a part of the Ba is substituted with Ca in a range of 0.20 mol part or less. The addition amount of the Ba compound with respect to 100 mol parts of the main component is converted to BaO and α mol parts, the addition amount of the Ca compound is converted to CaO with β mol parts, and the addition amount of the Ti compound with respect to 100 mol parts of the main components Is converted to TiO ₂ and f mol part, m, α, β, f after firing are
0.960 ≦ m + (α + β) /100≦1.030, and α + β <f
The dielectric material according to any one of claims 4 to 6, wherein a Ba raw material and a Ca compound are weighed so as to satisfy the requirements and mixed with the main component powder to produce a ceramic raw material powder. Manufacturing method of ceramic.   A dielectric ceramic manufactured by the manufacturing method according to claim 1.   After the ceramic raw material powder produced in the production process of the dielectric ceramic production method according to any one of claims 1 to 7 is formed into a sheet shape to produce a ceramic green sheet to be a dielectric ceramic layer Then, a conductive paste is applied to the surface of the ceramic green sheet to form a conductive pattern to be an internal electrode layer, and then a ceramic green sheet on which the conductive pattern is formed is laminated to form a laminate. A method for producing a multilayer ceramic capacitor comprising firing a body to produce a ceramic sintered body and forming external electrodes on the ceramic sintered body.   The conductive paste is characterized in that the conductive material contains Ni as a main component, and a method for manufacturing a multilayer ceramic capacitor.   A multilayer ceramic capacitor produced by the production method according to claim 9 or 10.

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