Multilayer ceramic capacitor and manufacturing method of multilayer ceramic capacitor

A multilayer ceramic capacitor includes: a multilayer structure in which each of a plurality of ceramic dielectric layers and each of a plurality of internal electrode layers including a ceramic co-material are alternately stacked, wherein a concentration of Mg in a ceramic grain that is included in the ceramic dielectric layer and contacts to the internal electrode layer is smaller than that in the co-material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-174102, filed on Sep. 6, 2016, the entire contents of which are incorporated herein by reference.

FIELD

A certain aspect of the present invention relates to a multilayer ceramic capacitor and a manufacturing method of a multilayer ceramic capacitor.

BACKGROUND

Recently, electronic devices such as smart phones or mobile phones are being downsized. Thereby, electronic components mounted on the electronic devices are rapidly being downsized. For example, in a field of multilayer ceramic electronic components of chip type represented by a multilayer ceramic capacitor, although property is secured, thicknesses of ceramic layers and internal electrodes are reduced in order to reduce a chip size.

Generally, a composition of a ceramic grain used as a co-material is the same as that of a dielectric layer (for example, see Japanese Patent Application Publications No. 2010-103198, No. 2014-067775 and No. 2014-236214.

SUMMARY OF THE INVENTION

For enlargement of a capacitance of a multilayer ceramic capacitor, reduction of a thickness of ceramic layers and enlargement of a dielectric constant of a material of the ceramic layers are effective. For the reduction of the thickness of the ceramic layers, a downsizing of a diameter of the material is effective. However, the downsizing causes reduction of the dielectric constant because of size effect. In order to solve the problem, there are many inventions relating to a composition of a dielectric body and control of a fine structure. As an example of a dopant, Mg (magnesium) is known. A function such as smoothing of a capacitance (dielectric constant) to a temperature property caused by formation of a core shell structure is known. However, the formation may cause reduction of the dielectric constant in a room temperature. When the smoothing of the temperature property is controlled by another element or the core shell structure is easily maintained by a temperature increase rate of the baking temperature, the high dielectric constant is obtained by reducing the doping amount of Mg or never doping Mg.

On the other hand, when a thickness of an internal electrode is reduced, it is possible to increase the number of multilayer and enlarge the capacitance. However, it is not possible to maintain the high continuity modulus even if the thickness is simply reduced. And, the capacitance may be reduced because of the continuity modulus reduction. The reliability may be degraded because of defect of a ceramic layer caused by expansion in a stack direction. Therefore, there is a problem that when the thickness is reduced, the continuity modulus may be reduced. In particular, a material not including Mg for a purpose of a high dielectric constant causes reduction of the continuity modulus of the internal electrode.

The present invention has a purpose of providing a multilayer ceramic capacitor and a manufacturing method of the multilayer ceramic capacitor that are capable of achieving high dielectric constant of dielectric layers and high continuity modulus of internal electrode layers.

According to an aspect of the present invention, there is provided a multilayer ceramic capacitor including: a multilayer structure in which each of a plurality of ceramic dielectric layers and each of a plurality of internal electrode layers including a ceramic co-material are alternately stacked, wherein a concentration of Mg in a ceramic grain that is included in the ceramic dielectric layer and contacts to the internal electrode layer is smaller than that in the co-material.

According another aspect of the present invention, there is provided a manufacturing method of a multilayer ceramic capacitor including: forming a green sheet including ceramic particles; forming a multilayer structure by alternately stacking the green sheet and a conductive paste for forming an internal electrode including a ceramic co-material; and baking the multilayer structure, wherein an atomic concentration of Mg with respect to a main component ceramic of the ceramic particles in the green sheet is smaller than an atomic concentration of Mg with respect to a main component ceramic in the co-material of the conductive paste for forming an internal electrode.

DETAILED DESCRIPTION

A description will be given of an embodiment with reference to the accompanying drawings.

Embodiment

A description will be given of a multilayer ceramic capacitor.FIG. 1illustrates a partial perspective view of a multilayer ceramic capacitor100. As illustrated inFIG. 1, the multilayer ceramic capacitor100includes a multilayer chip10having a rectangular parallelepiped shape, and a pair of external electrodes20and30that are respectively provided at two edge faces of the multilayer chip10facing each other.

The multilayer chip10has a structure designed to have dielectric layers11and internal electrode layers12alternately stacked. The dielectric layer11includes ceramic material acting as a dielectric material. End edges of the internal electrode layers12are alternately exposed to a first end face of the multilayer chip10and a second end face of the multilayer chip10that is different from the first end face. In the embodiment, the first face faces with the second face. The external electrode20is provided on the first end face. The external electrode30is provided on the second end face. Thus, the internal electrode layers12are alternately conducted to the external electrode20and the external electrode30. Thus, the multilayer ceramic capacitor100has a structure in which a plurality of dielectric layers11are stacked and each two of the dielectric layers11sandwich the internal electrode layer12. In the multilayer chip10, both end faces in the stack direction of the dielectric layers11and the internal electrode layers12(hereinafter referred to as stack direction) are covered by cover layers13. For example, a main component of the cover layer13is the same as that of the dielectric layer11.

For example, the multilayer ceramic capacitor100may have a length of 0.2 mm, a width of 0.1 mm and a height of 0.3 mm. The multilayer ceramic capacitor100may have a length of 0.6 mm, a width of 0.3 mm and a height of 0.3 mm. The multilayer ceramic capacitor100may have a length of 1.0 mm, a width of 0.5 mm and a height of 0.5 mm. The multilayer ceramic capacitor100may have a length of 3.2 mm, a width of 1.6 mm and a height of 1.6 mm. The multilayer ceramic capacitor100may have a length of 4.5 mm, a width of 3.2 mm and a height of 2.5 mm. However, the size of the multilayer ceramic capacitor100is not limited.

A main component of the internal electrode layers12and the external electrodes20and30is a base metal such as nickel (Ni), copper (Cu), tin (Sn) or the like. The external electrodes20and30and the internal electrode layers12may be made of noble metal such as platinum (Pt), palladium (Pd), silver (Ag), gold (Au) or alloy thereof.

For enlargement of a capacitance of the multilayer ceramic capacitor100, reduction of the thickness of the dielectric layer11and enlargement of dielectric constant of the material of the dielectric layer11are effective. For the reduction of the thickness of the dielectric layer11, a downsizing of the diameter of the material is effective. However, the downsizing causes reduction of the dielectric constant because of size effect. In order to solve the problem, there are many inventions relating to a composition of a dielectric body and control of a fine structure. As an example of a dopant, Mg (magnesium) is known. A function such as smoothing of a capacitance (dielectric constant) to a temperature property caused by formation of a core shell structure is known. However, the formation may cause reduction of the dielectric constant in a room temperature. When the smoothing of the temperature property is controlled by another element or the core shell structure is easily maintained by a temperature increase rate of the baking temperature, the high dielectric constant is obtained by reducing the doping amount of Mg or never doping Mg.

On the other hand, when the thickness of the internal electrode layer12is reduced, it is possible to increase the number of multilayer and enlarge the capacitance. However, it is not possible to maintain the high continuity modulus even if the thickness is simply reduced. And, the capacitance may be reduced because of the continuity modulus reduction. The reliability may be degraded because of defect of a ceramic layer caused by expansion in a stack direction. Therefore, it is preferable that the high continuity modulus can be maintained even if the thickness is reduced. In particular, when a ceramic material that does not include Mg and acts as a co-material is doped to the internal electrode layer12, the continuity modulus of the internal electrode layer12may be reduced. This may be caused by the following reasons. The internal electrode layer12is spheriodized in order to minimize surface energy when the sintering progresses. A metal component of the internal electrode layer12tends to be sintered, compared to the main component ceramic of the dielectric layer11. Therefore, when a temperature of the dielectric layer11is increased so that the main component ceramic is sintered, the metal component of the internal electrode layer12is excessively sintered and the metal component is spheriodized. In this case, when there is a defect acting a as a trigger, the internal electrode layer12is broken from the defect and the continuity modulus is reduced.

FIG. 2illustrates the continuity modulus. As illustrated inFIG. 2, in an observed region having a length of L0in the internal electrode layer12, the lengths of the metal portions of L1, L2, . . . to Ln are measured and summed. A ratio of the metal component ΣLn/L0is defined as the continuity modulus of a layer.

In the multilayer ceramic capacitor100in accordance with the embodiment, a Mg concentration in at least one of ceramic grains (crystal grains) that are included in the dielectric layer11and contact to the internal electrode layer12is smaller than that in the co-material included in the internal electrode layer12. Here, the Mg concentration in the ceramic grain is a Mg concentration (atm %) on a presumption that an amount of the B site of the main component ceramic ABO3-αof the ceramic grain is 100 atm %. The Mg concentration in the co-material is a Mg concentration (atm %) on a presumption that an amount of the B site of the main component ceramic ABO3-αof the co-material is 100 atm %. For example, when the main component ceramic is barium titanate, these concentrations are a concentration of Mg (atm %) on a presumption that an amount of barium titanate is 100 atm %. When a plurality of co-materials are spaced from each other in the internal electrode layer12, the Mg concentration of the ceramic grain (crystal grain) that is included in the dielectric layer11and contacts to the internal electrode layer12is smaller than that in at least one of the co-materials included in the internal electrode layer12. Alternatively, when a plurality of co-materials are spaced from each other in the internal electrode layer12, the Mg concentration in the co-material may be an average of the Mg concentration in the plurality of co-materials.

As illustrated inFIG. 3A, when the number of the ceramic grain14is one or two in at least one of regions of the dielectric layer11in the stack direction of the dielectric layer11and the internal electrode layer12, the Mg concentration in the one or two ceramic grains14in the dielectric layer11is smaller than that in the co-material15included in the internal electrode layer12. In this case, it is possible to suppress the influence of Mg in the dielectric layer11. And it is possible to achieve the effect of Mg in the internal electrode layer12. That is, it is possible to achieve both the high continuity modulus of the internal electrode layer12and the high dielectric constant of the dielectric layer11.

As illustrated inFIG. 3B, when the number of the ceramic grains14continuing in series in at least any one of positions in the dielectric layer11in the stack direction of the dielectric layer11and the internal electrode layer12is three or more, the Mg concentration in the one of the ceramic grains14contacting to the internal electrode layer12is smaller than that of a co-material15in the internal electrode layer12. Moreover, the Mg concentration of one or more of the ceramic grains14not contacting to the internal electrode layer12is smaller than that of the ceramic grain14contacting to the internal electrode layer12. In this case, the Mg concentration in the whole of the dielectric layer11is reduced. It is therefore possible to suppress the influence of Mg in the dielectric layer11. And it is possible to achieve the effect of Mg in the internal electrode layer12. That is, it is possible to achieve the high continuity modulus of the internal electrode layer12and the high dielectric constant of the dielectric layer11.

When the Mg concentration in the co-material15of the internal electrode layer12is excessively small, the internal electrode layer12may miss the high continuity modulus. And so, it is preferable that the Mg concentration in the co-material15of the internal electrode layer12has a lower limit. On the other hand, when the Mg concentration in the co-material15of the internal electrode layer12is excessively high, oxides of a metal included in the internal electrode layer12may excessively diffuse. Therefore, the lifetime of the internal electrode layer12may be degraded. And so, it is preferable that the Mg concentration in the co-material15of the internal electrode layer12has an upper limit. In concrete, it is preferable that the Mg concentration in the co-material15of the internal electrode layer12is 0.3 atm % or more and less than 1.5 atm %. It is more preferable that the Mg concentration in the co-material15of the internal electrode layer12is 0.3 atm % or more and less than 1.0 atm %. When a plurality of co-materials15in the internal electrode layer12are spaced from each other, the Mg concentration in at least one of the co-materials15included in the internal electrode layer12may be within the above-mentioned range. Alternatively, an average of the Mg concentrations of the plurality of co-materials15may be within the above-mentioned range.

When the Mg concentration in the ceramic grain14that is included in the dielectric layer11and contacts to the internal electrode layer12is excessively high, the dielectric layer may miss the high dielectric constant. And so, it is preferable that the Mg concentration in at least one of the ceramic grains14contacting to the internal electrode layer12has an upper limit. In concrete, it is preferable that the Mg concentration in at least one of the ceramic grains14contacting to the internal electrode layer12is less than 0.7 atm %. It is more preferable that the Mg concentration in at least one of the ceramic grains14contacting to the internal electrode layer12is less than 0.3 atm %. Alternatively, an average of the Mg concentrations of a plurality of ceramic grains14contacting to the internal electrode layer12may be less than 0.7 atm % or less than 0.3 atm %.

The dielectric layer11is formed by baking raw material powder of which a main component is ceramic structuring the dielectric layer11. During the baking, the raw material powder is exposed to a reductive atmosphere. Therefore, an oxygen defect may occur in the ceramic structuring the dielectric layer11. When Mo (Molybdenum) having a valence larger than that of a B site (four) is doped in the dielectric layer11, Mo acts as a donor element replaced to the B site. Thus, generation of the oxygen defect of the ceramic structuring the dielectric layer11is suppressed. And so, it is preferable that at least one of ceramic grains of the dielectric layer11includes Mo. In this case, a life property of the dielectric layer11is improved and the reliability of the dielectric layer11is improved. For example, it is preferable that at least one of the ceramic grains of the dielectric layer11includes Mo of 0.1 atm % or more on a presumption that an amount of Ti of the main component ceramic of the dielectric layer11is 100 atm %. Alternatively, an average of the Mo concentrations of the ceramic grains included in the dielectric layer11may be 0.1 atm % or more.

On the other hand, Mo may reduce a continuity modulus of the internal electrode layer12. When influence of the reduction of the continuity modulus of the internal electrode layer12is larger than influence of the life property improvement of the dielectric layer11, the reliability of the multilayer ceramic capacitor100may be degraded. It is preferable that the Mo concentration in the co-material15of the internal electrode layer12is smaller than that of the ceramic grains14of the dielectric layer11. For example, the Mo concentration in the co-material15of the internal electrode layer12is 0.1 atm % or less. It is preferable that the co-material15of the internal electrode layer12does not include Mo.

Next, a description will be given of a manufacturing method of the multilayer ceramic capacitor100.FIG. 4illustrates a manufacturing method of the multilayer ceramic capacitor100.

[Making Process of Raw Material Powder]

As illustrated inFIG. 4, raw material powder for forming the dielectric layer11is prepared. Generally, an A site element and a B site element are included in the dielectric layer11in a sintered phase of grains of BaTiO3. BaTiO3is tetragonal compound having a perovskite structure and has a high dielectric constant. Generally, BaTiO3is obtained by reacting a titanium material such as titanium dioxide with a barium material such as barium carbonate and synthesizing barium titanate. Various methods can be used as a synthesizing method of the ceramic structuring the dielectric layer11. For example, a solid-phase method, a sol-gel method, a hydrothermal method or the like can be used. The embodiment may use any of these methods.

An additive compound may be added to the ceramic powder, in accordance with purposes. The additive compound may be an oxide of Mo, Mn (manganese), V (vanadium), Cr (chromium) or a rare earth element (Y (yttrium), Dy (dysprosium), Tm (thulium), Ho (holmium), Tb (terbium), Yb (ytterbium), Sm (samarium), Eu (europium), Gd (gadolinium) and Er (erbium)), or an oxide of Co (cobalt), Ni, Li (lithium), B (boron), Na (sodium), K (potassium) and Si, or glass.

In the embodiment, it is preferable that ceramic particles structuring the dielectric layer11are mixed with compound including additives and are calcined in a temperature range from 820 degrees C. to 1150 degrees C. Next, the resulting ceramic particles are wet-blended with additives, are dried and crushed. Thus, ceramic powder is obtained. For example, it is preferable that an average grain diameter of the resulting ceramic particles used for manufacturing the multilayer ceramic capacitor100is 50 nm to 150 nm from a viewpoint of thickness reduction of the dielectric layer11. The grain diameter may be adjusted by crushing the resulting ceramic powder as needed. Alternatively, the grain diameter of the resulting ceramic power may be adjusted by combining the crushing and classifying.

Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer such as dioctyl phthalate (DOP) are added to the resulting ceramic powder and wet-blended. With use of the resulting slurry, a strip-shaped dielectric green sheet with a thickness of 0.8 μm or less is coated on a base material by, for example, a die coater method or a doctor blade method, and then dried.

Then, a pattern of the internal electrode layer12is provided on the surface of the dielectric green sheet by printing a conductive paste for forming an internal electrode with use of screen printing or gravure printing. The conductive paste includes an organic binder. A plurality of patterns are alternatively exposed to the pair of external electrodes. As co-materials, ceramic particles including Mg are added to the conductive paste. A main component of the ceramic particles is not limited. However, it is preferable that the main component of the ceramic particles is the same as that of the dielectric layer11. For example, BaTiO3of which an average particle sire is 50 nm or less is evenly dispersed.

Then, the dielectric green sheet on which the internal electrode layer pattern is printed is stamped into a predetermined size, and a predetermined number (for example, 100 to 500) of stamped dielectric green sheets are stacked while the base material is peeled so that the internal electrode layers12and the dielectric layers11are alternated with each other and the end edges of the internal electrode layers12are alternately exposed to both end faces in the length direction of the dielectric layer so as to be alternately led out to a pair of external electrodes of different polarizations. Cover sheets, which are to be the cover layers13, are stacked on the stacked green sheets and under the stacked sheets. The resulting compact is cut into a predetermined size (for example, 1.0 mm×0.5 mm). After that, conductive pastes to be the external electrodes20and30are coated on the both edge faces of the cut multilayer structure and are dried. Thus, a ceramic multilayer structure having a rectangular parallelepiped shape is obtained.

The binder is removed from the resulting ceramic multilayer structure in N2atmosphere of a temperature range of 250 degrees C. to 500 degrees C. After that, the resulting ceramic multilayer structure is baked for ten minutes to 2 hours in a reductive atmosphere in a temperature range of 1100 degrees C. to 1300 degrees C. Thus, each compound of the dielectric green sheet is sintered and grown into grains. In this manner, it is possible to manufacture the multilayer ceramic capacitor100that has the multilayer chip10having the multilayer structure in which the sintered dielectric layers11and the sintered internal electrode layers12are alternately stacked and has the cover layers13formed as outermost layers of the multilayer chip10in the stack direction.

In the baking process, a part of the co-materials may be moved to the dielectric green sheet and Mg from the co-material may diffuse into the dielectric green sheet, in a process in which the conductive paste for forming an internal electrode is sintered. Therefore, after the baking process, Mg in the co-materials15of the internal electrode layer12remains in the co-material15. On the other hand, another Mg may be included in the ceramic grain14contacting to the internal electrode layer12.

After that, a re-oxidizing process may be performed in N2gas atmosphere in a temperature range of 600 degrees C. to 1000 degrees C.

In another embodiment of the manufacturing method of the multilayer ceramic capacitor, the external electrodes20and30may be baked separately from the dielectric layer11. For example, after baking a multilayer structure in which a plurality of dielectric layers11are stacked, conductive pastes may be formed on both edge faces by baking and the external electrodes20and30may be formed. Alternatively, the external electrodes may be formed thickly on the both edge faces of the multilayer structure by a sputtering method.

With the manufacturing method, the co-material including Mg is added to the conductive paste for forming an internal electrode layer and Mg is not added to the dielectric green sheet for forming the dielectric layer11. In this case, the Mg concentration in the ceramic grain14that is included in the dielectric layer11and contacts to the internal electrode layer12is smaller than that the co-material15of the internal electrode layer12, after the baking process. Alternatively, the Mg concentration (atm %) of a main component ceramic in ceramic particles of the dielectric green sheet may be smaller than that in a main component ceramic of the co-material15of the conductive paste for forming an internal electrode. In this case, after the baking process, the Mg concentration in the ceramic grain14that is included in the dielectric layer11and contacts to the internal electrode layer12can be smaller than that of the co-materials15of the internal electrode layer12.

When the number of the ceramic grains14of the dielectric layer11in the stack direction of the dielectric layer11and the internal electrode layer12is one or two, the Mg concentration of the one or two ceramic grains14in the dielectric layer11can be smaller than the Mg concentration in the co-material15included in the internal electrode layer12. When the number of the ceramic grains14continuing in series in the stack direction of the dielectric layer11and the internal electrode layer12is three or more, the Mg concentration in one or more of the ceramic grains14contacting to the internal electrode layer12can be smaller than that of the co-material15included in the internal electrode layer12. Moreover, the Mg concentration in one or more of the ceramic grains14not contacting to the internal electrode layer12can be smaller than that of the ceramic grain14contacting to the internal electrode layer12. In this case, it is possible to suppress the influence of Mg in the dielectric layer11and achieve the effect of Mg in the internal electrode layer12. That is, it is possible to achieve both the high continuity modulus of the internal electrode layer12and the high dielectric constant of the dielectric layer11.

When Mo as the co-material is not added to the conductive paste for forming an internal electrode and Mo is added to the dielectric green sheet for forming the dielectric layer11, the life property of the dielectric layer11is improved and the reliability of the dielectric layer11is improved and the high continuity modulus of the internal electrode layer12is remained. Alternatively, the Mo concentration (atm %) with respect to the main component ceramic of the ceramic particles of the dielectric green sheet may be larger than the Mo concentration (atm %) with respect to the main component ceramic of the co-material in the conductive paste for forming an internal electrode.

EXAMPLES

The multilayer ceramic capacitors in accordance with the embodiment were made and the property was measured.

Examples 1 to 10

Ho2O3, MnCO3, V2O5, and SiO2were weighed so that a concentration of Ho was 0.4 atm %, a concentration of Mn was 0.2 atm %, a concentration of V was 0.1 atm % and a concentration of Si was 0.6 atm % on a presumption that an amount of Ti of barium titanate powder (an average particle diameter was 0.15 μm) was 100 atm %. And the materials were sufficiently wet-blended by a ball mill and were crushed. Thereby, a dielectric material was obtained. In examples 1 to 10, Mg was not added to the dielectric material. In the examples 2, 4, 7 and 8, MoO3was added to the dielectric material so that a concentration of Mo was 0.2 atm %. In the example 6, MoO3was added to the dielectric material so that a concentration of Mo was 0.1 atm %. In the example 9, MoO3was added to the dielectric material so that a concentration of Mo was 0.3 atm %. In the examples 1, 3, 5 and 10, Mo was not added to the dielectric material.

[Making of Conductive Paste for Forming an Internal Electrode]

Ho2O3, MnCO3, V2O5, and SiO2were weighed so that a concentration of Ho was 0.5 atm %, a concentration of Mn was 0.1 atm %, a concentration of V was 0.1 atm % and a concentration of Si was 0.2 atm % on a presumption that an amount of Ti of barium titanate powder (an average particle diameter is 0.05 μm) was 100 atm %. And the materials were sufficiently wet-blended by a ball mill and were crushed. Thereby, co-material was obtained. In the examples, 1 to 4, 6, 8 and 9, MgO was added to the co-material so that a concentration of Mg was 0.7 atm %. And the resulting materials were wet-blended and were crushed. In the examples 3 and 4, in addition to MgO, MoO3was added to the co-material so that a concentration of Mo was 0.1 atm %. And the resulting materials were wet-blended and were crushed. In the example 8, in addition to MgO, MoO3was added to the co-material so that a concentration of Mo was 0.05 atm %. And the resulting materials were wet-blended and were crushed. In the examples 5 and 7, MgO was added to the co-material so that a concentration of Mg was 0.3 atm %. And the resulting materials were wet-blended and were crushed. In the example 10, MgO was added to the co-material so that a concentration of Mg was 1.0 atm %. And the resulting materials were wet blended and were crushed.

Next, the resulting co-material of 20 weight parts was added to Ni metal powders of 100 weight parts whose diameter was 0.2 μm. Moreover, ethyl cellulose and α terpineol were added. The resulting material was kneaded by three rollers. And the conductive paste for forming an internal electrode was obtained.

[Making of a Multilayer Ceramic Capacitor]

Butyral acting as an organic binder, and toluene and ethyl alcohol acting as a solvent were added to the dielectric material. A dielectric green sheet of 1.2 μm was formed by a doctor blade method. A conductive paste for forming an internal electrode was screen-printed on the resulting dielectric sheet. 250 numbers of sheets on which the conductive paste for forming an internal electrode were stacked. Cover sheets having a thickness of 30 μm were stacked on a lower face and an upper face of the stacked sheets. After that, a multilayer structure was obtained by a thermo compression bonding. And the resulting multilayer structure was cut into a predetermined shape. Ni external electrodes were formed on the resulting multilayer structure by a dip method. After removing the binder in a N2atmosphere, the resulting multilayer structure was baked at 1250 degrees C. in a reductive atmosphere (O2partial pressure: 10−5to 10−8atm). And sintered multilayer structure was formed. A length was 0.6 mm. A width was 0.3 mm. A height was 0.3 mm. The sintered multilayer structure was re-oxidized in a N2atmosphere at 800 degrees C. After that, metals of Cu, Ni and Sn were coated on a surface of external electrode terminals by plating. And, a multilayer ceramic capacitor was formed. After baking, the thickness of the internal electrode layers12was 1.0 μm.

Comparative Examples 1 to 6

In a comparative example 1, neither Mg nor Mo was added to the dielectric material. Neither Mg nor Mo was added to the co-material. In a comparative example 2, MoO3was added to the dielectric material so that a concentration of Mo was 0.2 atm %, and Mg was not added to the dielectric material. Neither Mg nor Mo was added to the co-material. In a comparative example 3, MgO was added to the dielectric material so that a concentration of Mg in the dielectric material was 0.7 atm %, and MgO was added to the co-material so that a concentration of Mg in the co-material was 0.7 atm %. Mo wad added to neither the dielectric material nor the co-material. In a comparative example 4, MgO was added to the dielectric material so that a concentration of Mg is the dielectric material was 0.7 atm %, and MoO3was added to the dielectric material so that a concentration of Mo in the dielectric material was 0.2 atm %. Mg was added to t the co-material so that a concentration of Mg in the co-material was 0.7 atm %. Mo was not added to the co-material. In a comparative example 5, neither Mg nor Mo was added to the dielectric material. MgO was added to the co-material so that a concentration of Mg in the co-material was 1.5 atm %. Mo wad not added to the co-material. In a comparative example 6, MoO3was added to the dielectric material so that a Mo concentration in the dielectric material was 0.2 atm %. Mg was not added to the dielectric material. MgO was added to the co-material so that a concentration of Mg in the co-material was 1.5 atm %, Mo was not added to the co-material. The other conditions of the comparative examples 1 to 6 were the same as those of the examples 1 to 10.

A capacitance obtaining rate and HALT (Highly Accelerated Limit Test) defect rate of the multilayer ceramic capacitors were measured.

A capacitance was measured by an LCR meter. Measured values were compared with a design value that was calculated from a dielectric constant of a dielectric material (a dielectric constant was calculated by making a disc-shaped sintered material having a size of ϕ10 mm×T=1 mm from only a dielectric material in advance and measuring a capacitance), a crossing area of internal electrodes, a thickness of a dielectric ceramic layer and stack number. When a capacitance obtaining rate (measured value/design value×100) was 91% to 105%, it was determined as acceptance (circle).

HALT tests of 125 degrees C.—12 Vdc-120 min—100 numbers were performed. Samples whose short defect rate was less than 10% were determined as acceptance (circle). Samples whose short defect rate was less than 20% were determined as (triangle). Samples whose short defect rate was 20% or more were determined as not acceptance (cross).

Table 1 shows the measured results. In the examples 1 to 10, the capacitance obtaining rate was 91% or more. This may be because the concentration of Mg in the ceramic grain14that was included in the dielectric layer11and contacted to the internal electrode layer12was smaller than that in the co-material15of the internal electrode layer12, the influence of Mg was suppressed in the dielectric layer11, and the effect of Mg was achieved in the internal electrode layer12. In the examples 1 to 10, the HALT defect rate was less than 20%. This may be because the concentration of Mo in the co-material15of the internal electrode layer12was less than 1.5 atm %, and the diffusion of metal oxides structuring the internal electrode layer12was suppressed.

In the comparative examples 1 and 2, a capacitance obtaining rate was 90% or less. This may be because Mg was not added to the co-material and the high continuity modulus of the internal electrode layer12was not achieved. In the comparative examples 3 and 4, the capacitance obtaining rate was further reduced. This may be because Mg was added to the dielectric layer11and the dielectric constant was reduced.

In the comparative examples 5 and 6, the HALT defect rate was 20% or more. This may be because the concentration of MgO added to the co-material of the internal electrode layer12was 1.5 atm % and the metal oxides structuring the internal electrode layer12diffused.