JP2015053530A - Multilayer ceramic capacitor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a multilayer ceramic capacitor high in dielectric constant and having favorable temperature characteristics, even when a ceramic dielectric layer is reduced in thickness; and a method for manufacturing such the multilayer ceramic capacitor.SOLUTION: The multilayer ceramic capacitor is obtained by alternately laminating a ceramic dielectric layer and a conductor layer. The ceramic dielectric layer is baked so that core-shell particles having a core-shell structure and uniform solid-solution particles in which solid solubilization progresses uniformly are mixed therein. An area ratio of the core-shell particles to the total of sintered body particles constituting the ceramic dielectric layer is 5-15%, and an average particle size of the total sintered body particles combining the core-shell particles and the uniform solid-solution particles is 0.3-0.5 μm.

Description

  The present invention relates to a multilayer ceramic capacitor formed by alternately laminating ceramic dielectric layers and conductor layers, and a method for manufacturing the same.

  As digital electronic devices such as mobile phones become smaller and thinner, multilayer ceramic capacitors (MLCCs) that are surface-mounted on electronic circuit boards and the like are becoming smaller and larger in capacity. The multilayer ceramic capacitor has a structure in which ceramic dielectric layers as dielectrics and conductor layers as internal electrodes are alternately laminated.

  In general, when the size of the capacitor is reduced, the area of the internal electrode facing the dielectric is reduced, so that the capacitance is reduced. For this reason, in order to secure the capacitance of the capacitor toward the reduction in chip size, a high-density stacking technique in which the dielectric and internal electrode layers are thinned and stacked in multiple layers is indispensable.

By the way, conventionally, as a dielectric ceramic having good temperature characteristics, a sintered ceramic crystal particle having a core-shell structure is known. For example, by adding a secondary component containing a rare earth element or the like to the main component of barium titanate (BaTiO ₃ ) and firing while suppressing grain growth, a dielectric ceramic having a core-shell structure with little change in temperature of dielectric constant can be obtained. (See, for example, Patent Document 1).

  Conventionally, in dielectric ceramics having a core-shell structure, it is difficult to obtain a high dielectric constant because a shell part is formed by dissolving a secondary component having a relatively low dielectric constant in the outer shell of the core part. There was a problem. In addition, since the core-shell structure is formed while suppressing grain growth, the dielectric constant is also suppressed by the size effect of a relatively small grain diameter.

  On the other hand, by mixing particles having a core-shell structure and particles having a uniform particle structure (in the present application, this is referred to as “homogeneous solid solution particles”), so as to meet the demands for miniaturization and large capacity. A multilayer ceramic capacitor has been proposed (see, for example, Patent Document 2). Here, the uniform particle structure means a state in which the core-shell structure is no longer lost due to the progress of solid solution diffusion of subcomponents into the core during the ceramic firing process.

  For example, in the multilayer ceramic capacitor disclosed in Patent Document 2, the firing temperature and the area ratio of particles having a core-shell structure and uniform particles in an arbitrary cross section of the dielectric layer are mixed in the range of 2: 8 to 4: 6. A firing time is selected. Thereby, a temperature characteristic satisfying JIS standard D with a relative dielectric constant of 4500 or more is obtained.

JP 2004-345927 A JP 2001-15374 A

  In recent years, for higher-end products, it has a larger capacity (for example, a dielectric layer thickness of 2 μm or less and a relative dielectric constant of 5000 or more), and has better temperature characteristics (for example, EIA standard X5R equivalent). There is a need for multilayer ceramic capacitors.

  In a conventional multilayer ceramic capacitor in which core-shell particles and homogeneous particles are mixed in the dielectric layer, the temperature coefficient of capacitance (TCC) tends to deteriorate as the thickness of the dielectric layer decreases. . For example, under the conditions disclosed in Patent Document 2, when the thickness of the dielectric layer is reduced from 4.0 μm to 3.0 μm, TCC (20 ° C. to 85 ° C.) is deteriorated by about 5% point, The X5R standard is not already satisfied.

  The present invention has been made to solve such a problem, and even when the thickness of the ceramic dielectric layer is reduced to, for example, 2 μm or less, the multilayer ceramic capacitor has a high dielectric constant and good temperature characteristics. And a method of manufacturing such a multilayer ceramic capacitor.

  In order to solve the above-described problems, a multilayer ceramic capacitor according to the present invention is a multilayer ceramic capacitor in which ceramic dielectric layers and conductor layers are alternately stacked, and the ceramic dielectric layer has core-shell particles having a core-shell structure. And a cross section of the dielectric layer cut out at a position where the conductor layer intersects with a TEM (transmission electron microscope). The area ratio of the core-shell particles occupying the entire sintered particles in the field of view of the TEM is 5 to 15%, and the entire sintered particles combining the core-shell particles and the uniform solid solution particles The average particle size is 0.3 to 0.5 μm.

  In the multilayer ceramic capacitor, the thickness of the ceramic dielectric layer between the conductor layers after firing is preferably 2.0 μm or less, and the thickness of the ceramic dielectric layer is further 1.2 μm or less. preferable.

  In addition, the method for manufacturing a multilayer ceramic capacitor according to the present invention is a method for manufacturing a multilayer ceramic capacitor in which ceramic dielectric layers and conductor layers are alternately stacked, and the first particle size is composed of relatively small-diameter particles. The main component powder of the second particle size and the second particle size main component powder composed of relatively large particles at a predetermined blending ratio; and the first particle size and the second particle size of the main component powder On the other hand, adding a solid solution subcomponent powder to prepare a dielectric raw material powder, applying the dielectric raw material powder to produce a green sheet, and disposing a conductive paste on the green sheet Forming electrode patterns corresponding to left and right bipolar electrodes, laminating the green sheet so that the left and right bipolar electrode patterns alternate, and the ceramic dielectric The area ratio of the core-shell particles occupying the entire sintered body particles constituting 5 to 15%, and the average particle diameter of the entire sintered body particles including the core-shell particles and the uniform solid solution particles is 0 Firing the green sheet laminate to a thickness of 3 to 0.5 μm.

  In the method for manufacturing the multilayer ceramic capacitor, a particle size ratio of the main particle powder of the second particle size to a particle size of the main component powder of the first particle size is adjusted to 1.1 to 1.2 times, The predetermined blending ratio of the main component powder having one particle size and the second particle size (main particle powder having the first particle size: main component powder having the second particle size) is in the range of 8: 2 to 3: 7 by volume ratio. It is preferable to be within.

  According to the present invention, even when the thickness of the ceramic dielectric layer is reduced to 2.0 μm or less, the relative permittivity of the dielectric layer is set to 5000 or more, and at the same time, for example, a stable compliance with EIA standard X5R It is possible to provide a multilayer ceramic capacitor having a capacitance temperature characteristic. Therefore, it is possible to achieve both high capacity and good temperature characteristics in a miniaturized multilayer ceramic capacitor.

FIG. 1 is a longitudinal sectional view showing a schematic structure of a multilayer ceramic capacitor. FIG. 2 is a diagram schematically showing an enlarged image of a dielectric cross section observed with a microscope.

Hereinafter, as an embodiment of the present invention, a multilayer ceramic capacitor in which ceramic dielectric layers and conductor layers are alternately stacked will be described. FIG. 1 is a longitudinal sectional view showing a schematic structure of a multilayer ceramic capacitor 1 according to one embodiment of the present invention. The multilayer ceramic capacitor 1 includes a sintered body 10 having a chip size and a shape (for example, a rectangular parallelepiped of 1.0 mm × 0.5 mm × 0.5 mm) defined by a standard, and left and right formed on both sides of the sintered body 10. A pair of external electrodes 20 and 20 is provided. The sintered body 10 is formed by laminating a large number of dielectric layers 12 as ceramic dielectric layers and internal electrode layers 13 as conductor layers constituting internal electrodes of a capacitor, and a cover layer as an outermost layer thereof. 15 is formed. The dielectric layer 12 and the cover layer 15 are made of, for example, ceramics mainly composed of BaTiO ₃ , and the internal electrode layer 13 is fired mainly composed of a conductive metal containing Ni and / or Ag, for example.

  The dielectric layer 12 is fired with a mixture of core-shell particles having a core-shell structure and uniform solid solution particles in which solid solution has progressed uniformly. Here, the “core-shell structure” means that in the process of firing the sintered body 10, the main component remains in the central part (core part) of the particle crystal, and the subcomponents are dissolved in the outer shell part (shell part). The crystal grain structure fired in a state. “Uniform solid solution particles” refers to particles in which the structure of the crystal particles is made uniform by the progress of solid solution diffusion of subcomponents into the core.

  In the multilayer ceramic capacitor 1 according to the embodiment of the present invention, when the dielectric layer 12 is observed in cross section, the area ratio of the core-shell particles to the total area of the sintered particles is 5 to 15%. And it is preferable that the average grain diameter of the dielectric material layer 12, ie, the average particle diameter of the whole sintered compact particle | grains which match | combined the core-shell particle and the uniform solid solution particle | grain, is 0.3-0.5 micrometer. The thickness of the dielectric layer 12 between the internal electrode layers 13 after firing is preferably 2.0 μm or less. Furthermore, the thickness of the dielectric layer 12 is more preferably 1.2 μm or less.

  The multilayer ceramic capacitor 1 has a high-density multilayer structure in which the number of stacked dielectric layers 12 and internal electrode layers 13 is one hundred to several hundred. The cover layer 15 formed on the outermost layer portion of the sintered body 10 is provided to protect the dielectric layer 12 and the internal electrode layer 13 from contamination such as moisture and contamination from the outside, and to prevent their deterioration over time. It is done.

The multilayer ceramic capacitor 1 is manufactured through the following processes, for example. First, for example, ceramic raw materials such as TiO ₂ and BaO ₃ are weighed, mixed and calcined to prepare main component raw materials. Then, the prepared main component material is composed of a first main component powder having relatively small diameter (this is referred to as “small particle”) and a relatively large particle (hereinafter referred to as “large particle”). To a main component powder having a second particle size. For example, main component powders having particle sizes of 0.30 μm and 0.33 μm and different particle sizes can be prepared. The particle size of the main component powder can be managed by an average particle size (for example, median diameter d50) based on the particle size distribution. The particle size ratio of the large particle (second particle size main component powder) is adjusted to 1.1 to 1.2 times the particle size of the small particle (first particle size main component powder). Is preferred.

  Further, the tetragonality (c / a ratio) of the large-diameter particles (main particle powder of the second particle diameter) is preferably higher than that of the small-diameter particles (main particle powder of the first particle diameter). . For example, a main component material having a c / a ratio of 1.0100 is pulverized to prepare large-sized particles, and a main component material having a c / a ratio of 1.0094 is pulverized to obtain small-sized particles. it can. While most of the small-diameter particles having a low c / a ratio are made uniform by firing, a core-shell structure in the middle of the solid solution remains in a part of the large-diameter particles having a high c / a ratio. Note that the tetragonality (c / a ratio) of the crystal can be measured using an X-ray diffraction method.

  Therefore, by appropriately adjusting the blending ratio of the small-diameter particles and large-diameter particles in the main component powder of the dielectric, the ratio of the core-shell particles and homogeneous solid solution particles or the remaining ratio (area ratio) of the core-shell particles is desired to some extent. It becomes possible to control within the range.

  Next, the small-diameter particles (main component powder having the first particle size) and the large-diameter particles (main component powder having the second particle size) are mixed at a predetermined blending ratio. The mixing ratio of small diameter particles: large diameter particles is preferably in the range of 8: 2 to 3: 7 by volume ratio.

  A predetermined amount of solid solution subcomponent powder is added to the main component powder of the small particle and large particle as a subcomponent for constituting the shell portion, and wet mixing is performed to prepare a dielectric material powder. The subcomponent powder to be added is composed of, for example, a metal oxide and / or a metal organic complex, and as shown in the examples, rare earth such as Ho and Dy and / or elements such as Mg and Mn can be used.

  After the wet-mixed dielectric raw material powder is dried, an organic binder is mixed, applied to a strip-shaped green sheet having a thickness of 2 μm or less, for example, by a doctor blade method, and dried. Then, conductive paste is disposed on the green sheet to form electrode patterns of the internal electrode layer 12 corresponding to the left and right internal electrodes. The electrode pattern can be formed, for example, by screen printing a conductive paste on a green sheet.

  The green sheets are laminated so that the left and right electrode patterns are alternately arranged, and the cover sheets to be the cover layers 15 are pressure-bonded to the upper and lower sides of the laminated green sheets. Then, the laminated green sheet is cut into a laminated body having a predetermined chip size (for example, 1.0 mm × 0.5 mm), and the electrode patterns of the internal electrode layer 13 are exposed on both end faces of the laminated body. Subsequently, a conductive paste to be the external electrodes 20 and 20 is applied to both end surfaces of each laminate and dried. In addition, you may vapor-deposit the external electrodes 20 and 20 on the both end surfaces of a laminated body by sputtering method. Through these steps, a molded body of the multilayer ceramic capacitor 1 is obtained.

The capacitor molded body thus obtained was debindered in an N ₂ atmosphere at about 350 ° C., and then a reducing mixed gas of N ₂ , H ₂ and H ₂ O (with an oxygen partial pressure of about 1.0). × ¹⁰ -11 MPa) was heated to 1250 ° C. from the example 1150 ° C. in an atmosphere, and baked retains its temperature for example 10 minutes to 2 hours. After the temperature is lowered to obtain a sintered body, the temperature is raised from, for example, 800 ° C. to 1050 ° C. in an N ₂ atmosphere, and the re-oxidation treatment is performed while maintaining the temperature for, for example, 30 minutes to 2 hours. Thereby, the multilayer ceramic capacitor 1 in which the dielectric layer 12 has a predetermined average particle diameter and the core-shell particles and the uniform solid solution particles are mixed at a predetermined ratio is obtained.

  The above-mentioned preferable average particle diameter (0.3 to 0.5 μm) of the entire sintered body particles can be controlled to some extent by the firing conditions such as the temperature rising rate in the firing step. Moreover, the above-mentioned preferable area ratio (5 to 15%) of the core-shell particles occupying with respect to the entire sintered particles is not limited to the conditions such as the holding time in the firing step, but the small-sized particles and large-sized particles of the main component powder. The blending ratio, the types of added subcomponents, the composition ratio thereof, and the like can be appropriately adjusted and controlled.

  As another embodiment relating to the method of manufacturing the multilayer ceramic capacitor 1, the external electrode and the dielectric may be fired in separate steps. For example, the external electrodes 20 and 20 may be formed by firing a laminated body in which dielectrics are laminated and then baking a conductive paste on both ends thereof.

  Next, examples of the multilayer ceramic capacitor (MLCC) according to the present invention will be described. Under each condition shown in Table 1 (Groups I to VI: Condition Nos. 1 to 28), at least 10 MLCCs were produced and evaluated. The chip dimensions of the produced MLCC are all 1.0 mm × 0.5 mm × 0.5 mm (1005 size).

<Create MLCC>
(1) Preparation of Dielectric Material Powder BaTiO ₃ powder was used as a starting material of the main component for firing the dielectric layer of MLCC (here, barium titanate is abbreviated as “BT”). The BT was pulverized to prepare three types of BT powders having respective particle sizes of median diameter d50 of 0.33 μm, 0.30 μm, and 0.25 μm. As shown in Table 1, a set of particle sizes having different sizes (Groups I to VI) is determined for the BT powder, and the main component powder is changed by changing the blending ratio of the small and large particles for each group according to each condition. Mixed.

Oxidation containing Ho ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O ₃ , MgCO ₃ , MnCO ₃ , V ₂ O ₅ , and Li and B as solid solution subcomponents added to the BT powder (main component powder) A physical glass powder was used. The main component BaTiO ₃ is 100 mol, Ho ₂ O ₃ is 0.2 mol, Dy ₂ O ₃ is 0.2 mol, Gd ₂ O ₃ is 0.05 mol, MgCO ₃ is 0.5 mol, and MnCO ₃ is 0. .2 mol, V ₂ O ₅ was 0.1 mol, and the added amount of each subcomponent was adjusted so that the oxide glass powder containing Li and B had a composition ratio of 1.0 mol.

  As shown in Table 1, in Group I and IV MLCCs, the particle size ratio of large particles to small particles was adjusted to 1.1 times (= 0.33 / 0.30). In Group II and V MLCCs, the particle size ratio of large particles to small particles was adjusted to 1.2 times (= 0.30 / 0.25). In Group III and VI MLCCs, the particle size ratio of large particles to small particles was adjusted to 1.32 times (= 0.33 / 0.25).

(2) Production of MLCC molded body A dielectric raw material powder obtained by adding a solid solution subcomponent powder to a BT main component powder having a particle size different in size is wet-mixed with an organic binder containing a polyvinyl acetal resin and an organic solvent. Green sheets having two thicknesses of 1.5 μm and 1.0 μm were prepared by the blade method. Then, Ni conductive paste was screen-printed on these green sheets to form electrode patterns corresponding to the left and right internal electrodes.

  A total of 101 green sheets were laminated so that the left and right electrode patterns were arranged alternately. That is, the number n of MLCC layers is 100. The laminated green sheets were pressed and then cut into a predetermined chip size (1.0 mm × 0.5 mm). Then, Ni conductive paste was applied to both end faces of the laminate from which the electrode pattern was exposed, and left and right external electrodes 20 and 20 were formed.

(3) Firing of MLCC molded body The MLCC molded body thus obtained was debindered in an N ₂ atmosphere, and then a reducing mixed gas of N ₂ , H ₂ , and H ₂ O (with an oxygen partial pressure of about 1.0). The temperature was raised to 1250 ° C. in an atmosphere of × 10 ⁻¹¹ MPa. Table 1 shows the conditions of the temperature increase rate in the firing step. The holding time at 1250 ° C. was set to 2 hours to obtain MLCC sintered body 10. After the sintered body 10 was annealed, the surfaces of the external electrodes 20 and 20 were subjected to Ni—Sn plating treatment.

<Evaluation method>
(1) Area ratio of core-shell particles In the ceramic dielectric layer in which core-shell particles and homogeneous solid solution particles coexist, the ratio of the core-shell particles remaining to the entire sintered particles was measured by the area ratio of the observed cross section.

  Specifically, a cross section of the layer where the internal electrodes intersect is cut out from the MLCC, and the dielectric layer sample is obtained by exfoliating it to a thickness of 150 nm by an Ar ion milling method, and 100 using a TEM (transmission electron microscope). A plurality of fields of 15 μm × 15 μm in which one or more sintered particles can be observed are selected. And the ratio which the sum total of the area (cross-sectional area) of a core-shell particle occupies with respect to the total cross-sectional area of the whole sintered body particle | grains of a dielectric material layer is computed by image analysis from a visual field of at least 20 places. At this time, even in the case of particles that are partially out of view of the TEM, the area was taken into consideration.

  FIG. 2 is a diagram schematically showing an enlarged image of a dielectric cross section. In the image analysis, a pixel occupying a particle in which the core-shell structure is observed was selected, and the area occupied by the core-shell particle was calculated by counting the number of the selected pixel. On the other hand, pixels occupying uniform solid solution particles in which the core-shell structure is not observed were selected in the same manner, and the area occupied by the uniform solid solution particles was calculated by counting the number of pixels. The sum of the areas of the core-shell particles and the uniform solid-solution particles was defined as the total area of the sintered body particles, and the area ratio of the core-shell particles to this was evaluated as a percentage.

  In the TEM image analysis, the pixel corresponding to the portion that is neither the core-shell particle nor the homogeneous solid solution particle is considered to be a pore (hole) or void in the dielectric, or a secondary phase in which impurities are precipitated. Pixels were excluded from area calculations.

(2) Average particle diameter of sintered particles After the side surface of MLCC is polished to expose the layer cross section where the internal electrodes intersect, the sintered particle is based on an image obtained by photographing the dielectric layer portion of the cross section with TEM. The particle size of was measured. At least 20 or more arbitrary visual fields of 15 μm × 15 μm capable of observing 100 or more sintered particles were selected from the photographed TEM images. As shown in FIG. 2, the maximum grain boundary widths D1 and D2 in the stacking direction and the direction perpendicular to the laminating direction are measured with one sintered body particle, and the value obtained by adding them and dividing by 2 is the particle diameter of the particle. D (= (D1 + D2) / 2). The particle diameter of each sintered body particle was measured from a TEM image obtained by photographing 20 or more fields of view, and the arithmetic average thereof was evaluated as the average particle diameter of the sintered body particles.

(3) Relative permittivity From the measured value of the capacitance Cm of MLCC, the relative permittivity ε was determined using the following formula (1). In the examples of the present invention, the relative dielectric constant standard was set to 5000, and more than that was evaluated as conforming.

Cm = ε × ε ₀ × n × S / t (1)
Here, ε ₀ is the dielectric constant of vacuum, and n, S, and t are the number of dielectric layers, the area of the internal electrode layers, and the thickness of the dielectric layers, respectively.

  The capacitance Cm was measured using an impedance analyzer, and the voltage application conditions were 1 kHz and 1.0 Vrms. The number n of dielectric layers of the MLCC used in the examples is 100. The area of the internal electrode layer was the effective electrode area estimated from the design value of the electrode pattern in MLCC. The layer thickness of the dielectric layer was determined from a TEM image of the layer cross section of the produced MLCC.

(4) Temperature characteristics Whether the MLCC capacitance temperature change characteristic (TCC) satisfies the requirements of EIA standard X5R (capacitance change rate is within ± 15% in the temperature range of −55 to + 85 ° C.) Thus, the temperature characteristics were evaluated. Table 1 shows the TCC (= C _min −C _{25 ° C.} ) calculated from the maximum capacity change ΔC (= C _min −C _{25 ° C.} ) in the temperature range of −55 to 85 ° _C. with respect to the capacity C _{25 °} C. of _{25 ° C.} = ΔC / C _{25 ° C.} ) as a percentage.

<Evaluation results>
With reference to Table 1, the characteristic result about MLCC produced on each condition is demonstrated.

  In MLCCs of Group I and IV (Conditions Nos. 1-6, Nos. 15-20), BT powder having a small particle size of 0.30 μm and a large particle size of 0.33 μm is used, The residual ratio of the core-shell particles was changed under each condition by firing the ceramic dielectric layer at each compounding ratio indicated in each condition. As shown in Table 1, the layer thickness of the dielectric layer after firing differs between Group I and IV, that is, the layer thickness of the dielectric layer is 1.2 μm in Group I and 0.8 μm in Group IV.

  In these MLCCs of Group I and IV, in the MLCC (conditions No. 1 and 15 where the area ratio is 2%) in which the blending ratio of the large-sized particles to the small-sized particles is small and the core-shell particles are relatively small, It was worse than 15%. On the contrary, in MLCC (conditions No. 6 and 20 where the area ratio is 17%) in which many core-shell particles remain, the relative dielectric constant was lower than the prescribed 5000.

  On the other hand, the MLCCs under conditions No. 2 to 5 and 16 to 19 achieved temperature characteristics with a high relative dielectric constant of 5000 or more and TCC within ± 15%. The area ratio of the core-shell particles in these dielectrics with good property results was 5-15%.

  In MLCCs of Group II and V (Condition Nos. 7-10, Nos. 21-24), BT raw material powders having small diameter particles of 0.25 μm and large diameter particles of 0.30 μm are used. The mixing ratio of these small diameter particles and large diameter particles was 7: 3. By making the blend ratio of the small particles and the large particles constant, the area ratio of the core-shell particles after firing was 5% under these conditions.

  Using Group II and V MLCCs, the temperature increase rate of firing was changed stepwise from 1800 to 600 ° C./h, and the influence on the characteristics due to the difference in firing conditions was investigated. As a result, a relative dielectric constant of 5000 or more was obtained at a temperature rising rate of 1500 to 900 ° C./h, and a stable TCC within ± 15% was achieved (Condition Nos. 8, 9, 22, 23). ). Moreover, the average particle diameter of the sintered compact particle on these conditions was 0.3-0.5 micrometer.

  Qualitatively, it can be said that the slower the rate of temperature rise, that is, the longer the firing time, the more the grain growth is promoted. Further, from the results of Group II and V, it can be seen that the temperature characteristics tend to be better as the rate of temperature increase is slower, that is, as the average particle size of the sintered body particles is larger.

  In Group III and VI (Condition Nos. 11-14, Nos. 25-28), BT raw material powders having a small particle size of 0.25 μm and a large particle size of 0.33 μm were used. . Moreover, by setting the blending ratio of these small diameter particles and large diameter particles to a constant 3: 5, under these conditions, the area ratio of the core-shell particles after firing was relatively high at 15%.

  Also in Group III and VI MLCCs, the temperature increase rate of the calcination was changed stepwise in the range of 2000 to 600 ° C./h, and the influence on the characteristics due to the difference in the calcination conditions was examined. Among these conditions, an MLCC under conditions No. 12, 13, 26, and 27 (temperature increase rate: 1800 to 900 ° C./h) achieved a relative dielectric constant of 5000 or more and a TCC within ± 15%. Moreover, the average particle diameter of the sintered compact particle on the conditions with which the characteristic was evaluated favorable was 0.3-0.5 micrometer.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 10 Sintered body 12 Dielectric layer (ceramic dielectric layer)
13 Internal electrode layer (conductor layer)
15 Cover layer 20 External electrode

Claims (3)

A multilayer ceramic capacitor in which ceramic dielectric layers and conductor layers are alternately laminated,
The ceramic dielectric layer is composed of sintered particles including core-shell particles having a core-shell structure and uniform solid solution particles in which solid solution has progressed uniformly,
When the cross section of the dielectric layer cut out at a position where the conductor layers intersect is observed with a TEM (transmission electron microscope), the area of the core-shell particles occupying the entire sintered particles in the field of view of the TEM The ratio is 5-15%,
A multilayer ceramic capacitor having an average particle size of 0.3 to 0.5 μm as a whole of the sintered particles obtained by combining the core-shell particles and the uniform solid solution particles.   The multilayer ceramic capacitor according to claim 1, wherein the thickness of the ceramic dielectric layer between the conductor layers after firing is 2.0 μm or less.   The multilayer ceramic capacitor according to claim 2, wherein a thickness of the ceramic dielectric layer is 1.2 μm or less.

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