JP6451293B2 - Multilayer ceramic capacitor - Google Patents

Multilayer ceramic capacitor Download PDF

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JP6451293B2
JP6451293B2 JP2014255118A JP2014255118A JP6451293B2 JP 6451293 B2 JP6451293 B2 JP 6451293B2 JP 2014255118 A JP2014255118 A JP 2014255118A JP 2014255118 A JP2014255118 A JP 2014255118A JP 6451293 B2 JP6451293 B2 JP 6451293B2
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rare earth
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multilayer ceramic
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JP2016115876A (en
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豪 芝原
豪 芝原
満幸 静谷
満幸 静谷
田中 美知
美知 田中
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Tdk株式会社
Tdk株式会社
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Description

  The present invention relates to a multilayer ceramic capacitor in which dielectric layers and internal electrode layers are alternately stacked.

  A multilayer ceramic capacitor, which is an example of an electronic component, is formed by, for example, simultaneously firing a green chip obtained by alternately stacking ceramic green sheets made of a predetermined dielectric composition and internal electrode layers of a predetermined pattern and then integrating them. Manufactured.

  On the other hand, there is a high demand for miniaturization of electronic components due to the increase in the density of electronic circuits, and electronic components such as film capacitors and aluminum electrolytic capacitors that have been used in conventional electronic circuits are replaced with small multilayer ceramic capacitors. There is a growing demand to do so.

In order to meet such a demand, what is required of a multilayer ceramic capacitor is ensuring high temperature load characteristics in a high temperature region, which is a problem.
In response to such a problem, for example, the technique described in Patent Document 1 realizes a multilayer ceramic capacitor having high high-temperature load characteristics by using a ceramic composition having a specific composition.

  The technology described in Patent Document 2 realizes a multilayer ceramic capacitor having high high-temperature load characteristics by controlling the concentration of a solid solution phase in which the subcomponents are dissolved, which is contained in the dielectric particles of the multilayer ceramic capacitor. Yes.

Japanese Patent No. 3567759 JP 2012-193072 A

  However, there is a limit in the examination from the viewpoint of composition as in Patent Document 1. Moreover, even if the technique of Patent Document 2 is used, securing a high temperature load characteristic at a further high temperature and high voltage is a big problem.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a multilayer ceramic capacitor having high high temperature load characteristics.

The inventors of the present invention have obtained the present invention as a result of intensive studies to achieve the above object.
That is, the present invention is a ceramic capacitor in which dielectric layers and internal electrode layers are alternately laminated, wherein the dielectric layer is a main component phase mainly composed of a perovskite structure ceramic material represented by the general formula ABO 3. And crystal grains having at least one or more rare earth elements as a subcomponent dissolved in the main component phase around the main component phase, the subcomponent phase including the main component phase A region A surrounding the phase and in which the content of the rare earth element in solid solution does not change, and located on the side opposite to the main component phase with respect to the region A, and the content of the rare earth element is changed The region B is located on the opposite side of the region A with respect to the region B, and the rare earth element content is not changed, and is located between the region C and the grain boundary. Region D, and the region The rare earth element content in region A is C A , the rare earth element content in region B is C B , the rare earth element content in region C is C C , and the rare earth element content in region D is C D. Then, a relationship of C A > C B > C C > C D is established.

  The region where the rare earth element content does not change refers to a region where the rare earth content does not vary beyond the measurement variation of the composition analyzer (in this case, a measurement error range of ± 5% relative to the measured value).

  The present inventors consider the factors for obtaining such effects as follows. In the regions A and C, since the rare earth element concentration is different, lattice strain is likely to occur between the regions. Lattice strain has the effect of suppressing the movement of oxygen vacancies, which are believed to dominate the high temperature load characteristics of multilayer ceramic capacitors. As a result, the thermal runaway caused by the concentration of the electric field due to the movement of oxygen defects to the cathode side can be suppressed, and it is considered that the high temperature load characteristic higher than that of the prior art can be realized.

  As a desirable mode of the present invention, it is preferred that 30% or more of all crystal grains contained in the dielectric layer are the crystal grains.

  By containing 30% or more of the crystal particles, the effect of suppressing an increase in conduction electrons accompanying the generation of oxygen defects is further enhanced. As a result, the effect of making it difficult for the insulation resistance to deteriorate is enhanced, so that higher high temperature load characteristics can be obtained.

The content C A and the content C C preferably satisfy 15% ≦ (C A -C C ) / C C. Thereby, the effect | action which suppresses the movement of the oxygen defect by lattice distortion is improved more. As a result, high high temperature load characteristics can be obtained.

Desirable embodiments of the present invention, the width of R A of the area A, the width of the region C in the case of the R C, it is preferable to satisfy 40% ≦ R A / R C ≦ 150%. Thereby, the effect | action which suppresses the movement of the oxygen defect by lattice distortion is improved more. As a result, high high temperature load characteristics can be obtained.

  As a desirable mode of the present invention, the rare earth element is preferably at least one element selected from Y, La, Gd, Tb, Dy and Ho. By containing these rare earth elements as subcomponents, the region A and the region C can be easily formed. As a result, it becomes easy to form lattice strain, the effect of suppressing the movement of oxygen vacancies is enhanced, and higher high temperature load characteristics can be realized.

The content rates C A to C D and the widths A A and R C of the region A and the region C are defined by analysis using a scanning transmission electron microscope (STEM) as follows.

  First, with respect to an arbitrary cross section in the stacking direction of the capacitor element body 10 as shown in FIG. 1, a magnification (for example, a crystal particle forming the dielectric layer can be sufficiently identified using a scanning transmission electron microscope (STEM) (for example, Observation is performed at a magnification of 100,000 in the examples described later. Then, using an energy dispersive X-ray spectrometer (EDS) attached to the STEM, a rare earth element mapping analysis is performed under the condition that the main component phase and the subcomponent phase can be clearly distinguished (for example, FIG. 2). The phase in which the solid solution of the rare earth element is not recognized in the crystal particles is the main component phase (20 in FIG. 2), and the region in which the solid solution of the rare earth element is recognized corresponds to the subcomponent phase (21 in FIG. 2).

Next, 5 or more particles (for example, 10 particles in the examples described later) are extracted from the observation field of view. The longest line segment (L 1 in FIG. 3) that passes through the vicinity of the center of gravity of the main component phase, crosses the crystal grain, and has a grain boundary and a common point is obtained. Then at sufficiently closely spaced relative to the length of the line segment L 1 (for example, 100 equal parts in the Examples below), carrying out the analysis points using EDS. Among the obtained analysis results, a region in contact with the main component phase and having a flat rare earth content within a measurement error of ± 5% was defined as region A. A region having a concentration gradient located on the opposite side of the main component phase with respect to the region A was defined as a region B. Region C, which is located on the opposite side of region A with reference to region B and has a flat rare earth content within a measurement error of ± 5%, was designated as region C. A region located between the region C and the grain boundary was defined as a region D.

The average value of the content of rare earth elements was determined for each of the regions A to D. For each region intersecting with the line segment L 1, so that two by two the average value is obtained. C A1 and C A2 in FIG. 3 are average values of the content of rare earth elements in the region A. Next, a line segment L 2 that intersects the center of gravity of the main component phase perpendicularly to L 1 is drawn, and the rare earth content is determined for each region by the same method as in the case of L 1 . In the case of L 2 , two average values are obtained (C A3 and C A4 in FIG. 4 in the example of the region A). According to the above method, the average value of the rare earth content in each region is measured by averaging the four measurement values obtained for each region, and each region A to D is averaged by averaging the previously extracted particles. The average values C A to C D of the content of rare earth elements were set.

The widths R A and R C of the region A and the region C can be obtained by four points for each particle. R A1 to R A4 in FIG. 3 are the widths of the region A, and the widths R A and R C of the region A and the region C of each particle are obtained by averaging.

  ADVANTAGE OF THE INVENTION According to this invention, a multilayer ceramic capacitor with a high temperature load characteristic can be provided.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a measurement example of crystal particles according to an embodiment of the present invention, and is a diagram observed with an energy dispersive X-ray spectrometer (EDS). FIG. 3 is a schematic diagram showing an example of analysis of crystal particles according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a dielectric layer of the multilayer ceramic capacitor according to the embodiment of the present invention. FIG. 5 is a graph showing measurement results according to examples and comparative examples of the present invention.

  Although the form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings, the present invention is not limited to the embodiment described below. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

<Multilayer ceramic capacitor>
As shown in FIG. 1, a multilayer ceramic capacitor 1 according to an embodiment of the present invention includes a capacitor element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the capacitor element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

  The internal electrode layers 3 are laminated so that the end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor element body 10. The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

The dielectric layer 2 includes a plurality of crystal particles made of a perovskite structure ceramic material whose main component is represented by the general formula ABO 3 . In addition, rare earth elements, alkaline earth metal elements, transition metal oxides and mixtures thereof, composite oxides, and sintering aids containing SiO 2 as glass may be included as subcomponents. In that case, a part of the subcomponent is dissolved in the crystal grains to form a subcomponent phase, and the rest may segregate in the vicinity of the grain boundary. In addition, as long as the high temperature load characteristic which is the effect of this invention is not reduced significantly, it may contain a minute impurity and other subcomponents. Therefore, the content of the main component is not particularly limited, but is, for example, 50% or more and 100% or less with respect to the entire dielectric composition containing the main component.

  The dielectric layer 2 includes crystal particles having a main component phase substantially composed of only the main component and a subcomponent phase in which a rare earth element as a subcomponent is dissolved. In the prior art, the subcomponent phase is formed of a single region in which the concentration of the subcomponent changes continuously.

In the present embodiment, the subcomponent phase is intentionally formed in four regions having different rare earth element concentrations. That is, among the main component phase and subcomponent phase forming the crystal particles contained in the dielectric layer 2, the subcomponent phase is in contact with the main component phase and has a content of the rare earth element in solid solution. A region A that does not change, a region B that is located on the opposite side of the main component phase with respect to the region A, and in which the content of the rare earth element is changed, and the region A with respect to the region B Is located on the opposite side and has a region C where the content of the rare earth element does not change, and a region D located between the region C and a grain boundary, and the content of the rare earth element in the region A is When C A , the rare earth element content in region B is C B , the rare earth element content in region C is C C , and the rare earth element content in region D is C D , C A > C B > It was formed so that a relationship of C C > C D was established. With such a structure, a multilayer ceramic capacitor having good high-temperature load characteristics can be obtained.

  When 30% or more of all the crystal grains contained in the dielectric layer are the crystal grains, there is an effect of suppressing an increase in conduction electrons accompanying the generation of oxygen defects. As a result, the effect of making it difficult for the insulation resistance to deteriorate is enhanced, so that higher high temperature load characteristics can be obtained.

The effect of the present invention can be further enhanced by controlling the content C A and the content C C so as to satisfy the relationship of 15% ≦ (C A -C C ) / C C.

Further, by controlling the width R A and R C of the regions A and C in the range of 40% ≦ R A / R C ≦ 150%, it is possible to enhance the effect of the present invention.

  By selecting the rare earth element from at least one selected from Y, La, Gd, Tb, Dy and Ho, it is possible to obtain higher high temperature load characteristics.

  FIG. 4 is a diagram schematically showing crystal grains according to the present embodiment. The crystal grains are composed of a subcomponent phase composed of a region A (40a in FIG. 4), a region B (40b in FIG. 4), a region C (40c in FIG. 4) and a region D (40d in FIG. 4), and a main component phase (see FIG. 4 of 40e). Further, reference numeral 41 in FIG. 4 denotes crystal grains that do not have the regions A to D.

<Crystal grain structure>
The presence or absence of the regions A and C in the crystal particles can be determined by analyzing using a scanning transmission electron microscope (STEM), for example. Specifically, first, with respect to an arbitrary cross section in the stacking direction of the element body 10 as shown in FIG. 1, the crystal grains forming the dielectric layer can be sufficiently identified using a scanning transmission electron microscope (STEM). At a high magnification (for example, a magnification of 100,000 in the embodiments described later). Then, using an energy dispersive X-ray spectrometer (EDS) attached to the STEM, a rare earth element mapping analysis is performed under the condition that the main component phase and the subcomponent phase can be clearly distinguished (for example, FIG. 2). The phase in which the solid solution of the rare earth element is not recognized in the crystal grains is the main component phase (20 in FIG. 2), and the region in which the solid solution of the rare earth element is recognized is the subcomponent phase (21 in FIG. 2). Of the subcomponent phases, a region in contact with the main component phase is a region A (21a in FIG. 2). Among the subcomponent phases, the amount of the rare earth solid solution is smaller than that of the region A, and the region C has a relatively low luminance (21c in FIG. 2). The boundary between the regions A and C is the region B (21b in FIG. 2), and the portion sandwiched between the region C and the grain boundary (22 in FIG. 2) is the region D (21d in FIG. 2).

  The content ratio of the crystal particles having the regions A and C to the total crystal particles is calculated by performing mapping analysis as described above, counting the number of particles having the regions A and C, and then dividing by the total number of particles included in the field of view. Can be obtained.

Presence / absence of regions A to D in the subcomponent phase, rare earth content C A to C D , widths A A and R C of regions A and C are obtained by the method described in paragraphs [0017] to [0021]. be able to.

  In the present invention, the subcomponent phase in the crystal grains is provided with two regions where the content of rare earth elements does not change intentionally (in the present invention, the regions A and C are indicated).

  The formation of the region A and the region C can be controlled, for example, by changing a holding temperature, a holding time, a temperature lowering rate, and an atmosphere during firing described later. In addition, selection of the main component raw material powder and composition, atmosphere during annealing, holding time, and the like are also control methods for efficiently forming the regions A and C.

<Internal electrode layer>
The conductive material contained in the internal electrode layer 3 is not particularly limited, but a relatively inexpensive base metal can be used because the constituent material of the dielectric layer 2 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements selected from Mn, Cr, Co and Al, and the Ni content in the alloy is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components, such as P, may be contained about 0.1 wt% or less. The internal electrode layer 3 may be formed using a commercially available electrode paste. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use etc.

  The conductive material contained in the external electrode 4 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used. What is necessary is just to determine the thickness of the external electrode 4 suitably according to a use etc.

<Manufacturing method of multilayer ceramic capacitor>
The multilayer ceramic capacitor of this embodiment is similar to the conventional multilayer ceramic capacitor, in which a green chip is produced by a normal printing method or sheet method using a paste, and after firing this, an external electrode is printed or transferred. Manufactured by firing. Hereinafter, the manufacturing method will be specifically described.

  First, a dielectric material (dielectric composition powder) contained in the dielectric layer paste is prepared, and this is made into a paint to prepare a dielectric layer paste.

  The dielectric layer paste is an organic paint obtained by kneading a dielectric material and an organic vehicle.

As a dielectric material, in addition to ABO 3 type perovskite structure material (for example, BaTiO 3 , SrTiO 3 , NaKNbO 3, etc.) which is a main component, rare earth elements (Y, La, Gd, Tb, Dy, Ho, etc.) are used as subcomponents. , Sm, Yb, etc.), alkaline earth metals (Mg and Mn), transition metal (at least one selected from V, W, and Mo) oxides and mixtures thereof, complex oxidation A sintering aid containing SiO 2 can be used as the object and glass. In the state before the coating, a dielectric material having an average particle size of about 0.05 μm to 0.30 μm was used.

Ceramic material powder with ABO 3 type perovskite structure as the main ingredient is manufactured by various liquid phase methods (for example, oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.) in addition to the so-called solid phase method. What was manufactured by various methods, such as a thing, can be used.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. The organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as acetone and toluene.

  The internal electrode layer paste is prepared by kneading the above-described conductive material made of various conductive metals or alloys and the above-described organic vehicle.

  The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

  Next, a green chip is manufactured. In producing the green chip, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are further laminated to form a green chip.

  Next, the green chip is subjected to binder removal processing. As binder removal conditions, the rate of temperature rise is preferably 5 ° C./hour to 300 ° C./hour, the holding temperature is preferably 180 ° C. to 400 ° C., and the temperature holding time is preferably 0.1 hour to 24 hours. The binder removal atmosphere is air or a reducing atmosphere.

The firing of the green chip is preferably performed in a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of N 2 and H 2 can be used by humidification. Other conditions are preferably as follows.

  In the present embodiment, the firing step includes a temperature raising step, a first holding step, a second holding step, and a temperature lowering step.

  First, in the temperature raising step, the temperature rising rate was 2000 ° C./hour to 7200 ° C./hour, and the hydrogen concentration was 2% to 4%. The rare earth-containing ratio according to claim 1, wherein the hydrogen concentration in the temperature raising step is higher than the hydrogen concentration in the subsequent first holding step so that the rare earth content in the subcomponent phase (A region in the present invention) in the vicinity of the main component is increased. It can be controlled so as to have a magnitude relationship.

  After the first holding step, the hydrogen concentration is 0.3% to 1%, the holding temperature is preferably 1000 ° C. to 1200 ° C., and the holding time is preferably 5 hours to 50 hours. By adjusting the conditions of the first holding step, the widths of the regions A and C can be controlled to desired values.

In the second holding step, it is preferable to perform holding for a short time at a higher temperature than in the first holding step. The holding temperature is preferably 1250 ° C to 1350 ° C, and the holding time is preferably 0.5 hours to 5 hours. By adjusting the conditions of the second holding step, the content of rare earth elements contained in the regions A and C can be controlled. The oxygen partial pressure during firing may be appropriately determined according to the type of the conductive material in the internal electrode layer paste, but when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen content in the firing atmosphere The pressure is preferably 10 −10 Pa to 10 −3 Pa. When the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may be abnormally sintered and may be interrupted. Further, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized.

  The rate of temperature decrease after the end of the second holding step is preferably 50 ° C./hour to 2000 ° C./hour. By adjusting the cooling rate, the content ratio of the particles having the regions A and C to the total particles can be controlled.

  After firing in a reducing atmosphere, the capacitor element body is preferably annealed. Annealing is a process for re-oxidizing the dielectric layer, whereby a relatively high insulation resistance can be obtained.

The oxygen partial pressure in the annealing atmosphere is preferably 10 −3 Pa to 1.0 Pa. When the oxygen partial pressure is less than the above range, it is difficult to re-oxidize the dielectric layer, and when it exceeds the above range, oxidation of the internal electrode layer tends to proceed.

  The holding temperature at the time of annealing is preferably 1100 ° C. or less, particularly 500 ° C. to 1100 ° C., and the holding time is preferably 2 hours to 30 hours. When the holding temperature and holding time are less than the above ranges, the dielectric layer is not sufficiently oxidized, so that the insulation resistance is low and the high-temperature load life tends to be shortened. On the other hand, if the holding temperature exceeds the above range, not only the internal electrode layer is oxidized and the capacity is lowered, but also the internal electrode layer reacts with the dielectric substrate, the insulation resistance is lowered, and the high temperature load characteristic is also lowered. Is likely to occur.

As other annealing conditions, the temperature lowering rate is preferably 50 ° C./hour to 500 ° C./hour, more preferably 100 ° C./hour to 300 ° C./hour. In addition, as the atmosphere gas for annealing, as in the firing, for example, a reducing atmosphere using a humidified mixed gas of N 2 and H 2 or an inert gas atmosphere using a humidified N 2 gas or the like is used. The method is preferred.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N 2 gas or mixed gas. In this case, the water temperature is preferably about 5 ° C to 75 ° C.

  The binder removal treatment, firing and annealing may be performed continuously or independently.

  The capacitor element body 10 obtained as described above is subjected to end surface polishing by, for example, barrel polishing or sand blasting, and the external electrode paste is applied and baked to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

  The multilayer ceramic capacitor 1 of this embodiment manufactured in this way is mounted on a printed circuit board or the like by soldering or the like, and used for various electronic devices.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  Moreover, in the above-mentioned embodiment, in order to provide subcomponent phases having different rare earth element concentrations, the holding step in firing was divided into two, and the method of changing the conditions was given as an example. Two regions with different rare earth element concentrations can be obtained by changing the temperature in the middle of the holding time during firing, or by mixing a part of the subcomponent with the main component and heat-treating and then mixing with the remaining subcomponent. Can be provided.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
<Preparation of capacitor sample>
First, with respect to 100 mol of BaTiO 3 (hereinafter referred to as BT) powder as a main component, 5.0 mol of Yb 2 O 3 , 4.5 mol of MgO, 1.0 mol of MnO, and SiO 2 as subcomponents. Was mixed to obtain a mixture (dielectric material). To 100 parts by weight of this mixture, 10 parts by weight of polyvinyl butyral resin, 5 parts by weight of dibutyl phthalate (DOP) as a plasticizer, and 100 parts by weight of alcohol as a solvent are mixed by a ball mill to make a paste. A dielectric layer paste was obtained.

  In addition to the dielectric layer paste, three rolls of Ni particles: 44.6 parts by weight, terpineol: 52 parts by weight, ethyl cellulose: 3 parts by weight, and benzotriazole: 0.4 parts by weight Kneaded and slurried to prepare an internal electrode layer paste.

  Then, using the dielectric layer paste prepared above, a green sheet was formed on the PET film so that the thickness after drying was 10 μm. Next, using the internal electrode layer paste on this, the electrode layer is printed in a predetermined pattern, then peeled off from the PET film, laminated in plural, and pressure-bonded to form a green laminate, and this green laminate Was cut into a predetermined size to obtain a green chip.

Next, the obtained green chip was subjected to binder removal treatment, firing and annealing under the following conditions to obtain a multilayer ceramic fired body. The binder removal treatment conditions were temperature rising rate: 25 ° C./hour, holding temperature: 260 ° C., temperature holding time: 8 hours, and atmosphere: in the air. The firing conditions were as follows. In the temperature raising step, the temperature raising rate was 2000 ° C./hour, and the atmosphere gas was a humidified N 2 + 3.5% H 2 mixed gas (oxygen partial pressure was 10 −8 to 10 −9 Pa). The first holding step has a first holding temperature of 1150 ° C. and a first holding time of 40 hours, the second holding step has a second holding temperature of 1250 ° C. and a second holding time of 5 hours, and atmospheric gas: humidification The N 2 + 0.5% H 2 mixed gas (oxygen partial pressure was 10 −6 to 10 −7 Pa), and the temperature lowering step was a temperature lowering rate: 60 ° C./hour. The annealing conditions were as follows: temperature increase rate: 200 ° C./hour, retention temperature: 950 ° C., temperature retention time: 2 hours, temperature decrease rate: 200 ° C./hour, atmospheric gas: humidified N 2 gas (oxygen partial pressure: 1 Pa) did. A wetter was used for humidifying the atmospheric gas during firing and annealing.

  Next, after polishing the end face of the obtained multilayer ceramic fired body by sand blasting, In-Ga was applied as an external electrode to obtain a sample of the multilayer ceramic capacitor shown in FIG. The size of the obtained capacitor sample is 3.2 mm × 1.6 mm × 3.2 mm, the thickness of the dielectric layer is 8 μm, the thickness of the internal electrode layer is 1.5 μm, and the dielectric layer sandwiched between the internal electrode layers is The number was 10.

  About the obtained capacitor | condenser sample, the content rate with respect to all the particles of the crystal grain which has the area | regions A and C, the rare earth content ratio of the area | regions A-D, the ratio of the area | region width of the area | regions A and C, and a high temperature / high temperature load characteristic are shown below, respectively. Measured by the method.

<Content ratio of crystal grains having regions A and C to all particles (region AC particle content)>
By the method based on the above-described embodiment, particles having regions A and C are discriminated from particles having regions A and C from the three-field STEM mapping image obtained at a magnification of 100,000. After discrimination, the total number of crystal grains having regions A and C was divided by the total number of crystal grains to calculate the content ratio of the number of crystal grains having regions A and C. The results are shown in Table 2.

<Rare earth content in regions A to D>
In this example, point analysis was performed on 10 particles using an EDS attached to the STEM at a magnification of 100,000 times. Other methods were as shown in [0017] to [0021], and C A to C D were obtained. The results are shown in Table 2.

<Ratio of area widths of areas A and C>
For region A and region C determined above, RA and RC were calculated based on [0017] to [0021], and then the ratio of region widths was calculated by dividing RA by RC . The results are shown in Table 2.

<High temperature load characteristics>
As a high-temperature load characteristic evaluation, the high-temperature load characteristic was evaluated by measuring the lifetime of a capacitor sample by holding a DC electric field of 50 V / μm in a thermostat at 190 ° C. In this example, for each of the examples and comparative examples, the time from the start of application until the insulation resistance dropped by an order of magnitude was taken as the failure time, and the average failure time was calculated by performing Weibull analysis. . In this example, a sample having an average failure time of 10 hours or more at a high temperature accelerated life was judged to be good, and a sample having 25 hours or more was judged to be a sample having more preferable characteristics. The production conditions are shown in Table 1, and the results are shown in Table 2.

<Examples 2 and 3>
The temperature drop rate after the second holding in the firing step was changed to 500 ° C./hour and 2000 ° C./hour, respectively, and the other conditions were the same as in Example 1, and the content of the crystal grains having the regions A and C Samples with different regions (hereinafter referred to as region AC particle content) were prepared. The conditions are shown in Table 1, and the measurement results are shown in Table 2. All of these samples having a region AC particle content ratio of 30% or more showed better high temperature load characteristics than the sample of Example 1.

<Examples 4 and 5>
C A and C C were adjusted by changing the second holding step in the firing step. Other manufacturing conditions were the same as in Examples 2 and 3. The production conditions are shown in Table 1, and the results are shown in Table 2. By so as to satisfy the relation of 15% ≦ (C C -C A ) / C A, exhibited good high-temperature load characteristics than Example 2 and 3.

<Examples 6 to 8>
The width | variety of the area | region of the area | regions A and C was changed by changing the 1st holding process at the time of baking. Other conditions were the same as in Examples 4 and 5. The production conditions are shown in Table 1, and the results are shown in Table 2. The samples of Examples 6 and 7, with the area ratio or R A / R C in the range of 40% to 150%, have better high temperatures compared to the samples of Examples 4, 5, 8 that are out of range. Load characteristics were obtained.

<Examples 9 to 16>
The kind of rare earth added as a subcomponent was changed. The production conditions are shown in Table 1, and the results are shown in Table 2. The samples of Examples 9 to 15 in which at least one kind was selected from Y, La, Tb, Dy and Ho had better high temperature load characteristics than Example 16 to which Yb was added.

<Comparative Examples 1 and 2>
In the second holding step, a sample was produced under the same conditions as in Example 9 except that the holding time was 10 hours and 0 hour, respectively. The production conditions are shown in Table 1, and the measurement results are shown in Table 2. In the sample of Comparative Example 1 in which the holding time was 10 hours and the sample of Comparative Example 2 in which the holding time was not held, regions A and C did not exist in any particle, and as shown in FIG. The content of was not changed. At this time, the average failure time was 2 hours, and good results were not obtained.

<Comparative Example 3>
Based on Prior Patent Document 2, a sample of Comparative Example 3 was prepared. Specifically, using a main component and subcomponents having the same configuration as in Example 1, a green chip was prepared by the same method, subjected to binder removal processing, and then fired. Firing was carried out under the conditions shown in Table 1 separately for the first firing and the second firing. After firing, annealing treatment was performed under the conditions shown in Table 2. Subsequent steps were performed in the same manner as in Example 1 to obtain a capacitor sample. FIG. 5 shows an analysis result by STEM line analysis, and Table 2 shows an average failure time measurement result.
As shown in FIG. 5, the sample of Comparative Example 3 that does not have the region A and does not satisfy the scope of the present invention because C C <C D is good under the current average failure time measurement condition. Results were not obtained.

  As described above, the multilayer ceramic capacitor having high temperature load characteristics according to the present invention can be used as a small electronic component element used on an electronic circuit for in-vehicle components.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 2 ... Dielectric layer 3 ... Internal electrode layer 4 ... External electrode 10 ... Capacitor element main body 20 ... Main component phase 21 ... Subcomponent phase 21a ... Region A
21b ... Area B
21c ... Region C
21d ... Region D
22 ... Grain boundary 30 ... Main component phase 31 ... Subcomponent phase 32 ... Grain boundary 40 ... Crystal grain 40e ... Main component phase 40a ... Region A
40b ... area B
40c ... area C
40d ... area D
41 ... Crystal particles

Claims (5)

  1. A ceramic capacitor in which dielectric layers and internal electrode layers are alternately laminated,
    The dielectric layer includes a main component phase mainly composed of a perovskite structure ceramic material represented by a general formula ABO 3 and at least one rare earth element as a subcomponent around the main component phase. A crystal component having a subcomponent phase dissolved in the phase, and
    The subcomponent phase is located on the opposite side of the main component phase from the region A surrounding the main component phase and in which the content of the rare earth element in solid solution does not change, A region B where the content of the rare earth element is changed, a region C that is located on the opposite side of the region A with respect to the region B, and the region C where the content of the rare earth element does not change, and the region C And a region D located between and the grain boundary,
    The rare earth element content in region A is C A , the rare earth element content in region B is C B , the rare earth element content in region C is C C , and the rare earth element content in region D is C C. when D, multilayer ceramic capacitors, wherein C a> C B> C C > the relationship between C D holds.
  2.   The multilayer ceramic capacitor according to claim 1, wherein 30% or more of all crystal grains contained in the dielectric layer are the crystal grains.
  3. 3. The multilayer ceramic capacitor according to claim 1, wherein a relationship between the content ratio C A and the content ratio C C is 15% ≦ (C A −C C ) / C C.
  4. The width of the region A is R A , and the width of the region C is R C, and 40% ≦ R A / R C ≦ 150%. Multilayer ceramic capacitor.
  5. 5. The multilayer ceramic capacitor according to claim 1, wherein the rare earth element is at least one element selected from Y, La, Gd, Tb, Dy, and Ho.
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JP4858248B2 (en) * 2007-03-14 2012-01-18 Tdk株式会社 Dielectric porcelain composition and electronic component
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WO2011125543A1 (en) * 2010-04-02 2011-10-13 株式会社村田製作所 Dielectric ceramic and multilayered ceramic capacitor including same
JP5531863B2 (en) * 2010-08-31 2014-06-25 Tdk株式会社 Dielectric ceramic composition and ceramic electronic component
JP5372034B2 (en) * 2011-01-24 2013-12-18 京セラ株式会社 Dielectric porcelain and multilayer electronic components
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