JP2018002498A - Dielectric composition and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric composition that has satisfactory high-temperature load life in a high temperature atmosphere at 250°C suitable for the uses of vehicle mounting and power devices including SiC or GaN semiconductors, and an electronic component prepared therewith.SOLUTION: A dielectric composition has a main component represented by chemical formula a{K(BaSr)NbO}+b{Ba(TiZr)O}, where the x and y satisfy 0.35≤x≤0.75 and 0.02≤y≤0.25, and the relationship between the a and b satisfies a+b=1.00 and 0.35≤a≤0.65.SELECTED DRAWING: Figure 1

Description

  In particular, the present invention relates to a dielectric composition suitable for use in a high temperature environment such as in-vehicle use, and an electronic component using the dielectric composition as a dielectric layer.

  Multilayer ceramic capacitors are mounted on many electronic devices because of their high reliability and low cost. Specific electronic devices include information terminals such as mobile phones, home appliances, and automobile electrical components. Among these, multilayer ceramic capacitors used for in-vehicle use may be required to be guaranteed to a higher temperature range than multilayer ceramic capacitors used in home appliances and information terminals. High reliability that is difficult is necessary. As a characteristic necessary for preventing the function of the capacitor from deteriorating, it is not destroyed with respect to the applied voltage, that is, a high DC withstand voltage (the DC voltage value when the leakage current value reaches 10 mA when the DC voltage is applied) The insulation resistance does not deteriorate even if DC voltage is applied for a long time in a high temperature atmosphere for continuous use, that is, a high high temperature load life (temperature) And after applying the voltage, it is important to have a time (decrease by an order of magnitude on the basis of the initial insulation resistance value).

  In particular, a multilayer ceramic capacitor for removing a surge voltage mounted on an inverter circuit using a power semiconductor such as SiC or GaN, which is considered to be used in a high temperature range of 150 ° C. or higher, has a wide range from −55 ° C. to about 250 ° C. Therefore, high reliability is required at a certain temperature.

Patent Document 1 discloses a composition formula (1) which is a dielectric ceramic composition that exhibits a sufficient dielectric constant and can obtain a stable capacitance temperature characteristic and a high resistivity ρ even at a high temperature of about 175 ° C. _{-a) (K 1-x Na} x) (Sr 1-y-z Ba y Ca z) 2 Nb 5 O 15 -a (Ba 1-b Ca b) a tungsten bronze structure compound represented by TiO ₃ with Multilayer ceramic capacitor using a dielectric ceramic composition containing a mixed crystal system with a perovskite structure-based compound as a main component and containing 0.1 to 40 mol parts of subcomponents with respect to 100 mol parts of the main components Techniques related to this are disclosed.

  Patent Document 2 discloses a perovskite type compound containing Ba and Ti, which is a dielectric ceramic that can be fired at a sufficiently low temperature and has a high specific resistance at a high temperature (150 ° C.). A dielectric ceramic characterized in that it may be substituted with Ca, and a part of Ti may be substituted with Zr) as a main component and contains 3 mol% or more of subcomponents such as Cu and Bi. Is disclosed.

WO2008 / 155945 WO2012 / 128175

  However, Patent Document 1 and Patent Document 2 have good insulation for a specific resistance with a measurement time of about 1 minute in a high temperature region (175 ° C. or 150 ° C.), but the DC voltage is applied for a long time. No mention is made of whether it can be improved to a continuously applied high temperature load life.

  The present invention has been made in view of the above problems, and has a good high-temperature load life in a high-temperature atmosphere of 250 ° C. suitable for in-vehicle use and power devices using SiC or GaN-based semiconductors. A dielectric composition and an electronic component using the same.

In order to achieve the above object, the dielectric composition of the present invention comprises:
In the chemical formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b dielectric composition having a main component represented by _{{Ba (Ti 1-y Zr} y) O 3},
X and y are 0.35 ≦ x ≦ 0.75 and 0.02 ≦ y ≦ 0.25,
The relationship between a and b is a + b = 1.00, and 0.35 ≦ a ≦ 0.65
It is characterized by being.

  When the dielectric composition has the above characteristics, it is possible to provide a dielectric composition having a good high temperature load life suitable for use in a temperature range of about 250 ° C.

  Furthermore, by using a dielectric layer made of the dielectric composition, it can be used in in-vehicle applications that require use in a low temperature region of −55 ° C. to a region of about 150 ° C. It is possible to provide a snubber capacitor for a power device using a required SiC or GaN-based semiconductor, a capacitor used for noise removal in an automobile engine room, and the like.

  INDUSTRIAL APPLICABILITY The present invention relates to a dielectric composition having a good high temperature load life in a high temperature atmosphere of 250 ° C. suitable for use in vehicles and for power devices using SiC or GaN-based semiconductors, and the use of the same. Electronic components can be provided.

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

  First, a multilayer ceramic capacitor, which is a main use of the dielectric composition of the present invention, will be described. FIG. 1 shows a cross-sectional view of a general multilayer ceramic capacitor.

  The multilayer ceramic capacitor 1 has 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 capacitor 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 are connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

  The thickness of the dielectric layer 2 is not particularly limited, but is preferably 100 μm or less per layer, more preferably 30 μm or less. Although the minimum of thickness is not specifically limited, For example, it is about 0.5 micrometer. According to the dielectric composition of the present invention, even when the interlayer thickness is 0.5 μm to 30 μm, the multilayer ceramic capacitor 1 having a dielectric layer having a high DC withstand voltage and a long high temperature load life is formed. I can do it.

  The number of laminated dielectric layers 2 is not particularly limited, but is preferably 20 or more, more preferably 50 or more.

  The conductive material contained in the internal electrode layer 3 is not particularly limited, but Ni, Ni alloy, Cu or Cu-based alloy is preferable. In addition, in Ni, Ni-type alloy, Cu, or Cu-type alloy, various trace components, such as P, may be contained about 0.1 mass% 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.

  More preferably, the conductive material contained in the internal electrode layer 3 is Ni or a Ni-based alloy because the constituent material of the dielectric layer 2 has reduction resistance. It is more preferable that this Ni or Ni-based alloy is a main component and it contains one or more subcomponents selected from Al, Si, Li, Cr, and Fe.

  Ni or Ni-based alloy which is the main component of the internal electrode layer 3 contains one or more subcomponents selected from Al, Si, Li, Cr and Fe, so that Ni reacts with oxygen in the atmosphere. Before becoming NiO, the subcomponent reacts with oxygen to form a subcomponent oxide film on the surface of Ni. Thereby, since oxygen in the outside air cannot react with Ni unless it passes through the oxide film of the subcomponent, Ni is hardly oxidized. Thereby, even if it is continuously used at a high temperature of 250 ° C., deterioration of continuity and conductivity due to oxidation of the internal electrode layer containing Ni as a main component hardly occurs.

  The conductive material contained in the external electrode 4 is not particularly limited, but in the present invention, inexpensive Ni, Cu, highly heat-resistant Au, Ag, Pd, and alloys thereof can be used. The thickness of the external electrode 4 may be determined as appropriate according to the application and the like, but is usually preferably about 10 to 50 μm.

  Next, the dielectric composition according to this embodiment will be described in detail.

The dielectric composition according to the present embodiment, the main component of formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b {Ba (Ti 1-y Zr y) O 3} In the dielectric composition, x and y are 0.35 ≦ x ≦ 0.75 and 0.02 ≦ y ≦ 0.25, and the relationship between a and b is a + b = 1.00 Yes, 0.35 ≦ a ≦ 0.65.

  When the dielectric composition has the above characteristics, it is possible to provide a dielectric composition having a good high temperature load life suitable for use at 250 ° C. The factors for obtaining such effects are shown below.

The inventors have developed a perovskite type represented by the chemical formula Ba (Ti _1-y Zr _y ) O _{3 into} a tungsten bronze type complex oxide represented by the chemical formula K (Ba _1-x Sr _x ) ₂ Nb ₅ O _15. It has been found that by containing the composite oxide, an effect of suppressing the movement of oxygen defects, which is considered to be a cause of deterioration of the high temperature load life, can be obtained. As a result, in a dielectric composition containing only K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ as a main component and a dielectric composition, or a Ba (Ti _1-y Zr _y ) O ₃ only as a main component, It is believed that it was possible to improve the high temperature load life at 250 ° C., which was difficult to realize.

In the present embodiment, a tungsten bronze-type composite oxide represented by K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and a perovskite-type composite represented by Ba (Ti _1-y Zr _y ) O ₃ An oxide may exist as solid solution crystal particles, or may exist as individual crystal particles. In either case, a good high temperature load life can be obtained.

Ba of K (Ba _1-x Sr _x ) ₂ Nb ₅ O _{15 in} the chemical formula is substituted by Sr. The substitution amount x is 0.35 ≦ x ≦ 0.75. When the substitution amount x is less than 0.35, sufficient insulation is difficult to obtain, and as a result, a good high-temperature load life tends to be difficult to obtain. On the other hand, if the substitution amount x exceeds 0.75, the leakage current when a DC voltage is applied tends to increase rapidly at 250 ° C. As a result, it tends to be difficult to obtain a sufficient high temperature load life.

In the chemical formula, Ti in Ba (Ti _1-y Zr _y ) O ₃ is substituted by Zr. The substitution amount y is 0.02 ≦ y ≦ 0.25. When the amount of substitution y is less than 0.02, it is difficult to obtain a sufficient high temperature load life because the effect of suppressing the migration of oxygen vacancies considered to be a cause of deterioration of the high temperature load life is not obtained. On the other hand, if the substitution amount y exceeds 0.25, excess Zr tends to form a heterogeneous phase at the grain boundary, and the variation in the particle diameter of crystal grains in the dielectric composition tends to increase. As a result, a low high temperature load life is obtained.

  The relationship between a and b in the chemical formula is a + b = 1.00, and 0.35 ≦ a ≦ 0.65. If the value a is less than 0.35 or the value a exceeds 0.65, it is difficult to obtain an effect of suppressing the movement of oxygen defects, which is considered to be a cause of deterioration of the high temperature load life, and a sufficient high temperature load is obtained. It tends to be difficult to obtain a lifetime.

As a desirable mode of the present invention, when the dielectric composition is composed of a plurality of crystal particles and the area ratio of the entire crystal particles constituting the dielectric composition is 100%, K ( The area ratio of crystal grains composed of Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is α (%), and the area ratio of crystal grains composed of Ba (Ti _1-y Zr _y ) O ₃ is β ( %), The relationship between α and β is 0.55 ≦ α / β ≦ 1.85, and preferably 80% ≦ α + β.

  The inventors have found that the generation of electron avalanche at a high temperature can be further suppressed by controlling the dielectric composition to the above contents. For this reason, it has become possible to obtain a high DC withstand voltage at 250 ° C., which was difficult with conventional dielectric compositions. As a result, it is considered possible to provide a dielectric composition having both a high DC withstand voltage and a good high-temperature load life at 250 ° C., and an electronic component using the dielectric composition.

  In the case of a multilayer ceramic capacitor sample which is an example of the present embodiment, the above-described area ratio is obtained by performing microsampling using FIB (Focused Ion Beam) to produce a TEM sample of a dielectric layer, It is calculated | required by performing STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometry) mapping using a scanning transmission electron microscope. The field of view of mapping is 7 μm × 7 μm, and it is preferable to perform mapping of 10 fields or more for each sample. Further, the area ratio can also be obtained by performing element mapping on the polished dielectric layer cross section by EPMA (Elctron Probe Micro Analyzer). The visual field of mapping at that time is 10 μm × 10 μm, and mapping of five or more visual fields is performed for each sample, and the area ratio may be calculated from the obtained element map.

  Furthermore, as a desirable aspect of the present invention, the x, y, α, and β are 0.35 ≦ x ≦ 0.50, 0.04 ≦ y ≦ 0.15, 0.70 ≦ α / β ≦ 1. Preferably, 50, 90% ≦ α + β. Thereby, generation | occurrence | production of the electron avalanche at high temperature can be suppressed more, and the effect which suppresses the increase in the leakage current in a high temperature load test can be heightened more. As a result, it becomes easier to obtain a higher DC withstand voltage and a longer high temperature load life.

  As described above, since the dielectric composition according to the present embodiment exhibits good characteristics in the high temperature region, it is preferably used in the operating temperature range (−55 ° C. to 250 ° C.) of the SiC or GaN-based power device. it can. Further, it can be suitably used as an electronic component for removing noise in a severe environment such as an engine room of an automobile.

_{Incidentally, K (Ba 1-x Sr} x) 2 Nb 5 O 15 in the formula, the molar ratio of the K sites, Ba site, Nb site, O site basically 1: 2: 5: 15 However, as long as the tungsten bronze structure can be maintained, it may be slightly increased or decreased. Similarly, Ba (Ti _1-y Zr _y ) O ₃ basically has a molar ratio of each Ba site, Ti site, and O site of 1: 1: 3, but as long as the perovskite structure can be maintained, You may increase or decrease.

  In addition, the dielectric composition according to the present embodiment may contain minute impurities and subcomponents as long as the direct current withstand voltage at high temperatures and the high temperature load life that are the effects of the present invention are not significantly deteriorated. . For example, Mg, Mn, Si, V, Cr, etc. Therefore, the content of the main component is not particularly limited, but is, for example, 70 mol% or more and 100 mol% or less with respect to the entire dielectric composition containing the main component.

Next, a method for manufacturing the dielectric composition according to this embodiment will be described. A known method may be adopted as a method for manufacturing the dielectric composition. For example, a solid phase method or the like in which starting materials such as oxide powder and carbonate are mixed and the obtained mixed powder is heat-treated and synthesized may be employed. Here, two manufacturing methods are described. First production method (production method 1 of the dielectric _{composition),} the dielectric of _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b {Ba (Ti 1-y Zr y) O 3} body composition may be crystalline particles of solid solution, the solid solution crystal grains and _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 or _{Ba (Ti 1-y Zr y} ) O 3 crystal grains are composed of the Is a manufacturing method in the case where it may be mixed. Second production method (production method 2 of the dielectric _{composition), K (Ba 1-x Sr} x) 2 Nb 5 O 15 or _{Ba (Ti 1-y Zr y} ) O 3 crystal grains are composed of Is increased, that is, the area ratio of the crystal particles composed of the solid solution is decreased.

Dielectric composition manufacturing method 1
_{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 , the average particle diameter is prepared following _{K 2 CO 3, BaCO 3,} SrCO 3, Nb 2 O 5 powder 1.0μm as the starting material. _{Also, Ba (Ti 1-y Zr} y) O 3 has an average particle diameter is prepared following BaCO _{3, TiO 2,} ZrO 2 powder 1.0μm as the starting material. After these starting materials are weighed to a predetermined ratio, wet mixing is performed for a predetermined time using a ball mill or the like. After drying the mixed powder, heat treatment is performed at 1100 ° C. or lower in the air, and a {K (Ba _1−x Sr _x ) ₂ Nb ₅ O ₁₅ } + b {Ba () having an average particle diameter of 0.5 μm to 2.0 μm. _{Ti 1-y Zr y) O} 3} may obtain a calcined powder. Further, using the above starting materials, heat treatment at 1000 ° C. or less is performed, calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and heat treatment at 1100 ° C. or less are performed, and Ba (Ti _{1 1− y} Zr _y ) O ₃ calcined powder is prepared separately, and then calcined powder is mixed, and a {K (Ba _1-x Sr _x ) ₂ having an average particle size of 0.5 μm to 2.0 μm. _{nb 5 O 15} + b {} Ba (Ti 1-y Zr y) O 3} may obtain a calcined powder.

Production method 2 of dielectric composition
When increasing the area ratio of crystal grains composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ or Ba (Ti _1-y Zr _y ) O ₃ , the dielectric composition is changed as follows: To manufacture.

First, the calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is K ₂ CO ₃ , BaCO ₃ , SrCO ₃ , Nb ₂ O ₅ powder having an average particle size of 1.0 μm or less as a starting material. Prepare. After weighing to a predetermined ratio, wet mixing is performed for a predetermined time using a ball mill or the like. After drying the mixed powder, two steps of heat treatment at 1000 ° C. or less (formation of a single phase) and heat treatment at 850 ° C. or less (homogenization of the element distribution inside the particles) are performed in the atmosphere. obtain. Since the obtained calcined powder has been subjected to a two-step heat treatment, almost no heterogeneous phase is formed, and since there is little bias in the element part distribution inside the particles, abnormal grain growth during the main firing, It becomes possible to suppress a reaction with Ba (Ti _1-y Zr _y ) O ₃ .

Next, as the calcined powder of Ba (Ti _1-y Zr _y ) O ₃ , BaCO ₃ , TiO ₂ and ZrO ₂ powders having an average particle size of 1.0 μm or less are prepared as starting materials. Thereafter, in the same manner as the method for producing the calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ , after being weighed to a predetermined ratio, wet-mixed using a ball mill or the like, and in the air A two-stage heat treatment of a heat treatment of 1100 ° C. or lower and a heat treatment of 850 ° C. or lower is performed to obtain a calcined powder. Since the obtained calcined powder has been subjected to a two-step heat treatment, almost no heterogeneous phase is formed, and since there is little bias in the element part distribution inside the particles, abnormal grain growth during the main firing, it is possible to suppress the reaction between the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15.

Thereafter, the obtained calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and calcined powder of Ba (Ti _1-y Zr _y ) O ₃ are mixed and pulverized, and the average particle size is A mixed powder of 0.5 μm to 2.0 μm is prepared.

  Next, an example of a method for manufacturing the multilayer ceramic capacitor shown in FIG. 1 will be described.

  In the multilayer ceramic capacitor 1 of the present embodiment, a green chip is produced by a normal printing method or a sheet method using a paste as in the case of a conventional multilayer ceramic capacitor, fired, and then fired by applying an external electrode. It is manufactured by doing. Hereinafter, the manufacturing method will be specifically described.

  The mixed powder obtained above is made into a paint to prepare a dielectric layer paste. The dielectric layer paste may be an organic paint obtained by kneading a dielectric mixed powder and an organic vehicle, or may be a water-based paint.

  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 terpineol, butyl carbitol, acetone and the like according to a method to be used such as a printing method or a sheet method.

  Further, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder or a dispersant is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. may be used.

  The internal electrode layer paste is obtained by kneading the above-mentioned organic vehicle with various conductive metals and alloys as described above, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing. Prepare.

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

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1 mass%-about 5 mass% for a binder, and about 10 mass%-about 50 mass% for a solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by mass or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  When the sheet method is used, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are stacked to form a green chip.

Before firing, 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 500 ° C, and the temperature holding time is preferably 0.5 hours to 24 hours. The firing atmosphere is air or a reducing atmosphere. Further, in the above-described binder removal process, for example, a wetter or the like may be used to wet the N ₂ gas, mixed gas, or the like. In this case, the water temperature is preferably about 5 ° C to 75 ° C.

  Moreover, the holding temperature at the time of baking becomes like this. Preferably it is 1000 to 1400 degreeC, More preferably, it is 1100 to 1350 degreeC. If the holding temperature is lower than the above range, the densification becomes insufficient. If the holding temperature exceeds the above range, the electrode breaks due to abnormal sintering of the internal electrode layer, or the capacitance change rate deteriorates due to diffusion of the constituent material of the internal electrode layer. Is likely to occur. Moreover, when the said range is exceeded, there exists a possibility that a crystal grain may coarsen and a DC withstand voltage may be reduced.

Further, when increasing the area ratio of the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 with formed crystal grains and _{Ba (Ti 1-y Zr y} ) crystal grains composed of _{O 3} is below It is important to strictly control the conditions shown in (1). In order to obtain independent crystal particles without solid solution, the rate of temperature rise is preferably 100 ° C./hour to 5000 ° C./hour, more preferably 1000 ° C./hour to 5000 ° C./hour. Further, in order to control the particle size distribution after sintering within a range of 0.5 μm to 5.0 μm, in order to suppress volume diffusion between crystal particles, the temperature holding time is preferably 0.5 hours to 2.0 hours. Time, more preferably 0.5 hour to 1.0 hour, and the cooling rate is preferably 100 ° C./hour to 500 ° C./hour, more preferably 200 ° C./hour to 300 ° C./hour.

Moreover, as an atmosphere for baking, it is preferable to use a humidified mixed gas of N ₂ and H ₂ and to fire at an oxygen partial pressure of 10 ⁻² to 10 ⁻⁹ Pa. In the case of increasing the area ratio of crystal grains composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and crystal grains composed of Ba (Ti _1-y Zr _y ) O ₃ , an oxygen partial pressure of 10 ⁻ More preferably, it is ² to 10 ⁻⁵ Pa. By firing in an atmosphere having a high oxygen partial pressure, volume diffusion between crystal grains can be suppressed, so that an effect of making it difficult to form a solid solution is obtained. However, when firing in a state where the oxygen partial pressure is high, in the case of an internal electrode layer made of Ni, Ni is oxidized and the conductivity as an electrode is lowered. In this case, by adding one or more subcomponents selected from Al, Si, Li, Cr, and Fe to the conductive material mainly composed of Ni which is a more preferable form of the present embodiment, Ni Thus, even in an atmosphere having a high oxygen partial pressure, it is possible to ensure conductivity as an internal electrode layer.

  After firing, the obtained capacitor element body is annealed as necessary. The annealing conditions may be known conditions. For example, it is preferable that the oxygen partial pressure during annealing is higher than the oxygen partial pressure during firing, and the holding temperature is 1000 ° C. or lower.

  Moreover, although the manufacturing method which performs a binder removal process, baking, and an annealing process independently is described above, you may carry out continuously.

  The capacitor element main body obtained as described above is subjected to end face polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is applied and fired 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.

  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.

  EXAMPLES Hereinafter, although the specific Example of this invention is given and this invention is demonstrated further in detail, this invention is not limited to these Examples. Note that samples marked with * in the table are outside the scope of the present embodiment.

Example 1
In Example 1, the case where a calcined powder of a dielectric composition was produced according to the above-described dielectric composition production method 1 was described.
First, K ₂ CO ₃ , BaCO ₃ , SrCO ₃ , Nb ₂ O ₅ , TiO ₂ , ZrO ₂ powder having an average particle size of 1.0 μm or less is prepared as a starting material, and a chemical formula a {K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ } + b {Ba (Ti _1-y Zr _y ) O ₃ } was weighed so as to satisfy x, y, a, and b described in each sample number in Table 1. Thereafter, wet mixing was performed for 17 hours by a ball mill using ethanol as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a mixed raw material powder. Thereafter, heat treatment was performed in the atmosphere at a holding temperature of 1050 ° C. and a holding time of 24 hours to obtain a dielectric composition raw material powder.

  To 1000 g of the dielectric composition raw material powder obtained above, 700 g of a solvent obtained by mixing a toluene + ethanol solution, a plasticizer and a dispersant in a ratio of 90: 6: 4 is added, and a usual well-known dispersion method is used. Dispersion was carried out for 2 hours using a basket mill to prepare a dielectric layer paste. The viscosity of these pastes was adjusted to about 200 cps.

As the raw material for the internal electrode layer, Ni having an average particle diameter of 0.2 μm and Al and Si oxides of 0.1 μm or less are prepared, and the total amount of the secondary components Al and Si is 5% by mass with respect to Ni. Weighed so that Thereafter, heat treatment was performed in a humidified gas mixture of N ₂ and H ₂ at 1200 ° C. or higher, and pulverization was performed using a ball mill or the like, thereby preparing several raw material powders having an average particle size of 0.20 μm.

  The raw material powder 100% by mass, organic vehicle (ethyl cellulose resin 8% by mass dissolved in butyl carbitol 92% by mass) 30% by mass, and butyl carbitol 8% by mass are kneaded and formed into a paste by three rolls. An internal electrode layer paste was obtained.

  And the green sheet was formed on the PET film so that the thickness after drying might be set to 12 micrometers using the produced dielectric layer paste. Next, the internal electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled from the PET film to produce a green sheet having the internal electrode layer. Next, a plurality of green sheets having internal electrode layers were laminated and pressure-bonded to form a green laminate, and the green laminate was cut into a predetermined size to obtain a green chip.

  Next, the obtained green chip was subjected to binder removal processing, firing, and annealing treatment to obtain a multilayer ceramic sintered body. The conditions for the binder removal treatment, firing and annealing are as follows. Moreover, a wetter was used for humidifying each atmospheric gas.

(Binder removal)
Temperature increase rate: 100 ° C / hour Holding temperature: 400 ° C
Temperature holding time: 8.0 hours Atmospheric gas: Mixed gas of N ₂ and H ₂ humidified (firing)
Temperature increase rate: 500 ° C./hour holding temperature: 1100 ° C. to 1350 ° C.
Temperature holding time: 2.0 hours Cooling rate: 100 ° C./hour Atmosphere gas: Mixed gas of humidified N ₂ and H ₂ Oxygen partial pressure: 10 ⁻⁵ to 10 ⁻⁹ Pa
(Annealing treatment)
Holding temperature: 800 ° C to 1000 ° C
Temperature holding time: 2.0 hours temperature rise, temperature drop rate: 200 ° C./hour Atmosphere gas: humidified N ₂ gas

  As a result of the composition analysis of each sample using ICP emission spectroscopic analysis for each obtained multilayer ceramic sintered body, it was confirmed that it was a value almost equivalent to the dielectric composition described in Table 1. did.

  After polishing the end face of the obtained multilayer ceramic sintered body by sand blasting, an In—Ga eutectic alloy was applied as an external electrode, and sample No. 1 having the same shape as the multilayer ceramic capacitor shown in FIG. 1 to sample no. Twenty-four laminated ceramic capacitor samples were obtained. The size of the obtained multilayer ceramic capacitor sample was 3.2 mm × 1.6 mm × 1.2 mm, the dielectric layer thickness was 10 μm, the internal electrode layer thickness was 2 μm, and the dielectric sandwiched between the internal electrode layers The number of layers was 50.

The obtained sample No. 1 to sample no. About 24 laminated ceramic capacitor samples, relative dielectric constant, direct current withstand voltage, high temperature load life, crystal grains composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ by image analysis and Ba (Ti _1-y The area ratio of crystal grains composed of Zr _y ) O ₃ was measured and evaluated by the method shown below, and is shown in Table 2.

[Relative permittivity]
A signal having a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms was input to the multilayer ceramic capacitor sample at 250 ° C. with a digital LCR meter (Y284, 4284A), and the capacitance was measured. The relative dielectric constant (no unit) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the capacitance C obtained as a result of the measurement. A higher relative dielectric constant is preferable, and a value of 1000 or more was judged to be good.

[DC withstand voltage]
A DC voltage was applied to the multilayer ceramic capacitor sample at 250 ° C. at a voltage increase rate of 100 V / sec, and the DC withstand voltage was determined when the leakage current exceeded 10 mA. The DC withstand voltage is preferably 50 V / μm or more, and it is determined that 100 V / μm or more is good. More preferably, the DC withstand voltage is 150 V / μm or more.

[High temperature load life]
In the high-temperature load life test, a 200 voltage sample was applied to each sample number at a temperature of 250.degree. A sample whose insulation resistance was deteriorated by one digit was determined to be a failure, and an average failure time (MTTF) of 50% was determined from a Weibull analysis of the failure time. In the present invention, the mean failure time (MTTF) is defined as the high temperature load life. The longer the high temperature load life, the better, and it was judged that 80 hours or more, more preferably 120 hours or more was good.

[Evaluation of α and β by image analysis]
Microsampling was performed on the multilayer ceramic capacitor sample obtained by firing using FIB (Focused Ion Beam) to prepare a TEM sample of a dielectric layer. This TEM sample was subjected to STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometry) mapping using JEM2200FS, a scanning transmission electron microscope manufactured by JEOL. The visual field of mapping was 7 μm × 7 μm, and 10 or more visual fields were mapped to each sample. Using elemental map obtained by these _{methods, K (Ba 1-x Sr} x) 2 Nb 5 O 15 K is an element of, Ba, Sr, and _{Nb, Ba (Ti 1-y} Zr y) O The area of Ba, Ti, Zr which is the element of ₃ is specified, and the average area of the result of each 10 fields or more is used, and the crystal composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ Α (%), which is the area ratio of the particles, and β (%), which is the area ratio of the crystal particles composed of Ba (Ti _1-y Zr _y ) O ₃ were calculated. In this embodiment, in order to obtain a high DC withstand voltage and a good high-temperature load life, it is preferable that 0.55 ≦ α / β ≦ 1.85 and 80% ≦ α + β.

  According to the results shown in Table 2, sample No. 1 to Sample No. 24, the multilayer ceramic capacitor sample within the range of the present embodiment has a relative dielectric constant of 1000 or more at 250 ° C., and at 250 ° C., the direct current voltage is 20 V / μm with respect to the thickness of the dielectric layer. It was confirmed that the high temperature load life when continuously applied was 80 hours or more.

In contrast, sample no. 1 is because the chemical formula K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is less than 0.35 and x is out of the range of the present embodiment. It has reached the end of its life. Sample No. 7, x exceeded 0.75 and was outside the range of the present embodiment, so it was confirmed that the high temperature load life was as low as 55 hours.

Sample No. 8 suppresses the movement of oxygen defects considered to be a cause of deterioration of the high-temperature load life because _y of the chemical formula Ba (Ti _1-y Zr _y ) O ₃ is less than 0.02 and out of the range of the present embodiment. No action is obtained, and the lifetime is as low as 65 hours. On the other hand, sample No. No. 13, since y exceeds 0.25 and is outside the range of the present embodiment, excess Zr is liable to form a heterogeneous phase at the grain boundary, and there is also a variation in the particle size of crystal grains in the dielectric composition. Since it tends to be large, it was confirmed that the high temperature load life was as low as 40 hours.

  Furthermore, sample no. No. 14, a is less than 0.35, sample No. Since 20 is outside the range of this embodiment in which a exceeds 0.65, the high-temperature load life is as low as 65 hours and 55 hours, respectively.

Example 2
Here, by using the manufacturing method 2 of the dielectric composition indicated above, it is composed of the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 or _{Ba (Ti 1-y Zr y} ) O 3 The result of having verified about the case where the area ratio of the crystal grain which has been increased was shown.

_{First, K (Ba 1-x Sr} x) 2 Nb 5 O 15 was prepared an average particle size 1.0μm or less of _{K 2 CO 3, BaCO 3,} SrCO 3, Nb 2 O 5 powder as a starting material. The above starting materials were weighed so as to have x shown in Table 3, and wet mixed by a ball mill for 17 hours using ethanol as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a mixed raw material powder. Thereafter, a first heat treatment is performed at a holding temperature of 900 ° C. to 1000 ° C. for a holding time of 10 hours to 24 hours, and then a second heat treatment at a holding temperature of 750 ° C. to 850 ° C. for a holding time of 10 hours to 24 hours. by _performing, to obtain a calcined powder of _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15.

Next, Ba (Ti _1-y Zr _y ) O ₃ prepared BaCO ₃ , TiO ₂ , and ZrO ₂ powders having an average particle size of 1.0 μm or less as a starting material. The above starting materials were weighed so that y shown in Table 3 was obtained, and wet mixed by a ball mill for 17 hours using ethanol as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a mixed raw material powder. Thereafter, a first heat treatment is performed at a holding temperature of 950 ° C. to 1100 ° C. for a holding time of 10 hours to 24 hours, and then, a second heat treatment at a holding temperature of 750 ° C. to 850 ° C. for a holding time of 10 hours to 24 hours. By carrying out, a calcined powder of Ba (Ti _1-y Zr _y ) O ₃ was obtained.

The obtained calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and calcined powder of Ba (Ti _1-y Zr _y ) O ₃ were weighed so as to have the blending ratio shown in Table 3. Thereafter, wet mixing was performed for 17 hours to 36 hours with a ball mill using ethanol as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a dielectric composition raw material powder shown in Table 3.

  Thereafter, a dielectric layer paste and an internal electrode layer paste were prepared in the same manner as in Example 1.

  And the green chip was produced by the method similar to Example 1. FIG.

  Next, the obtained green chip was subjected to binder removal processing, firing, and annealing treatment to obtain a multilayer ceramic sintered body. It should be noted that the conditions for binder removal, firing and annealing are as follows. Moreover, a wetter was used for humidifying each atmospheric gas.

(Binder removal)
Temperature increase rate: 100 ° C / hour Holding temperature: 400 ° C
Temperature holding time: 8.0 hours Atmospheric gas: Mixed gas of N ₂ and H ₂ humidified (firing)
Temperature increase rate: 2000 ° C./hour holding temperature: 1100 ° C. to 1350 ° C.
Temperature holding time: 1.0 hour Cooling rate: 200 ° C./hour Atmospheric gas: Mixed gas of humidified N ₂ and H ₂ Oxygen partial pressure: 10 ⁻² to 10 ⁻⁵ Pa
(Annealing treatment)
Holding temperature: 500 ° C to 1000 ° C
Temperature holding time: 2.0 hours temperature rise, temperature drop rate: 200 ° C./hour Atmosphere gas: humidified N ₂ gas

When the X-ray diffraction (XRD) measurement of the crystal structure of the dielectric layer was performed on the obtained multilayer ceramic sintered body, K (Ba _1-x Sr _x ) ₂ Nb was obtained for the multilayer ceramic sintered body according to this embodiment. It was confirmed that ₅ O ₁₅ and Ba (Ti _1-y Zr _y ) O ₃ were each present alone.

  Further, as a result of the composition analysis of each sample using ICP emission spectroscopic analysis for each of the obtained multilayer ceramic sintered bodies, values almost equivalent to the dielectric compositions described in Tables 3 and 4 were obtained. It was confirmed that.

  After polishing the end face of the obtained multilayer ceramic sintered body by sand blasting, an In—Ga eutectic alloy was applied as an external electrode, and sample No. 1 having the same shape as the multilayer ceramic capacitor shown in FIG. 25 to sample no. 48 multilayer ceramic capacitor samples were obtained. The size of the obtained multilayer ceramic capacitor sample was 3.2 mm × 1.6 mm × 1.2 mm, the dielectric layer thickness was 10 μm, the internal electrode layer thickness was 2 μm, and the dielectric sandwiched between the internal electrode layers The number of layers was 50.

The obtained sample No. 25 to sample no. For 48 multilayer ceramic capacitor samples, using the same measurement method as in Example 1, relative dielectric constant, DC withstand voltage, high temperature load life, K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ by image analysis Table 4 shows the area ratios of the crystal grains composed and the crystal grains composed of Ba (Ti _1-y Zr _y ) O ₃ .

  According to the results shown in Table 4, Sample No. 25 to Sample No. 48, the multilayer ceramic capacitor sample in the range of the present embodiment, 0.55 ≦ α / β ≦ 1.85, and 80% ≦ α + β has a relative dielectric constant at 250 ° C. of 1000 or more. The DC withstand voltage at 250 ° C. is 100 V / μm, and the high temperature load life when the DC voltage is continuously applied at 250 ° C. so as to be 20 V / μm with respect to the thickness of the dielectric layer is 100 hours or more. Was confirmed.

Further, according to the results shown in Tables 2 and 4, the area ratio of crystal grains composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is expressed as α (%), Ba (Ti _1-y When the area ratio of crystal grains composed of Zr _y ) O ₃ is β (%), the relationship between α and β is 0.55 ≦ α / β ≦ 1.85, and 80% ≦ α + β is satisfied. It was confirmed that the multilayer ceramic capacitor sample that did not have a DC withstand voltage at 250 ° C. of less than 100 V / μm.
Thus, not only controlling the material composition of the dielectric composition but also controlling the composition of the crystal grains constituting the dielectric composition at 250 ° C., which has been difficult to realize so far. It was found that a high high temperature load life and a high DC withstand voltage can be achieved at the same time.

Example 3
Using the same method as in Example 2, the dielectric composition raw material powder shown in Table 5 was produced.

  A multilayer ceramic capacitor sample was produced from the obtained dielectric composition raw material powder using the same method as in Example 2, and the same measurement and evaluation as in Example 1 and Example 2 were performed. The results are shown in Table 6. It was.

  According to the results shown in Table 6, the sample No. in the range of the present embodiment. 49-Sample No. 69, x, y, α, β are 0.35 ≦ x ≦ 0.50, 0.04 ≦ y ≦ 0.15, 0.70 ≦ α / β ≦ 1.50, 90% ≦ α + β. The multilayer ceramic capacitor sample satisfying the above has a relative dielectric constant of 1000 or more at 250 ° C., a direct-current withstand voltage at 250 ° C. of 150 V / μm, and at 250 ° C., 20 V / μm with respect to the thickness of the dielectric layer. Thus, it was confirmed that the high-temperature load life when continuously applying a DC voltage was 120 hours or more, indicating better characteristics.

  It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the scope and meaning equivalent to the scope of claims.

  Since it has a high DC withstand voltage and high temperature load life in the high temperature region of 250 ° C, it is an electronic component mounted in the vicinity of the power device using SiC or GaN-based semiconductors in an environment close to the engine room for in-vehicle use. It can also be applied to other applications.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Dielectric layer 3 Internal electrode layer 4 External electrode 10 Capacitor element body

Claims (4)

In the chemical formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b dielectric composition having a main component represented by _{{Ba (Ti 1-y Zr} y) O 3},
X and y are 0.35 ≦ x ≦ 0.75 and 0.02 ≦ y ≦ 0.25,
The relationship between a and b is a + b = 1.00, and 0.35 ≦ a ≦ 0.65
A dielectric composition characterized by the above. The dielectric composition is composed of a plurality of crystal grains, and K (Ba _1-x Sr _x ) ₂ Nb ₅ when the area ratio of the entire crystal grains constituting the dielectric composition is 100%. When the area ratio of crystal grains composed of O ₁₅ is α (%) and the area ratio of crystal grains composed of Ba (Ti _1-y Zr _y ) O ₃ is β (%), α and β The dielectric composition according to claim 1, wherein 0.55 ≦ α / β ≦ 1.85 and 80% ≦ α + β.   X, y, α, β are 0.35 ≦ x ≦ 0.50, 0.04 ≦ y ≦ 0.15, 0.70 ≦ α / β ≦ 1.50, 90% ≦ α + β. The dielectric composition according to claim 2, characterized in that:   An electronic component having a dielectric layer and an internal electrode layer, wherein the dielectric layer is made of the dielectric composition according to any one of claims 1 to 3.

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