JP6665711B2 - Dielectric composition and electronic component - Google Patents

Description

  The present invention particularly relates to a dielectric composition suitable for use in a high-temperature environment such as for a vehicle, 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 examples of electronic devices include information terminals such as mobile phones, home appliances, and automotive electrical components. Among them, multilayer ceramic capacitors used for vehicles are sometimes required to be guaranteed up to higher temperatures than multilayer ceramic capacitors used for home appliances and information terminals, etc. High reliability, which is difficult, is required. As a characteristic necessary to prevent the function of the capacitor from deteriorating, it does not break down with respect to an applied voltage, that is, a high DC withstand voltage (a DC voltage is applied and a DC voltage value when a leakage current value reaches 10 mA is reduced). Insulation resistance hardly deteriorates even when a DC voltage is applied for a long time in a high-temperature atmosphere during continuous use, that is, a high high-temperature load life (temperature divided by the dielectric layer) After applying the voltage, it is important to have a time until the value is reduced by one digit based on the initial insulation resistance value).

  In particular, a multilayer ceramic capacitor for surge voltage removal 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 more, has a wide range from −55 ° C. to 250 ° C. High reliability is required at these temperatures.

Patent Literature 1 discloses a composition formula (1) that is a dielectric ceramic composition that shows a sufficient capacitance temperature characteristic and a high resistivity ρ at a high temperature of about 175 ° C. while showing a sufficient dielectric constant. _{-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 A multilayer ceramic capacitor using a dielectric ceramic composition containing, as a main component, a mixed crystal system with a perovskite structure-based compound, and also containing 0.1 to 40 mole parts of an auxiliary component with respect to 100 mole parts of the main component. Is disclosed.

Patent Document 2, the main composition having good temperature characteristics and high temperature load lifetime _{[(Ca x Sr 1-x)} O ] m _{[(Ti y Zr 1-y)} O 2 ] (Note, 0 ≦ x ≦ 1, 0 ≦ y ≦ 0.10 , is 0.75 ≦ m ≦ 1.04) Yes, Mn oxide as a secondary component, Al oxides and _{[(Ba z Ca 1-z)} O ] _v SiO ₂ A technique for a non-reducible dielectric porcelain material containing (where 0 ≦ z ≦ 1, 0.5 ≦ v ≦ 4.0) is disclosed.

WO2008 / 155945 Japanese Patent Application No. 10-90751

  However, the above-mentioned Patent Document 1 has a good insulating property with respect to a specific resistance of about 1 minute in a high temperature range (175 ° C.), but has a high temperature load in which a DC voltage is continuously applied for a long time. It is not mentioned whether the life can be improved. In Patent Document 2, although having an excellent high-temperature load life at 200 ° C., it is difficult to obtain a desired capacitance because the obtained dielectric constant is low.

  The present invention has been made in view of the above-mentioned problems, and has a relatively high relative dielectric constant under a high-temperature atmosphere of 250 ° C. corresponding to a vehicle-mounted device and a power device using a SiC or GaN-based semiconductor, An object of the present invention is to provide a dielectric composition having a good high-temperature load life and an electronic component using the same.

In order to achieve the above object, the dielectric composition of the present invention,
The dielectric composition having a main component represented by the chemical formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b {(Ca 1-y Sr y) (Zr 1-z Ti z) O 3} Wherein the x, y, and z are:
0.35 ≦ x ≦ 0.75, 0.01 ≦ y ≦ 0.25, 0.01 ≦ z ≦ 0.25,
The relationship between a and b is a + b = 1.00, and 0.32 ≦ a ≦ 0.66
It is characterized by being.

  Since the dielectric composition has the above characteristics, it is possible to provide a dielectric composition having a good high-temperature load life and a relatively high relative dielectric constant suitable for use in a temperature range of about 250 ° C. It becomes possible.

  Further, by using the dielectric layer composed of the dielectric composition, the temperature range is as low as −55 ° C. for use in vehicles required to be used in a range of about 150 ° C., and even higher in a range of about 250 ° C. It is possible to provide a required snubber capacitor for a power device using a SiC or GaN-based semiconductor, a capacitor for removing noise in an engine room of an automobile, and the like.

  The present invention relates to a dielectric material having a relatively high relative dielectric constant and a good high-temperature load life under a high-temperature atmosphere of 250 ° C., which is suitable for a vehicle and a power device using a SiC or GaN-based semiconductor. A composition and an electronic component using the composition can be provided.

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

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

  The multilayer ceramic capacitor 1 has a capacitor element body 10 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 alternately arranged inside the capacitor element body 10. The shape of the capacitor element body 10 is not particularly limited, but is generally a rectangular parallelepiped. The dimensions are not particularly limited, and may be appropriately determined according to the application.

  The internal electrode layers 3 are laminated such that each end face is alternately exposed on the surfaces of two opposing 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 faces of the alternately arranged internal electrode layers 3 to form 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. The lower limit of the thickness is not particularly limited, but is, for example, about 0.5 μm. According to the dielectric composition of the present invention, a multilayer ceramic capacitor 1 having a dielectric layer having a high DC withstand voltage and a long high-temperature load life is formed even when the interlayer thickness is 0.5 μm to 30 μm. I can do it.

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

  The conductive material contained in the internal electrode layer 3 is not particularly limited, but is preferably Ni, a Ni alloy, Cu, or a Cu-based alloy. Note that Ni, Ni-based alloy, Cu or Cu-based alloy may contain various trace components such as P in an amount of about 0.1% by mass or less. The internal electrode layer 3 may be formed using a commercially available electrode paste. The thickness of the internal electrode layer 3 may be appropriately determined according to the use and the like.

  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 Ni or a Ni-based alloy be a main component, and further contain one or more kinds of subcomponents selected from Al, Si, Li, Cr, and Fe.

  By allowing Ni or a Ni-based alloy, which is the main component of the internal electrode layer 3, to contain one or more subcomponents selected from Al, Si, Li, Cr, and Fe, Ni reacts with oxygen in the atmosphere. Before becoming NiO, the above-mentioned subcomponent reacts with oxygen to form an oxide film of the subcomponent on the surface of Ni. This makes it difficult for Ni in the outside air to react with Ni unless the oxygen in the outside air passes through the oxide film of the sub-component. As a result, even when used continuously 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, Au, Ag, Pd having high heat resistance, or an alloy thereof can be used. The thickness of the external electrode 4 may be appropriately determined according to the use or the like, but is usually preferably about 10 to 50 μm.

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

The dielectric composition according to the present embodiment has the formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b {(Ca 1-y Sr y) (Zr 1-z Ti z) O 3} Wherein x, y, and z are 0.35 ≦ x ≦ 0.75, 0.01 ≦ y ≦ 0.25, and 0.01 ≦ z ≦ 0. 25, wherein the relationship between a and b is a + b = 1.00, and 0.32 ≦ a ≦ 0.66.

  When the dielectric composition has the above characteristics, it is possible to provide a dielectric composition having a good high-temperature load life and a relatively high relative dielectric constant suitable for use at 250 ° C. The following is a description of the factors that have obtained such effects.

Inventors have the formula _{K (Ba 1-x Sr x} ) 2 Nb 5 tungsten bronze-type composite oxide represented by _{O 15,} formula _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O It has been found that the presence of the perovskite-type composite oxide represented by No. ₃ has an effect of suppressing the movement of oxygen vacancies, which is considered to be a cause of deterioration of the high-temperature load life. Main component _{result, K (Ba 1-x Sr} x) mainly composed of only ₂ Nb _{5 O 15} and the dielectric composition _and, only _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 It is believed that the dielectric composition described above can improve the high-temperature load life at 250 ° C., which was difficult to achieve. Furthermore, since the relative dielectric constant is contained less than 100 _{(Ca 1-y Sr y)} (Zr 1-z Ti z) to _{O 3 K (Ba 1-x} Sr x) 2 Nb 5 O 15, the dielectric The rate is also improved.

In the present _{embodiment, K (Ba 1-x Sr} x) and tungsten bronze type complex oxide represented by _{2 Nb 5 O 15, (Ca} 1-y Sr y) (Zr 1-z Ti z) O 3 The perovskite-type composite oxide represented by the formula (1) may be present as solid solution crystal particles, or may be present as individual crystal particles. In any case, a good high-temperature load life can be obtained.

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

Ca of the chemical formula _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 is replaced by Sr. The substitution amount y is 0.01 ≦ y ≦ 0.25. When the substitution amount y is less than 0.01, the effect of suppressing the movement of oxygen vacancies, which is considered to be the cause of deterioration of the high-temperature load life, cannot be obtained, and it is difficult to obtain a sufficient high-temperature load life. On the other hand, when the substitution amount y exceeds 0.25, as the temperature increases, the insulation property tends to decrease, resulting in a low high-temperature load life.

Zr of the chemical formula _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 is replaced by Ti. The substitution amount y is 0.01 ≦ z ≦ 0.25. When the substitution amount z is less than 0.01, the effect of suppressing the movement of oxygen vacancies, which is considered to be the cause of deterioration of the high-temperature load life, cannot be obtained, and it is difficult to obtain a sufficient high-temperature load life. On the other hand, if the substitution amount z exceeds 0.25, the insulating property is apt to be reduced as the temperature increases, and as a result, the high temperature load life becomes low.

  The relationship between a and b in the chemical formula is a + b = 1.00, and 0.32 ≦ a ≦ 0.66. If the value of a is less than 0.32 or the value of a exceeds 0.66, the effect of suppressing the movement of oxygen vacancies, which is considered to be the cause of the deterioration of the high-temperature load life, is hardly obtained. Life tends to be difficult to obtain.

Further, 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 whole crystal particles constituting the dielectric composition is 100%, K ( Ba _1-x Sr _x) the area ratio of crystals composed particles _{2 Nb 5 O 15 α (%} ), the crystal consists of _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 When the area ratio of the particles is β (%), the relationship between α and β is 0.50 ≦ α / β ≦ 1.90, preferably 80% ≦ α + β.

  The inventors have found that by controlling the dielectric composition in the manner described above, the occurrence of avalanche at high temperatures can be further suppressed. For this reason, it has become possible to obtain a high DC withstand voltage at 250 ° C., which was difficult with a conventional dielectric composition. As a result, it is considered that it has become 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 same.

  In the case of the multilayer ceramic capacitor sample which is an example of the present embodiment, the above-mentioned area ratio is micro-sampled using FIB (Focused Ion Beam), and a TEM sample of a dielectric layer is manufactured. It is obtained by performing STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometry) mapping using a scanning transmission electron microscope. The mapping visual field is 7 μm × 7 μm, and it is preferable to perform mapping of 10 or more visual fields for each sample. The area ratio can also be obtained by performing element mapping on the polished cross section of the dielectric layer by EPMA (Electron Probe Micro Analyzer). At this time, the visual field of the mapping is 10 μm × 10 μm, and mapping of 5 or more visual fields may be performed on each sample, and the area ratio may be calculated from the obtained element map.

  Further, in a desirable mode of the present invention, the x, y, z, α, β are 0.35 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.10, 0.02 ≦ z ≦ 0. 10, 0.60 ≦ α / β ≦ 1.50, 90% ≦ α + β. As a result, the occurrence of electron avalanches at high temperatures can be further suppressed, and the effect of suppressing an increase in leakage current in a high-temperature load test can be further enhanced. As a result, a higher DC withstand voltage and a longer high-temperature load life can be easily obtained.

  As described above, since the dielectric composition according to the present embodiment exhibits good characteristics in a high-temperature region, it can be suitably used in the operating temperature range (-55 ° C. to 250 ° C.) of a 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.

In the chemical formula, K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ has a molar ratio of each K site, Ba site, Nb site and O site of basically 1: 2: 5: 15. However, it may be slightly increased or decreased as long as the tungsten bronze structure can be maintained. _{Similarly, (Ca 1-y Sr y} ) (Zr 1-z Ti z) O 3 , each Ca site, Zr sites, the molar ratio of O sites basically 1: 1: is a 3, perovskite structure May be slightly increased or decreased as long as can be maintained.

  Further, the dielectric composition according to the present embodiment may include minute impurities and subcomponents, as long as it does not significantly deteriorate the DC withstand voltage at high temperature or the high-temperature load life, which is the effect of the present invention. . For example, Mg, Mn, Si, V, Cr and the like. Therefore, the content of the main component is not particularly limited, but is, for example, 70 mol% or more and 100 mol% or less based on the whole dielectric composition containing the main component.

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

Production method 1 for dielectric composition
_{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. _{Further, (Ca 1-y Sr y} ) (Zr 1-z Ti z) O 3 has an average particle diameter is prepared following _{CaCO 3, SrCO 3, TiO 2} , ZrO 2 powder 1.0μm as the starting material. After weighing these starting materials at a predetermined ratio, wet mixing is performed for a predetermined time using a ball mill or the like. After the mixed powder is dried, a heat treatment at 1000 ° C. or less is performed in the atmosphere, and a {K (Ba _1−x Sr _x ) ₂ Nb ₅ O ₁₅ } + b} (Ca) having an average particle size of 0.5 μm to 2.0 μm. _{1-y Sr y) (Zr} 1-z Ti z) O 3} may obtain a calcined powder. Further, using the above-mentioned starting materials, subjected to heat treatment at 1000 ° C. or _less, and calcined powder _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15, (Ca 1-y Sr y) (Zr 1-z Ti _z) was prepared separately and calcined powder of _{O 3,} followed by mixing the calcined powder, the average particle size is _{0.5μm~2.0μm a {K (Ba 1-} x Sr x) 2 Nb _{5 O 15} + b {(} Ca 1-y Sr y) (Zr 1-z Ti z) O 3} may obtain a calcined powder.

Method 2 for producing dielectric composition
When increasing the area ratio of the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 or _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 Configured crystal grains, as follows First, a dielectric composition is produced.

First, the calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is a K ₂ CO ₃ , BaCO ₃ , SrCO ₃ , Nb ₂ O ₅ powder having an average particle diameter 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, a two-stage heat treatment is performed in the air: heat treatment at a temperature of 1000 ° C. or less (formation of a single phase) and heat treatment at a temperature of 850 ° C. or less (uniform distribution of elements inside the particles). obtain. Since the obtained calcined powder is subjected to a two-stage heat treatment, almost no foreign phase is formed, and since there is little deviation in the distribution of element parts inside the particles, abnormal grain growth or it is possible to suppress the reaction between the _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3.

_{Next, (Ca 1-y Sr y} ) (Zr 1-z Ti z) calcined powder of _{O 3} has an average CaCO particle size below 1.0 .mu.m ₃ as starting _{materials, SrCO 3, TiO 2, ZrO} 2 Prepare powder. Thereafter, in the same manner as in the method of producing the calcined powder of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ described above, the powder is weighed to a predetermined ratio, and then wet-mixed using a ball mill or the like, and then, in air. A two-stage heat treatment of 1000 ° C. or less and 850 ° C. or less is performed to obtain a calcined powder. Since the obtained calcined powder is subjected to a two-stage heat treatment, almost no foreign phase is formed, and since there is little deviation in the distribution of element parts inside the particles, abnormal grain growth or It is possible to suppress the reaction with K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ .

Thereafter, the resultant _{K (Ba 1-x Sr x} ) and calcined powder of _{2 Nb 5 O 15, (Ca} 1-y Sr y) (Zr 1-z Ti z) mixing and solution of the calcined powder of _{O 3} Crushing to produce a mixed powder having an average particle size of 0.5 μm to 2.0 μm.

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

  The multilayer ceramic capacitor 1 of the present embodiment is similar to a conventional multilayer ceramic capacitor, in which a green chip is produced by a normal printing method or a sheet method using a paste, fired, and then external electrodes are applied and fired. It is manufactured by doing. Hereinafter, the manufacturing method will be specifically described.

  The mixed powder obtained above is formed 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 an aqueous paint.

  The 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 various ordinary 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, and acetone, depending on the method to be used, such as a printing method or a sheet method.

  When the paste for the dielectric layer is an aqueous paint, an aqueous vehicle in which a water-soluble binder or dispersant is dissolved in water may be kneaded with a dielectric material. The water-soluble binder used for the aqueous vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, a water-soluble acrylic resin, or the like may be used.

  The paste for the internal electrode layer is obtained by kneading the above-mentioned organic vehicle with the above-mentioned various conductive metals or alloys, or various kinds of oxides, organometallic compounds, resinates and the like which 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.

  The content of the organic vehicle in each of the above-mentioned pastes is not particularly limited, and may be a usual content, for example, about 1% to 5% by weight of a binder and about 10% to 50% by weight of a solvent. Further, 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 paste for the dielectric layer and the paste for the internal electrode layer are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then separated from the substrate to form a green chip.

  In the case of using the sheet method, a green sheet is formed using a dielectric layer paste, an internal electrode layer paste is printed thereon, and these are laminated to form a green chip.

Before firing, the green chip is subjected to a binder removal treatment. As the binder removal conditions, the temperature raising rate 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 hour to 24 hours. The firing atmosphere is air or a reducing atmosphere. Further, in the above-described binder removal processing, for example, a wetter or the like may be used to humidify the N ₂ gas, the mixed gas, or the like. In this case, the water temperature is preferably about 5C to 75C.

  Further, the holding temperature at the time of firing is preferably 1000 ° C to 1400 ° C, more preferably 1100 ° C to 1350 ° C. If the holding temperature is less than the above range, densification becomes insufficient, and if the holding temperature exceeds the above range, disconnection of the electrode due to abnormal sintering of the internal electrode layer or deterioration of the capacity change rate due to diffusion of the internal electrode layer constituent material occurs. It will be easier. In addition, if it exceeds the above range, the crystal grains may be coarsened, and the DC withstand voltage may be reduced.

Furthermore, the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 crystal grains and composed of _{((Ca 1-y Sr y} ) (Zr 1-z Ti z) crystal grains composed of _{O 3} In order to increase the area ratio, it is important to strictly control the following conditions: In order to form independent crystal grains without forming a solid solution, the heating rate is preferably 100 ° C./hour. To 5000 ° C./hour, more preferably 1000 ° C./hour to 5000 ° C./hour, and in order to control the particle size distribution after sintering to a range of 0.5 μm to 5.0 μm, In order to suppress volume diffusion, the temperature holding time is preferably 0.5 hours to 2.0 hours, more preferably 0.5 hours to 1.0 hour, and the cooling rate is preferably 100 ° C./hour to 500 ° C./hour. , More preferably 200 ° C./hour to 30 0 ° C./hour.

Further, as an atmosphere for baking, it is preferable to bake at a partial pressure of oxygen of 10 ⁻² to 10 ⁻⁹ Pa using a humidified mixed gas of N ₂ and H ₂ . Increasing the area ratio of crystals composed particles _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 crystal grains and composed of _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 In this case, the oxygen partial pressure is more preferably 10 ⁻² to 10 ⁻⁵ Pa. By performing calcination in an atmosphere having a high oxygen partial pressure, volume diffusion between crystal grains can be suppressed, so that an effect of hardly forming a solid solution can be obtained. However, if firing is performed 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 reduced. In this case, by adding one or more types of subcomponents selected from Al, Si, Li, Cr, and Fe to the conductive material containing Ni as a main component, which is a more preferable embodiment of the present embodiment, Ni Has improved oxidation resistance, and it is possible to secure conductivity as an internal electrode layer even in an atmosphere having a high oxygen partial pressure.

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

  Although the above description describes a manufacturing method in which binder removal, baking, and annealing are performed independently, they may be performed continuously.

  The end surface of the capacitor element body obtained as described above is polished by, for example, 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.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. However, the present 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
Example 1 described the case where the calcined powder of the dielectric composition was produced according to the above-described method 1 for producing the dielectric composition.
First, powders of K ₂ CO ₃ , BaCO ₃ , SrCO ₃ , CaCO ₃ , Nb ₂ O ₅ , TiO ₂ , and ZrO ₂ having an average particle diameter of 1.0 μm or less are prepared, and a chemical formula a 式 K (Ba _{1−1 x Sr x) 2 Nb 5 O} 15} + b {(Ca 1-y Sr y) (Zr 1-z Ti z) at _{O 3},} x according to the sample numbers of Table 1, y, z, a, It was weighed to satisfy b. Thereafter, the mixture was wet-mixed 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 under the conditions of a holding temperature of 950 ° 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 was added. The mixture was dispersed using a certain basket mill for 2 hours to prepare a dielectric layer paste. The viscosity of each of these pastes was adjusted to about 200 cps.

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

  100 mass% of the raw material powder, 30 mass% of an organic vehicle (8 mass% of ethylcellulose resin dissolved in 92 mass% of butyl carbitol), and 8 mass% of butyl carbitol are kneaded with three rolls to form a paste. Thus, an internal electrode layer paste was obtained.

  Then, using the prepared dielectric layer paste, a green sheet was formed on a PET film so that the thickness after drying was 12 μm. Next, after the internal electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, the sheet was peeled off from the PET film to produce a green sheet having the internal electrode layer. Next, a plurality of green sheets each having an internal electrode layer were laminated and bonded by pressure 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. In addition, a wetter was used for humidification of each atmosphere gas.

(Binder removal processing)
Heating rate: 100 ° C / hour Holding temperature: 400 ° C
Temperature holding time: 8.0 hours Atmosphere gas: humidified mixed gas of N ₂ and H ₂ (firing)
Heating rate: 500 ° C / hour Holding temperature: 1100 ° C to 1350 ° C
Temperature holding time: 2.0 hours Cooling rate: 100 ° C./hour Atmosphere gas: Humidified mixed gas of 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 / fall rate: 200 ° C./hour Atmosphere gas: humidified N ₂ gas

  Each of the obtained multilayer ceramic sintered bodies was subjected to composition analysis using ICP emission spectroscopy, and as a result, it was confirmed that the values were substantially equivalent to those of the dielectric compositions described in Table 1. did.

  After polishing the end face of the obtained multilayer ceramic sintered body by sandblasting, an In-Ga eutectic alloy was applied as an external electrode, and a sample No. 1 having the same shape as the multilayer ceramic capacitor shown in FIG. 1 to sample no. 32 multilayer ceramic capacitor samples were obtained. The size of each of the obtained multilayer ceramic capacitor samples was 3.2 mm × 1.6 mm × 1.2 mm, the thickness of the dielectric layer was 10 μm, the thickness of the internal electrode layer was 2 μm, and the dielectric material sandwiched between the internal electrode layers. The number of layers was 50 layers.

The obtained sample No. 1 to sample no. With respect to 32 multilayer ceramic capacitor samples, crystal particles composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ and relative to (Ca _1-y Sr) by relative dielectric constant, DC withstand voltage, high temperature load life, and image analysis _{y) (measured} by the method of indicating the area ratio of the formed crystal grains below in _{Zr 1-z Ti z) O} 3, were evaluated and 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. using a digital LCR meter (4284A manufactured by YHP), and the capacitance was measured. Then, the relative permittivity (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. The higher the relative permittivity, the better, and 200 or more was judged to be good.

[DC withstanding voltage]
A DC voltage was applied to the multilayer ceramic capacitor sample at a rate of 100 V / sec at 250 ° C., and a portion where the leakage current exceeded 10 mA was defined as a DC withstand voltage. The direct-current withstand voltage was preferably 50 V / μm or more, and it was judged that it was good if it was 100 V / μm or more. More preferably, the DC withstand voltage is 150 V / μm or more.

[High temperature load life]
In the high-temperature load life test, a DC voltage was applied to 200 samples of each sample number at a temperature of 250 ° C. so as to be 20 V / μm with respect to the thickness of the dielectric layer, and the change with time of the insulation resistance was measured. A sample in which the insulation resistance was deteriorated by one digit was determined to be faulty, and a mean time to failure (MTTF) of 50% was obtained from Weibull analysis of the faulty time. In the present invention, the mean time to failure (MTTF) is defined as the high temperature load life. It was determined that the high-temperature load life was longer, more preferably 80 hours or more, and more preferably 120 hours or more.

[Evaluation of α and β by image analysis]
Micro-sampling was performed on the multilayer ceramic capacitor sample obtained by firing using FIB (Focused Ion Beam) to prepare a TEM sample of the dielectric layer. STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometry) mapping was performed on this TEM sample using JEM2200FS, a scanning transmission electron microscope manufactured by JEOL. The mapping visual field was set to 7 μm × 7 μm, and mapping was performed for 10 or more visual fields for each sample. Using elemental map obtained by these _{methods, K (Ba 1-x Sr} x) 2 Nb 5 O is an element of ₁₅ K, Ba, Sr, and _{Nb, (Ca 1-y Sr} y) (Zr _1-z Ti _z) is an element of the _{O 3} Ca, Sr, Ti, identifies the area of the Zr, using the mean area of each 10 field above _{results, K (Ba 1-x Sr} x) 2 Nb 5 the area ratio of the formed crystal grains in O ₁₅ alpha and _{(%), (Ca 1-} y Sr y) (Zr 1-z Ti z) the area ratio of crystals composed particles _{O 3 β} (%) Was calculated. In the present embodiment, in order to obtain a high DC withstand voltage and a good high-temperature load life, it is preferable that 0.50 ≦ α / β ≦ 1.90 and 80% ≦ α + β.

  According to the results shown in Table 2, Sample No. No. 1 to No. 1 32, the multilayer ceramic capacitor sample within the range of the present embodiment has a relative dielectric constant at 250 ° C. of 200 or more and a DC voltage at 250 ° C. so as to be 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.

On the other hand, the sample No. No. 1 is a chemical formula K (Ba _1−x Sr _x ) ₂ Nb ₅ O ₁₅ where x is less than 0.35 and out of the range of the present embodiment, so that it is difficult to obtain sufficient insulating properties, and a high temperature load as low as 55 hours Life is over. In addition, the sample No. In No. 7, since x exceeded 0.75 and was outside the range of the present embodiment, it was confirmed that the high-temperature load life was as low as 70 hours.

In addition, the sample No. 8, sample no. 9 is probably because y of formula _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 is out of the scope of this embodiment and less than 0.01, a cause degradation of high-temperature load life The effect of suppressing the transfer of oxygen vacancies cannot be obtained, and the low-temperature high-load life of less than 80 hours is obtained. On the other hand, sample No. 14, sample no. It was confirmed that the sample No. 21 had a low high-temperature load life of less than 80 hours because the value of y exceeded 0.25 and was out of the range of the present embodiment.

In addition, the sample No. 8, sample no. 15 is considered to be because the chemical formula _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 and z is outside the scope of this embodiment and less than 0.01, a cause degradation of high-temperature load life The effect of suppressing the transfer of oxygen vacancies cannot be obtained, and the low-temperature high-load life of less than 80 hours is obtained. On the other hand, sample No. 20, sample no. It was confirmed that the sample No. 21 had a low high-temperature load life of less than 80 hours because z exceeded 0.25 and was out of the range of the present embodiment, so that the insulating property at a high temperature was low.

  Further, the sample No. In Sample No. 22, a was less than 0.32; 28 has a low high-temperature load life of less than 80 hours because a is outside the range of the present embodiment in which a exceeds 0.66.

Example 2
Here, by using the manufacturing method 2 of the dielectric composition indicated above, the _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15 or _{(Ca 1-y Sr y)} (Zr 1-z Ti z ₃ ) The results of verification of the case where the area ratio of the crystal grains composed of O ₃ was increased were 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 starting materials were weighed so that x shown in Table 3 was obtained, and wet-mixed 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, 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 thereafter, a second heat treatment is performed 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, (Ca 1-y Sr y} ) (Zr 1-z Ti z) O 3 was prepared an average particle size 1.0μm or less of _{CaCO 3, SrCO 3, TiO 2} , ZrO 2 powder as the starting material. The starting materials described above were weighed so as to obtain y and z shown in Table 3, and were wet-mixed 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, 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 is performed 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 _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3.

Blending the calcined powder obtained _{K (Ba 1-x Sr x} ) 2 Nb 5 O 15, (Ca 1-y Sr y) (Zr 1-z Ti z) O Table 3 calcined powder ₃ After weighing so as to obtain the ratio, the mixture was wet-mixed with a ball mill using ethanol as a dispersion medium for 17 hours to 36 hours. Thereafter, the obtained mixture was dried to obtain a dielectric composition raw material powder shown in Table 3.

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

  Then, a green chip was manufactured in the same manner as in Example 1.

  Next, the obtained green chip was subjected to binder removal processing, firing, and annealing treatment to obtain a multilayer ceramic sintered body. Note that the conditions for the binder removal treatment, firing and annealing are as follows. In addition, a wetter was used for humidification of each atmosphere gas.

(Binder removal processing)
Heating rate: 100 ° C / hour Holding temperature: 400 ° C
Temperature holding time: 8.0 hours Atmosphere gas: humidified mixed gas of N ₂ and H ₂ (firing)
Heating rate: 2000 ° C / hour Holding temperature: 1100 ° C to 1350 ° C
Temperature holding time: 1.0 hour Cooling rate: 200 ° C./hour Atmosphere 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 / fall rate: 200 ° C./hour Atmosphere gas: humidified N ₂ gas

The crystal structure of the dielectric layer of the obtained multilayer ceramic sintered body was measured by X-ray diffraction (XRD). As a result, K (Ba _1−x Sr _x ) ₂ Nb was obtained for the multilayer ceramic sintered body according to the present embodiment. ₅ O ₁₅ and a _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3 was confirmed to be present singly.

  In addition, as a result of performing composition analysis of each sample using ICP emission spectroscopy for each of the obtained multilayer ceramic sintered bodies, values substantially equivalent to those of the dielectric compositions described in Tables 3 and 4 were obtained. Was confirmed.

  After polishing the end face of the obtained multilayer ceramic sintered body by sandblasting, an In-Ga eutectic alloy was applied as an external electrode, and a sample No. 1 having the same shape as the multilayer ceramic capacitor shown in FIG. 33 to Sample No. 64 multilayer ceramic capacitor samples were obtained. The size of each of the obtained multilayer ceramic capacitor samples was 3.2 mm × 1.6 mm × 1.2 mm, the thickness of the dielectric layer was 10 μm, the thickness of the internal electrode layer was 2 μm, and the dielectric material sandwiched between the internal electrode layers. The number of layers was 50 layers.

The obtained sample No. 33 to Sample No. For 64 multilayer ceramic capacitor samples, using the same measurement method as in Example 1, the relative dielectric constant, DC withstand voltage, high-temperature load life, and K (Ba _1−x Sr _x ) ₂ Nb ₅ O ₁₅ by image analysis were used. measuring the area ratio of crystals composed particles comprised crystal grains and _{(Ca 1-y Sr y)} (Zr 1-z Ti z) O 3, were evaluated and shown in Table 4.

  According to the results shown in Table 4, Sample No. 33-Sample No. 64, the multilayer ceramic capacitor sample in the range of this embodiment, 0.50 ≦ α / β ≦ 1.90 and 80% ≦ α + β has a relative dielectric constant at 250 ° C. of 200 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.

Also, according to the results shown in Tables 2 and 4, the area ratio of the crystal grains composed of K (Ba _1-x Sr _x ) ₂ Nb ₅ O ₁₅ is α (%), (Ca _1-y Sr _y ) When the area ratio of the crystal grains composed of (Zr _{1 -zTiz} ) O ₃ is β (%), the relationship between α and β is 0.50 ≦ α / β ≦ 1.90. , 80% ≦ α + β, it was confirmed that the DC withstand voltage at 250 ° C. was less than 100 V / μm.
As described above, by controlling not only the material composition of the dielectric composition but also the composition of the crystal particles constituting the dielectric composition, it has been difficult to realize 250 ° C. It was found that both high high-temperature load life and high DC withstand voltage could be achieved.

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

  A multilayer ceramic capacitor sample was prepared from the obtained dielectric composition raw material powder in the same manner as in Example 2, and the same measurements and evaluations as in Examples 1 and 2 were performed. The results are shown in Table 6. Was.

  According to the results shown in Table 6, the sample No. within the range of the present embodiment. 65-Sample No. 85, the x, y, z, α, β are 0.35 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.10, 0.02 ≦ z ≦ 0.10, 0.60 ≦ The multilayer ceramic capacitor sample satisfying α / β ≦ 1.50 and 90% ≦ α + β has a relative dielectric constant at 250 ° C. of 200 or more, a DC withstand voltage at 250 ° C. of 150 V / μm, It was confirmed that the high-temperature load life when a DC voltage was continuously applied so as to be 20 V / μm with respect to the thickness of the dielectric layer was 120 hours or more, indicating better characteristics.

  The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the embodiments and examples, and is intended to include any modifications or variations within the meaning and range equivalent to the terms of the claims.

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

REFERENCE SIGNS LIST 1 multilayer ceramic capacitor 2 dielectric layer 3 internal electrode layer 4 external electrode 10 capacitor element body

Claims (4)

The dielectric composition having a main component represented by the chemical formula _{a {K (Ba 1-x} Sr x) 2 Nb 5 O 15} + b {(Ca 1-y Sr y) (Zr 1-z Ti z) O 3} Wherein the x, y, and z are:
0.35 ≦ x ≦ 0.75, 0.01 ≦ y ≦ 0.25, 0.01 ≦ z ≦ 0.25,
The relationship between a and b is a + b = 1.00, and 0.32 ≦ a ≦ 0.66
A dielectric composition, characterized in that: When the dielectric composition is composed of a plurality of crystal particles and the area ratio of the whole crystal particles constituting the dielectric composition is 100%, K (Ba _1−x Sr _x ) ₂ Nb ₅ the area ratio of the formed crystal grains in O ₁₅ α _(%), and _{(Ca 1-y Sr y)} (Zr 1-z Ti z) the area ratio of crystals composed particles _{O 3 β} (%) 2. The dielectric composition according to claim 1, wherein the relationship between α and β satisfies 0.50 ≦ α / β ≦ 1.90 and 80% ≦ α + β.   X, y, z, α, β are 0.35 ≦ x ≦ 0.50, 0.02 ≦ y ≦ 0.10, 0.02 ≦ z ≦ 0.10, 0.60 ≦ α / β ≦ 3. The dielectric composition according to claim 2, wherein 1.50, 90% ≦ α + β. 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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