WO2024057849A1 - Filtration material and method for producing multilayer ceramic capacitor using same - Google Patents

Filtration material and method for producing multilayer ceramic capacitor using same Download PDF

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WO2024057849A1
WO2024057849A1 PCT/JP2023/030304 JP2023030304W WO2024057849A1 WO 2024057849 A1 WO2024057849 A1 WO 2024057849A1 JP 2023030304 W JP2023030304 W JP 2023030304W WO 2024057849 A1 WO2024057849 A1 WO 2024057849A1
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inorganic particles
inorganic
multilayer ceramic
ceramic capacitor
internal electrode
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PCT/JP2023/030304
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French (fr)
Japanese (ja)
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正俊 奥田
睦矢 西
義貴 山口
栞 日▲高▼
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株式会社村田製作所
株式会社ロキテクノ
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Publication of WO2024057849A1 publication Critical patent/WO2024057849A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/30—Stacked capacitors

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  • the present invention relates to a filter material for filtering inorganic pastes, particularly inorganic pastes such as ceramic slurry for forming green sheets of multilayer ceramic capacitors and conductive pastes for forming internal electrodes.
  • green sheets used in the manufacture of multilayer ceramic capacitors are produced by uniformly applying ceramic slurry onto a carrier film. Before application to the carrier film, particles with a particle size outside a predetermined range are removed using a filter equipped with a filter material.
  • the microparticles mixed into the ceramic slurry promote grain growth of ceramic particles during firing, inhibiting the formation of a dense sintered body, and causing a decrease in the insulation resistance of multilayer ceramic capacitors. This was a factor that impaired reliability. Furthermore, when microparticles segregate within the device, there is a significant tendency for electrical characteristics to deteriorate.
  • conductive paste is used to form internal electrode layers, but even in the preparation of conductive paste, the particle size of inorganic particles such as metals is regulated within a predetermined range, and the electrical properties are It is important to maintain
  • An object of the present invention is to provide a filter material that can remove minute inorganic particles from inorganic pastes such as ceramic slurries and conductive pastes used in the manufacture of multilayer ceramic capacitors.
  • the present inventor discovered that minute inorganic particles can be effectively removed by using a filter material that is given a potential of opposite polarity to the potential of the inorganic particles contained in the inorganic paste, and completed the present invention. I ended up doing it.
  • the present invention is for filtering an inorganic paste containing first inorganic particles with a particle size of 20 nm or more and 300 nm or less, second inorganic particles with a particle size of less than 20 nm, an organic solvent, a binder, and a dispersant.
  • the filter medium is provided with a potential having a polarity opposite to that of the first inorganic particles and the second inorganic particles.
  • microparticles can be removed from inorganic pastes such as ceramic slurry and conductive paste used in the manufacture of multilayer ceramic capacitors, thereby suppressing a decrease in insulation resistance and improving the reliability of multilayer ceramic capacitors. It is possible to increase it.
  • FIG. 2 is an external view of a multilayer ceramic capacitor. 2 is a cross-sectional view taken along line AA of the multilayer ceramic capacitor shown in FIG. 1.
  • FIG. FIG. 3 is an exploded perspective view schematically showing an example of an inner layer part. 2 is a graph showing changes in the logarithmic value (Log IR) of the insulation resistance value of a multilayer ceramic capacitor.
  • inorganic pastes to be filtered using the filter medium of the present invention particularly ceramic slurries for forming green sheets of multilayer ceramic capacitors, conductive pastes for forming internal electrode layers, and filtration.
  • the composition of the material will be explained.
  • a two-terminal multilayer ceramic capacitor is exemplified as a multilayer ceramic capacitor manufactured using a ceramic slurry filtered through a filter medium or a conductive paste
  • the present invention is not limited thereto.
  • the drawings may be drawn in a schematic and simplified manner in order to explain the content of the invention, and the drawn components or the dimensional ratios between the components may be different from those described in the specification. The dimensions may not match the proportions.
  • constituent elements described in the specification are omitted in the drawings or drawn with their numbers omitted.
  • FIG. 1 is an external view of a multilayer ceramic capacitor 1.
  • FIG. 2 is a cross-sectional view (LT cross-sectional view) of the multilayer ceramic capacitor 1 taken along the line AA at the center in the width direction W shown in FIG.
  • FIG. 3 is a schematic diagram showing the structure of the inner layer portion 3.
  • the direction in which the dielectric layers and internal electrode layers are laminated is defined as the lamination direction T
  • the length direction L is perpendicular to the lamination direction T
  • the width direction W is perpendicular to the lamination direction T and the length direction L.
  • the structure of the ceramic capacitor 1 will be described.
  • the width direction W, the length direction L, and the lamination direction T are orthogonal to each other, but they are not necessarily orthogonal to each other, and may be intersecting to each other.
  • the multilayer ceramic capacitor 1 includes a multilayer body 2 having a rectangular parallelepiped shape.
  • the laminate 2 includes an inner layer part 3, and has a pair of first main surfaces TS1 and second main surfaces TS2 facing each other in the stacking direction T, and a pair of first main surfaces TS1 and second main surfaces TS2 facing each other in the length direction L perpendicular to the stacking direction T. It has a pair of first end surfaces LS1 and a second end surface LS2, and a pair of first side surfaces WS1 and second side surfaces WS2 that face each other in the width direction W perpendicular to both the stacking direction T and the length direction L. ing.
  • the dimensions of the multilayer ceramic capacitor 1 are not particularly limited, but for example, the dimensions in the height direction T are about 0.1 mm to 2.5 mm, and the dimensions in the length direction L are about 0.1 mm to 3.5 mm.
  • the width can be approximately 2 mm, and the dimension in the width direction W can be approximately 0.1 mm to 2.5 mm.
  • a first external electrode 4a and a second external electrode 4b are formed on the surface of the laminate 2.
  • the first external electrode 4a is formed on the first end surface LS1 of the stacked body 2.
  • the first external electrode 4a is formed in a cap shape, and the edge portion extends from the first end surface LS1 of the laminate 2 to the first main surface TS1, the second main surface TS2, the first side surface WS1, and the second side surface. It is formed extending to WS2.
  • the second external electrode 4b is formed on the second end surface LS2 of the laminate 2.
  • the second external electrode 4b is formed in a cap shape, and the edge portion extends from the second end surface LS2 of the laminate 2 to the first main surface TS1, the second main surface TS2, the first side surface WS1, and the second side surface. It is formed extending to WS2.
  • the first internal electrode layer 6a drawn out to the first end surface LS1 of the multilayer body 2 is connected to the first external electrode 4a. Further, the second internal electrode layer 6b drawn out to the second end surface LS2 of the laminate 2 is connected to the second external electrode 4b.
  • the external electrode 4 can have a structure including, for example, a base electrode layer and a plating layer disposed on the base electrode layer.
  • the base electrode layer is formed by applying a conductive paste containing glass and metal to the laminate and baking it.
  • the baking may be performed simultaneously with the firing of the laminate or after the laminate is fired.
  • the plating layer disposed on the base electrode layer includes, for example, at least one of metals such as Cu, Ni, Ag, Pd, and Au, or an alloy of Ag and Pd.
  • the plating layer may be one layer or multiple layers.
  • the plating layer can have, for example, a two-layer structure of a Ni plating layer and a Sn plating layer.
  • the inner layer portion 3 is composed of a plurality of dielectric layers 5 and a plurality of internal electrode layers 6 stacked together.
  • the internal electrode layer 6 is composed of a first internal electrode layer 6a and a second internal electrode layer 6b.
  • the first internal electrode layer 6a and the second internal electrode layer 6b are arranged on the dielectric layers 5a and 5b, respectively.
  • the internal electrode layer 6 extends in the length direction L and has a rectangular shape in plan view.
  • the first internal electrode layer 6a is drawn out to the first end surface LS1 of the laminate 2
  • the second internal electrode layer 6b is drawn out to the second end surface LS2 of the laminate 2.
  • the material of the dielectric layer 5 is arbitrary, for example, ceramic powder containing BaTiO 3 as a main component can be used. Further, instead of BaTiO 3 , a ceramic powder containing other materials as a main component such as CaTiO 3 or SrTiO 3 may be used.
  • the thickness of the dielectric layer 5 is not particularly limited; The thickness can be approximately .0 ⁇ m.
  • the number of layers of the dielectric layer 5 is not particularly limited, but for example, in the effective area of capacitance formation formed by the first internal electrode layer 6a and the second internal electrode layer 6b, the number of layers is 1 to 6000 layers. It can be done.
  • an outer layer portion 7 is provided, which is composed only of the dielectric layer 5 without the internal electrode layer 6 formed thereon.
  • the thickness of the outer layer portion 7 is not limited, but may be, for example, 15 ⁇ m to 150 ⁇ m. Note that the thickness of the dielectric layer in the outer layer portion 7 may be larger than the thickness of the dielectric layer in the effective area for forming capacitance where the internal electrode layer 6 is formed. Further, the material of the dielectric layer in the outer layer portion may be different from the material of the dielectric layer in the inner layer portion.
  • FIG. 3 shows the inner layer portion 3 broken down into dielectric layers 5 in the stacking direction T.
  • the internal electrode layer 6 is formed by sintering a conductive paste containing a metal powder that serves as a conductor, an organic solvent, a binder, and a dispersant on the dielectric layer.
  • the internal electrode layer 6 and the dielectric layer 5 are alternately stacked to form the inner layer portion 3.
  • the internal electrode layer 6 is composed of a first internal electrode layer 6a and a second internal electrode layer 6b, and the first internal electrode layer 6a and the second internal electrode layer 6b are disposed on the dielectric layers 5a and 5b, respectively.
  • metals such as Cu, Ni, Ag, Au, and Pt can be used. Further, these metals may be compounds containing these metal elements or alloys with other metals.
  • the thickness of the internal electrode layer 6 is not particularly limited, but may be, for example, about 0.3 ⁇ m to 1.5 ⁇ m.
  • a ceramic slurry for forming the dielectric layer 5 of the multilayer ceramic capacitor 1 is prepared.
  • a perovskite compound containing Ba and Ti can be used as the ceramic powder constituting the ceramic slurry.
  • the molar ratio A/B of A and B in the perovskite compound represented by the general formula A m BO 3 does not have to be a stoichiometric composition, but is preferably 0.98 or more and 1.02 or less.
  • Ba source a Ba compound such as BaCO 3 can be used, and as the Ti source, a Ti compound such as TiO 2 can be used.
  • perovskite compounds include CaTiO 3 and SrTiO 3 , and any one of these can be selected or a mixture of these can be used.
  • oxide powders and carbonate powders are not limited to oxide powders and carbonate powders, but may also be chloride powders, sols, metal organic compounds, and the like.
  • perovskite compounds there are no particular restrictions on the method for producing perovskite compounds, and known methods such as solid phase method, liquid phase method, hydrothermal synthesis method, and hydrolysis method can be used.
  • a ceramic slurry can be prepared by adding an organic solvent, a binder, and a dispersant to the ceramic powder obtained as described above and mixing the mixture using a ball mill or the like.
  • a ceramic slurry can be prepared by kneading ceramic powder and an organic vehicle.
  • An organic vehicle is a binder dissolved in an organic solvent.
  • the binder used in the organic vehicle is not particularly limited, and may be appropriately selected from various common binders such as ethyl cellulose and polyvinyl butyral.
  • the organic solvent used in the organic vehicle is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene.
  • the dispersibility of ceramic powder is improved by adding a dispersant.
  • the dispersant is not particularly limited and may be anionic, cationic, or nonionic, such as polyacrylic acid, its ammonium salt, polyacrylic acid ester copolymer, polyethylene oxide, polyoxyethylene alkyl amyl, etc. Ether, fatty acid diethanolamide, polyethyleneimine, copolymers of polyoxypropylene monoallyl monobutyl ether and maleic anhydride, etc. can be used.
  • the prepared ceramic slurry is filtered using a filter medium, details of which will be described later.
  • a conductive paste for forming internal electrode layers of a multilayer ceramic capacitor is prepared.
  • the conductive paste for the internal electrode layer contains inorganic particles made of metals such as Cu, Ni, Ag, Au, and Pt or compounds containing these metal elements, an organic solvent, a binder, and a dispersant. It will be done.
  • the conductive paste for the internal electrode layer is prepared by kneading the above-mentioned inorganic particles containing metal etc. and the above-mentioned organic vehicle. Further, the conductive paste may contain a common material.
  • the co-material is not particularly limited, but preferably has the same composition as the main component forming the dielectric layer.
  • the paste for external electrodes may be prepared in the same manner as the conductive paste for internal electrode layers described above.
  • each of the above pastes is not particularly limited, and the content may be a normal content, for example, about 1 to 5% by weight for the binder and about 10 to 50% by weight for the solvent. Further, each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, etc., as necessary. The total content of these is preferably 10% by weight or less.
  • the prepared conductive paste is filtered using a filter medium, details of which will be described later.
  • ceramic slurry and conductive paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled off from the substrate to form a green chip.
  • a green sheet is formed using ceramic slurry, a conductive paste is printed on it to form an internal electrode layer pattern, and then these are laminated to form a green chip.
  • the green chips are subjected to binder removal treatment.
  • the temperature increase rate is preferably 5 to 300°C/hour
  • the holding temperature is preferably 180 to 400°C
  • the temperature holding time is preferably 0.5 to 24 hours.
  • the binder removal atmosphere is air or a reducing atmosphere.
  • the temperature increase rate during firing is preferably 100 to 500°C/hour.
  • the holding temperature during firing is preferably 1300°C or lower, more preferably 1150 to 1280°C, and the holding time is preferably 0.5 to 8 hours, more preferably 2 to 3 hours. If the holding temperature is less than the above range, densification will be insufficient, and if it exceeds this range, discontinuities will occur due to abnormal sintering of the internal electrode layer, and the capacitance-temperature characteristics will deteriorate due to diffusion of the components that make up the internal electrode layer. , reduction of the dielectric ceramic composition is likely to occur.
  • the atmosphere for firing is preferably a reducing atmosphere, and for example, a humidified mixed gas of N 2 and H 2 can be used.
  • the oxygen partial pressure during firing can be determined as appropriate depending on the type of metal in the conductive paste, but when using base metals such as Ni or Ni alloys, the oxygen partial pressure in the firing atmosphere is It is preferably 10 -14 to 10 -10 MPa. If the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may undergo abnormal sintering and be interrupted. Furthermore, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized.
  • the temperature decreasing rate is preferably 50 to 500°C/hour.
  • the laminate After firing in a reducing atmosphere, the laminate is preferably annealed. Annealing is a process for re-oxidizing the dielectric layer, which can extend the life of the insulation resistance, thereby improving reliability.
  • the oxygen partial pressure of the atmosphere during annealing is preferably 10 -9 to 10 -5 MPa.
  • the oxygen partial pressure is less than the above range, it is difficult to reoxidize the dielectric layer, and when it exceeds the above range, the internal electrode layer tends to be oxidized.
  • the holding temperature during annealing is preferably 1100°C or less, particularly 1000 to 1100°C. If the holding temperature is below the above range, the dielectric layer will not be sufficiently oxidized, resulting in a low IR and a tendency to shorten the life of the insulation resistance. On the other hand, if the holding temperature exceeds the above range, not only will the internal electrode layer oxidize and the capacity will decrease, but the internal electrode layer will also react with the dielectric layer, resulting in deterioration of capacitance-temperature characteristics, decrease in insulation resistance, and The life of insulation resistance is likely to be shortened. Note that annealing may consist of only a temperature raising process and a temperature lowering process. In this case, the holding temperature is synonymous with the maximum temperature, and there is no temperature holding time.
  • the temperature holding time is preferably 0 to 20 hours, more preferably 2 to 4 hours, and the temperature cooling rate is preferably 50 to 500°C/hour, more preferably 100 to 300°C/hour.
  • the temperature cooling rate is preferably 50 to 500°C/hour, more preferably 100 to 300°C/hour.
  • a wetter or the like may be used, for example, to humidify N 2 gas, mixed gas, or the like.
  • the water temperature is preferably about 5 to 75°C.
  • the binder removal treatment, firing, and annealing may be performed continuously or independently.
  • the end face of the laminate obtained by the above process is polished by, for example, barrel polishing or sandblasting, and an 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.
  • microparticles with a particle size of less than 20 nm called chipping particles are generated during the dispersion process using a ball mill media. Due to its large specific surface area, it is a factor that promotes the growth of inorganic particles during firing and inhibits the formation of a dense sintered body, so it is necessary to remove it using a filter equipped with a specified filter material. be.
  • the inorganic paste contains inorganic particles, an organic solvent, a binder, and a dispersant, and the inorganic particles include first inorganic particles having a particle size of 20 nm to 300 nm, and second inorganic particles having a particle size of less than 20 nm. and inorganic particles.
  • the viscosity of the inorganic paste is preferably 15 mPa ⁇ s or more and 45 mPa ⁇ s or less. If the viscosity is less than 15 mPa ⁇ s, there is a problem that the slurry concentration is low in the filtration process and it takes time to pass a predetermined amount of raw material through the filtration process. This is because there is a problem that the filter may become clogged.
  • the materials of the filter media are listed below in bullet points.
  • the filter medium can be composed of a fibrous body or a porous body made of these materials.
  • ⁇ Synthetic resins polyolefin resins, polyester resins, polyamide resins, fluororesins, etc.
  • high-pressure low density polyethylene linear low density polyethylene (LLDPE), high density polyethylene, polypropylene, polypropylene random copolymer , polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polytetrafluoroethylene (PTFE), polyperfluoroalkoxyalkane (PFA), polyvinylidene fluoride ( PVDF), polyvinyl chloride, polyimide, polyacrylonitrile, polycarbonate, polystyrene, polyethersulfone, polysulfone, cellulose, etc.
  • ⁇ When manufacturing the filtration material mix a material with a cationic or anionic group. ⁇ Immobilize the material with a cationic or anionic group on the filtration material by coating or dipping. ⁇ Add a reactive group to the filtration material. ⁇ Irradiate the filtration material with radiation, plasma, etc. to immobilize the material that has a cationic or anionic group.
  • Filter the inorganic paste using a filter material Since the filter material is given a potential that is opposite in polarity to the potential of the inorganic particles contained in the inorganic paste, it is possible to capture microparticles smaller than the primary particles that could not be captured with conventional filter media. can.
  • the inorganic particles contained in the inorganic paste include first inorganic particles with a particle size of 20 nm or more and 300 nm or less and second inorganic particles with a particle size of less than 20 nm.
  • first inorganic particles with a particle size of 20 nm or more and 300 nm or less
  • second inorganic particles with a particle size of less than 20 nm.
  • the flow rate of the inorganic paste passing through the filter medium is preferably 0.5 kg/min or more and 2.0 kg/min or less. By filtering at such a flow rate, it becomes possible to efficiently trap the second inorganic particles in the filter medium.
  • the variation (CV value) in the logarithm of the insulation resistance value (Log IR) of samples using filter media to which no potential is applied is 8.03
  • the variation (CV value) in the logarithm of the insulation resistance value (Log IR) of samples using filter media to which no potential is applied is 8.03
  • the dispersion (CV value) of the logarithm value (Log IR) of the insulation resistance value was 3.60, and a good result could be confirmed.
  • Multilayer ceramic capacitor 2 Laminated body 3 Inner layer portion 4 External electrode 4a First external electrode 4b Second external electrode 5 Dielectric layer 5a Dielectric layer 5b Dielectric layer 6 Internal electrode layer 6a First internal electrode layer 6b Second internal electrode Layer 7 Outer layer portion TS1 First main surface TS2 Second main surface WS1 First side surface WS2 Second side surface LS1 First end surface LS2 Second end surface

Abstract

The present invention provides a filtration material which is capable of removing fine inorganic particles from an inorganic paste such as a ceramic slurry and an conductive paste, the inorganic paste being used during the production of a multilayer ceramic capacitor.　The present invention provides a filtration material for filtering an inorganic paste which contains first inorganic particles having a particle diameter of 20 nm to 300 nm, second inorganic particles having a particle diameter of less than 20 nm, an organic solvent, a binder and a dispersant; and a potential having a polarity reverse from the polarity of the first inorganic particles and the second inorganic particles is applied to this filtration material.

Description

ろ過材およびこれを用いた積層セラミックコンデンサの製造方法Filter material and method for manufacturing a multilayer ceramic capacitor using the same
　本発明は、無機ペースト、特に、積層セラミックコンデンサのグリーンシートを形成するためのセラミックスラリーや内部電極を形成するための導電性ペースト等の無機ペーストをろ過するためのろ過材に関する。 The present invention relates to a filter material for filtering inorganic pastes, particularly inorganic pastes such as ceramic slurry for forming green sheets of multilayer ceramic capacitors and conductive pastes for forming internal electrodes.
　従来より、積層セラミックコンデンサの製造において用いられるグリーンシートは、セラミックスラリーをキャリアフィルム上に均一に塗布することにより作製されるが、積層セラミックコンデンサの電気特性を一定に維持するため、セラミックスラリーは、キャリアフィルムへの塗布前に、ろ過材を備えたフィルタにより、所定範囲から逸脱した粒径の粒子を取り除くこととしている。 Conventionally, green sheets used in the manufacture of multilayer ceramic capacitors are produced by uniformly applying ceramic slurry onto a carrier film. Before application to the carrier film, particles with a particle size outside a predetermined range are removed using a filter equipped with a filter material.
　しかしながら、従来のろ過材では、一般的に粒径０．２μｍ以上の粒子を捕捉することができるものの、１次粒子より小さいサイズの微小粒子を捕捉することは困難であり、セラミックスラリーを調製するために行うメディアを用いた分散工程においては、チッピング粒子と呼ばれる粒径２０ｎｍ未満の微小粒子が発生するが、このような微小粒子は、そのままセラミックスラリーに混入していた。 However, although conventional filter media can generally capture particles with a particle size of 0.2 μm or more, it is difficult to capture microparticles smaller than primary particles, and it is difficult to prepare ceramic slurry. In the dispersion process using media, microparticles called chipping particles with a particle size of less than 20 nm are generated, but such microparticles were mixed into the ceramic slurry as they were.
　セラミックスラリーに混入した微小粒子は、その比表面積の大きさから、焼成時におけるセラミック粒子の粒成長を促進するため、緻密な焼結体の形成を阻害し、積層セラミックコンデンサの絶縁抵抗の低下など信頼性を損なう要因となっていた。また、微小粒子が素子内に偏析した場合、電気特性が低下する傾向も顕著となる。 Due to their large specific surface area, the microparticles mixed into the ceramic slurry promote grain growth of ceramic particles during firing, inhibiting the formation of a dense sintered body, and causing a decrease in the insulation resistance of multilayer ceramic capacitors. This was a factor that impaired reliability. Furthermore, when microparticles segregate within the device, there is a significant tendency for electrical characteristics to deteriorate.
　また、積層セラミックコンデンサの製造では、内部電極層を形成するために導電性ペーストを用いるが、導電性ペーストの調製においても、金属等の無機粒子の粒径を所定範囲内に規制し、電気特性を維持することが重要である。 In addition, in the manufacture of multilayer ceramic capacitors, conductive paste is used to form internal electrode layers, but even in the preparation of conductive paste, the particle size of inorganic particles such as metals is regulated within a predetermined range, and the electrical properties are It is important to maintain
　このため、積層セラミックコンデンサの信頼性を高めるため、セラミックスラリーや導電性ペースト等の無機ペーストから微小な無機粒子を取り除くことができるろ過材の開発が求められる。 Therefore, in order to improve the reliability of multilayer ceramic capacitors, there is a need to develop a filter material that can remove minute inorganic particles from inorganic pastes such as ceramic slurries and conductive pastes.
特開２０１９－１３１４３７号公報JP 2019-131437 Publication
　本発明は、積層セラミックコンデンサの製造において用いるセラミックスラリーや導電性ペースト等の無機ペーストから微小な無機粒子を取り除くことができるろ過材を提供することを目的とする。 An object of the present invention is to provide a filter material that can remove minute inorganic particles from inorganic pastes such as ceramic slurries and conductive pastes used in the manufacture of multilayer ceramic capacitors.
　本発明者は、無機ペーストに含有される無機粒子の電位と逆極性の電位が付与されたろ過材を用いることにより、微小な無機粒子を効果的に取り除くことができることを見出し、本発明を完成するに至った。 The present inventor discovered that minute inorganic particles can be effectively removed by using a filter material that is given a potential of opposite polarity to the potential of the inorganic particles contained in the inorganic paste, and completed the present invention. I ended up doing it.
　すなわち本発明は、粒径２０ｎｍ以上３００ｎｍ以下の第１の無機粒子と、粒径２０ｎｍ未満の第２の無機粒子と、有機溶剤と、バインダーと、分散剤と、を含む無機ペーストをろ過するためのろ過材であって、前記第１の無機粒子及び前記第２の無機粒子の電位と逆極性の電位が付与された、ろ過材である。 That is, the present invention is for filtering an inorganic paste containing first inorganic particles with a particle size of 20 nm or more and 300 nm or less, second inorganic particles with a particle size of less than 20 nm, an organic solvent, a binder, and a dispersant. The filter medium is provided with a potential having a polarity opposite to that of the first inorganic particles and the second inorganic particles.
　本発明のろ過材によれば、積層セラミックコンデンサの製造において用いるセラミックスラリーや導電性ペースト等の無機ペーストから微小粒子を取り除くことができるため、絶縁抵抗の低下を抑え、積層セラミックコンデンサの信頼性を高めることが可能となる。 According to the filter material of the present invention, microparticles can be removed from inorganic pastes such as ceramic slurry and conductive paste used in the manufacture of multilayer ceramic capacitors, thereby suppressing a decrease in insulation resistance and improving the reliability of multilayer ceramic capacitors. It is possible to increase it.
積層セラミックコンデンサの外観図である。FIG. 2 is an external view of a multilayer ceramic capacitor. 図１に示す積層セラミックコンデンサのＡ－Ａ線断面図である。2 is a cross-sectional view taken along line AA of the multilayer ceramic capacitor shown in FIG. 1. FIG. 内層部の一例を模式的に示す分解斜視図である。FIG. 3 is an exploded perspective view schematically showing an example of an inner layer part. 積層セラミックコンデンサの絶縁抵抗値の対数値（Log ＩＲ）の変化を示すグラフである。2 is a graph showing changes in the logarithmic value (Log IR) of the insulation resistance value of a multilayer ceramic capacitor.
　以下、本発明の実施形態として、本発明のろ過材によりろ過する無機ペースト、特に、積層セラミックコンデンサのグリーンシートを形成するためのセラミックスラリーや内部電極層を形成するための導電性ペースト、及びろ過材の構成について説明する。 Hereinafter, as embodiments of the present invention, inorganic pastes to be filtered using the filter medium of the present invention, particularly ceramic slurries for forming green sheets of multilayer ceramic capacitors, conductive pastes for forming internal electrode layers, and filtration. The composition of the material will be explained.
　なお、ろ過材によりろ過したセラミックスラリーや導電性ペーストを用いて製造される積層セラミックコンデンサとして２端子型積層セラミックコンデンサを例示的に示すが、本発明がこれに限定されることはない。また、図面は、発明の内容を説明するため、模式的に簡略化して描画している場合があり、描画された構成要素又は構成要素間の寸法の比率が、明細書に記載されたそれらの寸法の比率と一致していない場合がある。また、明細書に記載されている構成要素が、図面において省略されている場合や、個数を省略して描画されている場合などがある。 Note that although a two-terminal multilayer ceramic capacitor is exemplified as a multilayer ceramic capacitor manufactured using a ceramic slurry filtered through a filter medium or a conductive paste, the present invention is not limited thereto. In addition, the drawings may be drawn in a schematic and simplified manner in order to explain the content of the invention, and the drawn components or the dimensional ratios between the components may be different from those described in the specification. The dimensions may not match the proportions. In addition, there are cases where constituent elements described in the specification are omitted in the drawings or drawn with their numbers omitted.
（積層セラミックコンデンサ）
　図１～図３に、積層セラミックコンデンサ１の形状及び構造を示す。図１は、積層セラミックコンデンサ１の外観図である。図２は、図１に示す幅方向Ｗ中央部のＡ－Ａ線で切断した積層セラミックコンデンサ１の断面図(ＬＴ断面図)である。図３は、内層部３の構造を示す模式図である。なお、誘電体層と内部電極層を積層する方向を積層方向Ｔとし、積層方向Ｔに直交する長さ方向Ｌ、さらに積層方向Ｔと長さ方向Ｌに直交する幅方向Ｗを用いて、積層セラミックコンデンサ１の構造について言及する。なお、実施形態においては、幅方向Ｗ、長さ方向Ｌ、及び積層方向Ｔは、互いに直交しているが、必ずしも互いに直交する関係になるとは限らず、互いに交差する関係であってもよい。 (Multilayer ceramic capacitor)
1 to 3 show the shape and structure of a multilayer ceramic capacitor 1. FIG. 1 is an external view of a multilayer ceramic capacitor 1. FIG. 2 is a cross-sectional view (LT cross-sectional view) of the multilayer ceramic capacitor 1 taken along the line AA at the center in the width direction W shown in FIG. FIG. 3 is a schematic diagram showing the structure of the inner layer portion 3. As shown in FIG. Note that the direction in which the dielectric layers and internal electrode layers are laminated is defined as the lamination direction T, the length direction L is perpendicular to the lamination direction T, and the width direction W is perpendicular to the lamination direction T and the length direction L. The structure of the ceramic capacitor 1 will be described. In the embodiment, the width direction W, the length direction L, and the lamination direction T are orthogonal to each other, but they are not necessarily orthogonal to each other, and may be intersecting to each other.
　積層セラミックコンデンサ１は、直方体形状からなる積層体２を備えている。積層体２は、内層部３を含み、積層方向Ｔにおいて相互に対向する１対の第１主面ＴＳ１、第２主面ＴＳ２と、積層方向Ｔに直交する長さ方向Ｌにおいて相互に対向する１対の第１端面ＬＳ１、第２端面ＬＳ２と、積層方向Ｔ及び長さ方向Ｌの両方に直交する幅方向Ｗにおいて相互に対向する１対の第１側面ＷＳ１、第２側面ＷＳ２を有している。 The multilayer ceramic capacitor 1 includes a multilayer body 2 having a rectangular parallelepiped shape. The laminate 2 includes an inner layer part 3, and has a pair of first main surfaces TS1 and second main surfaces TS2 facing each other in the stacking direction T, and a pair of first main surfaces TS1 and second main surfaces TS2 facing each other in the length direction L perpendicular to the stacking direction T. It has a pair of first end surfaces LS1 and a second end surface LS2, and a pair of first side surfaces WS1 and second side surfaces WS2 that face each other in the width direction W perpendicular to both the stacking direction T and the length direction L. ing.
　積層セラミックコンデンサ１の寸法は、特に限定されるべきものではないが、例えば、高さ方向Ｔの寸法を０．１ｍｍ～２．５ｍｍ程度とし、長さ方向Ｌの寸法を０．１ｍｍ～３．２ｍｍ程度とし、幅方向Ｗの寸法を０．１ｍｍ～２．５ｍｍ程度とすることができる。 The dimensions of the multilayer ceramic capacitor 1 are not particularly limited, but for example, the dimensions in the height direction T are about 0.1 mm to 2.5 mm, and the dimensions in the length direction L are about 0.1 mm to 3.5 mm. The width can be approximately 2 mm, and the dimension in the width direction W can be approximately 0.1 mm to 2.5 mm.
　積層体２の表面に、第１外部電極４ａと第２外部電極４ｂが形成されている。 A first external electrode 4a and a second external electrode 4b are formed on the surface of the laminate 2.
　第１外部電極４ａは、積層体２の第１端面ＬＳ１に形成されている。第１外部電極４ａは、キャップ形状に形成されており、縁の部分が、積層体２の第１端面ＬＳ１から、第１主面ＴＳ１、第２主面ＴＳ２、第１側面ＷＳ１、第２側面ＷＳ２に延出して形成されている。 The first external electrode 4a is formed on the first end surface LS1 of the stacked body 2. The first external electrode 4a is formed in a cap shape, and the edge portion extends from the first end surface LS1 of the laminate 2 to the first main surface TS1, the second main surface TS2, the first side surface WS1, and the second side surface. It is formed extending to WS2.
　第２外部電極４ｂは、積層体２の第２端面ＬＳ２に形成されている。第２外部電極４ｂは、キャップ形状に形成されており、縁の部分が、積層体２の第２端面ＬＳ２から、第１主面ＴＳ１、第２主面ＴＳ２、第１側面ＷＳ１、第２側面ＷＳ２に延出して形成されている。 The second external electrode 4b is formed on the second end surface LS2 of the laminate 2. The second external electrode 4b is formed in a cap shape, and the edge portion extends from the second end surface LS2 of the laminate 2 to the first main surface TS1, the second main surface TS2, the first side surface WS1, and the second side surface. It is formed extending to WS2.
　積層セラミックコンデンサ１においては、積層体２の第１端面ＬＳ１に引出された第１内部電極層６ａが、第１外部電極４ａに接続されている。また、積層体２の第２端面ＬＳ２に引出された第２内部電極層６ｂが、第２外部電極４ｂに接続されている。 In the multilayer ceramic capacitor 1, the first internal electrode layer 6a drawn out to the first end surface LS1 of the multilayer body 2 is connected to the first external electrode 4a. Further, the second internal electrode layer 6b drawn out to the second end surface LS2 of the laminate 2 is connected to the second external electrode 4b.
　外部電極４は、例えば、下地電極層と、下地電極層上に配置されためっき層を備えた構造とすることができる。 The external electrode 4 can have a structure including, for example, a base electrode layer and a plating layer disposed on the base electrode layer.
　下地電極層は、ガラス及び金属を含む導電ペーストを積層体に塗布して焼き付けることによって形成される。焼付けは、積層体の焼成と同時に行ってもよいし、積層体の焼成後に行ってもよい。 The base electrode layer is formed by applying a conductive paste containing glass and metal to the laminate and baking it. The baking may be performed simultaneously with the firing of the laminate or after the laminate is fired.
　下地電極層上に配置されるめっき層は、例えば、Ｃｕ、Ｎｉ、Ａｇ、Ｐｄ、及びＡｕなどの金属、又はＡｇとＰｄの合金などのうちの少なくとも１つを含む。めっき層は、１層であってもよいし、複数層であってもよい。めっき層は、例えば、Ｎｉめっき層とＳｎめっき層の２層構造とすることができる。 The plating layer disposed on the base electrode layer includes, for example, at least one of metals such as Cu, Ni, Ag, Pd, and Au, or an alloy of Ag and Pd. The plating layer may be one layer or multiple layers. The plating layer can have, for example, a two-layer structure of a Ni plating layer and a Sn plating layer.
　内層部３は、複数の誘電体層５と複数の内部電極層６が積層されたものからなる。内部電極層６は、第１内部電極層６ａと第２内部電極層６ｂで構成される。第１内部電極層６ａと第２内部電極層６ｂは、それぞれ誘電体層５ａ、５ｂの上に配置されている。 The inner layer portion 3 is composed of a plurality of dielectric layers 5 and a plurality of internal electrode layers 6 stacked together. The internal electrode layer 6 is composed of a first internal electrode layer 6a and a second internal electrode layer 6b. The first internal electrode layer 6a and the second internal electrode layer 6b are arranged on the dielectric layers 5a and 5b, respectively.
　内部電極層６は、長さ方向Ｌに伸び、平面視において矩形形状をしている。そして、第１の内部電極層６ａが積層体２の第１端面ＬＳ１に引出され、第２の内部電極層６ｂが積層体２の第２端面ＬＳ２に引出されている。 The internal electrode layer 6 extends in the length direction L and has a rectangular shape in plan view. The first internal electrode layer 6a is drawn out to the first end surface LS1 of the laminate 2, and the second internal electrode layer 6b is drawn out to the second end surface LS2 of the laminate 2.
　誘電体層５の材質は任意であるが、例えば、ＢａＴｉＯ3を主成分とするセラミック粉末を使用することができる。また、ＢａＴｉＯ3に代えて、ＣａＴｉＯ3、ＳｒＴｉＯ3など、他の材質を主成分とするセラミック粉末を使用してもよい。 Although the material of the dielectric layer 5 is arbitrary, for example, ceramic powder containing BaTiO 3 as a main component can be used. Further, instead of BaTiO 3 , a ceramic powder containing other materials as a main component such as CaTiO 3 or SrTiO 3 may be used.
　誘電体層５の厚さは、特に限定されるべきものではないが、例えば、第１内部電極層６ａと第２内部電極層６ｂにより形成された容量形成の実効領域において、０．３μｍ～２．０μｍ程度とすることができる。 The thickness of the dielectric layer 5 is not particularly limited; The thickness can be approximately .0 μm.
　誘電体層５の層数は、特に限定されるべきものではないが、例えば、第１内部電極層６ａと第２内部電極層６ｂにより形成された容量形成の実効領域において、１層～６０００層とすることができる。 The number of layers of the dielectric layer 5 is not particularly limited, but for example, in the effective area of capacitance formation formed by the first internal electrode layer 6a and the second internal electrode layer 6b, the number of layers is 1 to 6000 layers. It can be done.
　内層部３の上下両側に、内部電極層６が形成されず、誘電体層５のみで構成された外層部７が設けられている。外層部７の厚さは限定されるものではないが、例えば、１５μｍ～１５０μｍとすることができる。なお、外層部７における誘電体層の厚さは、内部電極層６が形成されている容量形成の実効領域の誘電体層の厚さよりも大きくしてもよい。また、外層部における誘電体層の材質は、内層部における誘電体層の材質と異なっていてもよい。 On both upper and lower sides of the inner layer portion 3, an outer layer portion 7 is provided, which is composed only of the dielectric layer 5 without the internal electrode layer 6 formed thereon. The thickness of the outer layer portion 7 is not limited, but may be, for example, 15 μm to 150 μm. Note that the thickness of the dielectric layer in the outer layer portion 7 may be larger than the thickness of the dielectric layer in the effective area for forming capacitance where the internal electrode layer 6 is formed. Further, the material of the dielectric layer in the outer layer portion may be different from the material of the dielectric layer in the inner layer portion.
　図３は、内層部３を積層方向Ｔに誘電体層５ごとに分解して示したものである。 FIG. 3 shows the inner layer portion 3 broken down into dielectric layers 5 in the stacking direction T.
　内部電極層６は、導電体となる金属粉末と、有機溶剤と、バインダーと、分散剤と、を含む導電性ペーストを誘電体層上で焼結することにより形成される。内部電極層６と誘電体層５は交互に積層され内層部３を形成する。内部電極層６は、第１内部電極層６ａと第２内部電極層６ｂにより構成され、第１内部電極層６ａと第２内部電極層６ｂは、それぞれ誘電体層５ａ、５ｂの上に配置されている。 The internal electrode layer 6 is formed by sintering a conductive paste containing a metal powder that serves as a conductor, an organic solvent, a binder, and a dispersant on the dielectric layer. The internal electrode layer 6 and the dielectric layer 5 are alternately stacked to form the inner layer portion 3. The internal electrode layer 6 is composed of a first internal electrode layer 6a and a second internal electrode layer 6b, and the first internal electrode layer 6a and the second internal electrode layer 6b are disposed on the dielectric layers 5a and 5b, respectively.
　内部電極層６は、Ｃｕ、Ｎｉ、Ａｇ、Ａｕ、及びＰｔなどの金属を使用することができる。また、これらの金属は、これら金属元素を含む化合物や他の金属との合金であってもよい。 For the internal electrode layer 6, metals such as Cu, Ni, Ag, Au, and Pt can be used. Further, these metals may be compounds containing these metal elements or alloys with other metals.
　内部電極層６の厚さは特に限定されるものではないが、例えば、０．３μｍ～１．５μｍ程度とすることができる。 The thickness of the internal electrode layer 6 is not particularly limited, but may be, for example, about 0.3 μm to 1.5 μm.
（積層セラミックコンデンサの製造方法）
　積層セラミックコンデンサ１の製造方法の一例を以下に説明する。 (Manufacturing method of multilayer ceramic capacitor)
An example of a method for manufacturing the multilayer ceramic capacitor 1 will be described below.
　積層セラミックコンデンサ１の誘電体層５を形成するためのセラミックスラリーを用意する。セラミックスラリーを構成するセラミック粉末は、Ｂａ及びＴｉを含むペロブスカイト型化合物を用いることができる。 A ceramic slurry for forming the dielectric layer 5 of the multilayer ceramic capacitor 1 is prepared. As the ceramic powder constituting the ceramic slurry, a perovskite compound containing Ba and Ti can be used.
　一般式ＡmＢＯ3で表されるペロブスカイト型化合物のＡとＢのモル比Ａ／Ｂは、化学量論組成である必要はないが、０．９８以上１．０２以下であることが好ましい。 The molar ratio A/B of A and B in the perovskite compound represented by the general formula A m BO 3 does not have to be a stoichiometric composition, but is preferably 0.98 or more and 1.02 or less.
　Ｂａ源としては、ＢａＣＯ3などのＢａ化合物、Ｔｉ源としては、ＴｉＯ2などのＴｉ化合物を用いることができる。 As the Ba source, a Ba compound such as BaCO 3 can be used, and as the Ti source, a Ti compound such as TiO 2 can be used.
　その他、ペロブスカイト型化合物としては、ＣａＴｉＯ3、ＳｒＴｉＯ3等があり、これらの中からいずれかを選定し、あるいは、これらを混合して用いることができる。 Other perovskite compounds include CaTiO 3 and SrTiO 3 , and any one of these can be selected or a mixture of these can be used.
　なお、各種化合物の形態に特に制約はなく、酸化物の粉末、炭酸塩の粉末に限らず、塩化物の粉末、ゾルや金属有機化合物などであってもよい。 Note that there are no particular restrictions on the form of the various compounds, and they are not limited to oxide powders and carbonate powders, but may also be chloride powders, sols, metal organic compounds, and the like.
　ペロブスカイト型化合物の作製方法に特に制限はなく、固相法、液相法、水熱合成法、加水分解法などの公知の方法を使用することができる。 There are no particular restrictions on the method for producing perovskite compounds, and known methods such as solid phase method, liquid phase method, hydrothermal synthesis method, and hydrolysis method can be used.
　上記のようにして得たセラミック粉末に、有機溶剤と、バインダーと、分散剤を加えてボールミル等を用いて混合して、セラミックスラリーを作製することができる。 A ceramic slurry can be prepared by adding an organic solvent, a binder, and a dispersant to the ceramic powder obtained as described above and mixing the mixture using a ball mill or the like.
　セラミックスラリーは、セラミック粉末と有機ビヒクルとを混練して調製することができる。有機ビヒクルとは、バインダーを有機溶剤中に溶解したものである。 A ceramic slurry can be prepared by kneading ceramic powder and an organic vehicle. An organic vehicle is a binder dissolved in an organic solvent.
　有機ビヒクルに用いるバインダーは特に限定されるものではなく、エチルセルロース、ポリビニルブチラール等の通常の各種バインダーから適宜選択すればよい。また、有機ビヒクルに用いる有機溶剤も特に限定されず、テルピネオール、ブチルカルビトール、アセトン、トルエン等の各種有機溶剤から適宜選択すればよい。 The binder used in the organic vehicle is not particularly limited, and may be appropriately selected from various common binders such as ethyl cellulose and polyvinyl butyral. Further, the organic solvent used in the organic vehicle is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene.
　セラミック粉末の分散性は、分散剤を添加することにより向上する。分散剤は、特に限定されるものではなく、アニオン系、カチオン系、ノニオン系いずれでもよく、例えば、ポリアクリル酸やそのアンモニウム塩、ポリアクリル酸エステル共重合体、ポリエチレンオキサイド、ポリオキシエチレンアルキルアミルエーテル、脂肪酸ジエタノールアマイド、ポリエチレンイミン、ポリオキシプロピレンモノアリルモノブチルエーテルと無水マレイン酸等の共重合体等を用いることができる。 The dispersibility of ceramic powder is improved by adding a dispersant. The dispersant is not particularly limited and may be anionic, cationic, or nonionic, such as polyacrylic acid, its ammonium salt, polyacrylic acid ester copolymer, polyethylene oxide, polyoxyethylene alkyl amyl, etc. Ether, fatty acid diethanolamide, polyethyleneimine, copolymers of polyoxypropylene monoallyl monobutyl ether and maleic anhydride, etc. can be used.
　調製したセラミックスラリーは、ろ過材を用いてろ過するが、詳細は後述する。 The prepared ceramic slurry is filtered using a filter medium, details of which will be described later.
積層セラミックコンデンサの内部電極層を形成するための導電性ペーストを用意する。 A conductive paste for forming internal electrode layers of a multilayer ceramic capacitor is prepared.
　内部電極層用の導電性ペーストは、Ｃｕ、Ｎｉ、Ａｇ、Ａｕ、及びＰｔなどの金属又はこれら金属元素を含む化合物等からなる無機粒子と、有機溶剤と、バインダーと、分散剤と、が含まれる。 The conductive paste for the internal electrode layer contains inorganic particles made of metals such as Cu, Ni, Ag, Au, and Pt or compounds containing these metal elements, an organic solvent, a binder, and a dispersant. It will be done.
　内部電極層用の導電性ペーストは、上記の金属等を含む無機粒子と、上記の有機ビヒクルとを混練して調製する。また、導電性ペーストには、共材が含まれていてもよい。共材としては特に制限されないが、誘電体層を形成する主成分と同様の組成を有していることが好ましい。 The conductive paste for the internal electrode layer is prepared by kneading the above-mentioned inorganic particles containing metal etc. and the above-mentioned organic vehicle. Further, the conductive paste may contain a common material. The co-material is not particularly limited, but preferably has the same composition as the main component forming the dielectric layer.
　外部電極用ペーストは、上記した内部電極層用の導電性ペーストと同様にして調製すればよい。 The paste for external electrodes may be prepared in the same manner as the conductive paste for internal electrode layers described above.
　上記の各ペーストに含有される有機ビヒクルの量は特に制限されるものではなく、通常の含有量、例えば、バインダーは１～５重量％程度、溶剤は１０～５０重量％程度とすればよい。また、各ペースト中には、必要に応じて各種分散剤、可塑剤、誘電体、絶縁体等から選択される添加物が含有されてもよい。これらの総含有量は、１０重量％以下とすることが好ましい。 The amount of the organic vehicle contained in each of the above pastes is not particularly limited, and the content may be a normal content, for example, about 1 to 5% by weight for the binder and about 10 to 50% by weight for the solvent. Further, each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, etc., as necessary. The total content of these is preferably 10% by weight or less.
　調製した導電性ペーストは、ろ過材を用いてろ過するが、詳細は後述する。 The prepared conductive paste is filtered using a filter medium, details of which will be described later.
　誘電体層と内部電極層を積層する方法として、印刷法とシート法がある。 There are printing methods and sheet methods for laminating dielectric layers and internal electrode layers.
　印刷法は、セラミックスラリー及び導電性ペーストを、ＰＥＴ等の基板上に印刷、積層し、所定形状に切断した後、基板から剥離してグリーンチップとする。 In the printing method, ceramic slurry and conductive paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled off from the substrate to form a green chip.
　また、シート法は、セラミックスラリーを用いてグリーンシートを形成し、その上に導電性ペーストを印刷し内部電極層パターンを形成した後、これらを積層してグリーンチップとする。 In addition, in the sheet method, a green sheet is formed using ceramic slurry, a conductive paste is printed on it to form an internal electrode layer pattern, and then these are laminated to form a green chip.
　焼成前に、グリーンチップに脱バインダー処理を施す。脱バインダー処理の条件としては、昇温速度を好ましくは５～３００℃／時間、保持温度を好ましくは１８０～４００℃、温度保持時間を好ましくは０．５～２４時間とする。また、脱バインダー雰囲気は、空気もしくは還元性雰囲気とする。 Before firing, the green chips are subjected to binder removal treatment. As conditions for the binder removal treatment, the temperature increase rate is preferably 5 to 300°C/hour, the holding temperature is preferably 180 to 400°C, and the temperature holding time is preferably 0.5 to 24 hours. Further, the binder removal atmosphere is air or a reducing atmosphere.
　脱バインダー処理を施した後、グリーンチップの焼成を行う。焼成における昇温速度は、好ましくは１００～５００℃／時間である。焼成時の保持温度は、好ましくは１３００℃以下、より好ましくは１１５０～１２８０℃であり、その保持時間は、好ましくは０．５～８時間、より好ましくは２～３時間である。保持温度が上記範囲未満であると緻密化が不十分となり、この範囲を超えると、内部電極層の異常焼結による途切れの発生や、内部電極層を構成する成分の拡散により容量温度特性の悪化、誘電体磁器組成物の還元が生じ易くなる。 After the binder removal process, the green chips are fired. The temperature increase rate during firing is preferably 100 to 500°C/hour. The holding temperature during firing is preferably 1300°C or lower, more preferably 1150 to 1280°C, and the holding time is preferably 0.5 to 8 hours, more preferably 2 to 3 hours. If the holding temperature is less than the above range, densification will be insufficient, and if it exceeds this range, discontinuities will occur due to abnormal sintering of the internal electrode layer, and the capacitance-temperature characteristics will deteriorate due to diffusion of the components that make up the internal electrode layer. , reduction of the dielectric ceramic composition is likely to occur.
　焼成における雰囲気は、還元性雰囲気とすることが好ましく、例えば、Ｎ2とＨ2との混合ガスを加湿して用いることができる。 The atmosphere for firing is preferably a reducing atmosphere, and for example, a humidified mixed gas of N 2 and H 2 can be used.
　また、焼成時の酸素分圧は、導電性ペースト中の金属等の種類に応じて適宜決定することができるが、ＮｉやＮｉ合金等の卑金属を用いる場合、焼成雰囲気中の酸素分圧は、１０-14～１０-10ＭＰａとすることが好ましい。酸素分圧が上記範囲未満であると、内部電極層の導電材が異常焼結を起こし、途切れてしまうことがある。また、酸素分圧が上記範囲を超えると、内部電極層が酸化する傾向にある。降温速度は、好ましくは５０～５００℃／時間である。 In addition, the oxygen partial pressure during firing can be determined as appropriate depending on the type of metal in the conductive paste, but when using base metals such as Ni or Ni alloys, the oxygen partial pressure in the firing atmosphere is It is preferably 10 -14 to 10 -10 MPa. If the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may undergo abnormal sintering and be interrupted. Furthermore, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized. The temperature decreasing rate is preferably 50 to 500°C/hour.
　還元性雰囲気中で焼成した後、積層体にはアニールを施すことが好ましい。アニールは、誘電体層を再酸化するための処理であり、これにより絶縁抵抗の寿命を長くすることができるため、信頼性が向上する。 After firing in a reducing atmosphere, the laminate is preferably annealed. Annealing is a process for re-oxidizing the dielectric layer, which can extend the life of the insulation resistance, thereby improving reliability.
　アニールにおける雰囲気の酸素分圧は、１０-9～１０-5ＭＰａとすることが好ましい。酸素分圧が上記範囲未満であると誘電体層の再酸化が困難であり、上記範囲を超えると内部電極層の酸化が進行する傾向にある。 The oxygen partial pressure of the atmosphere during annealing is preferably 10 -9 to 10 -5 MPa. When the oxygen partial pressure is less than the above range, it is difficult to reoxidize the dielectric layer, and when it exceeds the above range, the internal electrode layer tends to be oxidized.
　アニールの際の保持温度は、１１００℃以下、特に１０００～１１００℃とすることが好ましい。保持温度が上記範囲未満であると誘電体層の酸化が不十分となるので、ＩＲが低く、また、絶縁抵抗の寿命が短くなり易い。一方、保持温度が上記範囲を超えると、内部電極層が酸化して容量が低下するだけでなく、内部電極層が誘電体層と反応してしまい、容量温度特性の悪化、絶縁抵抗の低下、絶縁抵抗の寿命の低下が生じやすくなる。なお、アニールは昇温過程及び降温過程だけで構成してもよい。この場合、保持温度は最高温度と同義であり、温度保持時間はない。 The holding temperature during annealing is preferably 1100°C or less, particularly 1000 to 1100°C. If the holding temperature is below the above range, the dielectric layer will not be sufficiently oxidized, resulting in a low IR and a tendency to shorten the life of the insulation resistance. On the other hand, if the holding temperature exceeds the above range, not only will the internal electrode layer oxidize and the capacity will decrease, but the internal electrode layer will also react with the dielectric layer, resulting in deterioration of capacitance-temperature characteristics, decrease in insulation resistance, and The life of insulation resistance is likely to be shortened. Note that annealing may consist of only a temperature raising process and a temperature lowering process. In this case, the holding temperature is synonymous with the maximum temperature, and there is no temperature holding time.
　上記以外のアニール条件としては、温度保持時間を好ましくは０～２０時間、より好ましくは２～４時間、降温速度を好ましくは５０～５００℃／時間、より好ましくは１００～３００℃／時間とする。また、アニールの雰囲気には、例えば、加湿したＮ2ガス等を用いることが好ましい。 As for annealing conditions other than the above, the temperature holding time is preferably 0 to 20 hours, more preferably 2 to 4 hours, and the temperature cooling rate is preferably 50 to 500°C/hour, more preferably 100 to 300°C/hour. . Furthermore, it is preferable to use, for example, humidified N 2 gas as the annealing atmosphere.
　上記の脱バインダー処理、焼成及びアニールにおいて、Ｎ2ガスや混合ガス等を加湿するには、例えば、ウェッター等を使用すればよい。この場合、水温は５～７５℃程度が好適である。 In the above-described binder removal treatment, firing, and annealing, a wetter or the like may be used, for example, to humidify N 2 gas, mixed gas, or the like. In this case, the water temperature is preferably about 5 to 75°C.
　脱バインダー処理、焼成及びアニールは、連続して行っても、独立に行ってもよい。 The binder removal treatment, firing, and annealing may be performed continuously or independently.
　上記の工程により得られた積層体に、例えば、バレル研磨やサンドブラストなどにより端面研磨を施し、外部電極用ペーストを塗布して焼成し、外部電極４を形成する。そして、必要に応じ、外部電極４表面に、めっき等により被覆層を形成する。 The end face of the laminate obtained by the above process is polished by, for example, barrel polishing or sandblasting, and an 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.
（無機ペーストのろ過）
　積層セラミックコンデンサの製造に用いるセラミックスラリーや導電性ペーストの無機ペーストは、ボールミルによるメディアを用いた分散工程において、チッピング粒子と呼ばれる粒径２０ｎｍ未満の微小粒子が発生するが、このような微小粒子は、その比表面積の大きさから、焼成時における無機粒子の粒成長を促進し、緻密な焼結体の形成を阻害する要因となるため、所定のろ過材を備えたフィルタを用いて取り除く必要がある。 (filtration of inorganic paste)
In the ceramic slurry and inorganic conductive paste used to manufacture multilayer ceramic capacitors, microparticles with a particle size of less than 20 nm called chipping particles are generated during the dispersion process using a ball mill media. Due to its large specific surface area, it is a factor that promotes the growth of inorganic particles during firing and inhibits the formation of a dense sintered body, so it is necessary to remove it using a filter equipped with a specified filter material. be.
　無機ペーストは、無機粒子と、有機溶剤と、バインダーと、分散剤と、を含有してなり、無機粒子は、粒径２０ｎｍ以上３００ｎｍ以下の第１の無機粒子と、粒径２０ｎｍ未満の第２の無機粒子と、が含まれる。 The inorganic paste contains inorganic particles, an organic solvent, a binder, and a dispersant, and the inorganic particles include first inorganic particles having a particle size of 20 nm to 300 nm, and second inorganic particles having a particle size of less than 20 nm. and inorganic particles.
　無機ペーストの粘度は、１５ｍＰａ・ｓ以上４５ｍＰａ・ｓ以下であることが好ましい。粘度が１５ｍＰａ・ｓ未満であると、ろ過工程においてスラリー濃度が小さく所定量の原料量を通液するために時間を要してしまう問題があり、４５ｍＰａ・ｓを超えると通液圧力が大きくなりフィルタが目詰まりを起こす問題がある為である。 The viscosity of the inorganic paste is preferably 15 mPa·s or more and 45 mPa·s or less. If the viscosity is less than 15 mPa・s, there is a problem that the slurry concentration is low in the filtration process and it takes time to pass a predetermined amount of raw material through the filtration process. This is because there is a problem that the filter may become clogged.
　ろ過材の材質を以下に箇条書きで記載する。ろ過材は、これらの材質による繊維体あるいは多孔質体等により構成することができる。 The materials of the filter media are listed below in bullet points. The filter medium can be composed of a fibrous body or a porous body made of these materials.
・合成樹脂
ポリオレフィン系樹脂、ポリエステル系樹脂、ポリアミド系樹脂、フッ素樹脂等、具体的には、高圧法低密度ポリエチレン、線状低密度ポリエチレン（ＬＬＤＰＥ）、高密度ポリエチレン、ポリプロピレン、ポリプロピレンランダム共重合体、ポリエステル（ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート等）、ポリアミド（ナイロン－６、ナイロン－６６等）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリパーフルオロアルコキシアルカン（ＰＦＡ）、ポリビニリデンフルオライド（ＰＶＤＦ）、ポリ塩化ビニル、ポリイミド、ポリアクリロニトリル、ポリカーボネート、ポリスチレン、ポリエーテルスルフォン、ポリスルフォン、セルロース等 ・Synthetic resins polyolefin resins, polyester resins, polyamide resins, fluororesins, etc. Specifically, high-pressure low density polyethylene, linear low density polyethylene (LLDPE), high density polyethylene, polypropylene, polypropylene random copolymer , polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66, etc.), polytetrafluoroethylene (PTFE), polyperfluoroalkoxyalkane (PFA), polyvinylidene fluoride ( PVDF), polyvinyl chloride, polyimide, polyacrylonitrile, polycarbonate, polystyrene, polyethersulfone, polysulfone, cellulose, etc.
・無機化合物
ガラス、シリカ、アルミナ、炭素、セラミック等 ・Inorganic compound glass, silica, alumina, carbon, ceramic, etc.
・金属
ステンレス等 ・Metal stainless steel, etc.
　ろ過材に正電極又は負電極の電位を付与する方法については、下記のような方法がある。以下に箇条書きで記載する。 There are the following methods for applying a positive or negative electrode potential to the filter medium. They are listed below in bullet points.
・ろ過材料製造時に、カチオン性基又はアニオン性基を有する材料を混ぜる
・ろ過材料に、カチオン性基又はアニオン性基を有する材料をコーティングや浸漬等により固定化する
・ろ過材料に、反応基を導入し、カチオン性基又はアニオン性基を有する材料を反応させ固定化する
・ろ過材料に、放射線やプラズマ等を照射し、カチオン性基又はアニオン性基を有する材料を固定化する ・When manufacturing the filtration material, mix a material with a cationic or anionic group. ・Immobilize the material with a cationic or anionic group on the filtration material by coating or dipping. ・Add a reactive group to the filtration material.・Irradiate the filtration material with radiation, plasma, etc. to immobilize the material that has a cationic or anionic group.
　無機ペーストをろ過材によりろ過する。ろ過材は、無機ペーストに含まれる無機粒子の電位と逆極性の電位を付与したものを用いることから、従来のろ過材では捕捉できなかった１次粒子より小さなサイズの微小粒子を捕捉することができる。 Filter the inorganic paste using a filter material. Since the filter material is given a potential that is opposite in polarity to the potential of the inorganic particles contained in the inorganic paste, it is possible to capture microparticles smaller than the primary particles that could not be captured with conventional filter media. can.
　無機ペーストに含有される無機粒子は、粒径２０ｎｍ以上３００ｎｍ以下の第１の無機粒子と粒径２０ｎｍ未満の第２の無機粒子があるが、第１の無機粒子及び第２の無機粒子の電位と逆極性の電位が付与されたろ過材を用いることにより、第２の無機粒子は、ろ過材に引き付けられ捕捉される。その結果、第１の無機粒子を含む無機ペーストを生成することができる。 The inorganic particles contained in the inorganic paste include first inorganic particles with a particle size of 20 nm or more and 300 nm or less and second inorganic particles with a particle size of less than 20 nm. By using a filter medium to which a potential of opposite polarity is applied, the second inorganic particles are attracted to and captured by the filter medium. As a result, an inorganic paste containing the first inorganic particles can be produced.
　ろ過材を通過する無機ペーストの流量は、０．５ｋｇ／ｍｉｎ以上２．０ｋｇ／ｍｉｎ以下であることが好ましい。このような流量でろ過することにより、第２の無機粒子を効率的にろ過材に捕捉することが可能となる。 The flow rate of the inorganic paste passing through the filter medium is preferably 0.5 kg/min or more and 2.0 kg/min or less. By filtering at such a flow rate, it becomes possible to efficiently trap the second inorganic particles in the filter medium.
　このようにして微小粒子を取り除くことにより、焼成する際の無機粒子の粒成長を抑制することができ、積層セラミックコンデンサの絶縁抵抗の低下を抑え、信頼性を向上させることが可能となる。 By removing the microparticles in this way, it is possible to suppress the grain growth of the inorganic particles during firing, and it is possible to suppress the decrease in insulation resistance of the multilayer ceramic capacitor and improve its reliability.
（比較試験）
　無機ペーストをろ過する効果を確認するため、無機粒子の電位と逆極性の電位を付与した繊維体からなるろ過材と、電位を付与しない繊維体からなる従来のろ過材を用いて比較試験を実施した。 (comparative test)
In order to confirm the effectiveness of filtering inorganic paste, a comparative test was conducted using a filter material made of fibers to which a potential of opposite polarity to that of the inorganic particles was applied, and a conventional filter material made of fibers to which no potential was applied. did.
　粘度３０ｍＰａ・ｓのセラミックスラリーを流量１．０ｋｇ／ｍｉｎにて各ろ過材でろ過した後、各ろ過材でろ過したセラミックスラリーを用いて製造した積層セラミックコンデンサを試料として物性を測定した。 After filtering a ceramic slurry with a viscosity of 30 mPa·s through each filter medium at a flow rate of 1.0 kg/min, the physical properties were measured using a multilayer ceramic capacitor manufactured using the ceramic slurry filtered through each filter medium as a sample.
（絶縁抵抗）
　各３０個の試料につき、室温下で、試料の外部電極間に４Ｖの直流電圧を印加して６０秒間保持して充電を行った。充電後の各サンプルの絶縁抵抗を測定し、その対数値Log ＩＲを求めた。結果を表１に示す。 (insulation resistance)
Each of the 30 samples was charged by applying a DC voltage of 4 V between the external electrodes of the sample and holding it for 60 seconds at room temperature. The insulation resistance of each sample after charging was measured, and its logarithm Log IR was determined. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように、電位を付与しないろ過材を用いた試料の絶縁抵抗値の対数値（Log ＩＲ）のばらつき（ＣＶ値）は８．０３であるのに対し、電位を付与したろ過材を用いた試料は、絶縁抵抗値の対数値（Log ＩＲ）のばらつき（ＣＶ値）が３．６０であり、良好な結果を確認することができた。 As shown in Table 1, the variation (CV value) in the logarithm of the insulation resistance value (Log IR) of samples using filter media to which no potential is applied is 8.03, while the variation (CV value) in the logarithm of the insulation resistance value (Log IR) of samples using filter media to which no potential is applied is 8.03; In the sample using this method, the dispersion (CV value) of the logarithm value (Log IR) of the insulation resistance value was 3.60, and a good result could be confirmed.
　つぎに、各７２個の試料について、温度１５０℃、印加電圧３．２Ｖの条件で絶縁抵抗ＩＲを継続して測定し、その対数値（Log ＩＲ）の変化を求めた。結果を図４に示す。 Next, the insulation resistance IR of each of the 72 samples was continuously measured under the conditions of a temperature of 150° C. and an applied voltage of 3.2 V, and the change in the logarithm value (Log IR) was determined. The results are shown in Figure 4.
　図４に示すように、電位を付与しないろ過材を用いた試料に比べ、電位を付与したろ過材を用いた試料は、時間の経過に伴う絶縁抵抗値の対数値（Log ＩＲ）の低下の度合いが小さいことを確認することができた。 As shown in Figure 4, compared to samples using filter media to which no potential is applied, samples using filter media to which a potential is applied are less likely to decrease the logarithm of insulation resistance (Log IR) over time. We were able to confirm that the degree of damage was small.
　以上、本発明の実施形態について説明したが、本発明は実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲において種々の態様で実施することが可能である。 Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and can be implemented in various forms without departing from the gist of the present invention.
　１　積層セラミックコンデンサ
　２　積層体
　３　内層部
　４　外部電極
　４ａ　第１外部電極
　４ｂ　第２外部電極
　５　誘電体層
　５ａ　誘電体層
　５ｂ　誘電体層
　６　内部電極層
　６ａ　第１内部電極層
　６ｂ　第２内部電極層
　７　外層部
　ＴＳ１　第１主面
　ＴＳ２　第２主面
　ＷＳ１　第１側面
　ＷＳ２　第２側面
　ＬＳ１　第１端面
　ＬＳ２　第２端面 1 Multilayer ceramic capacitor 2 Laminated body 3 Inner layer portion 4 External electrode 4a First external electrode 4b Second external electrode 5 Dielectric layer 5a Dielectric layer 5b Dielectric layer 6 Internal electrode layer 6a First internal electrode layer 6b Second internal electrode Layer 7 Outer layer portion TS1 First main surface TS2 Second main surface WS1 First side surface WS2 Second side surface LS1 First end surface LS2 Second end surface

Claims (8)

  1. 　粒径２０ｎｍ以上３００ｎｍ以下の第１の無機粒子と、粒径２０ｎｍ未満の第２の無機粒子と、有機溶剤と、バインダーと、分散剤と、を含む無機ペーストをろ過するためのろ過材であって、前記第１の無機粒子及び前記第２の無機粒子の電位と逆極性の電位が付与された、ろ過材。 A filtering material for filtering an inorganic paste containing first inorganic particles having a particle size of 20 nm or more and 300 nm or less, second inorganic particles having a particle size of less than 20 nm, an organic solvent, a binder, and a dispersant. and a filter medium to which a potential having a polarity opposite to that of the first inorganic particles and the second inorganic particles is applied.
  2. 　前記第１の無機粒子及び前記第２の無機粒子が、Ｂａ、Ｔｉ、Ｃａ、及びＳｒの中から選択される少なくとも１種以上の元素を含む、請求項１記載のろ過材。 The filter medium according to claim 1, wherein the first inorganic particles and the second inorganic particles contain at least one element selected from Ba, Ti, Ca, and Sr.
  3. 　前記第１の無機粒子及び前記第２の無機粒子が、Ｃｕ、Ｎｉ、Ａｇ、Ａｕ、及びＰｔの中から選択される少なくとも１種以上の元素を含む、請求項１記載のろ過材。 The filter medium according to claim 1, wherein the first inorganic particles and the second inorganic particles contain at least one element selected from Cu, Ni, Ag, Au, and Pt.
  4. 　前記無機ペーストの粘度が、１５ｍＰａ・ｓ以上４５ｍＰａ・ｓ以下である、請求項１乃至３のいずれかに記載のろ過材。 The filter medium according to any one of claims 1 to 3, wherein the inorganic paste has a viscosity of 15 mPa·s or more and 45 mPa·s or less.
  5. 　粒径２０ｎｍ以上３００ｎｍ以下の第１の無機粒子と、粒径２０ｎｍ未満の第２の無機粒子と、有機溶剤と、バインダーと、分散剤と、を含む無機ペーストを調製する工程と、前記第１の無機粒子及び前記第２の無機粒子の電位と逆極性の電位が付与されたろ過材を用いて前記無機ペーストをろ過する工程と、を含む、積層セラミックコンデンサの製造方法。 A step of preparing an inorganic paste containing first inorganic particles with a particle size of 20 nm or more and 300 nm or less, a second inorganic particle with a particle size of less than 20 nm, an organic solvent, a binder, and a dispersant; A method for manufacturing a multilayer ceramic capacitor, the method comprising: filtering the inorganic paste using a filter medium to which a potential of opposite polarity to the potential of the inorganic particles and the second inorganic particles is applied.
  6. 　前記第１の無機粒子及び前記第２の無機粒子が、Ｂａ、Ｔｉ、Ｃａ、及びＳｒの中から選択される少なくとも１種以上の元素を含む、請求項５記載の積層セラミックコンデンサの製造方法。 The method for manufacturing a multilayer ceramic capacitor according to claim 5, wherein the first inorganic particles and the second inorganic particles contain at least one element selected from Ba, Ti, Ca, and Sr.
  7. 　前記第１の無機粒子及び前記第２の無機粒子が、Ｃｕ、Ｎｉ、Ａｇ、Ａｕ、及びＰｔの中から選択される少なくとも１種以上の元素を含む、請求項５記載の積層セラミックコンデンサの製造方法。 Manufacturing the multilayer ceramic capacitor according to claim 5, wherein the first inorganic particles and the second inorganic particles contain at least one element selected from Cu, Ni, Ag, Au, and Pt. Method.
  8. 　０．５ｋｇ／ｍｉｎ以上２．０ｋｇ／ｍｉｎ以下の流量で前記無機ペーストをろ過する、請求項５乃至７のいずれかに記載の積層セラミックコンデンサの製造方法。 The method for manufacturing a multilayer ceramic capacitor according to any one of claims 5 to 7, wherein the inorganic paste is filtered at a flow rate of 0.5 kg/min or more and 2.0 kg/min or less.
PCT/JP2023/030304 2022-09-15 2023-08-23 Filtration material and method for producing multilayer ceramic capacitor using same WO2024057849A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58192317A (en) * 1982-05-07 1983-11-09 株式会社トーキン Method of producing internal electrode of porcelain condenser
JP2003123558A (en) * 2001-10-11 2003-04-25 Murata Mfg Co Ltd Manufacturing method of paste for thick film and manufacturing device of paste for thick film
JP2003519561A (en) * 2000-01-14 2003-06-24 マイクロリス・コーポレイシヨン System and method for liquid filtration based on neutral filter material
JP2005334865A (en) * 2004-01-19 2005-12-08 Hiroshima Univ Solid particle classifier and solid particle classification method utilizing the same
JP2011125801A (en) * 2009-12-18 2011-06-30 Denki Kagaku Kogyo Kk Wet classifier and wet classification method thereof
JP2014094323A (en) * 2012-11-07 2014-05-22 Mitsubishi Electric Corp Filter device for water heat exchanger, refrigeration cycle device including this water heat exchanger, and method of suppressing adhesion of substance to be captured to water heat exchanger

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58192317A (en) * 1982-05-07 1983-11-09 株式会社トーキン Method of producing internal electrode of porcelain condenser
JP2003519561A (en) * 2000-01-14 2003-06-24 マイクロリス・コーポレイシヨン System and method for liquid filtration based on neutral filter material
JP2003123558A (en) * 2001-10-11 2003-04-25 Murata Mfg Co Ltd Manufacturing method of paste for thick film and manufacturing device of paste for thick film
JP2005334865A (en) * 2004-01-19 2005-12-08 Hiroshima Univ Solid particle classifier and solid particle classification method utilizing the same
JP2011125801A (en) * 2009-12-18 2011-06-30 Denki Kagaku Kogyo Kk Wet classifier and wet classification method thereof
JP2014094323A (en) * 2012-11-07 2014-05-22 Mitsubishi Electric Corp Filter device for water heat exchanger, refrigeration cycle device including this water heat exchanger, and method of suppressing adhesion of substance to be captured to water heat exchanger

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