Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
  • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/06—Metallic powder characterised by the shape of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/06—Metallic powder characterised by the shape of the particles
  • B22F1/068—Flake-like particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
  • B22F1/102—Metallic powder coated with organic material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/14—Treatment of metallic powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G4/00—Fixed capacitors; Processes of their manufacture
  • H01G4/30—Stacked capacitors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators

Definitions

• the present invention relates to a conductive powder primarily composed of copper, a conductive paste using the conductive powder, and a method for manufacturing electronic components using the conductive paste.
• the invention relates to a conductive powder suitable for forming terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators.
• Layered ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators are generally manufactured as follows:
• a conductive paste for the internal electrodes is printed in a predetermined pattern on a dielectric ceramic green sheet such as a barium titanate ceramic. Then, multiple such sheets are stacked and pressed together to obtain an unfired laminate in which ceramic green sheets and internal electrode paste layers are alternately stacked. The resulting laminate is then cut into chips of a predetermined shape to obtain a laminated body. Note that the laminated body may be fired at a high temperature at this stage, or it may not be fired at this stage and may be co-fired later with a terminal electrode paste layer formed using a conductive paste for the terminal electrodes. In either case, the laminate in its state before the terminal electrode paste layer is formed is referred to as a "laminated body.”
• a conductive paste for the terminal electrodes composed of conductive powder, binder resin, organic solvent, glass frit, etc., is printed on the exposed ends of the internal electrodes of the laminated body using a method such as dip printing to form a conductive paste layer, which is then dried as necessary and fired at a high temperature to form the terminal electrodes.
• a plating layer of nickel, tin, etc. may be formed on the terminal electrode by electroplating or other methods.
• the terminal electrodes are typically fired in a non-oxidizing atmosphere with as low an oxygen partial pressure as possible, such as an inert gas atmosphere with an oxygen content of several ppm to several tens of ppm, at a high peak temperature of around 800°C, to prevent these base metals from oxidizing during firing.
• a non-oxidizing atmosphere with as low an oxygen partial pressure as possible, such as an inert gas atmosphere with an oxygen content of several ppm to several tens of ppm, at a high peak temperature of around 800°C, to prevent these base metals from oxidizing during firing.
• binder which burns, decomposes, and scatters organic components such as binder resin. If the binder is not removed sufficiently at the relatively low temperature stage in the early stages of firing, before the glass fluidizes and the copper powder sinters, carbon and organic residues will become trapped in the film after sintering begins, causing various problems such as blister defects in the subsequent high-temperature stage.
• Patent Document 1 discloses a conductor paste for terminal electrodes that uses an aliphatic amine as a surface treatment agent for copper-based conductive powder, thereby improving the dispersibility of the conductive powder and significantly improving binder removal, thereby enabling the formation of dense terminal electrodes with excellent adhesiveness and conductivity.
• Patent Document 1 the conductive paste described in Patent Document 1 is designed for firing at high temperatures, such as 800°C. Therefore, firing at low temperatures, such as 720°C, does not allow for the formation of terminal electrodes that meet the above requirements.
• the present invention aims to provide a conductive powder whose main component is copper that can be suitably used in a conductive paste that can form thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures.
• the present invention also aims to provide a conductive paste that can form thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures.
• the present invention also aims to provide a method for manufacturing an electronic component that includes thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures.
• the inventors discovered that by using a copper-based conductive powder with the following composition, it can be suitably used in a conductive paste that can form thin, dense, and highly continuous terminal electrodes.
• the present invention (1) is A conductive powder containing copper as a main component, the conductive powder has a volume-based cumulative 50% particle diameter D50 of 0.3 ⁇ m or more and 7.5 ⁇ m or less, as measured by laser diffraction particle size distribution measurement; a ratio of a major diameter X defined below to a middle diameter Y defined below is 1.0 or more and 3.0 or less, and a ratio of a major diameter X defined below to a minor diameter Z defined below is 1.5 or more and 8.0 or less,
• the conductive powder has an aliphatic amine on at least a portion of its surface,
• the present invention provides a copper-based conductive powder, characterized in that the aliphatic amine is an aliphatic amine such that, when the copper-based conductive powder is heated from 38°C to 900°C at a heating rate of 10°C/min in an inert atmosphere by TG-MS, at least one peak is detected in a chromatogram with a mass number of 44, and the ratio of
• the paste composition was cast onto a PET film using an applicator to form a coating film with a thickness of 250 ⁇ m.
• the coating film was dried in an air atmosphere at 150°C for 10 minutes to form a dry film.
• the cross section of the dry film was exposed using an ion milling device, and the cross section of the dry film was observed with a scanning electron microscope. 100 particles were randomly selected, and the average value of the length of the short side of a rectangle circumscribing each particle so as to have the smallest area was defined as the minor axis Z.
• the present invention (2) also provides a copper-based conductive powder as described in (1), in which the aliphatic amine includes at least one of a primary amine and a secondary amine.
• the present invention (3) provides a copper-based conductive powder according to (1) or (2), in which, when the peak with the strongest intensity among the peaks within the range of 250°C or higher and 400°C or lower is defined as the main peak, at least one of the peak and shoulder peak exists within the range of from above the peak top temperature of the main peak to 400°C or lower.
• the present invention (4) provides a copper-based conductive powder according to any one of (1) to (3), in which, in a differential graph obtained by differentiating the chromatogram, there is an upwardly convex peak in the range of 250°C to 350°C, and when the peak with the strongest peak intensity among the upwardly convex peaks is defined as the main peak of the differential graph, there is at least one further upwardly convex peak in the range of 400°C or less above the peak top temperature of the main peak of the differential graph.
• the present invention (5) also provides a copper-based conductive powder according to any one of (1) to (4), in which the aliphatic amine is at least one selected from stearylamine and dodecylamine.
• the present invention (6) also provides a conductive paste containing the copper-based conductive powder of any one of (1) to (5), glass frit, a binder resin, and an organic solvent.
• the present invention (7) also provides a method for manufacturing electronic components, comprising: a laminated body preparation step for preparing a laminated body for a multilayer electronic component, which comprises a plurality of ceramic layers and a plurality of internal electrode layers; and a terminal electrode formation step for applying the conductive paste of (6) to the exposed ends of the internal electrodes of the laminated body, and then firing the applied conductive paste to form terminal electrodes.
• the present invention (8) provides a method for manufacturing an electronic component according to (7), in which the peak temperature when the conductive paste is fired is 720°C or less.
• the present invention provides a copper-based conductive powder that can be suitably used in a conductive paste that can form thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures. It also provides a conductive paste that can form thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures. It also provides a method for manufacturing electronic components that include thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures.
• FIG. 1 is a diagram for explaining how to determine the minor axis Z in the present invention.
• the copper-based conductive powder of the present invention has a volume-based cumulative 50% particle diameter D50 of 0.3 ⁇ m or more and 7.5 ⁇ m or less as measured by laser diffraction particle size distribution measurement, a ratio of the major axis X to the median axis Y of 1.0 or more and 3.0 or less, and a ratio of the major axis X to the minor axis Z of 1.5 or more and 8.0 or less, and has an aliphatic amine on at least a part of the surface, and the aliphatic amine is detected by TG-MS when the copper-based conductive powder is heated under an inert atmosphere.
• This aliphatic amine is one that, when heated from 38°C to 900°C at a heating rate of 10°C/min, detects one or more peaks in a chromatogram of mass number 44, and the ratio of the area of the peak within the range of 250°C to 400°C to the area of the peak within the range of 250°C to 900°C is less than 0.9, and the ratio of the area of the peak within the range of 250°C to 500°C to the area of the peak within the range of 250°C to 900°C is 0.9 or greater.
• the copper-based conductive powder of the present invention has a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m to 7.5 ⁇ m, a ratio of long diameter X to middle diameter Y of 1.0 to 3.0, and a ratio of long diameter X to short diameter Z of 1.5 to 8.0, and contains an aliphatic amine on at least a portion of the surface.
• the filling ability of the conductive powder in the coating film of the conductive paste is improved, which facilitates sintering of the conductive powder even when firing at a low temperature, making it easier to obtain a dense conductive film.
• the inventors then conducted further research and discovered that when the copper-based conductive powder is heated from 38°C to 900°C at a heating rate of 10°C/min in an inert atmosphere using TG-MS, one or more peaks are detected in a chromatogram with a mass number of 44, and the ratio of the area of the peak within the range of 250°C to 400°C to the area of the peak within the range of 250°C to 900°C is less than 0.9, and the ratio of the area of the peak within the range of 250°C to 500°C to the area of the peak within the range of 250°C to 900°C is 0.9 or greater, making it easier to obtain terminal electrodes with high continuity in the corners, leading to the completion of the present invention.
• the "major diameter X,”"intermediate diameter Y,” and “minor diameter Z" defined in this specification are defined as follows.
• (Long diameter X and medium diameter Y) One hundred particles are randomly selected by scanning electron microscope observation, and the average length of the long sides of the rectangle circumscribing each particle so as to have the smallest area is defined as the major axis X, and the average length of the short sides is defined as the median axis Y.
• (Short axis Z) 100 parts by mass of the copper-based conductive powder and 7 parts by mass of an acrylic resin dissolved in terpineol were mixed, then kneaded using a three-roll mill, and then diluted with terpineol.
• the viscosity at 25°C and a shear rate of 4 s -1 was adjusted to 30 Pa s to prepare a paste composition.
• the paste composition was cast onto a PET film using an applicator to form a coating film with a thickness of 250 ⁇ m.
• the coating film was dried in an air atmosphere at 150°C for 10 minutes to form a dry film.
• the cross section of the dry film was exposed using an ion milling device, and the cross section of the dry film was observed with a scanning electron microscope. 100 particles were randomly selected, and the average value of the length of the short side of a rectangle circumscribing each particle so as to have the smallest area was defined as the minor axis Z.
• FIG. 1 is a photograph of a cross section of a dried film obtained by drying a coating film, observed with a scanning electron microscope.
• the average length of the short sides 3 of the rectangle 2 circumscribing the cross section 1 of the conductive particle, which has the smallest area, is defined as the minor axis Z.
• the conductive powder of the present invention may be any powder containing copper as its primary component.
• "primary component” refers to a component exceeding 50% by mass.
• the copper component exceeds 50% by mass of the entire conductive powder, including the aforementioned mixed powders and alloy powders.
• the copper content in the conductive powder is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, even more preferably 95% by mass or more and 100% by mass or less, and particularly preferably 100% by mass (pure copper). Having a copper content in the conductive powder within the above range facilitates sintering of the conductive powder particles, making it easier to obtain a dense sintered film.
• the conductive powder of the present invention contains copper as its primary component, it may be a mixed powder of copper powder and other metal powders, such as nickel powder or silver powder, or an alloy powder of copper and other metal elements, such as nickel or silver. Furthermore, it may be a composite powder in which copper powder is coated with glass or ceramic, or may have an oxide film on its surface. Furthermore, the conductive powder may be surface-treated with an organometallic compound or a surfactant, and two or more of these conductive powders may be mixed together.
• the copper-based conductive powder of the present invention may have a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m or more and 7.5 ⁇ m or less, but is preferably 0.3 ⁇ m or more and 7.0 ⁇ m or less, more preferably 0.3 ⁇ m or more and 6.5 ⁇ m or less, more preferably 0.3 ⁇ m or more and 6.0 ⁇ m or less, more preferably 0.3 ⁇ m or more and 5.5 ⁇ m or less, more preferably 0.3 ⁇ m or more and 5.0 ⁇ m or less, even more preferably 0.3 ⁇ m or more and 4.5 ⁇ m or less, and particularly preferably 0.3 ⁇ m or more and 4.0 ⁇ m or less.
• D50 volume-based cumulative 50% particle diameter measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m or more and 7.5 ⁇ m or less, but is preferably 0.3 ⁇ m or more and 7.0 ⁇ m or less, more preferably 0.3 ⁇
• the copper-based conductive powder of the present invention may have a ratio of the major axis X to the median axis Y of 1.0 or more and 3.0 or less, preferably 1.0 or more and 2.5 or less.
• a ratio of the major axis X to the median axis Y of the copper-based conductive powder is within the above range, sintering proceeds easily even when firing at low temperatures, making it easier to form a dense fired film. It also makes it easier to form a thin, highly continuous fired film (terminal electrode).
• the major axis X and median axis Y can both be measured, for example, by scanning electron microscope observation.
• a plurality of conductive particles can be randomly selected using a scanning electron microscope, and the average length of the long sides of the rectangle circumscribing each particle to minimize its area can be measured as the major axis X and the average length of the short sides as the median axis Y.
• the copper-based conductive powder of the present invention may have a ratio of major axis X to minor axis Z of 1.5 or more and 8.0 or less, preferably 2.0 or more and 7.5 or less, more preferably 2.5 or more and 7.0 or less, more preferably 3.0 or more and 6.5 or less, even more preferably 3.5 or more and 6.0 or less, and particularly preferably 4.0 or more and 5.5 or less.
• a ratio of major axis X to minor axis Z of the copper-based conductive powder is within the above range, sintering proceeds easily even when firing at low temperatures, making it easier to form a dense fired film. It also makes it easier to form a thin, highly continuous fired film (terminal electrode).
• the minor axis Z can be measured, for example, by scanning electron microscopy of the cross section of a dried film formed using a paste composition containing the conductive powder of the present invention. More specifically, for example, 100 parts by mass of the conductive powder of the present invention and 7 parts by mass of an acrylic resin (Dianal MB-2677, manufactured by Mitsubishi Chemical Corporation) dissolved in terpineol are mixed, kneaded using a three-roll mill (manufactured by Inoue Seisakusho), diluted with terpineol, and then heated at 25°C and a shear rate of 4 s A paste-like composition is prepared by adjusting the viscosity at -1 to 30 Pa s, and the paste-like composition is cast onto a PET film using an applicator to form a coating film with a thickness of 250 ⁇ m.
• a paste composition containing the conductive powder of the present invention More specifically, for example, 100 parts by mass of the conductive powder of the present invention and 7 parts by mass of
• the copper-based conductive powder of the present invention has an aliphatic amine on at least a portion of its surface.
• the copper-based conductive powder can prevent oxidation of the copper-based conductive powder and improve the dispersibility of the conductive powder in the paste, thereby improving the packing of the conductive powder in the coating film of the conductive paste of the present invention, and thereby forming a fired film with excellent density even when fired at a low temperature.
• the conductive powder can be easily dispersed in the paste, it becomes easier to form thin, highly continuous terminal electrodes.
• the aliphatic amine in the present invention preferably includes at least one of a primary amine and a secondary amine, preferably a primary amine or a secondary amine, and particularly preferably a primary amine.
• primary amines include octylamine, dodecylamine, myristylamine, stearylamine, oleylamine, tallow amine, and tallow propylenediamine
• secondary amines include distearylamine, N-methylstearylamine, and di-n-octylamine.
• N-methylstearylamine, stearylamine, and dodecylamine are preferred, with stearylamine and dodecylamine being more preferred, and stearylamine being particularly preferred. This allows the effects of the present invention to be optimally achieved.
• the molecular weight of the aliphatic amine in the present invention may be, for example, 100 or more and 400 or less, or 150 or more and 350 or less.
• the boiling point or thermal decomposition temperature of the aliphatic amine in the present invention in a nitrogen atmosphere is preferably 500°C or lower, more preferably 450°C or lower, and even more preferably 400°C or lower. This makes it easier to achieve the effects of the present invention.
• thermal decomposition temperature There is no particular lower limit to the thermal decomposition temperature, and for example, an amine of 200°C or higher can be used.
• the number of carbon atoms in the main chain of the aliphatic amine in the present invention is preferably 8 or more and 20 or less, more preferably 10 or more and 20 or less, even more preferably 12 or more and 20 or less, still more preferably 14 or more and 20 or less, even more preferably 16 or more and 20 or less, and particularly preferably 17 or more and 19 or less.
• the aliphatic amine in the present invention may be a saturated aliphatic amine or an unsaturated aliphatic amine, but is preferably a saturated aliphatic amine.
• the alkyl group of the aliphatic amine in the present invention may be linear or branched.
• the content of aliphatic amine in the copper-based conductive powder of the present invention is preferably 0.01 to 1.0 parts by mass, more preferably 0.02 to 0.10 parts by mass, even more preferably 0.02 to 0.08 parts by mass, and particularly preferably 0.02 to 0.06 parts by mass, per 100 parts by mass of the copper-based conductive powder. Having the amount of aliphatic amine within the above range improves the dispersibility of the conductive powder in the paste and makes it easier to remove the aliphatic amine during firing, making it easier to form thin, dense, and highly continuous terminal electrodes.
• the peak with the strongest intensity among the peaks within the range of 250°C or higher and 400°C or lower is defined as the main peak, it is preferable that at least one of the peak and shoulder exists within the range of above the peak top temperature of the main peak and 400°C or lower. This allows the effects of the present invention to be preferably achieved.
• the differential graph obtained by differentiating the chromatogram there is an upwardly convex peak in the range of 250°C to 350°C, and when the peak with the strongest peak intensity among the upwardly convex peaks is taken as the main peak of the differential graph, it is preferable that at least one further upwardly convex peak be present in the range of 400°C or less above the peak top temperature of the main peak of the differential graph. This allows the effects of the present invention to be preferably achieved.
• a NETZSCH STA2500 Regulus TG-DTA for heating the sample and a JEOL JMS-Q1500GC MS for mass spectrometry of the substances vaporized by heating the sample can be used.
• the copper-based conductive powder of the present invention preferably has a carbon content of 0.00% by mass or more and 0.10% by mass or less, and particularly preferably 0.00% by mass or more and 0.08% by mass or less. Having a carbon content within the above range makes it easier to form thin, dense, and highly continuous terminal electrodes.
• the carbon content (%) can be measured using a carbon/sulfur analyzer (HORIBA, EMIA-320V).
• the copper-based conductive powder of the present invention preferably has a shrinkage rate (%) at 700°C, as measured by thermomechanical analysis (TMA), of 12% or less, more preferably 10% or less, and particularly preferably 9% or less. This facilitates the formation of thin, highly continuous terminal electrodes.
• the shrinkage rate (%) can be measured by pressing 200 mg of copper powder, the main component of which is copper, at a pressure of 1.0 kN for 3 minutes to form it into a cylindrical shape with a diameter of 5 mm and a height of 2 mm.
• the sample is then heated from room temperature to 900°C at a rate of 10°C/min in a nitrogen atmosphere using a TMA device (e.g., Bruker TMA4000S), and the shrinkage rate (%) is measured as the percentage (%) of the sample height at each temperature relative to the sample height (2 mm).
• a TMA device e.g., Bruker TMA4000S
• the copper-based conductive powder of the present invention preferably has a bottom surface and a surface facing the bottom surface, and can be shaped, for example, as a flattened surface, a cylindrical surface, an elliptical cylindrical surface, a truncated cone, a truncated elliptical cone, or a rectangular parallelepiped.
• This facilitates sintering even when firing at low temperatures, making it easier to form a dense fired film. It also makes it easier to form a thin, highly continuous fired film (terminal electrode).
• both the bottom surface and the surface facing the bottom surface are completely flat, but they may have irregularities as long as they do not impair the effects of the present invention.
• the average angle of the surface facing the bottom surface is preferably between 0° and 45°, more preferably between 0° and 30°, and even more preferably between 0° and 15°. 0°, i.e., parallel, is particularly preferred.
• the surface with the larger area is referred to as the "bottom surface,” and the other surface is referred to as the “surface opposing the bottom surface.” If the two opposing surfaces have the same area, one of them, selected arbitrarily, is referred to as the “bottom surface” and the other as the “opposing surface.”
• the conductive powder of the present invention does not exclude powders of other shapes, such as spherical ones.
• the conductive powder as a whole may have the "ratio of major diameter X to median diameter Y," "ratio of major diameter X to minor diameter Z,” and "D50" that satisfy the aforementioned numerical ranges.
• the content of the conductive powder that satisfies the numerical ranges relative to the total conductive powder is not particularly limited, but is preferably more than 50% by mass, more preferably 55% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.
• the ratio (D90 - D10)/D50 is preferably 7.5 or less, more preferably 6.5 or less, more preferably 5.0 or less, even more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.0 or less.
• the (D90 - D10)/D50 of the copper-based conductive powder is within the above range, i.e., when the particle size distribution of the conductive powder is narrow, sintering of the conductive powder can proceed uniformly throughout the entire film. In other words, localized sintering within the film can be suppressed, ensuring an appropriate binder removal path throughout the entire film, resulting in the formation of a thin, dense, and highly continuous terminal electrode. It also prevents the terminal electrode from becoming too thick due to extremely large conductive powder.
• the copper-based conductive powder of the present invention preferably has a specific surface area of 0.2 m 2 /g or more and 3.0 m 2 /g or less, particularly preferably 0.3 m 2 /g or more and 2.0 m 2 /g or less.
• a specific surface area within the above range, sintering proceeds easily even when fired at a low temperature, making it easier to form a dense fired film. It also makes it easier to form a thin fired film.
• the method for producing the copper-based conductive powder of the present invention is not particularly limited, and can be produced, for example, by producing spherical conductive powder using a wet method such as liquid-phase reduction, or a dry method such as atomization, spray pyrolysis, physical vapor deposition, or chemical vapor deposition. If necessary, the conductive powder is then surface-treated with a surface treatment agent such as an aliphatic amine, and then pulverized using a bead mill, ball mill, stamp mill, or the like. If necessary, classification can be performed before or after pulverization to adjust the particle size distribution. Wet methods are preferred in terms of obtaining powder with a uniform particle size distribution, while dry methods are preferred in terms of obtaining powder with excellent crystallinity.
• the conductive paste of the present invention contains the above-mentioned conductive powder containing copper as a main component of the present invention, glass frit, a binder resin, and an organic solvent.
• the conductive paste of the present invention is preferably used by applying the conductive paste to a laminated element or the like to form a coating film, drying the coating film as needed to form a dry film, and then firing it.
• a temperature of 600°C or higher but 720°C or lower is preferred, and a temperature of 600°C or higher but 700°C or lower is particularly preferred.
• the glass frit of the present invention preferably has a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m or more and 2.0 ⁇ m or less, more preferably 0.5 ⁇ m or more and 1.5 ⁇ m or less.
• D50 of the glass frit is in the above range, a dense fired film can be easily formed, and a fired film (terminal electrode) with excellent continuity can be easily formed.
• (D90 - D10)/D50 is preferably 7.5 or less, more preferably 6.5 or less, even more preferably 5.0 or less, even more preferably 3.5 or less, and particularly preferably 2.5 or less.
• the glass frit's (D90 - D10)/D50 is within the above range, i.e., when the glass frit has a narrow particle size distribution, uniformly sized glass frit is uniformly distributed within the pre-fired film, which is densely packed with conductive powder, making it easier for the conductive powder to sinter uniformly throughout the film. This also makes it possible to suppress localized sintering within the film, ensuring an appropriate debindering path throughout the film, resulting in the formation of a thin, dense, and highly continuous terminal electrode.
• the low level of extremely small glass frit which exists in agglomerates and is prone to softening and flow, makes it easier to suppress localized sintering and localized debindering problems resulting from this sintering.
• the low level of extremely large glass frit also suppresses exposure of the laminated body due to voids that form in areas where the glass frit flows during the firing process, thereby improving the continuity of the terminal electrode.
• composition of the glass frit in the present invention is not particularly limited, and examples of glasses that can be used include BaO-ZnO-based, BaO-ZnO-B 2 O 3- based, RO-ZnO-B 2 O 3 -MnO 2 -based, RO-ZnO - based, RO-ZnO-MnO 2 -based, RO-ZnO-SiO 2 -based, ZnO-B 2 O 3 -based, SiO 2 -B 2 O 3 -R' 2 O-based, and SiO 2 -RO-R' 2 O-based (wherein R is an alkaline earth metal element and R' is an alkali metal element).
• the glass transition point of the glass frit in the present invention is preferably 400°C or higher and 550°C or lower. When the glass transition point of the glass frit is within this range, the glass easily wets and spreads throughout the film even when fired at a low temperature, making it easier to form a dense fired film.
• the softening point of the glass frit in the present invention is preferably 500°C or higher and 650°C or lower. When the softening point of the glass frit is within this range, the glass easily wets and spreads throughout the film even when fired at a low temperature, making it easier to form a dense fired film.
• the specific surface area of the glass frit in the present invention is preferably 2.0 m 2 /g or more and 7.0 m 2 /g or less, particularly preferably 3.0 m 2 /g or more and 6.0 m 2 /g or less.
• the specific surface area of the glass frit is in the above range, the glass frit is easily dispersed uniformly in the film, and a dense fired film is easily formed.
• the amount of glass frit is preferably 1 part by mass to 20 parts by mass, more preferably 4 parts by mass to 18 parts by mass, even more preferably 6 parts by mass to 16 parts by mass, and particularly preferably 8 parts by mass to 14 parts by mass, per 100 parts by mass of conductive powder. Having the amount of glass frit within the above range makes it easier to form a dense fired film.
• the binder resin in the present invention is not particularly limited, but preferably contains an acrylic resin.
• the ratio of the acrylic resin to the total binder resin is preferably more than 50% by mass, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.
• an acrylic resin When an acrylic resin is used, it has excellent thermal decomposition properties in a nitrogen atmosphere, so the binder resin can be successfully removed without oxidizing copper.
• the amount of binder resin is not particularly limited, but is preferably 3 to 11 parts by mass, more preferably 4 to 10 parts by mass, even more preferably 5 to 9 parts by mass, and particularly preferably 6 to 8 parts by mass, per 100 parts by mass of conductive powder. Having the amount of binder resin within the above range makes it easier to form thin, dense, and highly continuous terminal electrodes.
• the weight-average molecular weight of the acrylic resin used in the present invention is not particularly limited, but for example, a resin between 20,000 and 1,000,000 can be used. It is also possible to combine two or more acrylic resins with different weight-average molecular weights, structures, etc.
• Organic solvent in the present invention is not particularly limited, and examples thereof include terpineol, dihydroterpineol, dihydroterpineol acetate, secondary butyl alcohol, butyl carbitol, butyl carbitol acetate, and benzyl alcohol.
• the conductive paste of the present invention may contain additives such as antifoaming agents, plasticizers, dispersants, and rheology modifiers, as needed, as long as the effects of the present invention are not impaired.
• plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, butyl benzyl phthalate, dioctyl adipate, diisononyl adipate, dibutyl sebacate, diethyl sebacate, dioctyl sebacate, tricresyl phosphate, chlorinated paraffin, and cyclohexane 1,2-dicarboxylic acid diisononyl ester.
• rheology modifiers include silica powder.
• the viscosity of the conductive paste of the present invention at a shear rate of 4 s -1 when measured at 25°C is not particularly limited, but is preferably 10.0 Pa s or more and 80.0 Pa s or less, and particularly preferably 20.0 Pa s or more and 60.0 Pa s or less.
• the viscosity of the conductive paste is in the above range, it becomes easier to form thin, dense, and highly continuous terminal electrodes.
• the ratio of the viscosity of the conductive paste of the present invention at a shear rate of 0.4 s - 1 to the viscosity at a shear rate of 40 s-1 when measured at 25°C is not particularly limited, but is preferably 2.0 or more and 20.0 or less, and particularly preferably 3.0 or more and 8.0 or less.
• the viscosity ratio of the conductive paste is within the above range, it becomes easier to form thin, dense, and highly continuous terminal electrodes.
• the value of the phase difference ⁇ between the strain and the stress generated by the strain is not particularly limited, but is preferably 45° or more and 80° or less, and particularly preferably 45° or more and 78° or less. Having a phase difference ⁇ value of the conductive paste within the above range makes it easier to form thin, dense, and highly continuous terminal electrodes.
• the conductive paste of the present invention can be used to calculate the electrode area ratio of the terminal electrodes, the average maximum thickness of the terminal electrodes, and the average minimum thickness of the terminal electrodes, as described below, using evaluation test samples prepared, for example, by the following method.
• the evaluation test sample can be prepared, for example, by preparing a rectangular parallelepiped laminated element having a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, in which multiple dielectric layers containing barium titanate and internal electrode layers containing nickel are stacked.
• the conductive paste is applied to the exposed ends of the laminated element by dip printing, with the laminated element lowered at a rate of 300 ⁇ m/s and raised at a rate of 100 ⁇ m/s.
• the conductive paste of the present invention is suitable as a conductive paste for forming terminal electrodes on a laminated body for a multilayer ceramic electronic component.
• the method for manufacturing electronic components using the conductive paste of the present invention comprises a laminated body preparation step of preparing a laminated body for a multilayer ceramic electronic component consisting of multiple ceramic layers and multiple internal electrode layers, and a terminal electrode formation step of applying a conductive paste to the exposed ends of the internal electrodes of the laminated body and then firing the applied conductive paste to form terminal electrodes.
• the laminated element preparation process is a process for preparing a laminated element for a multilayer ceramic electronic component.
• Laminated bodies for multilayer ceramic electronic components consist of multiple ceramic layers and multiple internal electrode layers. In laminated bodies for multilayer ceramic electronic components, the ceramic layers and internal electrode layers are stacked alternately. Examples of laminated bodies for multilayer ceramic electronic components include laminated bodies for multilayer ceramic capacitors, laminated bodies for multilayer ceramic inductors, and laminated bodies for piezoelectric actuators.
• Materials for forming the ceramic layers that make up the laminated body for multilayer ceramic electronic components include barium titanate, strontium titanate, calcium titanate, barium zirconate, strontium zirconate, calcium zirconate, and strontium calcium zirconate.
• the materials forming the internal electrode layers that make up the laminated element for multilayer ceramic electronic components include nickel, palladium, silver, copper, and gold, as well as alloys containing one or more of these (for example, an alloy of silver and palladium).
• the terminal electrode formation process is a process in which the conductive paste of the present invention is applied to the exposed ends of the internal electrodes of a laminated body for a multilayer ceramic electronic component, and the applied conductive paste is fired to form terminal electrodes.
• the method for applying the conductive paste is not particularly limited, and examples include dip printing, screen printing, and roll coating. Of these, dip printing is preferred. After applying the conductive paste to the laminated body, it may be dried and then fired.
• a plating layer can be formed on the surface of the electrodes.
• both ends of the laminated element where the internal electrodes are exposed are referred to as "ends," the surfaces of the ends where the internal electrodes are particularly exposed are referred to as “end faces,” and the outer edges of the end faces are referred to as “corners.”
• the paste is applied so as to cover the end faces and corners.
• the size of the laminated element in which the conductive paste of the present invention is used is not particularly limited, and it can be used, for example, in laminated elements for 2012-size laminated ceramic capacitors, 1608-size laminated elements for 1005-size laminated ceramic capacitors, 0603-size laminated elements for 0402-size laminated ceramic capacitors, and 0201-size laminated elements for multilayer ceramic capacitors.
• Thinner terminal electrodes are particularly required for small multilayer ceramic capacitors, and the conductive paste of the present invention can be suitably used in laminated elements for 1005-size laminated ceramic capacitors, 0603-size laminated elements for 0402-size laminated ceramic capacitors, and 0201-size laminated elements for multilayer ceramic capacitors.
• the electrode area ratio of the terminal electrodes of the multilayer ceramic electronic component obtained by the present invention is not particularly limited, but is preferably 90% or more, and particularly preferably 99% or more. This makes it easier to prevent the plating solution from penetrating into the laminated body when plating the terminal electrodes.
• the aforementioned electrode area ratio can be calculated, for example, by the following method: 20 electronic components are embedded in resin, and each electronic component is cut through the center of each end face of the electronic component in the lamination direction (perpendicular to the dielectric layers and internal electrode layers) to expose a cross section of each electronic component. The cross section is then observed with a scanning electron microscope (e.g., 10 fields of view per electronic component), and the ratio of the electrode area within the observed field of view can be calculated as the electrode area ratio.
• a scanning electron microscope e.g. 10 fields of view per electronic component
• the maximum thickness of the terminal electrodes measured using the method described below is preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less, more preferably 20 ⁇ m or less, even more preferably 15 ⁇ m or less, and particularly preferably 10 ⁇ m or less.
• the average maximum thickness of the terminal electrodes calculated using the method described below is preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less, more preferably 20 ⁇ m or less, even more preferably 15 ⁇ m or less, and particularly preferably 10 ⁇ m or less. This allows the size of the multilayer ceramic electronic component to be reduced.
• an electronic component can be embedded in resin and cut in the lamination direction (perpendicular to the dielectric layers and internal electrode layers) so as to pass through the center of both end face portions of the electronic component to expose a cross section of the electronic component. The cross section can then be observed with a scanning electron microscope, and a perpendicular line can be drawn from the outer periphery of the terminal electrode to the end face portion of the laminated element.
• the point at which the length of the perpendicular line is longest can be measured as the maximum thickness. While there are no particular limitations on the method for calculating the average maximum thickness, for example, the average maximum thickness of the terminal electrodes can be calculated by measuring the maximum thickness of each of 20 electronic components using the method described above and averaging the maximum thicknesses.
• the minimum thickness of the terminal electrodes measured using the method described below is preferably 1.0 ⁇ m or more, more preferably 2.5 ⁇ m or more, and particularly preferably 5.0 ⁇ m or more. Furthermore, the average value of the minimum thickness of the terminal electrodes calculated using the method described below is preferably 1.0 ⁇ m or more, more preferably 2.5 ⁇ m or more, and particularly preferably 5.0 ⁇ m or more. This makes it easier to prevent the plating solution from penetrating into the laminated body when plating the terminal electrodes.
• the method for measuring the minimum thickness mentioned above is not particularly limited, but for example, an electronic component can be embedded in resin and cut in the lamination direction (perpendicular to the dielectric layers and internal electrode layers) so as to pass through the center of both end face portions of the electronic component to expose a cross section of the electronic component.
• the cross section can then be observed with a scanning electron microscope, and the thickness of the point where the length of a perpendicular line drawn from the outer periphery of the terminal electrode to the end face portion of the laminated element body is smallest, and the thickness of the point where the distance between the corner of the laminated element body and the outer periphery of the terminal electrode is shortest, and the thickness of the thinnest of these points can be measured as the minimum thickness.
• the method for calculating the average minimum thickness mentioned above is not particularly limited, but for example, the average minimum thickness of the terminal electrodes can be calculated by measuring the minimum thickness of each of 20 electronic components using the method described above and averaging the minimum thicknesses.
• spherical copper powder produced by a known dry method (atomization) was prepared as the raw powder.
• zirconia beads with a diameter of 0.1 mm, the spherical copper powder, secondary butyl alcohol, and a predetermined lubricant (aliphatic amine) were mixed together, and a physical force was applied to the spherical copper powder using a bead mill by appropriately adjusting the flow rate and number of passes until the ratio of the major axis X to the minor axis Z reached the value shown in Table 1, thereby obtaining the copper powders of Experimental Examples 1 to 11.
• ⁇ D50> The volume-based cumulative 50% particle diameter D50 ( ⁇ m) was measured using a laser diffraction particle size distribution analyzer (HORIBA, LA-960).
• ⁇ Ratio of major diameter X to minor diameter Y and ratio of major diameter X to minor diameter Z The ratio of the major diameter X to the medial diameter Y and the ratio of the major diameter X to the minor diameter Z were calculated using the values of the major diameter X, the middle diameter Y, and the minor diameter Z measured by the following method. (Long diameter X and medium diameter Y) One hundred particles were randomly selected and observed under a scanning electron microscope. The average length of the long sides of a rectangle circumscribing each particle so as to minimize its area was measured as the major axis X and the average length of the short sides was measured as the middle axis Y.
• the cross section of the dry film was exposed using an ion milling device (IM4000 manufactured by Hitachi High-Technologies Corporation).
• the cross section of the dry film was observed with a scanning electron microscope (SU-8020 manufactured by Hitachi High-Technologies Corporation). Based on the observation, 100 copper particles were randomly selected, and the average value of the length of the short side of a rectangle circumscribing each particle so as to minimize the area was measured as the minor diameter Z.
• TG-MS thermogravimetry-mass spectrometry
• peak intensity the transition of the amount of gas generated (peak intensity) with respect to temperature change was measured when the temperature of a molecule having a mass number of 44 was raised from 38°C to 900°C at a heating rate of 10°C/min in an inert helium atmosphere, and the peak area was measured within each temperature range.
• Table 1 also shows the peak-top temperatures of predetermined peaks and the presence or absence of peaks and shoulders within predetermined temperature ranges.
• the transition of the amount of gas generated (peak intensity) with respect to temperature change of the molecule having a mass number of 44 was differentiated, and the peak-top temperatures and presence or absence of peaks of upwardly convex peaks within predetermined temperature ranges in the graph obtained by this differentiation are shown in Table 1.
• Electron ionization (EI) was used as the ionization method for MS.
• NETZSCH's STA2500 Regulus was used as the TG-DTA for heating the sample, and JEOL's JMS-Q1500GC was used as the MS for mass spectrometry of the substances vaporized by heating the sample.
• TMA thermomechanical analysis
• ⁇ Terminal electrode evaluation test> (Preparation of conductive paste) 100 parts by mass of copper powder, 7 parts by mass of an acrylic resin (Dianal MB-2677, manufactured by Mitsubishi Chemical Corporation) dissolved in terpineol as a resin, and 10 parts by mass of glass frit (BaO-ZnO-based glass) were mixed, then kneaded using a three-roll mill (manufactured by Inoue Seisakusho), and then diluted with terpineol.
• a conductive paste was prepared by adjusting the viscosity to 30 Pa s at 25°C and a shear rate of 4 s .
• a roughly rectangular parallelepiped laminated element measuring 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height was prepared, which consisted of multiple laminated layers of dielectric layers containing barium titanate and internal electrode layers containing nickel.
• a conductive paste was applied to the exposed ends of the laminated element by dip printing, with the laminated element lowered at a rate of 300 ⁇ m/s and raised at a rate of 100 ⁇ m/s.
• the laminated element was then held at 150°C in an air atmosphere for 10 minutes.
• the temperature was then increased at a rate of 50°C/min in a nitrogen atmosphere, and after reaching 700°C, the temperature was held for 15 minutes to form terminal electrodes, thereby producing an electronic component equipped with terminal electrodes.
• Electrode area ratio is 90% or more
• B Electrode area ratio is less than 90% (evaluation of fired film thickness of terminal electrode)
• the above-mentioned evaluation test samples were observed with a scanning electron microscope, and the thicknesses of the thickest and thinnest parts of the terminal electrodes (fired films) (maximum and minimum thicknesses) were measured, and the average values of the maximum and minimum thicknesses were calculated for each experimental example. The average values of the maximum and minimum thicknesses were evaluated based on the following evaluation criteria.
• A The average value of the maximum thickness is ⁇ 20 ⁇ m and the average value of the minimum thickness is ⁇ 2.5 ⁇ m
• B The average value of the maximum thickness is greater than 20 ⁇ m, or the average value of the minimum thickness is less than 2.5 ⁇ m

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