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
  • 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
  • B22F1/10—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
  • B22F9/00—Making metallic powder or suspensions thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper

Definitions

• the present invention relates to a conductive powder whose main component is copper, a conductive paste using the conductive powder, a method for manufacturing electronic components using the conductive paste, and a method for manufacturing a conductive powder whose main component is copper.
• the invention relates to a conductive powder that is suitable for forming terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators.
• 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.
• Patent Document 1 discloses a conductive thick film composition containing Cu powder, glass powder, and an organic vehicle, characterized in that the Cu powder is composed of spherical powder and scaly powder.
• 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, and a method for manufacturing the same.
• 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 electronic components that include thin, dense, and highly continuous terminal electrodes even when fired at low temperatures.
• a copper-based conductive powder having a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m to 4.5 ⁇ m, a ratio of the major axis X to the middle axis Y of 1.0 to 3.0 and a ratio of the major axis X to the minor axis Z of 1.5 to 5.0, and satisfying at least one of the following: (A) a carbon content of 0.00% to 0.10% by mass, (B) a TMA shrinkage rate of 0% to less than 2% at 400°C, and (C) an average change in TMA shrinkage rate per unit temperature [%/°C] from 400°C to 700°C of 0.05 or greater can be suitably used in a conductive paste capable of forming thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures, leading to the completion of the present invention.
• the present invention (1) is a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m or more and 4.5 ⁇ m or less; 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 5.0 or less,
• the present invention provides a conductive powder containing copper as a main component, which satisfies the following (A) and (B): (A) The carbon content is 0.00% by mass or more and 0.10% by mass or less.
• the TMA shrinkage rate is 0% or more and less than 2% at 400°C.
• 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.
• TMA shrinkage rate A sample was obtained by pressing 200 mg of the copper-based conductive powder 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. Then, using a TMA device, the sample was heated from room temperature to 900°C at a rate of 10°C/min in a nitrogen atmosphere. The percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm) was defined as the TMA shrinkage rate.
• the present invention (2) also provides a copper-based conductive powder (1) that satisfies the following (C): (C)
• the average change in the TMA shrinkage per unit temperature from 400°C to 700°C [%/°C] is 0.05 or more.
• the present invention (3) provides a copper-based conductive powder according to (1) or (2), in which the ratio of the TMA shrinkage rate at 600°C to the maximum TMA shrinkage rate is 0.73 or more.
• the present invention (4) provides a copper-based conductive powder according to any one of (1) to (3), in which the ratio of the TMA shrinkage rate at 700°C to the maximum TMA shrinkage rate is 0.90 or more.
• the present invention (5) provides a copper-based conductive powder according to any one of (1) to (4), in which the ratio of the TMA shrinkage at 720°C to the maximum TMA shrinkage is 0.94 or more.
• the present invention (6) also provides a conductive powder containing copper as a main component according to any one of (1) to (5), which has a tap density, as defined below, of more than 3.5 g/ cm3 .
• (tap density) 20 g of the copper-based conductive powder was weighed and placed in a 20 cm3 container. The tapping stroke was set to 20 mm and the number of tappings was set to 200, and the powder was tapped using a tap density measuring device. The ratio of the sample weight (g) to the sample volume ( cm3 ) after tapping was calculated and defined as the tap density.
• the present invention (7) also provides a copper-based conductive powder according to any one of (1) to (6), in which the ratio of the crystallite size to the D50 is 6.0 ⁇ 10 -3 or more.
• the present invention (8) provides a copper-based conductive powder according to any one of (1) to (7), which has an aliphatic amine on at least a portion of its surface.
• the present invention (9) also provides a conductive paste containing the copper-based conductive powder of any one of (1) to (8), glass frit, a binder resin, and an organic solvent.
• the present invention (10) also provides a method for manufacturing electronic components, comprising a laminated body preparation step of preparing a laminated body for a multilayer ceramic electronic component, which comprises multiple ceramic layers and multiple internal electrode layers, and a terminal electrode formation step of applying the conductive paste (9) 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 (11) also provides a method for manufacturing an electronic component according to (10), in which the peak temperature of the firing is 720°C or less.
• the present invention (12) also provides a method for producing a copper-based conductive powder according to any one of (1) to (8), comprising: a first step of preparing a copper-based raw metal powder produced by cooling molten copper-based metal droplets dispersed in a gas phase; and a second step of applying a physical force to the copper-based raw metal powder until the ratio of the major axis X to the minor axis Z reaches 1.5 or more and 5.0 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, and a method for producing the same. 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 producing 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 measured by laser diffraction particle size distribution measurement of 0.3 ⁇ m to 4.5 ⁇ m, a ratio of the major axis X to the median axis Y of 1.0 to 3.0 and a ratio of the major axis X to the minor axis Z of 1.5 to 5.0, and satisfies the following: (A) a carbon content of 0.00% by mass to 0.10% by mass, and (B) a TMA shrinkage of 0% to less than 2% at 400° C.
• the powder can be suitably used in a conductive paste capable of forming thin, dense, and highly continuous terminal electrodes, even when fired at low temperatures.
• the above-mentioned copper-based conductive powder in the conductive paste improves the packing of the conductive powder in the conductive paste coating, making it easier for the conductive powder to sinter even when fired at low temperatures. Furthermore, most resins used in conductive paste for terminal electrodes, particularly those fired at 720°C or less, thermally decompose at 400°C or less. Because the above-mentioned copper-based conductive powder does not sinter easily up to 400°C, shrinkage is suppressed, the binder resin is effectively removed, and carbon is less likely to remain during the firing process. Furthermore, sintering rapidly progresses above 400°C, making it less likely for blistering defects to occur during the high-temperature firing stage and making it easier to form thin, dense, and highly continuous terminal electrodes.
• the terms "major diameter X,”"intermediate diameter Y,””minor diameter Z,” and “TMA shrinkage rate” 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.
• TMA shrinkage rate A sample was obtained by pressing 200 mg of the copper-based conductive powder 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. Then, using a TMA device, the sample was heated from room temperature to 900°C at a rate of 10°C/min in a nitrogen atmosphere. The percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm) was defined as the TMA shrinkage rate.
• 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 main component.
• main component refers to a component that accounts for more than 50% by mass of the total.
• this refers to a copper component exceeding 50% by mass of the total conductive powder, including the mixed powders and alloy powders described below.
• the copper ratio 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 the copper ratio in the conductive powder within the above range facilitates sintering of the conductive powder particles, making it easier to obtain a dense fired film.
• the conductive powder in the present invention contains copper as the main component, it may be a mixed powder of copper powder and other metal powders such as nickel powder or silver powder, or it may be an alloy powder of copper and other metal elements such as nickel or silver. It may also be a composite powder in which copper powder is coated with glass or ceramic, or it may have an oxide film on the surface. It may also be surface-treated with an organometallic compound or surfactant, and two or more of these conductive powders may be mixed and used.
• 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 4.5 ⁇ m or less, more preferably 0.4 ⁇ m or more and 4.0 ⁇ m or less, even more preferably 0.5 ⁇ m or more and 3.5 ⁇ m or less, and particularly preferably 0.6 ⁇ m or more and 3.0 ⁇ 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 4.5 ⁇ m or less, more preferably 0.4 ⁇ m or more and 4.0 ⁇ m or less, even more preferably 0.5 ⁇ m or more and 3.5 ⁇ m or less, and particularly preferably 0.6 ⁇ m or more and 3.0 ⁇ m or less.
• the ratio of the major diameter X to the median diameter Y of the copper-based conductive powder of the present invention may be 1.0 or more and 3.0 or less, and preferably 1.0 or more and 2.5 or less.
• the ratio of the major diameter X to the median diameter 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 above-mentioned major axis X and median axis Y can both be measured by observation with a scanning electron microscope. That is, 100 conductive particles are randomly selected using a scanning electron microscope, and the average length of the long sides of the rectangle circumscribing each particle so as 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 ratio of the major axis X to the minor axis Z of the copper-based conductive powder of the present invention may be 1.5 or more and 5.0 or less, preferably 1.5 or more and 4.5 or less, more preferably 1.5 or more and 4.0 or less, more preferably 1.5 or more and 3.5 or less, even more preferably 1.5 or more and 3.0 or less, and particularly preferably 1.5 or more and 2.5 or less.
• the ratio of the major axis X to the 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. Furthermore, because shrinkage is suppressed, it is easier to form a thin, highly continuous fired film (terminal electrode).
• the above-mentioned minor axis Z can be measured by scanning electron microscopy of the cross section of a dried film formed using a paste-like composition containing the conductive powder of the present invention.
• terpineol e.g., Dianall MB-2677, manufactured by Mitsubishi Chemical Corporation
• terpineol e.g., Dianall MB-2677, manufactured by Mitsubishi Chemical Corporation
• 100 parts by mass of the conductive powder of the present invention and 7 parts by mass of an acrylic resin dissolved in terpineol are mixed together, kneaded using a three-roll mill (e.g., manufactured by Inoue Seisakusho), diluted with terpineol, and then heated at 25°C at 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.
• the coating film is dried in an air atmosphere at 150°C for 10 minutes to form a dry film.
• a cross section of the dry film is exposed using an ion milling device (e.g., IM4000 manufactured by Hitachi High-Technologies Corporation).
• the cross section of the dry film is observed using a scanning electron microscope (e.g., SU-8020 manufactured by Hitachi High-Technologies Corporation). 100 conductive particles are randomly selected from the observation, and the average length of the short sides of the rectangles circumscribing the conductive particles can be measured as the minor axis Z.
• the copper-based conductive powder of the present invention simultaneously satisfies the following requirements: (A) a carbon content of 0.00% to 0.10% by mass, and (B) a TMA shrinkage rate of 0% to less than 2% at 400°C.
• A a carbon content of 0.00% to 0.10% by mass
• B a TMA shrinkage rate of 0% to less than 2% at 400°C.
• sintering does not proceed easily up to 400°C, suppressing shrinkage and allowing for good binder resin removal.
• the low carbon content of the conductive powder itself makes it difficult for carbon to remain during the firing process.
• sintering tends to proceed rapidly above 400°C, making it less likely for blister defects to occur during the high-temperature firing stage, making it easier to form thin, dense, and highly continuous terminal electrodes.
• the carbon content may be between 0.00% and 0.10% by mass, but is preferably between 0.00% and 0.08% by mass, more preferably between 0.00% and 0.06% by mass, even more preferably between 0.00% and 0.05% by mass, and particularly preferably between 0.00% and 0.04% by mass. This makes it easier to achieve the aforementioned effects.
• the carbon content (%) can be measured using a carbon/sulfur analyzer (HORIBA, EMIA-320V).
• the TMA shrinkage rate at 400°C of the copper-based conductive powder of the present invention may be between 0% and 2%, preferably between 0% and 1%, and most preferably 0%. This allows the aforementioned effects to be obtained more significantly.
• the copper-based conductive powder of the present invention preferably simultaneously satisfies all of the above (A), (B), and (C): the average change in TMA shrinkage per unit temperature [%/°C] from 400°C to 700°C is 0.05 or more. This makes it difficult for sintering to proceed up to 400°C, thereby suppressing shrinkage and allowing for good binder resin removal.
• the conductive powder itself has a low carbon content, making it difficult for carbon to remain during the firing process.
• 400°C is exceeded, sintering proceeds rapidly, making it difficult for blister defects to occur during the high-temperature firing stage, making it particularly easy to form thin, dense, and highly continuous terminal electrodes.
• There is no particular upper limit to the average change but it can be set to, for example, 0.5 or less.
• the copper-based conductive powder of the present invention preferably has a ratio of the TMA shrinkage at 720°C to the maximum TMA shrinkage of 0.94 or more, more preferably 0.95 or more, even more preferably 0.96 or more, even more preferably 0.97 or more, and particularly preferably 1.0. This makes it easier to form highly dense terminal electrodes even when fired at low temperatures.
• the maximum TMA shrinkage refers to the largest shrinkage among the TMA shrinkages measured at each temperature when the conductive powder is heated from room temperature to 900°C using the method described above.
• the copper-based conductive powder of the present invention preferably has a ratio of the TMA shrinkage at 700°C to the maximum TMA shrinkage of 0.90 or more, more preferably 0.92 or more, more preferably 0.94 or more, even more preferably 0.95 or more, even more preferably 0.96 or more, and particularly preferably 1.0. This makes it even easier to form highly dense terminal electrodes even when fired at low temperatures.
• the copper-based conductive powder of the present invention preferably has a ratio of the TMA shrinkage at 600°C to the maximum TMA shrinkage of 0.73 or more, more preferably 0.85 or more, even more preferably 0.90 or more, and particularly preferably 0.93 or more. This makes it particularly easy to form highly dense terminal electrodes, even when fired at low temperatures.
• the copper-based conductive powder of the present invention preferably has a TMA shrinkage rate at 600°C of 16% or less, more preferably 15% or less, and especially preferably 14% or less. This makes it easier to form thin, highly continuous terminal electrodes.
• the copper-based conductive powder of the present invention preferably has a TMA shrinkage rate at 700°C of 21% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less. This makes it easier to form thin, highly continuous terminal electrodes.
• the copper-based conductive powder of the present invention preferably has a TMA shrinkage rate at 720°C of 22% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less. This makes it easier to form thin, highly continuous terminal electrodes.
• the copper-based conductive powder of the present invention preferably has a TMA shrinkage rate at 800°C of 22% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less. This makes it easier to form thin, highly continuous terminal electrodes.
• the copper-based conductive powder of the present invention preferably has an average change in TMA shrinkage per unit temperature [%/°C] from 400°C to 600°C of 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, even more preferably 0.06 or more, and particularly preferably 0.07 or more. This makes it easier to form highly dense terminal electrodes even when fired at low temperatures. There is no particular upper limit to the average change, but it can be set to 0.5 or less, for example.
• the copper-based conductive powder of the present invention preferably has a tap density of more than 3.5 g/cm 3 , more preferably 3.7 g/cm 3 or more, even more preferably 3.9 g/cm 3 or more, and particularly preferably 4.1 g/cm 3 or more.
• tap density is within the above range, it becomes easier to form thin, highly continuous terminal electrodes.
• the tap density (g/cm 3 ) can be calculated, for example, by measuring 20 g of the copper-based conductive powder of the present invention in a 20 cm 3 cell using a tap density measuring device (KYT-4000, manufactured by Seishin Enterprise Co., Ltd.), setting the tapping stroke to 20 mm and the number of taps to 200, and then calculating the ratio of the sample weight (g) to the sample volume (cm 3 ) after tapping.
• KYT-4000 manufactured by Seishin Enterprise Co., Ltd.
• the copper-based conductive powder of the present invention preferably has a crystallite diameter of 17 nm or more, more preferably 18 nm or more, even more preferably 19 nm or more, and particularly preferably 20 nm or more.
• a crystallite diameter within the above range, sintering does not proceed easily up to a certain temperature such as 400°C, thereby suppressing shrinkage and allowing for good binder resin removal.
• sintering rapidly proceeds above 400°C, making it easier to form highly dense terminal electrodes.
• the crystallite diameter There is no particular upper limit to the crystallite diameter, and it can be, for example, 25 nm or less, 24 nm or less, or 23 nm or less.
• the crystallite size can be calculated, for example, by using an XRD measurement device (Rigaku Corporation, SmartLab) with CuK ⁇ radiation (wavelength ⁇ : 1.5418 ⁇ ) at a tube voltage of 40 kV, a tube current of 30 mA, a step angle of 0.01°, and a scanning speed of 10.0°/min, performing XRD measurements over a diffraction angle 2 ⁇ of 20.0 to 100.0°, detecting the peak corresponding to the (111) plane (near 43°), measuring the half-width, and using the Scherrer equation.
• the copper-based conductive powder of the present invention preferably has a crystallite size to D50 ratio of 6.0 x 10 -3 or more, more preferably 7.0 x 10 -3 or more, more preferably 8.0 x 10 -3 or more, even more preferably 9.0 x 10 -3 or more, and particularly preferably 1.0 x 10 -2 or more.
• a crystallite size to D50 ratio is within the above range, sintering does not proceed easily up to a certain temperature, such as 400 ° C, so shrinkage is suppressed and the binder resin is removed well. However, sintering rapidly proceeds above 400 ° C, making it easier to form highly dense terminal electrodes.
• the upper limit of the crystallite size to D50 ratio is not particularly limited, but can be, for example, 1.0 x 10 -1 or less, 5.0 x 10 -2 or less, or 3.0 x 10 -2 or less.
• the copper-based conductive powder of the present invention is preferably one having a ratio of the major axis X to the minor axis Z in the above-mentioned range, since the dry film density is increased, and the higher the dry film density, the more suppressed the shrinkage.
• the dry film density (g/cm 3 ) can be calculated by casting the above-mentioned paste composition on a PET film to a thickness of 250 ⁇ m to form a coating film, drying the coating film in an air atmosphere at 100°C for 15 minutes, and then drying it in an air atmosphere at 150°C for 15 minutes to form a dry film, cutting the obtained dry film into a circle, measuring the weight and volume of the cut dry film, and then calculating the ratio of weight (g) to volume (cm 3 ).
• 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, cylindrical, elliptical cylindrical, truncated cone, truncated elliptical cone, or 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 the effects of the present invention are not impaired.
• 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°, and it is particularly preferable that the angle is 0°, i.e., parallel.
• the surface with the larger area will be referred to as the "bottom surface,” and the other surface will be referred to as the “surface opposing the bottom surface.” If the areas of the two opposing surfaces are the same, one of them will be arbitrarily selected 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, and it is sufficient that the "ratio of major diameter X to middle diameter Y," "ratio of major diameter X to minor diameter Z,” and "D50" of the conductive powder as a whole satisfy the aforementioned numerical ranges.
• the content of the conductive powder satisfying these 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.
• (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.
• There is no particular lower limit for (D90 - D10)/D50 but it can be, for example, 0.2 or more.
• 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 copper-based conductive powder of the present invention preferably 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 conductive paste, it becomes easier to form thin, highly continuous terminal electrodes.
• the amount of aliphatic amine is preferably 0.01 to 1.0 part 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.
• a variety of aliphatic amines can be used in the present invention, including primary amines such as octylamine, laurylamine, myristylamine, stearylamine, oleylamine, tallowamine, and tallowpropylenediamine; secondary amines such as distearylamine; and tertiary amines such as triethylamine, dimethyloctylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, dimethylbehenylamine, dimethyllaurylamine, and trioctylamine.
• primary amines such as octylamine, laurylamine, myristylamine, stearylamine, oleylamine, tallowamine, and tallowpropylenediamine
• secondary amines such as distearylamine
• tertiary amines such as triethylamine, dimethyloctylamine
• aliphatic amines Two or more of these amines may be used in combination, and mixtures of several aliphatic amines, typically sold commercially as "aliphatic amines," can also be used.
• the copper-based conductive powder of the present invention can be produced by the following method.
• the method for producing copper-based conductive powder of the present invention comprises a first step of preparing a copper-based raw metal powder produced by cooling molten copper-based metal droplets dispersed in a gas phase, and a second step of applying physical force to the copper-based raw metal powder until the ratio of the major axis X to the minor axis Z reaches 1.5 or more and 5.0 or less. This allows the copper-based conductive powder of the present invention to be produced in an optimal manner.
• the first step in the manufacturing method of the present invention is to prepare a raw metal powder containing copper as a main component by cooling molten metal droplets containing copper as a main component dispersed in a gas phase.
• the method for preparing the raw metal powder containing copper as a main component by cooling molten metal droplets containing copper as a main component dispersed in a gas phase is not particularly limited, and the following method can be used, for example.
• powder containing copper element is dispersed in a gas phase by a carrier gas, and then the copper element-containing powder dispersed in the gas phase is heat-treated at a temperature equal to or higher than the temperature at which the copper element-containing powder melts, thereby generating metal droplets containing molten copper as a main component dispersed in the gas phase, and then the metal droplets are cooled, thereby preparing the raw metal powder containing copper as a main component.
• the metal primarily composed of copper is heated to melt it and form a molten metal, and then the molten metal is dispersed in a gas phase to generate molten metal droplets primarily composed of copper, and then the metal droplets are cooled, thereby preparing the raw metal powder primarily composed of copper.
• the metal primarily composed of copper is heated to melt it and form a molten metal, then at least a portion of the molten metal is evaporated to generate metal vapor, then the metal vapor is cooled to form metal droplets, and then the metal droplets are cooled, thereby preparing the raw metal powder primarily composed of copper.
• a solution containing a copper salt is sprayed to form droplets, and the droplets are heat-treated at a temperature equal to or higher than the decomposition temperature of the copper salt and equal to or higher than the melting point of copper, thereby generating metal droplets whose main component is molten copper and dispersed in the gas phase, and then the metal droplets are cooled, thereby preparing a raw metal powder whose main component is copper.
• a thermally decomposable metal compound powder containing copper element is dispersed in a gas phase by a carrier gas, and then the thermally decomposable metal compound powder containing copper element dispersed in the gas phase is heat-treated at a temperature equal to or higher than the thermal decomposition temperature and equal to or higher than the melting point of copper to generate metal droplets containing molten copper as the main component dispersed in the gas phase, and then the metal droplets are cooled to prepare the raw metal powder containing copper as the main component.
• the raw metal powder containing copper as its main component prepared in the first step preferably has a carbon content of 0.00% by mass or more and 0.10% by mass or less, preferably 0.00% by mass or more and 0.08% by mass or less, more preferably 0.00% by mass or more and 0.06% by mass or less, even more preferably 0.00% by mass or more and 0.04% by mass or less, even more preferably 0.00% by mass or more and 0.02% by mass or less, even more preferably 0.00% by mass or more and 0.01% by mass or less, and especially preferably 0.00% by mass.
• the copper-based conductive powder of the present invention is preferably prepared by the above-mentioned method (the so-called dry method) using the copper-based raw metal powder prepared in the first step.
• the conductive powder obtained through the second step described below is the copper-based conductive powder of the present invention, there are no particular restrictions on the manufacturing method, and it is not intended to rule out the use of copper-based raw metal powder prepared using the so-called wet method.
• the second step in the manufacturing method of the present invention is a step of applying physical force to the raw metal powder containing copper as a main component until the ratio of the major axis X to the minor axis Z becomes 1.5 or more and 5.0 or less to produce the copper-based conductive powder of the present invention.
• a method of applying physical force to copper-based raw metal powder until the ratio of major axis X to minor axis Z becomes 1.5 or more and 5.0 or less includes, for example, mixing media with the copper-based raw metal powder prepared in the first step, a solvent, and, if necessary, a lubricant, and then applying physical force to the copper-based raw metal powder using the media until the ratio of major axis X to minor axis Z becomes 1.5 or more and 5.0 or less.
• the media include beads and balls.
• the size of the media can be, for example, 0.1 mm in diameter.
• the material of the media is not particularly limited, but examples include zirconia.
• the solvent is not particularly limited, but examples include secondary butyl alcohol.
• the lubricant is not particularly limited, and examples include fatty acids and aliphatic amines, with aliphatic amines being preferred.
• the method for producing the copper-based conductive powder of the present invention may include the first and second steps described above, but may also include an additional step before the first step, an additional step between the first and second steps, or an additional step after the second step.
• 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. Having a glass transition point within this range allows the glass to easily wet and spread throughout the film even when fired at low temperatures, making it easier to form a dense fired film. Furthermore, since the glass frit does not wet and spread easily below 400°C, using it in combination with the copper-based conductive powder of the present invention, which does not sinter well up to 400°C and suppresses shrinkage, dramatically reduces residual carbon, making blister defects less likely to occur and further facilitating the formation of thin, dense, and highly continuous terminal electrodes, which is preferable. Furthermore, using it in combination with the binder resin described below that is suitably thermally decomposed below below is preferable because the above-mentioned effects are more pronounced, making it particularly easy to form thin, dense, and highly continuous terminal electrodes.
• 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 binder resin of the present invention preferably exhibits a weight loss of 98% or more by mass at temperatures of 400°C or less, as measured by thermogravimetric analysis (nitrogen atmosphere, heating at 10°C/min), more preferably a weight loss of 99% or more by mass, and particularly preferably a weight loss of 100% by mass.
• the binder resin of the present invention may be a combination of two or more types, but the thermogravimetric analysis preferably results in the above-mentioned range for the resin as a whole.
• 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 electrode area ratio of the terminal electrodes, the average maximum thickness of the terminal electrodes, and the average minimum thickness of the terminal electrodes can be calculated for the conductive paste of the present invention using an evaluation test sample prepared, for example, by the following method.
• an evaluation test sample can be prepared by preparing a rectangular parallelepiped laminated element measuring 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, 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 laminate is then held at 150°C in an air atmosphere for 10 minutes, and then heated at a rate of 50°C/min in a nitrogen atmosphere. After reaching 700°C, the element is held for 15 minutes to form terminal electrodes, thereby producing 20 electronic components equipped with terminal electrodes.
• Each of the 20 electronic components is then embedded in resin, and each electronic component is cut through the center of each end face in the stacking direction (perpendicular to the dielectric layers and internal electrode layers) to expose the cross section of the electronic component.
• 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 in which a laminated body for a multilayer ceramic electronic component consisting of multiple ceramic layers and multiple internal electrode layers is prepared, and a terminal electrode formation step in which a conductive paste is applied to the exposed ends of the internal electrodes of the laminated body, and then the applied conductive paste is fired to form terminal electrodes.
• the conductive paste of the present invention in the above-mentioned method for manufacturing electronic components, it is possible to form terminal electrodes that are thin, dense, and highly continuous, even when firing is performed at a low temperature in the terminal electrode formation process.
• the above-mentioned method for manufacturing electronic components makes it possible to manufacture electronic components equipped with terminal electrodes that are thin, dense, and highly continuous, even when firing is performed at a low temperature in the terminal electrode formation process.
• 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 stacking 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 using a scanning electron microscope in 10 fields of view for each electronic component, and the ratio of the electrode area within the observed field of view can be calculated as the electrode area ratio.
• the maximum thickness of the terminal electrodes 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.
• the thinner the terminal electrodes the larger the size of the laminated body can be; that is, the greater the electrode area and number of layers can be increased, thereby improving the performance of the multilayer ceramic electronic component.
• the method for measuring the aforementioned maximum thickness 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 when a perpendicular line is drawn from the outer periphery of the terminal electrode to the end face portion of the laminated body, the point at which the length of the perpendicular line is longest can be measured as the maximum thickness.
• the method for calculating the aforementioned average maximum thickness is also not particularly limited, but 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 wet process (liquid-phase reduction) and spherical copper powder produced by a known dry process (atomization) were prepared as raw material powders.
• zirconia beads with a diameter of 0.1 mm, the spherical copper powder, secondary butyl alcohol, and a predetermined lubricant (dimethylstearylamine) were mixed together.
• physical force was applied to the spherical copper powder by adjusting the flow rate and number of passes as appropriate 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 listed in Table 1.
• the raw material powders were used as is without undergoing the above-mentioned treatment.
• Experimental examples marked with an "*" are outside the scope of the present invention.
• ⁇ D50> The volume-based cumulative 10% 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. Of the two mutually perpendicular sides of a rectangle circumscribing the particle so as to minimize its area, the length of the longer side was defined as the major axis X, and the length of the shorter side was defined 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 length of the shorter of the two mutually perpendicular sides of a rectangle circumscribing the particles so as to minimize their area was measured as the minor axis Z.
• XRD measurement was performed using CuK ⁇ radiation (wavelength ⁇ : 1.5418 ⁇ ) at a tube voltage of 40 kV, a tube current of 30 mA, a step angle of 0.01°, and a scanning speed of 10.0°/min over a diffraction angle 2 ⁇ of 20.0 to 100.0°.
• the peak (near 43°) corresponding to the (111) plane was detected, the half-width was measured, and the crystallite diameter was calculated using the Scherrer equation.
• ⁇ Tap density> Using a tap density measuring device (KYT-4000, manufactured by Seishin Enterprise Co., Ltd.), 20 g of copper powder was weighed and placed in a 20 cm3 cell, and measurements were taken with a tapping stroke of 20 mm and a tapping count of 200. The tap density (g/ cm3 ) was calculated as the ratio of the sample weight (g) to the sample volume ( cm3 ) after tapping.
• ⁇ Shrinkage rate thermomechanical analysis (TMA)> 200 mg of copper powder was pressed at a pressure of 1.0 kN for 3 minutes to form a cylindrical shape with a diameter of 5 mm and a height of approximately 2 mm.
• the sample was heated from room temperature to 900°C at a rate of 10°C/min in a nitrogen atmosphere using a TMA apparatus (TMA4000S manufactured by Bruker Corporation), and the shrinkage rate (%) in the height direction of the sample was measured.
• TMA apparatus TMA4000S manufactured by Bruker Corporation
• the obtained value was rounded to the nearest whole number to obtain the shrinkage rate. That is, for example, if the obtained value was -0.4%, the shrinkage rate was 0%, and if the obtained value was 1.4%, the shrinkage rate was 1%.
• ⁇ 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 evaluation of terminal electrode density (electrode area ratio)
• the above-mentioned evaluation test samples were observed with a scanning electron microscope, with 10 visual fields per sample, for a total of 200 visual fields, and the ratio of the electrode area to the visual fields was calculated as the electrode area ratio.
• the electrode area ratio value was evaluated based on the following evaluation criteria. A rating of A was deemed to be acceptable.
• Electrode area ratio is 99% or more.
• 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 ⁇ 40 ⁇ m and the average value of the minimum thickness is ⁇ 1.0 ⁇ m (However, this does not apply to cases that fall under A above.)
• C The average value of the maximum thickness is greater than 40 ⁇ m, or the average value of the minimum thickness is less than 1.0 ⁇ m

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