Method for manufacturing conductive powder, conductive paste, and electronic components, with copper as the main component.

Abstract

This conductive powder is mainly composed of copper, in which a D50 is 0.3-7.5 μm, a major axis X / middle diameter Y is 1.0-3.0, a major axis X / minor axis Z is 1.5-8.0, and an aliphatic amine is present on the surface. The aliphatic amine is such that at least one peak is detected in a chromatogram with a mass number 44 when the conductive powder containing copper as a main component is heated in TG-MS from 38°C to 900°C at a heating rate of 10°C / min in an inert atmosphere, the ratio of the area of the peak at 250-400°C to the area of the peak in the range of 250-900°C is less than 0.9, and the ratio of the area of the peak in the range of 250-500°C to the area of the peak in the range of 250-900°C is 0.9 or more. According to the present invention, it is possible to provide a conductive powder containing copper as a main component that can be suitably used for a conductive paste allowing formation of a terminal electrode that is thin, dense, and excellent in continuity, even by firing at a low temperature.

Description

[Technical Field]

[0001] This invention relates to a conductive powder mainly composed of copper, a conductive paste using the conductive powder, and a method for manufacturing electronic components using the conductive paste. In particular, it relates to a method suitable for forming terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators. [Background technology]

[0002] Multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators are generally manufactured as follows.

[0003] First, a conductive paste for internal electrodes is printed in a predetermined pattern onto a dielectric ceramic green sheet, such as a barium titanate ceramic. Then, multiple sheets of this material are stacked and pressed together to obtain an unfired laminate in which ceramic green sheets and internal electrode paste layers are alternately stacked. The obtained laminate is then cut into chips of a predetermined shape to obtain a laminated base body. The laminated base body may be fired at a high temperature at this stage, or it may not be fired at this stage and may be fired together with the terminal electrode paste layer that is later formed using the conductive paste for terminal electrodes. In this specification, in either case, the laminate in the state before the formation of the terminal electrode paste layer is referred to as the "laminated base body".

[0004] Subsequently, a conductive paste for terminal electrodes, consisting of conductive powder, binder resin, organic solvent, glass frit, etc., is printed onto the exposed ends of the internal electrodes of the laminated body by dip printing or the like to form a conductive paste layer. After drying as necessary, the paste is further fired at a high temperature to form the terminal electrodes.

[0005] Furthermore, a plating layer of nickel, tin, or other materials may be formed on the terminal electrodes by electroplating or other methods, as needed.

[0006] Traditionally, precious metals such as palladium, silver-palladium, and platinum were used as internal electrode materials. However, due to demands for resource conservation and cost reduction, and especially in sintered types, there are requirements to prevent delamination and cracking caused by oxidative expansion during sintering of palladium and silver-palladium. For this reason, in recent years, base metals such as nickel, cobalt, and copper have become the mainstream choice. Consequently, as terminal electrode materials, copper, nickel, cobalt, or alloys thereof, which readily form good electrical connections with base metal internal electrodes, are being used instead of the conventional silver and silver-palladium.

[0007] When base metals are used for the internal electrodes and terminal electrodes in this manner, the firing of the terminal electrodes is usually carried out at a high temperature of around 800°C in a non-oxidizing atmosphere with the lowest possible oxygen partial pressure, for example, in an inert gas atmosphere with an oxygen content of several ppm to several tens of ppm, so as not to oxidize these base metals during firing.

[0008] However, when firing metal powders, especially those primarily composed of copper, in a low-oxygen atmosphere, it is difficult to properly debinder the organic components such as binder resin by burning, decomposing, and scattering them. If debinder removal is not sufficiently performed at the relatively low temperature stage in the initial firing phase, before the glass fluidizes and the copper powder sintersects, carbon and organic residues become trapped in the film after sintering begins, leading to various problems such as blister defects at the subsequent high-temperature stage.

[0009] Therefore, a key challenge for conductive pastes using base metals, particularly copper-based metal powders, has traditionally been how to efficiently remove the binder in the initial stages of firing and reduce residual carbon before the copper powder sintersects at high temperatures.

[0010] As a technology to solve this problem, for example, Patent Document 1 discloses a conductive paste for terminal electrodes in which an aliphatic amine is used as a surface treatment agent for copper-based conductive powder, thereby improving the dispersibility of the conductive powder and significantly improving its binder-free properties, and thus enabling the formation of dense terminal electrodes with excellent adhesion and conductivity. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2006-004734 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0012] Incidentally, in recent years, there has been a demand to lower the firing temperature when forming the aforementioned terminal electrodes in order to reduce environmental impact, manufacturing costs, and thermal stress on the laminated body. In addition, there is a demand for miniaturization of electronic components, which in turn demands thinner terminal electrodes. In other words, there is a need to be able to properly remove the binder before the copper powder sintering progresses, to properly sinter and densify even at a low peak firing temperature, and to form thin terminal electrodes.

[0013] However, the conductive paste described in Patent Document 1 is designed for firing at high temperatures such as 800°C. Therefore, it is not possible to form terminal electrodes that meet the above requirements when firing at low temperatures such as 720°C.

[0014] Therefore, the present invention aims to provide a copper-based conductive powder that can be suitably used in conductive pastes that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. Furthermore, the present invention aims to provide a conductive paste that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. Furthermore, the present invention aims to provide a method for manufacturing electronic components equipped with thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. [Means for solving the problem]

[0015] As a result of diligent research to solve the above problems, the present inventors have found that a conductive powder mainly composed of copper having the following structure can be suitably used in a conductive paste that can form thin, dense, and highly continuous terminal electrodes.

[0016] In other words, the present invention (1) is, A conductive powder having copper as its main component, The conductive powder has a volume-based cumulative 50% particle size D50 of 0.3 μm or more and 7.5 μm or less in laser diffraction particle size distribution measurement. The ratio of the major axis X defined below to the medium axis Y defined below is between 1.0 and 3.0, and the ratio of the major axis X defined below to the minor axis Z defined below is between 1.5 and 8.0. 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, 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 the mass number 44 chromatogram, the ratio of the area of ​​the peak in the range of 250°C to 400°C to the area of ​​the peak in the range of 250°C to 900°C is less than 0.9, and the ratio of the area of ​​the peak in the range of 250°C to 500°C to the area of ​​the peak in the range of 250°C to 900°C is 0.9 or more. (Longest axis X and medium axis Y) Using a scanning electron microscope, 100 particles are randomly selected, and the average length of the longer side of the rectangle circumscribing each particle to minimize its area is defined as the major axis X, and the average length of the shorter side is defined as the medium axis Y. (minor axis Z) 100 parts by mass of conductive powder mainly composed of copper and 7 parts by mass of acrylic resin dissolved in terpineol are mixed, then kneaded using a three-roll mill, then diluted with terpineol, and processed at 25°C and a shear rate of 4s. -1The viscosity in [the composition system] was adjusted to 30 Pa·s to prepare a paste-like composition. The paste-like composition was cast onto a PET film using an applicator to form a coated film with a thickness of 250 μm. The coated film was dried under the conditions of an air atmosphere, 150 °C, and 10 minutes to form a dried film. The cross-section of the dried film was exposed using an ion milling apparatus, and the cross-section of the dried film was observed with a scanning electron microscope. 100 particles were randomly selected, and the average value of the length of the shorter side of the rectangle circumscribing each particle so that the area was minimized was defined as the minor diameter Z.

[0017] Further, the present invention (2) provides the conductive powder mainly composed of copper according to (1), wherein the aliphatic amine contains at least one of primary amines and secondary amines.

[0018] Further, the present invention (3) provides the conductive powder mainly composed of copper according to (1) or (2), wherein when the peak having the strongest peak 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 a peak and a shoulder peak exists within the range exceeding the peak top temperature of the main peak and 400 °C or lower.

[0019] Further, the present invention (4) provides the conductive powder mainly composed of copper according to any one of (1) to (3), wherein in the differential graph obtained by differentiating the chromatogram, a peak convex upward exists within the range of 250 °C or higher and 350 °C or lower, and when the peak having the strongest peak intensity among the peaks convex upward is defined as the main peak of the differential graph, at least one more peak convex upward exists within the range exceeding the peak top temperature of the main peak of the differential graph and 400 °C or lower.

[0020] Further, the present invention (5) provides the conductive powder mainly composed of copper according to any one of (1) to (4), wherein the aliphatic amine is at least one selected from stearylamine and dodecylamine.

[0021] Furthermore, the present invention (6) provides a conductive paste containing a conductive powder mainly composed of copper, one of (1) to (5), glass frit, a binder resin, and an organic solvent.

[0022] Furthermore, the present invention (7) provides a method for manufacturing an electronic component, comprising: a laminated body preparation step of preparing a laminated body for a laminated electronic component consisting of a plurality of ceramic layers and a plurality of internal electrode layers; and a terminal electrode formation step of 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.

[0023] Furthermore, the present invention (8) provides a method for manufacturing the electronic component of (7) wherein the peak temperature when the conductive paste is fired is 720°C or lower. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a copper-based conductive powder that can be suitably used in conductive pastes that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. Furthermore, it is possible to provide a conductive paste that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. Furthermore, it is possible to provide a method for manufacturing electronic components equipped with thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 illustrates how to determine the minor axis Z in the present invention. [Modes for carrying out the invention]

[0026] <Conductive powder with copper as the main component> The copper-based conductive powder of the present invention has a volume-based cumulative 50% particle size D50 of 0.3 μm to 7.5 μm in laser diffraction particle size distribution measurement, a ratio of the major axis X to the medium 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 8.0, and has an aliphatic amine on at least a part of its surface, wherein the aliphatic amine is obtained by TG-MS, and the copper-based conductive powder is elevated in an inert atmosphere. This aliphatic amine, when heated from 38°C to 900°C at a heating rate of 10°C / min, exhibits one or more peaks in a chromatogram of mass number 44, where the ratio of the area of ​​the peaks in the range of 250°C to 400°C to the area of ​​the peaks in the range of 250°C to 900°C is less than 0.9, and the ratio of the area of ​​the peaks in the range of 250°C to 500°C to the area of ​​the peaks in the range of 250°C to 900°C is 0.9 or more. This makes it suitable for use in conductive pastes that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures.

[0027] Conventionally, when using flake-shaped powder with a large ratio of major axis to minor axis, it was necessary to sinter the powder at high temperatures such as 800°C to form a dense conductive film, and a dense conductive film could not be obtained even when sintered at low temperatures such as 720°C. In contrast, the copper-based conductive powder of the present invention has a volume-based cumulative 50% particle size D50 of 0.3 μm to 7.5 μm as measured by laser diffraction particle size distribution measurement, a ratio of major axis X to medium axis Y of 1.0 to 3.0 and a ratio of major axis X to minor axis Z of 1.5 to 8.0, and has an aliphatic amine on at least a portion of its surface. Therefore, when used in a conductive paste, the packing ability of the conductive powder in the coated film of the conductive paste is improved, making it easier for the sintering of the conductive powder to proceed even when sintered at low temperatures, and thus easier to obtain a dense conductive film.

[0028] However, when the inventors conducted further investigations based on this finding, they confirmed that while favorable results were obtained in terms of low-temperature firing, the continuity of the corner portions of the formed terminal electrodes sometimes decreased.

[0029] The inventors then conducted further investigations and discovered that the aliphatic amine is such that, when the conductive powder mainly composed of copper is heated from 38°C to 900°C at a heating rate of 10°C / min in an inert atmosphere by TG-MS, one or more peaks are detected in the chromatogram of mass number 44, the ratio of the area of ​​the peak in the range of 250°C to 400°C to the area of ​​the peak in the range of 250°C to 900°C is less than 0.9, and the ratio of the area of ​​the peak in the range of 250°C to 500°C to the area of ​​the peak in the range of 250°C to 900°C is 0.9 or more, making it easier to obtain terminal electrodes with high continuity at the corners, thus completing the present invention.

[0030] In this specification (the present invention), "major axis X," "intermediate axis Y," and "minor axis Z" are defined as follows. (Longest axis X and medium axis Y) Using a scanning electron microscope, 100 particles are randomly selected, and the average length of the longer side of the rectangle circumscribing each particle to minimize its area is defined as the major axis X, and the average length of the shorter side is defined as the medium axis Y. (minor axis Z) 100 parts by mass of conductive powder mainly composed of copper and 7 parts by mass of acrylic resin dissolved in terpineol are mixed, then kneaded using a three-roll mill, then diluted with terpineol, and processed at 25°C and a shear rate of 4s. -1A paste-like composition is prepared by adjusting the viscosity 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 μm. The coating film is dried in an air atmosphere at 150°C for 10 minutes to form a dry film, and the cross-section of the dry film is exposed using an ion milling apparatus. The cross-section of the dry film is observed with a scanning electron microscope, 100 particles are randomly selected, and the average length of the short side of the rectangle circumscribing each particle to minimize its area is defined as the minor axis Z.

[0031] Figure 1 will be used to explain how to find the minor axis Z. Figure 1 shows a cross-section of the dried film obtained by drying the coated film, as observed with a scanning electron microscope. The minor axis Z is the average value of the lengths of the shorter sides 3 of the rectangle that minimizes the area of ​​the rectangle 2 circumscribing the cross-section 1 of the conductive particle.

[0032] The conductive powder of the present invention may be any powder whose main component is copper. In this specification, "main component" means that the component accounts for more than 50% by mass of the whole, and in particular, in the case of a conductive powder whose main component is copper, it means that the copper component accounts for more than 50% by mass of the total conductive powder, including the mixed powder and alloy powder mentioned above. The ratio of copper 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). When the ratio of copper in the conductive powder is within the above range, the conductive powders become easier to sinter with each other, making it easier to obtain a dense fired film. In addition, as long as the conductive powder in the present invention is a main component of copper, it may be a mixed powder of copper powder with other elemental metal powders such as nickel powder or silver powder, or an alloy powder of copper with other elemental metals such as nickel or silver. Furthermore, it may be a composite powder in which copper powder is coated with glass or ceramic, or it may have an oxide film on its surface. Furthermore, the conductive powders may be surface-treated with organometallic compounds or surfactants, and two or more of these conductive powders may be mixed and used.

[0033] The volume-based cumulative 50% particle size D50 of the copper-based conductive powder of the present invention, measured by laser diffraction particle size distribution, may be 0.3 μm or more and 7.5 μm or less, but is preferably 0.3 μm or more and 7.0 μm or less, more preferably 0.3 μm or more and 6.5 μm or less, more preferably 0.3 μm or more and 6.0 μm or less, more preferably 0.3 μm or more and 5.5 μm or less, more preferably 0.3 μm or more and 5.0 μm or less, even more preferably 0.3 μm or more and 4.5 μm or less, and particularly preferably 0.3 μm or more and 4.0 μm or less. When the D50 of the copper-based conductive powder is within the above range, sintering of the conductive powder proceeds more easily even when fired at low temperatures, and it becomes easier to form a dense fired film. It also becomes easier to form a thin fired film.

[0034] The copper-based conductive powder of the present invention has a ratio of major axis X to medium axis Y of 1.0 to 3.0, preferably between 1.0 and 2.5. Having the ratio of major axis X to medium axis Y within this range facilitates sintering even at low temperatures, making it easier to form a dense fired film. It also facilitates the formation of thin, continuous fired films (terminal electrodes). Both the major axis X and medium axis Y can be measured, for example, by scanning electron microscopy. Specifically, by randomly selecting multiple conductive particles (e.g., 100) using scanning electron microscopy, the average length of the long side of a rectangle circumscribing each particle to minimize its area can be measured as the major axis X, and the average length of the short side as the major axis Y.

[0035] The copper-based conductive powder of the present invention has a ratio of major axis X to minor axis Z of 1.5 to 8.0, preferably 2.0 to 7.5, more preferably 2.5 to 7.0, more preferably 3.0 to 6.5, even more preferably 3.5 to 6.0, and particularly preferably 4.0 to 5.5. Having the ratio of major axis X to minor axis Z of the copper-based conductive powder within the above range facilitates sintering even at low temperatures, making it easier to form a dense fired film. Furthermore, it facilitates the formation of a thin, continuous fired film (terminal electrode).

[0036] The aforementioned minor axis Z can be measured, for example, by scanning electron microscopy observation of a cross-section of a dried film formed using a paste-like 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 acrylic resin (Dianal MB-2677, manufactured by Mitsubishi Chemical Corporation) dissolved in terpineol are mixed, then kneaded using a three-roll mill (manufactured by Inoue Seisakusho), then diluted with terpineol, and the mixture is heated at 25°C and a shear rate of 4s. -1 A paste-like composition is prepared by adjusting the viscosity 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 μm. The coating film is dried in an air atmosphere at 150°C for 10 minutes to form a dried film, and the cross-section of the dried film is exposed using an ion milling device (e.g., IM4000 from Hitachi High-Tech Corporation). The cross-section of the dried film is observed using a scanning electron microscope (e.g., SU-8020 from Hitachi High-Tech Corporation), and 100 conductive particles are randomly selected from this observation. The average length of the short side of the rectangle circumscribing these conductive particles can be measured as the minor axis Z.

[0037] The copper-based conductive powder of the present invention has an aliphatic amine on at least a portion of its surface. By having an aliphatic amine on at least a portion of its surface, the copper-based conductive powder is prevented from oxidizing and its dispersibility in the paste is improved. As a result, the packing of the conductive powder in the coated film of the conductive paste of the present invention can be improved, and a dense fired film can be formed even when fired at low temperatures. Furthermore, because the dispersibility of the conductive powder in the paste is improved, it becomes easier to form thin terminal electrodes with good continuity.

[0038] The aliphatic amine in the present invention preferably contains at least one aliphatic amine from among primary and secondary amines, preferably a primary or secondary amine, and particularly preferably a primary amine. Examples of primary amines include octylamine, dodecylamine, myristylamine, stearylamine, oleylamine, tallowamine, and tallowpropylenediamine, and examples of secondary amines include distearylamine, N-methylstearylamine, and di-n-octylamine. Among these, N-methylstearylamine, stearylamine, and dodecylamine are preferred, stearylamine and dodecylamine are more preferred, and stearylamine is particularly preferred. This allows the effects of the present invention to be favorably obtained.

[0039] The molecular weight of the aliphatic amine in the present invention may be, for example, 100 to 400, or 150 to 350.

[0040] The boiling point or thermal decomposition temperature of the aliphatic amine in the present invention is preferably 500°C or lower, preferably 450°C or lower, and preferably 400°C or lower in a nitrogen atmosphere. This makes it easier to obtain the effects of the present invention. The lower limit of the thermal decomposition temperature is not particularly limited, and for example, one with a temperature of 200°C or higher can be used.

[0041] In the present invention, the number of carbon atoms in the main chain of the aliphatic amine is preferably 8 to 20, more preferably 10 to 20, more preferably 12 to 20, more preferably 14 to 20, even more preferably 16 to 20, and particularly preferably 17 to 19.

[0042] The aliphatic amine in the present invention may be a saturated aliphatic amine or an unsaturated aliphatic amine, but it is preferably a saturated aliphatic amine.

[0043] The alkyl group of the aliphatic amine in the present invention may be linear or branched.

[0044] The aliphatic amine content in the copper-based conductive powder of the present invention is preferably 0.01 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of copper-based conductive powder, more preferably 0.02 parts by mass or more and 0.10 parts by mass or less, even more preferably 0.02 parts by mass or more and 0.08 parts by mass or less, and particularly preferably 0.02 parts by mass or more and 0.06 parts by mass or less. Having the aliphatic amine content 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, thus making it easier to form thin, dense, and continuous terminal electrodes.

[0045] Furthermore, when the peak with the strongest peak intensity among the peaks within the range of 250°C to 400°C is designated as the main peak, it is preferable that at least one of the peaks and shoulders exists within a range exceeding the peak top temperature of the main peak but not exceeding 400°C. This allows the effects of the present invention to be favorably obtained.

[0046] Furthermore, in the differential graph obtained by differentiating the chromatogram, it is preferable that an upwardly convex peak exists within 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, there is preferably at least one more upwardly convex peak within the range of 400°C or less, exceeding the peak top temperature of the main peak of the differential graph. This allows the effects of the present invention to be suitably obtained.

[0047] As mentioned above, for example, the NETZSCH STA2500 Regulus can be used as a TG-DTA for heating the sample, and the JEOL JMS-Q1500GC can be used as an MS for mass spectrometry of the vaporized substance due to the heating of the sample.

[0048] 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 this range facilitates the formation of thin, dense, and highly continuous terminal electrodes. The carbon content (%) can be measured using a carbon-sulfur analyzer (EMIA-320V, manufactured by HORIBA).

[0049] The copper-based conductive powder of the present invention preferably has a shrinkage rate (%) at 700°C measured by thermomechanical analysis (TMA) of 12% or less, more preferably 10% or less, and particularly preferably 9% or less. This makes it easy to form thin, highly continuous terminal electrodes. The shrinkage rate (%) can be measured by first obtaining a sample by pressing 200 mg of copper powder, mainly composed of copper, under a pressure of 1.0 kN for 3 minutes to form a cylindrical shape with a diameter of 5 mm and a height of 2 mm. Then, using a TMA apparatus (e.g., Bruker TMA4000S), the sample is heated from room temperature to 900°C at a rate of 10°C / min in a nitrogen atmosphere, and the shrinkage rate (%) is measured as the percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm).

[0050] 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, flat, cylindrical, elliptic-cylindrical, frustoconical, elliptic-frustoconical, or rectangular parallelepiped. This facilitates sintering even when fired at low temperatures, making it easier to form a dense fired film. It also makes it easier to form a thin, continuous fired film (terminal electrode). The bottom surface and the surface facing the bottom surface are preferably perfectly 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 0° to 45°, more preferably 0° to 30°, even more preferably 0° to 15°, and particularly preferably 0°, i.e., parallel.

[0051] In this specification (the present invention), of two opposing surfaces, the surface with the larger area is referred to as the "bottom surface," and the other surface is referred to as the "surface opposite the bottom surface." If the areas of the two opposing surfaces are the same, one of them is arbitrarily chosen and referred to as the "bottom surface," and the other as the "opposing surface." The present invention does not exclude the conductive powder from containing powders of other shapes, such as perfectly spherical shapes, and it is sufficient that the "ratio of the major axis X to the medium axis Y," the "ratio of the major axis X to the minor axis Z," and "D50" of the conductive powder as a whole satisfy the aforementioned numerical ranges. In that case, the content of the conductive powder that satisfies the said numerical ranges relative to the total conductive powder is not particularly limited, but it 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.

[0052] The conductive powder of the present invention, mainly composed of copper, preferably has a (D90-D10) / D50 of 7.5 or less, more preferably 6.5 or less, more preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.0 or less, when the cumulative 10% particle diameter on a volume basis in laser diffraction particle size distribution measurement is D10 and the cumulative 90% particle diameter is D90. The lower limit of (D90-D10) / D50 is not particularly limited, but for example, it can be 0.2 or more.

[0053] The (D90-D10) / D50 of the copper-based conductive powder is within the above range, meaning that the particle size distribution of the conductive powder is narrow, which allows for uniform sintering of the conductive powder throughout the entire film. In other words, localized sintering within the film can be suppressed, ensuring proper binder removal pathways throughout the film, and as a result, a thin, dense, and highly continuous terminal electrode can be formed. Furthermore, it is possible to suppress the thickening of the terminal electrode film caused by extremely large conductive powder particles.

[0054] The specific surface area of ​​the copper-based conductive powder of the present invention is preferably 0.2 m². 2 / g or more 3.0m 2 Less than or equal to / g, particularly preferably 0.3m 2 / g or more 2.0m 2 The specific surface area of ​​the conductive powder, which is mainly composed of copper, is within the above range, which facilitates sintering even when fired at low temperatures, making it easier to form a dense fired film. It also makes it easier to form a thin fired film.

[0055] The method for producing the copper-based conductive powder of the present invention is not particularly limited. For example, spherical conductive powder can be produced by a wet method such as a liquid-phase reduction method, or by a dry method such as atomization, spray pyrolysis, physical vapor phase method, or chemical vapor phase method. Then, if necessary, the conductive powder can be surface-treated with a surface treatment agent such as an aliphatic amine described later, and then pulverized using a bead mill, ball mill, stamp mill, etc. The particle size distribution can also be adjusted by classification before or after the pulverization process, if necessary. The wet method is preferred in terms of obtaining a powder with a uniform particle size distribution, while the dry method is preferred in terms of obtaining a powder with excellent crystallinity.

[0056] <Conductive paste> The conductive paste of the present invention contains the aforementioned conductive powder mainly composed of copper, glass frit, binder resin, and organic solvent.

[0057] The conductive paste of the present invention is preferably used by applying the conductive paste to a laminated body or the like to form a coating film, drying the coating film as needed to form a dried film, and then firing it. The peak firing temperature is not particularly limited, and firing can be performed at 600°C or higher, which is lower than the conventional firing temperature. From the viewpoint of reducing environmental impact, reducing manufacturing costs, and reducing thermal stress on the laminated body, it is preferably 600°C to 720°C, and particularly preferably 600°C to 700°C.

[0058] <Glass frit> In the present invention, the volume-based cumulative 50% particle size D50 of the glass frit in laser diffraction particle size distribution measurement is preferably 0.3 μm or more and 2.0 μm or less, and more preferably 0.5 μm or more and 1.5 μm or less. Having the glass frit's D50 within the above range makes it easier to form a dense fired film and a fired film (terminal electrode) with excellent continuity.

[0059] In the present invention, when the cumulative 10% particle diameter on a volume basis in laser diffraction particle size distribution measurement of glass frit is defined as D10 and the cumulative 90% particle diameter as D90, (D90-D10) / D50 is preferably 7.5 or less, more preferably 6.5 or less, more preferably 5.0 or less, even more preferably 3.5 or less, and particularly preferably 2.5 or less. The lower limit of (D90-D10) / D50 is not particularly limited, but for example, it can be 0.2 or more.

[0060] Because the (D90-D10) / D50 of the glass frit is within the above range, i.e., the particle size distribution of the glass frit is narrow, uniformly sized glass frit particles are uniformly distributed even within the pre-firing film densely packed with conductive powder, making it easier for the conductive powder to sinter uniformly throughout the entire film. Furthermore, this suppresses the progression of localized sintering within the film, ensuring an appropriate debinder pathway throughout the entire film, resulting in the formation of a thin, dense, and highly continuous terminal electrode. The absence of extremely small glass frit particles that exist in aggregate and are prone to softening and flowing makes it easier to suppress the progression of localized sintering and the resulting localized debinder defects. In addition, the absence of extremely large glass frit particles suppresses the exposure of the laminated element due to voids created where the glass frit flows during the firing process, thereby improving the continuity of the terminal electrode.

[0061] The composition of the glass frit in the present invention is not particularly limited, and for example, glasses such as BaO-ZnO system, BaO-ZnO-B2O3 system, RO-ZnO-B2O3-MnO2 system, RO-ZnO system, RO-ZnO-MnO2 system, RO-ZnO-SiO2 system, ZnO-B2O3 system, SiO2-B2O3-R'2O system, and SiO2-RO-R'2O system (where R is an alkaline earth metal element and R' is an alkali metal element) can be used.

[0062] 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 the above range, even when firing at a low temperature, the glass is likely to wet and spread in the film, making it easier to form a dense fired film.

[0063] 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 the above range, even when firing at a low temperature, the glass is likely to wet and spread in the film, making it easier to form a dense fired film.

[0064] 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. When the specific surface area of the glass frit is within the above range, the glass frit is likely to disperse uniformly in the film, making it easier to form a dense fired film.

[0065] The amount of the glass frit in the present invention is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 4 parts by mass or more and 18 parts by mass or less, still more preferably 6 parts by mass or more and 16 parts by mass or less, and particularly preferably 8 parts by mass or more and 14 parts by mass or less with respect to 100 parts by mass of the conductive powder. When the amount of the glass frit is within the above range, it becomes easier to form a dense fired film.

[0066] <Binder resin> 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 whole binder resin is preferably more than 50% by mass, more preferably 60% by mass or more, still more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. When an acrylic resin is used, it has excellent thermal decomposability in a nitrogen atmosphere, so the binder resin can be removed well without oxidizing copper.

[0067] The amount of binder resin in the present invention 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 terminal electrodes that are thin, dense, and have excellent continuity.

[0068] The weight-average molecular weight of the acrylic resin in this invention is not particularly limited, but for example, one with a molecular weight of 20,000 to 1,000,000 can be used. Furthermore, two or more acrylic resins with different weight-average molecular weights and structures may be used in combination.

[0069] <Organic solvents> The organic solvent used in this invention is not particularly limited and includes terpineol, dihydroterpineol, dihydroterpineol acetate, secondary butyl alcohol, butyl carbitol, butyl carbitol acetate, benzyl alcohol, and the like.

[0070] <Additives> The conductive paste of the present invention may contain additives such as defoaming agents, plasticizers, dispersants, and rheology modifiers, as needed, in addition to the above components, as long as the effects of the present invention are not impaired. Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, din-octyl phthalate, butyl benzyl phthalate, dioctyl adipate, diisononyl adipate, dibutyl sebacate, diethyl sebacate, dioctyl sebacate, tricresyl phosphate, chlorinated paraffin, and diisononyl cyclohexane-1,2-dicarboxylic acid ester. Examples of rheology modifiers include silica powder.

[0071] <Physical properties of conductive paste> The shear rate of the conductive paste of the present invention, measured at 25°C, is 4s. -1The viscosity of the conductive paste is not particularly limited, but is preferably between 10.0 Pa·s and 80.0 Pa·s, and particularly preferably between 20.0 Pa·s and 60.0 Pa·s. Having the viscosity of the conductive paste within this range makes it easier to form thin, dense, and continuous terminal electrodes.

[0072] The shear rate of the conductive paste of the present invention, measured at 25°C, was 40 s. -1 Shear rate of 0.4 s for viscosity -1 The viscosity ratio in this case is not particularly limited, but is preferably 2.0 to 20.0, and particularly preferably 3.0 to 8.0. Having the viscosity ratio of the conductive paste within this range makes it easier to form thin, dense, and continuous terminal electrodes.

[0073] When a strain of 1% is applied to the conductive paste of the present invention at an angular frequency of 1 Hz, the value of the phase difference δ between the strain and the stress generated by the strain is not particularly limited, but is preferably 45° to 80°, and particularly preferably 45° to 78°. Having the phase difference δ of the conductive paste within this range makes it easier to form thin, dense, and highly continuous terminal electrodes.

[0074] The conductive paste of the present invention can be used, for example, to calculate the electrode area ratio of the terminal electrodes, the average value of the maximum thickness of the terminal electrodes, and the average value of the minimum thickness of the terminal electrodes, using an evaluation test sample prepared by the following method. For the evaluation test, for example, a laminated body is prepared, which is a rectangular parallelepiped shape with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, and consists of multiple layers of dielectric layers containing barium titanate and internal electrode layers containing nickel. The conductive paste is applied to the exposed end of the laminated body by dip printing, with a descent speed of 300 μm / s and an elevation speed of 100 μm / s. Then, it is held in an air atmosphere at 150°C for 10 minutes, and then heated in a nitrogen atmosphere at a heating rate of 50°C / min until it reaches 700°C, and held for 15 minutes to form terminal electrodes. Twenty electronic components equipped with terminal electrodes are thus produced. Each of the 20 electronic components is then embedded in resin, and each electronic component is cut in the direction of lamination (perpendicular to the dielectric layer and internal electrode layer), passing through the center of both end faces of the electronic component, thereby exposing the cross-section of each electronic component.

[0075] <Manufacturing methods for electronic components> The conductive paste of the present invention is suitable as a conductive paste for forming terminal electrodes on a multilayer ceramic electronic component substrate.

[0076] The present invention provides a method for manufacturing electronic components using a conductive paste, comprising: a laminate preparation step of preparing a laminated body for a multilayer ceramic electronic component consisting of a plurality of ceramic layers and a plurality of 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. By using the conductive paste of the present invention in the above-described method for manufacturing electronic components, it is possible to form thin, dense, and highly continuous terminal electrodes even when firing at a low temperature in the terminal electrode formation step. In other words, according to the above-described method for manufacturing electronic components, it is possible to manufacture electronic components equipped with thin, dense, and highly continuous terminal electrodes even when firing at a low temperature in the terminal electrode formation step.

[0077] The aforementioned laminated body preparation step is a step of preparing a laminated body for a multilayer ceramic electronic component.

[0078] A multilayer ceramic electronic component laminate consists of multiple ceramic layers and multiple internal electrode layers. In a multilayer ceramic electronic component laminate, the ceramic layers and internal electrode layers are stacked alternately. Examples of multilayer ceramic electronic component laminates include those for multilayer ceramic capacitors, multilayer ceramic inductors, and piezoelectric actuators.

[0079] Examples of materials used to form the ceramic layer that constitutes the multilayer body for multilayer ceramic electronic components include barium titanate, strontium titanate, calcium titanate, barium zirconate, strontium zirconate, calcium zirconate, and strontium calcium zirconate.

[0080] Examples of materials used to form the internal electrode layer of a multilayer ceramic electronic component include nickel, palladium, silver, copper, and gold, or alloys containing one or more of these elements (for example, an alloy of silver and palladium).

[0081] The terminal electrode formation process involves applying the conductive paste of the present invention to the exposed ends of the internal electrodes of a multilayer ceramic electronic component, and then firing the applied conductive paste to form terminal electrodes.

[0082] 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 baked after drying.

[0083] In the terminal electrode formation process, after the terminal electrode has been formed, a plating layer can be formed on the surface of the electrode.

[0084] In this specification, both ends of the laminated body where the internal electrodes are exposed are referred to as "ends," the surface of the end where the internal electrodes are particularly exposed is referred to as the "end face," and the outer edge of the end face is referred to as the "corner." Normally, when conductive paste is applied to the ends in the terminal electrode formation process, the conductive paste is applied so as to cover both the end face and the corner.

[0085] The size of the laminated element in which the conductive paste of the present invention is used is not particularly limited. For example, it can be used in laminated elements for 2012 size multilayer ceramic capacitors, 1608 size multilayer ceramic capacitors, 1005 size multilayer ceramic capacitors, 0603 size multilayer ceramic capacitors, 0402 size multilayer ceramic capacitors, and 0201 size multilayer ceramic capacitors. Thinning of the terminal electrodes is particularly required in small multilayer ceramic capacitors, and the conductive paste of the present invention can be suitably used in laminated elements for 1005 size multilayer ceramic capacitors, 0603 size multilayer ceramic capacitors, 0402 size multilayer ceramic capacitors, and 0201 size multilayer ceramic capacitors.

[0086] The electrode area ratio of the terminal electrodes of the multilayer ceramic electronic component obtained by the present invention is not particularly limited, but it is preferably 90% or more, and particularly preferably 99% or more. This makes it easier to prevent the plating solution from penetrating the multilayer body when plating the terminal electrodes. The aforementioned electrode area ratio can be calculated, for example, by the following method. That is, 20 electronic components are each embedded in resin, and each electronic component is cut so as to pass through the center of both end faces of the electronic component and in the stacking direction (perpendicular to the dielectric layer and the internal electrode layer) to expose the cross-section of each electronic component, and the cross-section is observed with a scanning electron microscope (for example, 10 fields of view for each electronic component), and the ratio of the electrode area occupied in the observed field of view can be calculated as the electrode area ratio.

[0087] The maximum thickness of the terminal electrode measured by the method described later is preferably 40 μm or less, more preferably 30 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less. Furthermore, the average value of the maximum thickness of the terminal electrode calculated by the method described later is preferably 40 μm or less, more preferably 30 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less. This makes it possible to reduce the size of the multilayer ceramic electronic component.

[0088] Furthermore, in multilayer ceramic electronic components of a predetermined size, the thinner the terminal electrodes, the larger the size of the laminated body can be, that is, the electrode area and the number of layers can be increased, thereby improving the performance of the multilayer ceramic electronic component. The method for measuring the maximum thickness described above is not particularly limited, but for example, the electronic component can be embedded in resin, and the electronic component can be cut in the direction of lamination (perpendicular to the dielectric layer and the internal electrode layer) so as to pass through the center of both end faces of the electronic component, exposing the 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 circumference of the terminal electrode to the end face of the laminated body, the point where the length of the perpendicular line is maximum can be measured as the maximum thickness. The method for calculating the average value of the maximum thickness described above is not particularly limited, but for example, the maximum thickness of the terminal electrodes can be measured using the above method for 20 electronic components, and the average value of the maximum thickness of the terminal electrodes can be calculated by averaging these maximum thicknesses.

[0089] The minimum thickness of the terminal electrode measured by the method described later is preferably 1.0 μm or more, more preferably 2.5 μm or more, and particularly preferably 5.0 μm or more. Furthermore, the average value of the minimum thickness of the terminal electrode calculated by the method described later is preferably 1.0 μm or more, more preferably 2.5 μm or more, and particularly preferably 5.0 μm or more. This makes it easier to prevent the plating solution from penetrating the laminated substrate when plating the terminal electrode.

[0090] The method for measuring the minimum thickness described above is not particularly limited, but for example, an electronic component can be embedded in resin, and the electronic component can be cut in the direction of lamination (perpendicular to the dielectric layer and the internal electrode layer) passing through the center of both end faces of the electronic component to expose its cross-section. The cross-section can then be observed with a scanning electron microscope, and the thickness at the point where the length of the perpendicular line drawn from the outer circumference of the terminal electrode to the end face of the laminated body is minimized, and the thickness at the point where the distance between the corner of the laminated body and the outer circumference of the terminal electrode is shortest can be measured, and the thickness of the thinnest of these two points can be measured as the minimum thickness. Furthermore, the method for calculating the average value of the minimum thickness described above is not particularly limited, but for example, the minimum thickness of the terminal electrode can be measured using the above method with 20 electronic components, and the average value of the minimum thickness of the terminal electrode can be calculated by averaging these minimum thicknesses. [Examples]

[0091] The present invention will be described below based on specific experimental examples, but the present invention is not limited to these.

[0092] <Manufacturing of copper powder> First, spherical copper powder produced by a known dry method (atomization method) was prepared as the raw material powder. Next, zirconia beads with a diameter of 0.1 mm, the aforementioned spherical copper powder, secondary butyl alcohol, and a predetermined lubricant (aliphatic amine) were mixed, and physical force was applied to the spherical copper powder using a bead mill, 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 in Table 1, thereby obtaining the copper powders of Experimental Examples 1 to 11. Table 1 shows the physical properties of the copper powders used in Experimental Examples 1 to 11, obtained by the measurement methods described below, and the evaluation results of the electronic components fabricated using the copper powders from Experimental Examples 1 to 11, obtained by the evaluation methods described below. Note that in Table 1, experimental examples marked with an asterisk (*) are outside the scope of the present invention. Furthermore, "Present (Shoulder)" in Table 1 indicates that there is no peak, but there is a shoulder peak.

[0093] <d50> The volume-based cumulative 50% particle size D50 (μm) was measured using a laser diffraction particle size distribution analyzer (HORIBA LA-960).

[0094] <Ratio of major axis X to medium axis Y and ratio of major axis X to minor axis Z> Using the values ​​of the major axis X, medium axis Y, and minor axis Z measured by the method described below, the ratio of the major axis X to the medium axis Y and the ratio of the major axis X to the minor axis Z were calculated. (Longest axis X and medium axis Y) Using a scanning electron microscope, 100 particles were randomly selected, and the length of the rectangle circumscribing each particle to minimize its area was measured. The average length of the longer side was defined as the major axis X, and the average length of the shorter side was defined as the medium axis Y. (minor axis Z) Mix 100 parts by mass of copper powder with 7 parts by mass of acrylic resin (Mitsubishi Chemical Corporation, Dianaal MB-2677) dissolved in terpineol, then knead using a three-roll mill (Inoue Seisakusho Co., Ltd.), then dilute with terpineol, and process at 25°C and a shear rate of 4s. -1 A paste-like composition was prepared by adjusting the viscosity to 30 Pa·s. This paste-like composition was cast onto a PET film using an applicator to form a coating film with a thickness of 250 μm. This 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 apparatus (Hitachi High-Tech Corporation IM4000), and the cross-section of the dry film was observed with a scanning electron microscope (Hitachi High-Tech Corporation SU-8020). 100 copper particles were randomly selected from this observation, and the average length of the short side of the rectangle circumscribing each particle to minimize its area was measured as the minor axis Z.

[0095] <tg-ms> Using TG-MS (thermogravimetric-mass spectrometry), the change in gas generation (peak intensity) with respect to temperature was measured when the temperature of a mass number 44 molecule was increased from 38°C to 900°C at a heating rate of 10°C / min under an inert helium atmosphere, and the area of ​​the peaks in each temperature range was measured. In addition, the peak top temperature of a given peak, the presence or absence of peaks and shoulders in a given temperature range are shown in Table 1. Furthermore, the change in gas generation (peak intensity) with respect to temperature of the mass number 44 molecule described above was differentiated, and the peak top temperature and presence or absence of peaks in the upward-convex peaks in a given temperature range in the graph obtained from this differentiation are shown in Table 1. The ionization method used for MS was EI (Electron Ionization). A NETZSCH STA2500 Regulus was used as the TG-DTA for heating the sample, and a JEOL JMS-Q1500GC was used as the MS for mass spectrometry of the vaporized substance produced by heating the sample.

[0096] <Shrinkage Rate (Thermomechanical Analysis (TMA))> A sample was obtained by pressurizing 200 mg of copper powder under a pressure of 1.0 kN for 3 minutes to form a cylindrical shape with a diameter of 5 mm and a height of 2 mm. Then, using a TMA apparatus (Bruker, TMA4000S), 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 sample height at each temperature relative to the sample height (2 mm) was measured as the shrinkage rate.

[0097] <Evaluation test of terminal electrodes> (Preparation of conductive paste) Mix 100 parts by mass of copper powder, 7 parts by mass of acrylic resin (Mitsubishi Chemical Corporation, Dianaal MB-2677) dissolved in terpineol, and 10 parts by mass of glass frit (BaO-ZnO glass). Then, knead the mixture using a three-roll mill (Inoue Seisakusho Co., Ltd.), and then dilute with terpineol. Prepare the mixture at 25°C and a shear rate of 4s. -1 The viscosity was adjusted to 30 Pa·s to prepare a conductive paste.

[0098] (Fabrication of electronic components equipped with terminal electrodes) A laminated substrate was prepared, approximately rectangular in shape with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, consisting of multiple layers of dielectric layers containing barium titanate and internal electrode layers containing nickel. Conductive paste was applied to the exposed end of this laminated substrate by dip printing, with the substrate descending at a rate of 300 μm / s and pulling up at a rate of 100 μm / s. The substrate was then held in an air atmosphere at 150°C for 10 minutes. Subsequently, the substrate was heated in a nitrogen atmosphere at a heating rate of 50°C / min until it reached 700°C, and held for 15 minutes to form terminal electrodes, thereby fabricating an electronic component equipped with terminal electrodes.

[0099] (Preparation of samples for evaluation testing) Twenty of the aforementioned electronic components were prepared for each experimental example. Each electronic component was embedded in resin, and each electronic component was cut in the direction of stacking (perpendicular to the dielectric layer and the internal electrode layer) passing through the center of both end faces of the electronic component, thereby exposing the cross-section of each electronic component and creating a sample for evaluation testing. The evaluations described below were then performed. (Evaluation of terminal electrode density (electrode area ratio)) The aforementioned evaluation test samples were observed using a scanning electron microscope, with 10 fields of view for each sample, for a total of 200 fields of view. The ratio of electrode area to field of view was calculated as the electrode area ratio. This electrode area ratio was evaluated based on the following evaluation criteria.

[0100] A: Electrode area ratio of 90% or more B: Electrode area ratio is less than 90% (Evaluation of the firing film thickness of terminal electrodes) The aforementioned evaluation test samples were observed using a scanning electron microscope, and the thickness of the terminal electrode (fired film) at its thickest point (maximum thickness) and thinnest point (minimum thickness) was measured. The average values ​​of the maximum thickness and minimum thickness were calculated for each experimental example. The average values ​​of the maximum thickness and minimum thickness were evaluated based on the following evaluation criteria.

[0101] A: Average maximum thickness ≤ 20 μm, and average minimum thickness ≥ 2.5 μm B: Average maximum thickness > 20 μm, or average minimum thickness < 2.5 μm

[0102] [Table 1] [Explanation of symbols]

[0103] 1. Cross-section of conductive particles 2. A rectangle circumscribing the cross-section of the conductive particle. 3. Short side of the rectangle 4. Longer side of the rectangle

Claims

1. A conductive powder having copper as its main component, The conductive powder has a volume-based cumulative 50% particle size D50 of 0.3 μm or more and 7.5 μm or less in laser diffraction particle size distribution measurement. The ratio of the major axis X defined below to the medium axis Y defined below is 1.0 or more and 3.0 or less, and the ratio of the major axis X defined below to the minor axis 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 aliphatic amine is 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 the mass number 44 chromatogram, the ratio of the area of ​​the peak in the range of 250°C to 900°C to the area of ​​the peak in the range of 250°C to 400°C is 0 or more and less than 0.9, and the ratio of the area of ​​the peak in the range of 250°C to 500°C to the area of ​​the peak in the range of 250°C to 900°C is 0.9 or more and 1.0 or less. A conductive powder having copper as its main component, characterized by the following features. (Longest axis X and medium axis Y) Using a scanning electron microscope, 100 particles are randomly selected, and the average length of the longer side of the rectangle circumscribing each particle to minimize its area is defined as the major axis X, and the average length of the shorter side is defined as the medium axis Y. (Short axis Z) 100 parts by mass of conductive powder mainly composed of copper and 7 parts by mass of acrylic resin dissolved in terpineol are mixed, then kneaded using a three-roll mill, then diluted with terpineol, and processed at 25°C and a shear rate of 4s. －１ A paste-like composition is prepared by adjusting the viscosity to 30 Pa·s, the paste-like composition is cast onto a PET film using an applicator to form a coating film with a thickness of 250 μm, the coating film is dried in an air atmosphere at 150°C for 10 minutes to form a dry film, the cross-section of the dry film is exposed using an ion milling apparatus, the cross-section of the dry film is observed with a scanning electron microscope, 100 particles are randomly selected, and the average length of the short side of the rectangle circumscribing each particle to minimize its area is defined as the minor axis Z.

2. The copper-based conductive powder according to Claim 1, wherein the ratio of the area of ​​the peak in the range of 250°C to 400°C to the area of ​​the peak in the range of 250°C to 900°C is 0.7 or more and less than 0.

9.

3. The copper-based conductive powder according to claim 1, wherein the aliphatic amine comprises at least one aliphatic amine from among primary amines and secondary amines.

4. The copper-based conductive powder according to claim 1, wherein when the peak with the strongest peak intensity among the peaks located in the range of 250°C to 400°C is designated as the main peak, at least one of the peaks and shoulder peaks exists in a range exceeding the peak top temperature of the main peak but not exceeding 400°C.

5. The conductive powder mainly composed of copper according to claim 1, wherein in the differential graph obtained by differentiating the chromatogram, there exists 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, there exists at least one further upward convex peak in the range exceeding the peak top temperature of the main peak of the differential graph and up to 400°C.

6. The copper-based conductive powder according to claim 1, wherein the aliphatic amine comprises at least one selected from stearylamine and dodecylamine.

7. A conductive paste comprising a conductive powder mainly composed of copper as described in any one of claims 1 to 6, glass frit, a binder resin, and an organic solvent.

8. A laminated body preparation step for preparing a laminated body for a multilayer ceramic electronic component consisting of multiple ceramic layers and multiple internal electrode layers, A terminal electrode forming step involves applying the conductive paste described in claim 7 to the exposed end of the internal electrode of the laminated body, and then firing the applied conductive paste to form a terminal electrode, A method for manufacturing electronic components, comprising:

9. The method for manufacturing an electronic component according to claim 8, wherein the peak temperature when firing the conductive paste is 720°C or lower.

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