Electroconductive powder comprising copper as main component, electroconductive paste, method for manufacturing electronic component, and method for manufacturing electroconductive powder

Abstract

This electroconductive powder comprises copper as the main component, and is configured such that: the D50 is 0.3 μm to 4.5 μm; the ratio of the major axis X to the intermediate diameter Y is 1.0 to 3.0; the ratio of the major axis X to the minor axis Z is 1.5 to 5.0; and the following (A) and (B) are satisfied. (A) The carbon content is 0.00 to 0.10 mass%. (B) The TMA shrinkage rate, as defined, is at least 0% but less than 2% at 400°C. The present invention can provide: an electroconductive powder comprising copper as the main component, the electroconductive powder being suitably usable for an electroconductive paste capable of forming terminal electrodes that are thin, dense, and excellent in continuity even when fired at a low temperature; and a method for manufacturing the electroconductive powder.

Description

Copper-based conductive powder, conductive paste, manufacturing method for electronic components, and manufacturing method for conductive powder

[0001] The present invention relates to a copper-based conductive powder, a conductive paste using the conductive powder, a method for manufacturing electronic components using the conductive paste, and a method for manufacturing a copper-based conductive powder, particularly to a conductive powder suitable for forming terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer inductors, and multilayer piezoelectric actuators.

[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 the internal electrodes is printed in a predetermined pattern on a dielectric ceramic green sheet such as a barium titanate-based 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 cut into chips of a predetermined shape to obtain a laminated body. The laminated body may be fired at a high temperature at this stage, or it may not be fired at this stage but may be co-fired later with a terminal electrode paste layer formed using a conductive paste for the terminal electrodes. In either case, the laminated body in its state before the terminal electrode paste layer is formed is referred to as a "laminated body."

[0004] Thereafter, a conductive paste for terminal electrodes, which contains components such as conductive powder, binder resin, organic solvent, and glass frit, is printed on the exposed ends of the internal electrodes of the laminated body by a dip printing method or the like to form a conductive paste layer, which is then dried as necessary and further fired at a high temperature to form the terminal electrodes.

[0005] Furthermore, thereafter, a plating layer of nickel, tin, or the like may be formed on the terminal electrodes by electroplating or the like, if necessary.

[0006] Traditionally, precious metals such as palladium, silver-palladium, and platinum have been used as internal electrode materials. However, there are demands for resource conservation and cost reduction, and particularly for sintered types, there is a demand for preventing delamination and cracking caused by oxidative expansion of palladium and silver-palladium during sintering. In recent years, therefore, the use of base metals such as nickel, cobalt, and copper has become mainstream. For this reason, copper, nickel, cobalt, or alloys of these metals, which easily form good electrical connections with base metal internal electrodes, have been used as terminal electrode materials instead of the conventional silver and silver-palladium.

[0007] When base metals are used for the internal electrodes and terminal electrodes in this way, the terminal electrodes are usually fired in a non-oxidizing atmosphere with as low an oxygen partial pressure as possible, for example, in an inert gas atmosphere with an oxygen content of several ppm to several tens of ppm, at a high peak temperature of 800°C, so as to prevent the base metals from being oxidized during firing.

[0008] However, particularly when firing a metal powder whose main component is copper in a low-oxygen atmosphere, it is difficult to properly remove the binder, which burns, decomposes, and scatters organic components such as binder resin. If the binder is not removed sufficiently at the relatively low-temperature stage in the early stages of firing, before the glass fluidizes and the copper powder sinters, carbon and organic residues become trapped in the film after sintering begins, and then, at the high-temperature stage thereafter, the organic decomposition products gasify, causing blisters (air bubbles) and various other problems that impair the density of the fired film, such as blister defects.

[0009] Therefore, in the past, an important issue for conductive pastes using metal powders whose main component is base metals, particularly copper, was how to efficiently remove the binder in the early stages of firing and reduce residual carbon before the sintering of the copper powder progresses at high temperatures.

[0010] As a technology for solving this problem, for example, Patent Document 1 discloses a conductive thick film composition containing Cu powder, glass powder, and an organic vehicle, wherein the Cu powder is composed of spherical powder and scaly powder.

[0011] Japanese Patent Application Publication No. 8-180731

[0012] Recently, there has been a demand for lower firing temperatures when forming the terminal electrodes to reduce environmental impact, manufacturing costs, and thermal stress on the laminated body. In addition, there is a demand for smaller electronic components, which in turn requires thinner terminal electrodes. That is, there is a demand for a method for properly removing the binder before the copper powder sinters, for properly sintering and densifying the copper powder even at a low peak firing temperature, and for forming thin terminal electrodes.

[0013] However, the conductive paste described in Patent Document 1 is designed assuming firing at a high temperature of 800° C. Therefore, terminal electrodes that satisfy the above requirements cannot be formed by firing at a low temperature of 720° C.

[0014] Therefore, an object of the present invention is to provide 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. Another object of the present invention is to provide a conductive paste that can form thin, dense, and highly continuous terminal electrodes even when fired at low temperatures. Another object of the present invention is to provide a method for producing an electronic component that has thin, dense, and highly continuous terminal electrodes even when fired at low temperatures.

[0015] As a result of intensive research to solve the above problems, the present inventors have found that a conductive powder containing copper as a main component, which has a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 μm to 4.5 μm, 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 satisfies at least one of the following: (A) a carbon content of 0.00% by mass 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 from 400°C to 700°C [% / °C] of 0.05 or more, can be suitably used in a conductive paste capable of forming a thin, dense, and highly continuous terminal electrode, even when fired at a low temperature, and have completed the present invention.

[0016] That is, present invention (1) provides a conductive powder containing copper as a main component, which has a volume-based cumulative 50% particle diameter D50 of 0.3 μm or more and 4.5 μm or less as measured by laser diffraction particle size distribution measurement, a ratio of the major diameter X defined below to the median diameter Y defined below of 1.0 or more and 3.0 or less, and a ratio of the major diameter X defined below to the minor diameter Z defined below of 1.5 or more and 5.0 or less, and 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, and (B) the TMA shrinkage rate, defined below, is 0% or more and less than 2% at 400°C. (Major diameter X and median diameter Y) One hundred particles are randomly selected by scanning electron microscope observation, and the average length of the long side of a rectangle circumscribing each particle so as to have the smallest area is defined as the major diameter X and the median diameter Y. (Minor diameter 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, kneaded using a triple roll mill, diluted with terpineol, and then kneaded at 25°C at a shear rate of 4 s －１A paste-like composition is prepared by adjusting the viscosity at 250 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. The cross section of the dry film is exposed using an ion milling device, and the cross section of the dry film is observed using a scanning electron microscope. 100 particles are randomly selected, and the average value of the length of the short side of the rectangle circumscribing each particle so as to minimize the area is defined as the minor axis Z. (TMA Shrinkage Rate) 200 mg of the copper-based conductive powder is compressed 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 2 mm, and then the sample is heated from room temperature to 900° C. in a nitrogen atmosphere using a TMA device at a rate of 10° C. / min. The TMA shrinkage rate is defined as the percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm).

[0017] The present invention (2) also provides a copper-based conductive powder according to (1), which 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.

[0018] The present invention (3) also provides a copper-based conductive powder according to (1) or (2), in which the ratio of the TMA shrinkage at 600°C to the maximum TMA shrinkage is 0.73 or more.

[0019] 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 at 700°C to the maximum TMA shrinkage is 0.90 or more.

[0020] 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.

[0021] In addition, the present invention (6) is a method for producing a polyester fiber having a tap density defined below of 3.5 g / cm ３(Tap density) 20 g of the copper-based conductive powder is measured and tapped to 20 cm ３ The sample was placed in a container, and tapped using a tap density measuring device with a tapping stroke of 20 mm and a tapping count of 200 times. The sample volume after tapping (cm ３ The value calculated as the ratio of the sample weight (g) to the total weight (g) is defined as the tap density.

[0022] In addition, the present invention (7) is characterized in that the ratio of the crystallite size to the D50 is 6.0 × 10 －３ The present invention provides a conductive powder containing copper as a main component as described above in any one of (1) to (6).

[0023] The present invention (8) also provides a conductive powder containing copper as a main component according to any one of (1) to (7) above, which has an aliphatic amine on at least a portion of its surface.

[0024] 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.

[0025] The present invention (10) also provides a method for manufacturing an electronic component, comprising: a laminated body preparation step of preparing a laminated body for a multilayer ceramic electronic component, which comprises a plurality of ceramic layers and a plurality of internal electrode layers; and a terminal electrode formation step of applying the conductive paste of (9) to the exposed ends of the internal electrodes of the laminated body, and then firing the applied conductive paste to form terminal electrodes.

[0026] The present invention (11) also provides a method for producing an electronic component according to (10), wherein the peak temperature of the firing is 720° C. or less.

[0027] 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 becomes 1.5 or more and 5.0 or less.

[0028] According to the present invention, it is possible to provide 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 a low temperature, and a method for producing the same. It is also possible to provide a conductive paste that can form thin, dense, and highly continuous terminal electrodes even when fired at a low temperature. It is also possible to provide a method for producing an electronic component that includes thin, dense, and highly continuous terminal electrodes even when fired at a low temperature.

[0029] FIG. 1 is a diagram for explaining how to determine the minor axis Z in the present invention.

[0030] <Conductive Powder Containing Copper as a Main Component> The conductive powder containing copper as a main component of the present invention has a volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement of 0.3 μm to 4.5 μm, 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. Thus, the conductive 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.

[0031] By using the copper-based conductive powder in the conductive paste, the filling of the conductive powder in the coating film of the conductive paste is improved, making it easier to sinter the conductive powder even when firing at low temperatures. Furthermore, most resins used in conductive pastes for terminal electrodes, especially those fired at 720°C or less, thermally decompose at 400°C or less. The copper-based conductive powder is difficult to sinter up to 400°C, suppressing shrinkage and effectively removing the binder resin, leaving little carbon residue during the firing process. Furthermore, sintering rapidly progresses above 400°C, making it less likely for blistering to occur during the high-temperature firing stage, making it easier to form thin, dense, and highly continuous terminal electrodes.

[0032] The terms "major diameter X," "intermediate diameter Y," "minor diameter Z," and "TMA shrinkage" defined in this specification (the present invention) are defined as follows. (Major diameter X and intermediate diameter Y) One hundred particles are randomly selected by observation with a scanning electron microscope, and the average length of the long side of a rectangle circumscribing each particle so as to have the smallest area is defined as the major diameter X, and the average length of the short side is defined as the intermediate diameter Y. (Minor diameter Z) 100 parts by mass of the copper-based conductive powder and 7 parts by mass of an acrylic resin dissolved in terpineol are mixed, then kneaded using a three-roll mill, then diluted with terpineol, and kneaded at 25°C at a shear rate of 4 s －１A paste-like composition is prepared by adjusting the viscosity at 250 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. The cross section of the dry film is exposed using an ion milling device, and the cross section of the dry film is observed using a scanning electron microscope. 100 particles are randomly selected, and the average value of the length of the short side of the rectangle circumscribing each particle so as to minimize the area is defined as the minor axis Z. (TMA Shrinkage Rate) 200 mg of the copper-based conductive powder is compressed 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 2 mm, and then the sample is heated from room temperature to 900° C. in a nitrogen atmosphere using a TMA device at a rate of 10° C. / min. The TMA shrinkage rate is defined as the percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm).

[0033] The method for determining the minor axis Z will be explained using Figure 1. Figure 1 is a diagram of the cross section of a dried film obtained by drying a coating film, observed with a scanning electron microscope. The minor axis Z is the average value of the length of the short side 3 of the rectangle 2 circumscribing the cross section 1 of the conductive particle, which has the smallest area.

[0034] The conductive powder of the present invention may be any powder containing copper as its main component. In this specification, the term "main component" refers to a component exceeding 50% by mass relative to the total. In particular, in a conductive powder containing copper as its main component, the copper component exceeds 50% by mass relative to the total conductive powder, including the mixed powder and alloy powder described below. The copper content in the conductive powder is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, even more preferably 95% by mass or more and 100% by mass or less, and particularly preferably 100% by mass (pure copper). When the copper content in the conductive powder is within the above range, the conductive powder particles are easily sintered together, making it easier to obtain a dense sintered film.

[0035] In addition, as long as the conductive powder in the present invention contains copper as the main component, it may be a mixed powder of copper powder with other metal powders such as nickel powder or silver powder, or an alloy powder of copper with other metal elements such as nickel or silver. Furthermore, it may be a composite powder in which copper powder is coated with glass or ceramic, or may have an oxide film on the surface. Furthermore, it may be surface-treated with an organometallic compound, a surfactant, or the like, and two or more of these conductive powders may be mixed and used.

[0036] The copper-based conductive powder of the present invention may have a volume-based cumulative 50% particle diameter D50 of 0.3 μm or more and 4.5 μm or less, as measured by laser diffraction particle size distribution measurement, but is more preferably 0.4 μm or more and 4.0 μm or less, even more preferably 0.5 μm or more and 3.5 μm or less, and particularly preferably 0.6 μm or more and 3.0 μm or less. When the copper-based conductive powder has a D50 within the above range, sintering of the conductive powder proceeds easily even when fired at a low temperature, making it easier to form highly dense terminal electrodes. Furthermore, it is easier to form thin terminal electrodes.

[0037] The copper-based conductive powder of the present invention may have a ratio of the major diameter X to the median diameter Y of 1.0 or more and 3.0 or less, preferably 1.0 or more and 2.5 or less. When 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 a low temperature, making it easier to form a dense fired film. In addition, it is easier to form a thin, highly continuous fired film (terminal electrode).

[0038] The major axis X and the median axis Y can both be measured by scanning electron microscope observation. That is, 100 conductive particles are randomly selected by scanning electron microscope observation, and the average length of the long side of a rectangle circumscribing each particle so as to minimize its area is measured as the major axis X and the average length of the short side of the rectangle is measured as the median axis Y.

[0039] The ratio of the major diameter X to the minor diameter 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. When the ratio of the major diameter X to the minor diameter 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, since shrinkage is suppressed, it is easier to form a thin fired film (terminal electrode) with excellent continuity. The above-mentioned minor diameter 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.

[0040] More specifically, 100 parts by mass of the conductive powder of the present invention and 7 parts by mass of an acrylic resin dissolved in terpineol (e.g., Dianall MB-2677, manufactured by Mitsubishi Chemical Corporation) 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 －１ A paste-like composition is prepared by adjusting the viscosity at 250 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. 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 value of the length of the short sides of the rectangles circumscribing the conductive particles can be measured as the short diameter Z.

[0041] The copper-based conductive powder of the present invention simultaneously satisfies (A) a carbon content of 0.00% by mass or more and 0.10% by mass or less, and (B) a TMA shrinkage rate of 0% to less than 2% at 400° C. As a result, sintering does not proceed easily up to 400° C., thereby suppressing shrinkage and allowing for good removal of the binder resin. In addition, the low carbon content of the conductive powder itself makes it difficult for carbon to remain during the firing process. Furthermore, sintering tends to proceed rapidly above 400° C., making it difficult for blister defects to occur during the high-temperature firing stage, and making it easier to form thin, dense, and highly continuous terminal electrodes.

[0042] The carbon content may be 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 0.05% by mass or less, and particularly preferably 0.00% by mass or more and 0.04% by mass or less. This makes it easier to achieve the above-mentioned effects. The carbon content (%) can be measured using a carbon / sulfur analyzer (EMIA-320V, manufactured by HORIBA).

[0043] The TMA shrinkage rate of the copper-based conductive powder of the present invention at 400°C may be 0% or more and less than 2%, preferably 0% or more and 1% or less, and particularly preferably 0%, so that the above-mentioned effects can be obtained more significantly.

[0044] The copper-based conductive powder of the present invention preferably simultaneously satisfies all of the above (A), (B), and (C) requirements: an average change in TMA shrinkage per unit temperature [% / °C] from 400°C to 700°C of 0.05 or more. This allows for slow sintering up to 400°C, thereby suppressing shrinkage and effectively removing the binder resin. Furthermore, the conductive powder itself has a low carbon content, making it less likely for carbon to remain during the firing process. Furthermore, sintering rapidly progresses above 400°C, making it less likely for blistering to occur during the high-temperature firing stage, making it particularly easy to form thin, dense, and highly continuous terminal electrodes. The upper limit of the average change is not particularly limited, but it can be, for example, 0.5 or less.

[0045] 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, still more preferably 0.97 or more, and particularly preferably 1.0, which makes it easier to form highly dense terminal electrodes even when fired at low temperatures.

[0046] The maximum TMA shrinkage in this specification (invention) refers to the largest shrinkage among the TMA shrinkages at each temperature measured by heating the conductive powder from room temperature to 900°C using the method described above.

[0047] In the copper-based conductive powder of the present invention, the ratio of the TMA shrinkage at 700°C to the maximum TMA shrinkage is preferably 0.90 or more, more preferably 0.92 or more, more preferably 0.94 or more, even more preferably 0.95 or more, still more preferably 0.96 or more, and particularly preferably 1.0, which makes it easier to form highly dense terminal electrodes even when fired at low temperatures.

[0048] 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, which makes it particularly easy to form highly dense terminal electrodes even when fired at low temperatures.

[0049] The copper-based conductive powder of the present invention preferably has a TMA shrinkage at 600° C. of 16% or less, more preferably 15% or less, and particularly preferably 14% or less, which makes it easier to form thin, highly continuous terminal electrodes.

[0050] The copper-based conductive powder of the present invention preferably has a TMA shrinkage at 700° C. of 21% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less, which makes it easier to form thin, highly continuous terminal electrodes.

[0051] The copper-based conductive powder of the present invention preferably has a TMA shrinkage at 720°C of 22% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less, which makes it easier to form thin, highly continuous terminal electrodes.

[0052] The copper-based conductive powder of the present invention preferably has a TMA shrinkage at 800° C. of 22% or less, more preferably 18% or less, even more preferably 16% or less, and particularly preferably 15% or less, which makes it easier to form thin, highly continuous terminal electrodes.

[0053] 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. The upper limit of the average change is not particularly limited, but can be, for example, 0.5 or less.

[0054] The copper-based conductive powder of the present invention has a tap density of 3.5 g / cm ３ Preferably, it is greater than 3.7 g / cm ３ More preferably, it is 3.9 g / cm or more. ３ More preferably, it is 4.1 g / cm or more. ３ When the tap density is in the above range, it becomes easier to form thin, highly continuous terminal electrodes.

[0055] The tap density (g / cm ３) is measured by, for example, measuring 20 g of the copper-based conductive powder of the present invention using a tap density measuring device (KYT-4000, manufactured by Seishin Enterprise Co., Ltd.) and measuring the density by 20 cm ３ The sample was placed in a cell, and the tapping stroke was set to 20 mm and the number of taps was set to 200. The sample volume after tapping (cm ３ The mass of the sample can be calculated as the ratio of the mass of the sample (g) to the mass of the sample (g).

[0056] 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. With a crystallite diameter within the above range, sintering is difficult up to a certain temperature, such as 400 ° C, so shrinkage is suppressed and the binder resin is effectively removed. However, sintering rapidly progresses above 400 ° C, making it easier to form highly dense terminal electrodes. The upper limit of the crystallite diameter is not particularly limited, and can be, for example, 25 nm or less, 24 nm or less, or 23 nm or less.

[0057] The crystallite size can be calculated, for example, by using an XRD measurement device (manufactured by Rigaku Corporation, SmartLab) with CuKα radiation (wavelength λ: 1.5418 Å) under conditions of 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 measurement at a diffraction angle 2θ of 20.0 to 100.0°, detecting a peak (near 43°) corresponding to the (111) plane, measuring the half-width, and using the Scherrer formula.

[0058] The copper-based conductive powder of the present invention has a crystallite size ratio to D50 of 6.0 × 10 －３ It is preferable that the ratio is 7.0×10 or more. －３ More preferably, it is 8.0 × 10 or more. －３ More preferably, it is 9.0 × 10 or more. －３ More preferably, it is 1.0 × 10 or more. －２When the ratio of the crystallite diameter to D50 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, and when the temperature exceeds 400°C, sintering tends to proceed rapidly, making it easier to form a highly dense terminal electrode. In addition, the upper limit of the ratio of the crystallite diameter to D50 is not particularly limited, but it is preferable that it is, for example, 1.0 × 10 －１ can be 5.0×10 －２ It can also be 3.0 × 10 －２ It can also be the following:

[0059] The copper-based conductive powder of the present invention is preferable because the ratio of the major axis X to the minor axis Z is in the above-mentioned range, and the higher the dry film density, the more the shrinkage is suppressed. ３ The volume (cm) was calculated by casting the paste composition onto a PET film to a thickness of 250 μm to form a coating film, drying the coating film in an air atmosphere at 100° C. for 15 minutes, and then drying 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 calculating the volume (cm). ３ It can be calculated as the ratio of weight (g) to total weight (g).

[0060] The copper-based conductive powder of the present invention preferably has a bottom surface and a surface opposite to the bottom surface, and can have a shape such as a flattened shape, a cylindrical shape, an elliptical cylindrical shape, a truncated cone shape, an elliptical truncated cone shape, or a rectangular parallelepiped shape. This facilitates sintering even when firing at a low temperature, making it easier to form a dense fired film. It also facilitates the formation of a thin, highly continuous fired film (terminal electrode).

[0061] The bottom surface and the surface opposite to the bottom surface are preferably completely flat, but may have irregularities as long as the effects of the present invention are not impaired. The average angle of the surface opposite to the bottom surface is preferably 0° to 45°, more preferably 0° to 30°, and even more preferably 0° to 15°, and is particularly preferably 0°, i.e., parallel.

[0062] In this specification (the present invention), of the 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 opposing the bottom surface." When the areas of the two opposing surfaces are the same, one arbitrarily selected surface is referred to as the "bottom surface," and the other surface is referred to as the "opposing surface."

[0063] The conductive powder of the present invention does not exclude powders of other shapes, such as spherical ones, and the conductive powder as a whole may have the "ratio of major diameter X to middle diameter Y," "ratio of major diameter X to minor diameter Z," and "D50" satisfy the aforementioned numerical ranges. In this case, the content of the conductive powder satisfying the numerical ranges relative to the total conductive powder is not particularly limited, but is preferably more than 50% by mass, more preferably 55% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0064] In the copper-based conductive powder of the present invention, when the cumulative 10% particle diameter on a volume basis in laser diffraction particle size distribution measurement is defined as D10 and the cumulative 90% particle diameter is defined as D90, the ratio (D90-D10) / D50 is preferably 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. The lower limit of (D90-D10) / D50 is not particularly limited, but can be, for example, 0.2 or more.

[0065] The (D90-D10) / D50 ratio of the copper-based conductive powder is within the above range, i.e., the particle size distribution of the conductive powder is narrow, allowing the conductive powder to be sintered uniformly throughout the entire film. This means that localized sintering within the film can be suppressed, ensuring an appropriate binder removal path throughout the film, resulting in the formation of a thin, dense, and highly continuous terminal electrode. Furthermore, the terminal electrode can be prevented from becoming too thick due to excessively large conductive powder particles.

[0066] The specific surface area of ​​the copper-based conductive powder of the present invention is preferably 0.2 m ２ / g or more 3.0m２ / g or less, particularly preferably 0.3m ２ / g or more 2.0m ２ When the specific surface area of ​​the conductive powder containing copper as a main component is within the above range, sintering proceeds easily even when firing at a low temperature, and a dense fired film is easily formed. In addition, a thin fired film is easily formed.

[0067] The copper-based conductive powder of the present invention preferably 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 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, thereby enabling the formation of a fired film with excellent density even when fired at a low temperature. Furthermore, the good dispersibility of the conductive powder in the conductive paste makes it easier to form thin, highly continuous terminal electrodes.

[0068] In the present invention, the amount of the aliphatic amine is preferably 0.01 part by mass or more and 1.0 part by mass or less, more preferably 0.02 part by mass or more and 0.10 part by mass or less, even more preferably 0.02 part by mass or more and 0.08 part by mass or less, and particularly preferably 0.02 part by mass or more and 0.06 part by mass or less, relative to 100 parts by mass of the conductive powder containing copper as a main component. When the amount of the aliphatic amine is within the above range, the dispersibility of the conductive powder in the paste is improved and the aliphatic amine is easily removed during firing, making it easier to form thin, dense, and highly continuous terminal electrodes.

[0069] As the aliphatic amine in the present invention, various types can be used, 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. Two or more of these amines may be used in combination, and mixtures of several aliphatic amines that are typically commercially available as "aliphatic amines" can also be used. In particular, from the standpoints of ease of coating treatment on copper powder and metal adsorption, alkylamines having a main chain of approximately 8 to 20 carbon atoms, or aliphatic amines containing such alkylamines as the main component, are preferred.

[0070] <Method for producing conductive powder containing copper as a main component> The conductive powder containing copper as a main component of the present invention can be produced by the following method.

[0071] The method for producing a 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 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. This allows the copper-based conductive powder of the present invention to be suitably produced.

[0072] [First Step] The first step in the manufacturing method of the present invention is a step of preparing 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.

[0073] That is, for example, in the first step, 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.

[0074] Furthermore, for example, in the first step, at least a portion of a metal primarily composed of copper is heated to melt it to form a molten metal, the molten metal is then dispersed in a gas phase to generate molten metal droplets primarily composed of copper, and the metal droplets are then cooled, thereby preparing the raw metal powder primarily composed of copper.

[0075] Furthermore, for example, in the first step, at least a portion of a 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.

[0076] Furthermore, for example, in the first step, 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 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 a raw metal powder containing copper as the main component.

[0077] Furthermore, for example, in the first step, 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 a raw metal powder containing copper as the main component.

[0078] The copper-based raw metal powder 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, more preferably 0.00% by mass or more and 0.04% by mass or less, still 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 particularly preferably 0.00% by mass. This makes it easier to obtain the copper-based conductive powder of the present invention in the second step described below.

[0079] The copper-based conductive powder of the present invention is preferably prepared by preparing the copper-based raw metal powder prepared in the first step by the above-mentioned method (the so-called dry method). However, as long as the conductive powder obtained through the second step described below is the copper-based conductive powder of the present invention, the manufacturing method is not particularly limited, and it is not intended to deny the use of copper-based raw metal powder prepared using the so-called wet method.

[0080] [Second Step] 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.

[0081] A method for applying a physical force to a copper-based raw metal powder until the ratio of the major axis X to the minor axis Z becomes 1.5 to 5.0, for example, includes mixing media, the copper-based raw metal powder prepared in the first step, a solvent, and, if necessary, a lubricant, and applying a physical force to the copper-based raw metal powder using the media until the ratio of the major axis X to the minor axis Z becomes 1.5 to 5.0. Examples of the media include beads and balls. The size of the media can be, for example, 0.1 mm in diameter.

[0082] The material of the media is not particularly limited, and examples thereof include zirconia. The solvent is not particularly limited, and examples thereof include secondary butyl alcohol. The lubricant is not particularly limited, and examples thereof include fatty acids and aliphatic amines, with aliphatic amines being preferred. By adjusting the size and material of the media, the type of solvent, the type of lubricant, and the flow rate and number of passes (residence time) of the mixture thereof, as described above, the shape of the copper-based conductive powder produced in this process can be controlled within a suitable range.

[0083] The method for producing a 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.

[0084] <Conductive Paste> The conductive paste of the present invention contains the above-described conductive powder containing copper as a main component of the present invention, glass frit, a binder resin, and an organic solvent.

[0085] 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 dry film, and then firing the paste. The peak firing temperature is not particularly limited, and firing is possible at a temperature of 600°C or higher, which is lower than conventional firing temperatures. From the viewpoints of reducing the environmental load, reducing production costs, and reducing thermal stress on the laminated body, a temperature of 600°C or higher and 720°C or lower is preferred, and a temperature of 600°C or higher and 700°C or lower is particularly preferred.

[0086] <Glass Frit> 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 μm or more and 2.0 μm or less, more preferably 0.5 μm or more and 1.5 μm or less. When the D50 of the glass frit is in the above range, a dense fired film can be easily formed, and a fired film (terminal electrode) having excellent continuity can be easily formed.

[0087] In the present invention, when the cumulative 10% particle diameter on a volume basis in laser diffraction particle size distribution measurement is defined as D10 and the cumulative 90% particle diameter is defined 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 can be, for example, 0.2 or more.

[0088] When the glass frit's (D90-D10) / D50 is within the above range, i.e., when the particle size distribution of the glass frit is narrow, uniformly sized glass frit is uniformly distributed within the pre-fired film, which is densely packed with conductive powder, facilitating uniform sintering of the conductive powder throughout the film. This also suppresses localized sintering within the film, ensuring appropriate debindering paths throughout the film, resulting in the formation of thin, dense, and highly continuous terminal electrodes. The lack of extremely small glass frit, which exists in agglomerates and is prone to softening and flow, facilitates the suppression of localized sintering and localized debindering failures resulting from the sintering. Furthermore, the lack of extremely large glass frit suppresses exposure of the laminated body due to voids that occur where the glass frit flows during the firing process, thereby improving the continuity of the terminal electrodes.

[0089] The composition of the glass frit in the present invention is not particularly limited, and examples thereof include BaO-ZnO-based, BaO-ZnO-B ２ O ３ RO-ZnO-B ２ O ３ -MnO ２ RO-ZnO system, RO-ZnO-MnO system ２ RO-ZnO-SiO ２ ZnO-B ２ O ３ system, SiO ２ -B ２ O ３ -R' ２ O-based, SiO ２ -RO-R' ２ Glasses such as O-based (where R is an alkaline earth metal element and R' is an alkali metal element) can be used.

[0090] 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, 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. Furthermore, since the glass frit does not wet and spread easily at temperatures below 400°C, using it in combination with the copper-based conductive powder of the present invention, which does not easily sinter 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 a binder resin that is suitably thermally decomposed at temperatures below 400°C makes the above-mentioned effects more pronounced, making it particularly easy to form thin, dense, and highly continuous terminal electrodes, which is preferable.

[0091] 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 in the above 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.

[0092] The specific surface area of ​​the glass frit in the present invention is preferably 2.0 m ２ / g or more 7.0m ２ / g or less, particularly preferably 3.0m ２ / g or more 6.0m ２ When the specific surface area of ​​the glass frit is in the above range, the glass frit is easily dispersed uniformly in the film, and therefore a dense fired film is easily formed.

[0093] The amount of 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, even 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, relative to 100 parts by mass of the conductive powder. When the amount of glass frit is within the above range, a dense fired film can be easily formed.

[0094] <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 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. 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.

[0095] The binder resin of the present invention preferably exhibits a weight loss of 98% by mass or more, more preferably 99% by mass or more, and particularly preferably 100% by mass, at a temperature of 400°C or less, as determined by thermogravimetric analysis (nitrogen atmosphere, temperature increase at 10°C / min). The binder resin of the present invention may be a combination of two or more types, but the resin as a whole preferably exhibits a weight loss within the aforementioned range in the thermogravimetric analysis. By combining the binder resin, which is suitably thermally decomposed at 400°C or less as described above, with the copper-based conductive powder of the present invention, which is resistant to sintering and shrinkage up to 400°C, residual carbon is dramatically reduced, resulting in less blister defects and making it easier to form thin, dense, and highly continuous terminal electrodes, which is particularly preferred.

[0096] 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, relative to 100 parts by mass of the conductive powder. When the amount of binder resin is within the above range, it becomes easier to form thin, dense, and highly continuous terminal electrodes.

[0097] The weight-average molecular weight of the acrylic resin in the present invention is not particularly limited, but may be, for example, from 20,000 to 1,000,000. Two or more acrylic resins having different weight-average molecular weights, structures, etc. may be used in combination.

[0098] <Organic Solvent> The 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.

[0099] <Additives> In addition to the above components, 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. Examples of 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. Examples of rheology modifiers include silica powder.

[0100] <Physical Properties of Conductive Paste> The shear rate of the conductive paste of the present invention measured at 25°C was 4 s －１ The viscosity of the conductive paste 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. When the viscosity of the conductive paste is in the above range, it becomes easier to form thin, dense, and highly continuous terminal electrodes.

[0101] The conductive paste of the present invention has a shear rate of 40 s when measured at 25°C. －１ Viscosity at a shear rate of 0.4 s －１ The viscosity ratio in the conductive paste 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. When the viscosity ratio of the conductive paste is in the above range, it becomes easier to form a thin, dense, and highly continuous terminal electrode.

[0102] 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°. When the phase difference δ of the conductive paste is within the above range, it becomes easier to form thin, dense, and highly continuous terminal electrodes.

[0103] The conductive paste of the present invention can be used to calculate the electrode area ratio of the terminal electrodes, the average maximum thickness of the terminal electrodes, and the average minimum thickness of the terminal electrodes, as described below, using an evaluation test sample prepared, for example, by the following method.

[0104] The evaluation test sample can be prepared, for example, by preparing a rectangular parallelepiped laminated body having a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, in which a plurality of dielectric layers containing barium titanate and internal electrode layers containing nickel are stacked, and applying the conductive paste to the end of the laminated body where the internal electrodes are exposed by a dip printing method with the laminated body lowered at a rate of 300 μm / s and pulled up at a rate of 100 μm / s, and then holding the laminated body in an air atmosphere at 150°C for 10 minutes, and then heating the laminated body in a nitrogen atmosphere at a heating rate of 50°C / min, and after reaching 700°C, holding the body for 15 minutes to form terminal electrodes, thereby producing 20 electronic components equipped with terminal electrodes, and embedding each of the 20 electronic components in resin. Each electronic component can be prepared by cutting the electronic component so as to pass through the center of each end face of the electronic component and in the stacking direction (perpendicular to the dielectric layers and internal electrode layers) to expose a cross section of the electronic component.

[0105] <Method for Manufacturing Electronic Components> 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.

[0106] The method for manufacturing an electronic component using the conductive paste of the present invention includes a laminated body preparation step of preparing a laminated body for a multilayer ceramic electronic component, which comprises 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.

[0107] By using the conductive paste of the present invention in the method for manufacturing an electronic component described above, 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 step. That is, according to the method for manufacturing an electronic component described above, it is possible to manufacture an electronic component having terminal electrodes that are thin, dense, and highly continuous, even when firing is performed at a low temperature in the terminal electrode formation step.

[0108] The laminated element preparing step is a step of preparing a laminated element for a multilayer ceramic electronic component.

[0109] A laminated element for a multilayer ceramic electronic component comprises a plurality of ceramic layers and a plurality of internal electrode layers. In the laminated element for a multilayer ceramic electronic component, the ceramic layers and the internal electrode layers are alternately stacked. Examples of laminated elements for multilayer ceramic electronic components include laminated elements for multilayer ceramic capacitors, laminated elements for multilayer ceramic inductors, and laminated elements for piezoelectric actuators.

[0110] Examples of materials for forming the ceramic layers constituting the laminated element for a laminated ceramic electronic component include barium titanate, strontium titanate, calcium titanate, barium zirconate, strontium zirconate, calcium zirconate, and strontium calcium zirconate.

[0111] Examples of materials for forming the internal electrode layers constituting the laminated body for a multilayer ceramic electronic component include nickel, palladium, silver, copper, and gold, or alloys containing one or more of these (e.g., an alloy of silver and palladium).

[0112] The terminal electrode forming step is a step of applying the conductive paste of the present invention to the exposed ends of the internal electrodes of a laminated body for a multilayer ceramic electronic component, and firing the applied conductive paste to form terminal electrodes.

[0113] The method for applying the conductive paste is not particularly limited, and examples thereof include dip printing, screen printing, and roll coating. Among these, dip printing is preferred. After the conductive paste is applied to the laminated body, it may be dried and then fired.

[0114] In the terminal electrode forming step, after the terminal electrodes are formed, a plating layer can be formed on the surface of the electrodes.

[0115] In this specification, 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 edge portions of the end faces are referred to as "corners." Typically, when applying a conductive paste to the ends in the terminal electrode formation process, the conductive paste is applied so as to cover the end faces and corners.

[0116] The size of the laminated element in which the conductive paste of the present invention is used is not particularly limited, and the paste can be used, for example, in laminated elements for 2012-size multilayer ceramic capacitors, laminated elements for 1608-size multilayer ceramic capacitors, laminated elements for 1005-size multilayer ceramic capacitors, laminated elements for 0603-size multilayer ceramic capacitors, laminated elements for 0402-size multilayer ceramic capacitors, and laminated elements for 0201-size multilayer ceramic capacitors. Thinner terminal electrodes are 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, laminated elements for 0603-size multilayer ceramic capacitors, laminated elements for 0402-size multilayer ceramic capacitors, and laminated elements for 0201-size multilayer ceramic capacitors.

[0117] 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 electrode area ratio can be calculated, for example, by the following method. That is, 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 to the observed field of view can be calculated as the electrode area ratio.

[0118] The maximum thickness of the terminal electrodes, measured by the method described below, 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. The average maximum thickness of the terminal electrodes, calculated by the method described below, 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 allows the size of the multilayer ceramic electronic component to be reduced. Furthermore, for a multilayer ceramic electronic component of a given size, the thinner the terminal electrodes, the larger the size of the laminated body, i.e., the greater the electrode area and the number of layers can be increased, thereby improving the performance of the multilayer ceramic electronic component.

[0119] The method for measuring the maximum thickness is not particularly limited, but for example, an electronic component is embedded in a resin, and the electronic component is 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, and the cross section is observed with a scanning electron microscope. When a perpendicular line is drawn from the outer periphery of the terminal electrode to the end face portion of the laminated body on the cross section, the point where the length of the perpendicular line is longest can be measured as the maximum thickness. The method for calculating the average maximum thickness is 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.

[0120] The minimum thickness of the terminal electrodes measured by the method described below is preferably 1.0 μm or more, more preferably 2.5 μm or more, and particularly preferably 5.0 μm or more. The average value of the minimum thickness of the terminal electrodes calculated by the method described below 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 into the laminated body when plating the terminal electrodes.

[0121] The method for measuring the minimum thickness is not particularly limited, but for example, an electronic component can be embedded in resin, cut through the center of both end face portions of the electronic component in the lamination direction (perpendicular to the dielectric layers and internal electrode layers) to expose a cross section of the electronic component, observe the cross section with a scanning electron microscope, and measure 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 portion 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. Furthermore, the method for calculating the average minimum thickness 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 above method and averaging the minimum thicknesses.

[0122] The present invention will be described below based on specific experimental examples, but the present invention is not limited to these.

[0123] <Production of Copper Powder> First, spherical copper powder produced by a known wet process (liquid-phase reduction method) and spherical copper powder produced by a known dry process (atomization method) were prepared as raw material powders. Next, zirconia beads with a diameter of 0.1 mm, the spherical copper powder, secondary butyl alcohol, and a predetermined lubricant (dimethylstearylamine) were mixed together. Using a bead mill, physical force was applied to the spherical copper powder by appropriately adjusting the flow rate and number of passes until the ratio of the major axis X to the minor axis Z reached the value shown in Table 1, thereby obtaining the copper powders listed in Table 1. Note that the copper powders described in Experimental Examples 1 and 3 were used as raw material powders without undergoing the above-mentioned treatment. Experimental examples marked with an "*" are outside the scope of the present invention.

[0124] <D50> The volume-based cumulative 10% particle diameter D50 (μm) was measured using a laser diffraction particle size distribution analyzer (LA-960, manufactured by HORIBA).

[0125] <Ratio of major diameter X to median diameter Y and ratio of major diameter X to minor diameter Z> The ratio of major diameter X to median diameter Y and the ratio of major diameter X to minor diameter Z were calculated using the values ​​of major diameter X, median diameter Y, and minor diameter Z measured by the following method. (Major diameter X and median diameter Y) 100 particles were randomly selected by observation with a scanning electron microscope, and the length of the longer of the two mutually perpendicular sides of a rectangle circumscribing the particle so as to minimize the area was measured as the major diameter X and the length of the shorter side as the median diameter Y. (Minor diameter Z) 100 parts by mass of copper powder and 7 parts by mass of acrylic resin (Dianal MB-2677, manufactured by Mitsubishi Chemical Corporation) dissolved in terpineol were mixed, then kneaded using a three-roll mill (manufactured by Inoue Seisakusho), then diluted with terpineol, and kneaded at 25°C and a shear rate of 4 s －１A paste-like composition was prepared by adjusting the viscosity at 2000 kJ / min to 30 Pa s, and the paste-like composition was cast onto a PET film using an applicator to form a coating film with a thickness of 250 μm. 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 (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.

[0126] <Crystallite diameter> Using an XRD measurement device (Rigaku Corporation, SmartLab), XRD measurement was performed using CuKα radiation (wavelength λ: 1.5418 Å) under conditions of 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 at a diffraction angle 2θ of 20.0 to 100.0°. A 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.

[0127] <Tap Density> Using a tap density measuring device (KYT-4000, manufactured by Seishin Enterprise Co., Ltd.), 20 g of copper powder was weighed and measured at a tap density of 20 cm ３ The sample was placed in a cell, and the tapping stroke was set to 20 mm and the number of taps was set to 200. The sample volume after tapping (cm ３ Tap density (g / cm) as the ratio of sample weight (g) to sample density (g / cm) ３ ) was calculated.

[0128] <Carbon Content> Carbon content was measured using a carbon / sulfur analyzer (HORIBA, EMIA-320V).

[0129] <Shrinkage (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. Using a TMA device (TMA4000S manufactured by Bruker), the sample was heated from room temperature to 900°C at a rate of 10°C / min in a nitrogen atmosphere, and the shrinkage (%) in the height direction of the sample was measured. The obtained value was rounded to the nearest whole number to obtain the shrinkage. That is, for example, if the obtained value was -0.4%, the shrinkage was 0%, and if the obtained value was 1.4%, the shrinkage was 1%.

[0130] <Evaluation Test of Terminal Electrodes> (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), then diluted with terpineol, and kneaded at 25°C at a shear rate of 4 s －１ The viscosity at 1000 kJ / min was adjusted to 30 Pa·s to prepare a conductive paste.

[0131] (Fabrication of Electronic Component with Terminal Electrodes) A ​​roughly rectangular parallelepiped laminated element having a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm was prepared, in which multiple dielectric layers containing barium titanate and internal electrode layers containing nickel were stacked. A conductive paste was applied to the end of this laminated element where the internal electrodes were exposed by dip printing, with the laminated element lowered at a rate of 300 μm / s and raised at a rate of 100 μm / 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 fabricating an electronic component with terminal electrodes.

[0132] (Preparation of Evaluation Test Samples) In each experimental example, 20 of the above-described electronic components were prepared. Each electronic component was embedded in resin, and cut through the center of each end face of each electronic component in the lamination direction (perpendicular to the dielectric layers and internal electrode layers) to expose the cross section of each electronic component, thereby preparing an evaluation test sample. The following evaluations were performed.

[0133] (Evaluation of Terminal Electrode Density (Electrode Area Ratio)) The above-mentioned evaluation test samples were observed using 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.

[0134] A: Electrode area ratio is 99% or more. B: Electrode area ratio is 90% or more but less than 99%. C: Electrode area ratio is less than 90%.

[0135] (Evaluation of fired film thickness of terminal electrode) The above-mentioned evaluation test samples were observed with a scanning electron microscope, and the thickness of the thickest part (maximum thickness) and the thinnest part (minimum thickness) of the terminal electrode (fired film) were measured, and the average value of the maximum thickness and the average value of the minimum thickness were calculated for each experimental example. The average values ​​of the maximum thickness and the average value of the minimum thickness were evaluated based on the following evaluation criteria. Note that those with an evaluation of A and those with an evaluation of B were considered to be passing.

[0136] A: The average value of the maximum thickness is ≦20 μm, and the average value of the minimum thickness is ≧2.5 μm. B: The average value of the maximum thickness is ≦40 μm, and the average value of the minimum thickness is ≧1.0 μm (excluding the cases corresponding to A above). C: The average value of the maximum thickness is >40 μm, or the average value of the minimum thickness is <1.0 μm.

[0137]

[0138] 1 Cross section of conductive particle 2 Rectangle circumscribing the cross section of the conductive particle 3 Short side of the rectangle 4 Long side of the rectangle

Claims

1. A conductive powder whose main component is copper, wherein the volume-based cumulative 50% particle diameter D50 measured by laser diffraction particle size distribution measurement is 0.3 μm or more and 4.5 μm or less, the ratio of the major diameter X defined below to the median diameter Y defined below is 1.0 or more and 3.0 or less, and the ratio of the major diameter X defined below to the minor diameter Z defined below is 1.5 or more and 5.0 or less, and the powder satisfies the following (A) and (B): (A) The carbon content is 0.00% by mass or more and 0.10% by mass or less, and (B) The TMA shrinkage rate, defined below, is 0% or more and less than 2% at 400°C. (Major diameter X and median diameter Y) One hundred particles are randomly selected by scanning electron microscope observation, and the average length of the long side of the rectangle circumscribing each particle so as to have the smallest area is defined as the major diameter X and the median diameter Y, respectively. (Minor diameter 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, kneaded using a triple roll mill, diluted with terpineol, and then kneaded at 25°C at a shear rate of 4 s －１ A paste-like composition is prepared by adjusting the viscosity at 250 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. The cross section of the dry film is exposed using an ion milling device, and the cross section of the dry film is observed using a scanning electron microscope. 100 particles are randomly selected, and the average value of the length of the short side of the rectangle circumscribing each particle so as to minimize the area is defined as the minor axis Z. (TMA Shrinkage Rate) 200 mg of the copper-based conductive powder is compressed 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 2 mm, and then the sample is heated from room temperature to 900° C. in a nitrogen atmosphere using a TMA device at a rate of 10° C. / min. The TMA shrinkage rate is defined as the percentage (%) of the height of the sample at each temperature relative to the height of the sample (2 mm).

2. The copper-based conductive powder according to claim 1, which 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.

3. A copper-based conductive powder according to claim 1, in which the ratio of the TMA shrinkage at 600°C to the maximum TMA shrinkage is 0.73 or more.

4. The copper-based conductive powder according to claim 1, wherein the ratio of the TMA shrinkage at 700°C to the maximum TMA shrinkage is 0.90 or more.

5. A copper-based conductive powder according to claim 1, wherein the ratio of the TMA shrinkage at 720°C to the maximum TMA shrinkage is 0.94 or more.

6. The tap density defined below is 3.5 g / cm ３ The copper-based conductive powder according to claim 1, wherein the tap density is greater than 20 cm ３ The sample was placed in a container, and tapped using a tap density measuring device with a tapping stroke of 20 mm and a tapping count of 200 times. The sample volume after tapping (cm ３ The value calculated as the ratio of the sample weight (g) to the total weight (g) is defined as the tap density.

7. The ratio of the crystallite size to the D50 is 6.0 × 10 －３ 2. The copper-based conductive powder according to claim 1, wherein the copper-based conductive powder is a copper-based conductive powder.

8. The copper-based conductive powder according to claim 1, which has an aliphatic amine on at least a portion of its surface.

9. A conductive paste containing the copper-based conductive powder according to any one of claims 1 to 8, glass frit, a binder resin, and an organic solvent.

10. 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 a plurality of ceramic layers and a plurality of internal electrode layers; and a terminal electrode formation step of applying the conductive paste according to claim 9 to the exposed ends of the internal electrodes of the laminated body, and then firing the applied conductive paste to form terminal electrodes.

11. The method for producing an electronic component according to claim 10, wherein the peak temperature of the firing is 720°C or less.

12. A method for producing a copper-based conductive powder according to any one of claims 1 to 8, comprising: a first step of preparing a raw copper-based 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.