Conductive paste and method for manufacturing electronic component

Abstract

A conductive paste containing a conductive powder mainly composed of copper, a glass frit, a binder resin, and an organic solvent, the conductive powder mainly composed of copper having a volume-based cumulative 50% particle diameter D50C of 0.3 [mu] m to 4.5 [mu] m (inclusive) in a laser diffraction particle size distribution measurement; the ratio of the average major axis (X) to the average minor axis (Y) is 1.0-3.0, the ratio of the average major axis (X) to the average thickness (Z) is 1.1-9.0, and the volume-based cumulative 50% particle diameter (D50G) of the glass frit in a laser diffraction particle size distribution measurement is 0.3-2.0 [mu] m. According to the present invention, even when fired at a low temperature, it is possible to form a thin, dense, and continuous terminal electrode while maintaining high productivity. Furthermore, even when fired at a low temperature, it is possible to manufacture an electronic component provided with a thin, dense, and excellent-continuity terminal electrode while maintaining high productivity.

Description

Technical Field

[0001] The present invention relates to a conductive paste using conductive powder mainly composed of copper. In particular, it relates to a conductive paste for forming terminal electrodes of multilayer ceramic capacitors, multilayer inductors, multilayer piezoelectric actuators and other multilayer electronic components. In addition, the present invention relates to a method for manufacturing multilayer electronic components. In particular, it relates to a method for manufacturing an electronic component by forming a terminal electrode on a multilayer substrate for multilayer electronic components. Background Art

[0002] Multilayer ceramic capacitors, multilayer inductors, multilayer piezoelectric actuators and other multilayer ceramic electronic components are generally manufactured in the following manner.

[0003] First, a conductive paste for internal electrodes is printed on a dielectric ceramic green sheet such as barium titanate-based ceramics in a given pattern. Then, a plurality of such sheets are laminated and pressed to obtain an unfired laminate in which ceramic green sheets and internal electrode paste layers are alternately laminated. The obtained laminate is cut into chips of a given shape to obtain a multilayer substrate. It should be noted that the multilayer substrate may be fired at a high temperature at this time, or may not be fired at this time, and is fired simultaneously with a terminal electrode paste layer formed later using a conductive paste for terminal electrodes. In this specification, in either case, the laminate in the state before forming the terminal electrode paste layer is referred to as a "multilayer substrate".

[0004] Then, a conductive paste for terminal electrodes composed of conductive powder, binder resin, organic solvent, glass powder, etc. is printed on the exposed ends of the internal electrodes of the multilayer substrate by an impregnation printing method or the like to form a conductive paste layer, dried as needed, and further fired at a high temperature to form a terminal electrode.

[0005] In addition, thereafter, a plating layer of nickel, tin, etc. may be formed on the terminal electrode by electroplating or the like as needed.

[0006] As the internal electrode material, noble metals such as palladium, silver-palladium, and platinum have been used in the past. However, there are requirements for resource saving, cost reduction, etc. In particular, in the firing type, there are requirements for preventing delamination and crack generation caused by oxidation expansion during firing of palladium and silver-palladium. Therefore, in recent years, the use of base metals such as nickel, cobalt, and copper has become mainstream. Therefore, as the terminal electrode material, copper, nickel, cobalt, or their alloys that are easily capable of forming a good electrical connection with the base metal internal electrode are used instead of silver and silver-palladium in the past.

[0007] Thus, when base metals are used for the internal electrodes and the terminal electrodes, the firing of the terminal electrodes is usually carried out in a non-oxidizing atmosphere with an extremely low oxygen partial pressure, such as an inert gas atmosphere with an oxygen content of several ppm to several tens of ppm, at a high temperature with a peak temperature of 800°C, in such a manner that these base metals are not oxidized during firing.

[0008] However, particularly in the case of firing using metal powder mainly composed of copper in a low-oxygen atmosphere, it is difficult to appropriately carry out debinding for burning, decomposing, and dispersing organic components such as binder resin. When debinding is not sufficient at a relatively low temperature stage in the initial stage of firing, before the fluidization of glass and the sintering of copper powder occur, carbon and organic residues are sealed into the film after the start of sintering, causing various problems such as poor blistering in the subsequent high-temperature stage.

[0009] Therefore, how to efficiently carry out debinding in the initial stage of firing and reduce residual carbon before the sintering of copper powder in the high-temperature region is an important technical problem for conventional conductive pastes using base metals, particularly metal powder mainly composed of copper.

[0010] As a method for solving this problem, for example, Patent Document 1 discloses a conductor paste for terminal electrodes, which uses aliphatic amine as a surface treatment agent for copper-based conductive powder, resulting in good dispersibility of the conductive powder and significantly improved debinding property, so that a dense terminal electrode with excellent adhesiveness and conductivity can be formed.

[0011] In addition, Patent Document 2 discloses a conductive paste containing copper powder, glass powder, and an organic carrier, wherein the copper powder is composed of 0 to 70 vol% of coarse copper powder with an average particle size of 1.0 μm to 3.0 μm and 30 to 100 vol% of fine copper powder with an average particle size of 0.1 to 0.8 μm. In addition, an electronic component is disclosed, which includes: a laminate having a plurality of ceramic layers and internal electrodes; and an external electrode formed on the outer surface of the laminate and electrically connected to the internal electrodes, which is formed by sintering the above-mentioned conductive paste, wherein the carbon amount in the external electrode at the time when the sintering density of the external electrode is 80% is 0.007 wt% or less.

[0012] Prior Art Documents

[0013] Patent Documents

[0014] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-004734

[0015] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-187225 Summary of the Invention

[0016] Technical problems to be solved by the invention

[0017] However, in recent years, in order to reduce the environmental load, reduce the manufacturing cost, and reduce the thermal stress on the laminated substrate, it has also been required to reduce the firing temperature when forming the terminal electrodes. In addition, miniaturization of electronic components has been required, and along with this, thinning of the terminal electrodes has been required. That is, there is a need for a conductive paste suitable for thinning that can appropriately remove the binder and reduce the firing temperature.

[0018] The conductive pastes described in Patent Document 1 and Patent Document 2 are designed for firing at a high temperature such as 800°C. Therefore, when firing at 800°C, sintering is sufficiently performed after removing the binder, and a dense fired film is obtained. However, when the present inventors tried firing at a low temperature such as 720°C using the above-mentioned paste, as a result, sintering could not be sufficiently performed after removing the binder within a firing time of several tens of minutes or several hours.

[0019] Therefore, an object of the present invention is to provide a conductive paste that can form a thin, dense, and highly continuous terminal electrode while maintaining high productivity even when fired at a low temperature. In addition, an object of the present invention is to provide a manufacturing method that can manufacture an electronic component having a thin, dense, and highly continuous terminal electrode while maintaining high productivity even when fired at a low temperature.

[0020] Technical means for solving the problems

[0021] In order to solve the above problems, intensive studies were repeatedly conducted, and as a result, the present inventors found that by using a fine conductive powder having copper as a main component, a cumulative 50% particle size D50 based on volume in laser diffraction particle size distribution measurement C of 0.3 μm or more and 4.5 μm or less, a ratio of the average major axis X to the average minor axis Y of 1.0 or more and 3.0 or less, and a ratio of the average major axis X to the average thickness Z of 1.1 or more and 9.0 or less, and combining a fine glass powder having a cumulative 50% particle size D50 G of 0.3 μm or more and 2.0 μm or less based on volume in laser diffraction particle size distribution measurement, it is possible to form a thin, dense, and highly continuous terminal electrode while maintaining high productivity even when fired at a low temperature, thereby completing the present invention.

[0022] That is, the present invention (1) provides a conductive paste containing a conductive powder having copper as a main component, a glass powder, a binder resin, and an organic solvent, wherein

[0023] the cumulative 50% particle size D50 of the conductive powder having copper as a main component in laser diffraction particle size distribution measurementC is 0.3 μm or more and 4.5 μm or less, and the ratio of the average major axis X to the average minor axis Y is 1.0 or more and 3.0 or less, and the ratio of the average major axis X to the average thickness Z defined below is 1.1 or more and 9.0 or less.

[0024] The cumulative 50% particle size D50 on a volume basis in the measurement of the particle size distribution by laser diffraction of the glass powder G is 0.3 μm or more and 2.0 μm or less.

[0025] (Average thickness)

[0026] The conductive paste containing the conductive powder mainly composed of copper is cast on a PET film by a coater to form a coating film with a film thickness of 250 μm, and the coating film is 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 is exposed by ion milling, and the cross-section of the dried film is observed with a scanning electron microscope. 500 conductive particles are randomly selected, and the average value of the thickness is obtained by measuring with the minor axis as the thickness. The value of this average value is defined as the "average thickness".

[0027] In addition, the present invention (2) provides the conductive paste according to (1), wherein

[0028] at least a part of the surface of the conductive powder mainly composed of copper has an aliphatic amine.

[0029] In addition, the present invention (3) provides the conductive paste according to (2), wherein

[0030] the aliphatic amine is 0.01 part by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the conductive powder mainly composed of copper.

[0031] In addition, the present invention (4) provides the conductive paste according to any one of (1) to (3), wherein

[0032] the cumulative 10% particle size on a volume basis in the measurement of the particle size distribution by laser diffraction of the glass powder is defined as D10 G and the cumulative 90% particle size is defined as D90 G When G (D90 G - D10 G ) / D50

[0033] In addition, the present invention (5) provides the conductive paste according to any one of (1) to (4), wherein

[0034] the cumulative 10% particle size on a volume basis in the measurement of the particle size distribution by laser diffraction of the conductive powder mainly composed of copper is defined as D10C When the cumulative 90% particle size is defined as D90 C , (D90 C - D10 C ) / D50 C is 7.5 or less.

[0035] In addition, the present invention (6) provides the conductive paste according to any one of (1) to (5), which satisfies at least any one of the following conditions:

[0036] The ratio of the viscosity at a shear rate of 0.4 s -1 when measured at 25 °C to the viscosity at a shear rate of 40 s -1 is 2.0 or more and 20.0 or less; and

[0037] When a strain of 1% is applied to the conductive paste 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 45° or more and 80° or less.

[0038] In addition, the present invention (7) provides the conductive paste according to any one of (1) to (6), which satisfies all of the following conditions:

[0039] The electrode area ratio of the terminal electrode calculated by the following respective evaluation tests is 90% or more;

[0040] The average value of the maximum thickness of the terminal electrode is 40 μm or less; and

[0041] The average value of the minimum thickness of the terminal electrode is 1.0 μm or more.

[0042] <Evaluation test for the electrode area ratio of the terminal electrode>

[0043] The evaluation test samples prepared by the method for preparing the evaluation test samples described below are observed with a scanning electron microscope for 10 fields of view for each sample, and the ratio of the electrode area occupied in the observed fields of view is calculated as the electrode area ratio of the terminal electrode.

[0044] <Evaluation test for the maximum thickness of the terminal electrode>

[0045] The evaluation test samples prepared by the method for preparing the evaluation test samples described below are observed with a scanning electron microscope. In the evaluation test samples, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face portion of the laminated substrate, the portion where the length of the perpendicular line is the maximum is measured as the maximum thickness, and the maximum thicknesses of 20 electronic components for which the maximum thickness has been measured are averaged, thereby calculating the average value of the maximum thickness of the terminal electrode.

[0046] <Evaluation test for the minimum thickness of the terminal electrode>

[0047] The evaluation test sample prepared by the following method for preparing an evaluation test sample is observed with a scanning electron microscope. In this evaluation test sample, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face portion of the laminated substrate, the thickness of the portion where the length of this perpendicular line becomes the minimum and the thickness of the portion where the distance between the corner portion of the laminated substrate and the outer peripheral portion of the terminal electrode becomes the shortest are measured, and the thickness of the thinnest part among them is measured as the minimum thickness. The average value of the minimum thickness of the terminal electrode is calculated by averaging the minimum thickness of 20 electronic components for which the minimum thickness has been measured.

[0048] <Method for preparing evaluation test sample>

[0049] Prepare a rectangular parallelepiped-shaped laminated substrate with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, in which a dielectric layer containing barium titanate and an internal electrode layer containing nickel are laminated in multiple layers. At the end portion where the internal electrode of the laminated substrate is exposed, set the descending speed of the laminated substrate to 300 μm / s and the lifting speed to 100 μm / s, and apply the conductive paste by the dip printing method. Then, keep it at 150 °C for 10 minutes in an air atmosphere. Then, in a nitrogen atmosphere, heat it at a heating rate of 50 °C / minute, and after reaching 720 °C, keep it for 15 minutes to form a terminal electrode, thereby preparing 20 electronic components equipped with terminal electrodes. The 20 electronic components are respectively resin-embedded, and in each electronic component, cut each electronic component in a manner passing through the central portion of the two end face portions and in the lamination direction (the direction perpendicular to the dielectric layer and the internal electrode layer) to expose the cross section of each electronic component, thereby preparing an evaluation test sample.

[0050] In addition, the present invention (8) provides a method for manufacturing an electronic component, which has:

[0051] A laminated substrate preparation step of preparing a laminated substrate for a laminated type electronic component including a plurality of ceramic layers and a plurality of internal electrode layers; and

[0052] A terminal electrode formation step of applying a conductive paste to the exposed end portion of the internal electrode of the laminated substrate, and then firing the applied conductive paste to form a terminal electrode.

[0053] The conductive paste is the conductive paste described in any one of (1) to (7).

[0054] In addition, the present invention (9) provides the method for manufacturing an electronic component according to (7), wherein

[0055] The peak temperature of the firing is 720 °C or lower.

[0056] In addition, the present invention (10) provides the conductive paste according to any one of (1) to (7), wherein,

[0057] the conductive paste is a fired conductive paste used for firing. When the peak temperature of the firing is T 1 °C, the glass powder is placed in a cylindrical container with an inner diameter of 5 mm, and a pressure of 3 MPa is applied axially for 10 seconds to form a cylindrical compact with a diameter of 5 mm and a height of 1 mm. The compact is placed on a copper plate with a surface roughness Ra of 100 nm in such a manner that the flat surface of the compact contacts the copper plate, and the compact is heated in a nitrogen atmosphere at a heating rate of 10 °C / min to T 1 °C. When the glass constituting the compact is melted, the contact angle of the glass with respect to the copper plate is 80° or less.

[0058] In addition, the present invention (11) provides the conductive paste according to any one of (1) to (7) and (10), wherein,

[0059] the viscosity at a shear rate of 4 s -1 when measured at 25 °C is 10.0 Pa·s or more and 80.0 Pa·s or less.

[0060] In addition, the present invention (12) provides a method for manufacturing an electronic component according to (8) or (9), wherein,

[0061] the electrode area ratio of the terminal electrode calculated by the following calculation method is 90% or more,

[0062] <Calculation method for the electrode area ratio of the terminal electrode>

[0063] Twenty of the electronic components are each resin-embedded. In each electronic component, the electronic component is cut in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a manner as to pass through the central portion of both end faces of each electronic component, so that the cross section of each electronic component is exposed. The cross section of each electronic component is observed with a scanning electron microscope for 10 fields of view each, and the ratio of the electrode area occupied in the observed fields of view is calculated as the electrode area ratio.

[0064] In addition, the present invention (13) provides a method for manufacturing an electronic component according to any one of (8), (9), and (12), wherein,

[0065] the average value of the maximum thickness of the terminal electrode calculated by the following calculation method is 40 μm or less.

[0066] <Calculation method for the average value of the maximum thickness of the terminal electrode>

[0067] Twenty of the said electronic components are each resin-embedded, and in each electronic component, the component is cut in a direction passing through the central portions of the end faces of the component and in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer), thereby exposing the cross section of each electronic component. The cross section is observed with a scanning electron microscope. In this cross section, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face of the stacked substrate, the portion where the length of this perpendicular line is the maximum is measured as the maximum thickness. The maximum thicknesses of the 20 electronic components for which the maximum thickness has been measured are averaged, thereby calculating the average value of the maximum thickness of the said terminal electrode.

[0068] Furthermore, the present invention (14) provides a method for manufacturing an electronic component according to any one of (8), (9), (12), and (13), wherein

[0069] the average value of the minimum thickness of the said terminal electrode calculated by the following calculation method is 1.0 μm or more.

[0070] <Calculation method for the average value of the minimum thickness of the terminal electrode>

[0071] Twenty of the said electronic components are each resin-embedded, and in each electronic component, the component is cut in a direction passing through the central portions of the end faces of the component and in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer), thereby exposing the cross section of each electronic component. The cross section is observed with a scanning electron microscope. In this cross section, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face of the stacked substrate, the thickness of the portion where the length of this perpendicular line is the minimum and the thickness of the portion where the distance between the corner of the stacked substrate and the outer peripheral portion of the terminal electrode is the shortest are measured. The thickness of the thinnest part among them is measured as the minimum thickness, and the average value of the minimum thicknesses of the 20 electronic components for which the minimum thickness has been measured is calculated to obtain the average value of the minimum thickness of the said terminal electrode.

[0072] Advantages of the Invention

[0073] According to the present invention, even in the case of firing at a low temperature, it is possible to form a thin, dense, and highly continuous terminal electrode while maintaining high productivity. Furthermore, even in the case of firing at a low temperature, it is possible to manufacture an electronic component having a thin, dense, and highly continuous terminal electrode while maintaining high productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 Figure 1 is a schematic diagram illustrating a method for measuring the fired film thickness of a terminal electrode formed from a conductive paste. DETAILED DESCRIPTION OF THE INVENTION ​​

[0075] <Conductive paste>

[0076] The conductive paste of the present invention contains a conductive powder mainly composed of copper, a glass powder, a binder resin, and an organic solvent. Among them, the volume-based cumulative 50% particle size D50C of the conductive powder in laser diffraction particle size distribution measurement is 0.3 μm or more and 4.5 μm or less, and the ratio of the average major axis X to the average minor axis Y is 1.0 or more and 3.0 or less, and the ratio of the average major axis X to the average thickness Z is 1.1 or more and 9.0 or less. The volume-based cumulative 50% particle size D50 of the glass powder in laser diffraction particle size distribution measurement G is 0.3 μm or more and 2.0 μm or less. Thus, even in the case of firing at a low temperature, it is possible to form a thin, dense, and highly continuous terminal electrode while maintaining high productivity. In particular, when the conductive powder mainly composed of copper in the present invention has an aliphatic amine described below on at least a part of the surface, the effects of the present invention are more significantly exhibited.

[0077] By using the conductive powder mainly composed of copper, the filling property of the conductive powder in the coating film of the conductive paste is improved. Therefore, even in the case of firing at a low temperature, sintering of the conductive powder is easy to proceed. In addition, by using D50 G of the glass powder within the above range, the fine glass powder is uniformly dispersed even inside the film before firing in which the conductive powder is densely filled. Therefore, the conductive powder is easily sintered uniformly throughout the film. In addition, a debinding path can be appropriately ensured throughout the film. As a result, a thin, dense, and highly continuous terminal electrode can be formed. In addition, by setting the upper limit of D50 G to the above value, the discontinuous portion of the terminal electrode caused by voids generated after glass flow can be reduced.

[0078] It should be noted that by surface-treating the conductive powder, the dispersibility of the conductive powder is improved, and thus the filling property of the conductive powder in the coating film is further improved. However, due to the improvement of the filling property, the debinding path becomes narrow, so the debinding property is reduced, and a debinder for the surface treatment agent itself is also required. Therefore, other problems such as poor sinterability or blistering defects caused by insufficient debinder may occur instead. In a preferred embodiment of the present invention, by using an aliphatic amine described below as the surface treatment agent, even when the conductive powder is filled at a high density, the debinding can be appropriately performed. That is, by using the conductive powder in the present invention surface-treated with an aliphatic amine, the conductive powder is filled at a higher density in the coating film before firing, and the glass powder in the present invention is used and the surface treatment agent of the conductive powder is an aliphatic amine to improve the debinding property. Therefore, even when firing at a low temperature, sintering is easy, and a dense fired film is more easily obtained.

[0079] The conductive paste of the present invention is preferably applied to a laminated substrate or the like to form a coating film, and after drying the coating film as needed to form a dry film, it is fired and used. The peak temperature of firing is not particularly limited, and as long as it is 600 °C or higher, which is lower than the conventional firing temperature, firing can be performed. From the viewpoints of reducing the environmental load, reducing the manufacturing cost, and reducing the thermal stress on the laminated substrate, it is preferably 600 °C or higher and 720 °C or lower, and particularly preferably 600 °C or higher and 700 °C or lower.

[0080] <Conductive powder>

[0081] In the present invention, the conductive powder only needs to have copper as the main component. The proportion 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, further preferably 95% by mass or more and 100% by mass or less, and particularly preferably 100% (pure copper). By making the proportion of copper in the conductive powder within the above range, the conductive powders are easily sintered with each other, and thus a dense fired film can be easily obtained. It should be noted that as long as the conductive powder in the present invention has copper as the main component, it may be a mixed powder of other elemental metal powders such as nickel powder and silver powder and copper powder, or it may be an alloy powder of other elements such as nickel and silver and copper. In addition, it may also be a composite powder obtained by coating copper powder with glass, ceramics, etc. In addition, it may also be a powder having an oxide film on the surface. In addition, surface treatment can be performed with an organometallic compound, a surfactant, etc., and two or more of these conductive powders can be mixed and used. It should be noted that in this specification, the "main component" means that the proportion of this component exceeds 50% by mass of the whole. In particular, in the conductive powder having copper as the main component, it means that the copper component exceeds 50% by mass of all the conductive powders contained in the conductive paste of the present invention including the above-mentioned mixed powder, alloy powder, etc.

[0082] The volume-based cumulative 50% particle size D50 of the conductive powder having copper as the main component in the present invention in the laser diffraction particle size distribution measurement C only needs to be 0.3 μm or more and 4.5 μm or less, preferably 0.3 μm or more and 4.0 μm or less, more preferably 0.5 μm or more and 4.0 μm or less, more preferably 0.5 μm or more and 3.0 μm or less, more preferably 0.7 μm or more and 3.0 μm or less, further preferably 1.0 μm or more and 3.0 μm or less, and particularly preferably 1.5 μm or more and 2.5 μm or less. By making the D50 of the conductive powder having copper as the main component C within the above range, even in the case of firing at a low temperature, the sintering of the conductive powder is easily carried out, and a dense fired film is easily formed. In addition, a thin fired film is easily formed.

[0083] The ratio of the average major axis X to the average minor axis Y of the conductive powder having copper as the main component in the present invention only needs to be 1.0 or more and 3.0 or less, preferably 1.0 or more and 2.5 or less. By making the ratio of the average major axis X to the average minor axis Y of the conductive powder having copper as the main component within the above range, even in the case of firing at a low temperature, the sintering is easily carried out, and a dense fired film is easily formed. In addition, a thin and highly continuous fired film (terminal electrode) is easily formed.

[0084] The average major axis X and the average minor axis Y can both be measured by, for example, observation with a scanning electron microscope. That is, a plurality of (for example, 500) conductive particles are randomly selected and observed with a scanning electron microscope, the major axis and the minor axis are measured, and the respective average values are obtained, thereby performing the measurement. In addition, for example, measurement can be performed with a flow particle image analysis device. That is, the major axis and the minor axis of a plurality of (for example, 500) conductive particles are measured using a flow particle image analysis device, and the respective average values are obtained for the measurement. As the flow particle image analysis device, for example, FPIA-3000S manufactured by SYSMEX Corporation can be used.

[0085] In the present invention, it is sufficient that the ratio of the average major axis X of the copper-based conductive powder to the average thickness Z defined below is 1.1 or more and 9.0 or less, preferably 1.1 or more and 7.5 or less, more preferably 1.2 or more and 7.5 or less, more preferably 1.2 or more and 6.0 or less, more preferably 1.5 or more and 5.0 or less, more preferably 1.6 or more and 4.5 or less, more preferably 1.6 or more and 4.0 or less, further preferably 1.7 or more and 3.0 or less, and particularly preferably 1.8 or more and 2.5 or less. By making the ratio of the average major axis X of the copper-based conductive powder to the average thickness Z within the above range, even in the case of firing at a low temperature, sintering is likely to proceed, and a dense fired film is easily formed. In addition, a thin and highly continuous fired film (terminal electrode) is easily formed.

[0086] (Average thickness)

[0087] The conductive paste containing the copper-based conductive powder is cast on a PET film with a coater to form a coating film with a film thickness of 250 μm, the coating film is 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 is exposed by ion milling, the cross-section of the dried film is observed with a scanning electron microscope, 500 conductive particles are randomly selected, and the average value of the thickness is obtained by measuring with the minor axis as the thickness. The value of this average value is defined as the "average thickness" in this specification (the present invention).

[0088] In addition, the average thickness Z can be measured, for example, by observing the cross-section of a dry film formed using the conductive paste of the present invention with a scanning electron microscope. More specifically, for example, it can be measured as follows: The conductive paste of the present invention is cast onto a PET film by a coater to form a coating film with a film thickness of 250 μm, and this coating film is dried under the conditions of an air atmosphere, 150°C, and 10 minutes to form a dry film. The cross-section of this dry film is exposed by an ion milling device (e.g., IM4000 manufactured by HITACHI HIGH-TECH Corporation), and the cross-section of this dry film is observed with a scanning electron microscope (e.g., SU-8020 manufactured by HITACHI HIGH-TECH Corporation). Through this observation, a plurality of (e.g., 500) conductive particles are randomly selected, the minor axis is measured as the thickness, and the average value of this thickness is obtained, thereby performing the measurement. As the conductive paste of the present invention, for example, a paste can be used in which 100 parts by mass of a conductive powder mainly composed of copper, an acrylic resin dissolved in terpineol (7 parts by mass as the resin), and 10 parts by mass of glass powder are mixed. Then, it is kneaded using a three-roll mill, and then diluted with terpineol to adjust the viscosity to 30 Pa·s at 25°C and a shear rate of 4 s -1 . It should be noted that even when other powders such as glass powder are included in addition to the conductive powder mainly composed of copper, the average thickness of the conductive powder mainly composed of copper can be measured by distinguishing it from the other powders. As a method of distinction, for example, the element distribution in the cross-section of the dry film can be observed by EDX (Energy Dispersive X-ray Spectroscopy), and the conductive powder mainly composed of copper and other powders can be distinguished.

[0089] As long as the conductive powder mainly composed of copper in the present invention has a D50 C of 0.3 μm or more and 4.5 μm or less, and the ratio of the average major axis X to the average minor axis Y is 1.0 or more and 3.0 or less, and the ratio of the average major axis X to the average thickness Z is 1.1 or more and 9.0 or less, there is no particular limitation on the shape, and for example, it can be in a flat shape, a cylindrical shape, an elliptical cylindrical shape, a frustum of a cone shape, an elliptical frustum of a cone shape, a cuboid shape, etc. It should be noted that the conductive powder of the present invention does not exclude powders of other shapes such as spherical shapes. As the conductive powder as a whole, "D50 CIt is only necessary that the "average aspect ratio", "ratio of the average major axis X to the average minor axis Y", and "ratio of the average major axis X to the average thickness Z" satisfy the numerical range. At this time, the content rate of the conductive powder satisfying this numerical range with respect to all the conductive powders is not particularly limited, and 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, further preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0090] In the conductive powder mainly composed of copper in the present invention, when the cumulative 10% particle size based on volume in the laser diffraction particle size distribution measurement is set as D10 C and the cumulative 90% particle size is set as D90 C , (D90 C - D10 C ) / D50 C is preferably 7.5 or less, more preferably 6.5 or less, more preferably 5.0 or less, more preferably 4.0 or less, further preferably 3.0 or less, and particularly preferably 2.0 or less. The lower limit value of (D90 C - D10 C ) / D50 C is not particularly limited, and for example, it may be 0.2 or more. By making (D90 C - D10 C ) / D50 C of the conductive powder mainly composed of copper within the above range, that is, the particle size distribution of the conductive powder is narrow, the sintering of the conductive powder can be uniformly carried out throughout the film. That is, the progress of local sintering in the film can be suppressed, so that the debinder path can be appropriately ensured throughout the film. As a result, a thin, dense, and highly continuous terminal electrode can be formed. In addition, the film thickness of the terminal electrode can be suppressed from becoming thick due to extremely large conductive powders.

[0091] The specific surface area of the conductive powder is preferably 0.2 m 2 / g or more and 3.0 m 2 / g or less, and particularly preferably 0.3 m 2 / g or more and 2.0 m 2 / g or less. By making the specific surface area of the conductive powder mainly composed of copper within the above range, even in the case of firing at a low temperature, sintering is easy to proceed, and a dense fired film is easily formed. In addition, a thin fired film is easily formed.

[0092] The method for manufacturing the conductive powder in the present invention is not particularly limited. For example, spherical conductive powder can be manufactured by spray pyrolysis method, physical vapor deposition method, chemical vapor deposition method, liquid phase reduction method, atomization method, etc. Then, if necessary, the conductive powder is surface-treated with a surface treatment agent such as an aliphatic amine described below. Then, pulverization treatment is performed using a bead mill, ball mill, mortar, etc., thereby manufacturing. In addition, the particle size distribution can be adjusted by performing classification before or after the pulverization treatment as needed.

[0093] <Glass powder>

[0094] The cumulative 50% particle size D50 on a volume basis in the laser diffraction type particle size distribution measurement of the glass powder of the present invention G is 0.3 μm or more and 2.0 μm or less, preferably 0.5 μm or more and 1.5 μm or less. By making the D50 of the glass powder G within the above range, it is easy to form a dense fired film, and in addition, it is easy to form a fired film (terminal electrode) with excellent continuity.

[0095] Let the cumulative 10% particle size in the laser diffraction type particle size distribution measurement of the glass powder of the present invention be D10 G , and the cumulative 90% particle size be D90 G . When G -D10 G ) / D50 G is preferably 7.5 or less, more preferably 6.5 or less, still more preferably 5.0 or less, further preferably 3.5 or less, and particularly preferably 2.5 or less. (D90 G -D10 G ) / D50 G has no particular limitation for the lower limit value, and can be, for example, 0.2 or more. By making (D90 G -D10 G ) / D50 G within the above range, that is, the particle size distribution of the glass powder is narrow, so that the glass powder with uniform size is evenly distributed even inside the film before firing in which the conductive powder is densely filled. Therefore, the conductive powder is easily sintered uniformly throughout the film. In addition, local sintering in the film can be suppressed thereby, and thus a debinder path can be appropriately ensured throughout the film. As a result, a thin, dense and continuous terminal electrode can be formed. There is little extremely small glass powder that exists agglomerated and is easily softened / flowed, so it is easy to suppress the progress of local sintering and local debinder defects caused by the progress of this sintering. In addition, since there is little extremely large glass powder, exposure of the laminated substrate due to voids generated where this glass powder flows during the sintering process can be suppressed, and thus the continuity of the terminal electrode can be improved.

[0096] The conductive paste of the present invention is a fired conductive paste used for firing. When the peak temperature of the firing is T 1 °C, the glass powder is placed in a cylindrical container with an inner diameter of 5 mm, and a pressure of 3 MPa is applied axially for 10 seconds to form a cylindrical compact with a diameter of 5 mm and a height of 1 mm. The compact is placed on a copper plate with a surface roughness Ra of 100 nm in such a way that the flat surface of the compact contacts the copper plate, and the compact is heated in a nitrogen atmosphere at a heating rate of 10°C / min to T 1 °C. When the glass constituting the compact melts, the contact angle of the glass with respect to the copper plate is preferably 80° or less, more preferably 75° or less, still more preferably 70° or less, even more preferably 65° or less, further preferably 60° or less, and particularly preferably 55° or less. The lower limit value of the contact angle of the glass with respect to the copper plate is not particularly limited and can be, for example, 10° or more. By making the contact angle of the glass with respect to the copper plate within the above range, the wettability of the glass with respect to the conductive powder mainly composed of copper becomes good. In order to appropriately remove the binder, the flow of the glass is suppressed until the desired temperature, and at the time point when the desired temperature is reached, the glass can quickly wet and spread near the conductive powder. Therefore, it is easy to form a thin, dense, and highly continuous terminal electrode.

[0097] The composition of the glass powder in the present invention is not particularly limited. For example, BaO-ZnO-based, BaO-ZnO-B 2 O 3 -based, RO-ZnO-B 2 O 3 -MnO 2 -based, RO-ZnO-based, RO-ZnO-MnO 2 -based, RO-ZnO-SiO 2 -based, ZnO-B 2 O 3 -based, SiO 2 -B 2 O 3 -R' 2 O-based, SiO 2 -RO-R' 2 O-based (wherein R is an alkaline earth metal element and R′ is an alkali metal element) and other glasses can be used.

[0098] The glass transition temperature of the glass powder in the present invention is preferably 400°C or higher and 550°C or lower. By making the glass transition temperature of the glass powder within the above range, even in the case of firing at a low temperature, the glass is easily wetted and spread in the film, so it is easy to form a dense fired film.

[0099] The softening point of the glass powder in the present invention is preferably 500 °C or higher and 650 °C or lower. By setting the softening point of the glass powder within the above range, even when fired at a low temperature, the glass is likely to wet and spread in the film, and thus it is easy to form a dense fired film.

[0100] The specific surface area of the glass powder 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. By setting the specific surface area of the glass powder within the above range, the glass powder is likely to be uniformly dispersed in the film, and thus it is easy to form a dense fired film.

[0101] The amount of the glass powder relative to 100 parts by mass of the conductive powder 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. By setting the amount of the glass powder within the above range, it is easy to form a dense fired film.

[0102] <Surface treatment agent>

[0103] The conductive powder mainly composed of copper in the present invention preferably has aliphatic amine on at least a part of its surface. The conductive powder mainly composed of copper can prevent the oxidation of the conductive powder mainly composed of copper and improve the dispersibility of the conductive powder in the paste by having aliphatic amine on at least a part of its surface. Therefore, the filling property of the conductive powder in the coating film of the conductive paste of the present invention can be improved, and thus a fired film having excellent denseness even when fired at a low temperature can be formed. In addition, the dispersibility of the conductive powder in the paste can be improved, and thus it is easy to form a thin and highly continuous terminal electrode.

[0104] The aliphatic amine in the present invention 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 1.0 part by mass or less, still more preferably 0.03 part by mass or more and 1.0 part by mass or less, still more preferably 0.04 part by mass or more and 1.0 part by mass or less, still more preferably 0.05 part by mass or more and 1.0 part by mass or less, and particularly preferably 0.1 part by mass or more and 0.5 part by mass or less relative to 100 parts by mass of the conductive powder mainly composed of copper. By setting the amount of the aliphatic amine within the above range, the dispersibility of the conductive powder in the paste is improved, and the debinding property during firing is improved. Therefore, it is easy to form a thin, dense and highly continuous terminal electrode.

[0105] As the aliphatic amine in the present invention, various aliphatic amines such as primary amines like octylamine, laurylamine, myristylamine, stearylamine, oleylamine, tallow amine, tallow propylenediamine, secondary amines like distearylamine, and tertiary amines like triethylamine, dimethyloctylamine, dimethylmyristylamine, dimethylpalmitamine, dimethylstearylamine, dimethylbehenylamine, dimethyllaurylamine, trioctylamine, etc. can be used. Two or more of these amines can be used in combination, or a mixture of several aliphatic amines commonly commercially available as "aliphatic amines" can be used. In particular, from the viewpoints of the ease of coating treatment of copper powder and the adsorption to metals, an alkylamine having about 8 to 20 carbon atoms in the main chain or an aliphatic amine mainly composed of the same is preferred.

[0106] <Binder resin>

[0107] The binder resin in the present invention is not particularly limited, and an acrylic resin is preferably included. The proportion of the acrylic resin relative 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, since the thermal decomposability in a nitrogen atmosphere is excellent, the binder resin can be removed well without oxidizing copper.

[0108] The amount of the binder resin relative to 100 parts by mass of the conductive powder is not particularly limited, and is preferably 3 parts by mass or more and 11 parts by mass or less, more preferably 4 parts by mass or more and 10 parts by mass or less, still more preferably 5 parts by mass or more and 9 parts by mass or less, and particularly preferably 6 parts by mass or more and 8 parts by mass or less. By the amount of the binder resin being in the above range, it is easy to form a thin, dense and highly continuous terminal electrode.

[0109] The weight average molecular weight of the acrylic resin is not particularly limited, and for example, an acrylic resin having a weight average molecular weight of 20,000 or more and 1,000,000 or less can be used. It should be noted that two or more acrylic resins having different weight average molecular weights, structures, etc. can also be used in combination.

[0110] <Organic solvent>

[0111] The organic solvent in the present invention is not particularly limited, and examples thereof include terpineol, dihydroterpineol, dihydroterpineol acetate, sec-butyl alcohol, butyl carbitol, butyl carbitol acetate, benzyl alcohol, etc.

[0112] <Additive>

[0113] As long as the effects of the present invention are not impaired, the conductive paste of the present invention may contain additives such as defoamers, plasticizers, dispersants, and rheology modifiers, in addition to the above components, as needed. Examples of the plasticizer 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, diisononyl cyclohexane-1,2-dicarboxylate, and the like. Examples of the rheology modifier include silica powder.

[0114] <Physical properties of the conductive paste>

[0115] The viscosity of the conductive paste of the present invention at a shear rate of 4 s when measured at 25°C -1 is not particularly limited, and 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 within the above range, it is easy to form a thin, dense, and highly continuous terminal electrode.

[0116] The viscosity of the conductive paste of the present invention at a shear rate of 0.4 s when measured at 25°C -1 with respect to the viscosity at a shear rate of 40 s -1 is not particularly limited, and 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 within the above range, it is easy to form a thin, dense, and highly continuous terminal electrode.

[0117] The value of the phase difference δ between the strain and the stress generated by the strain when a strain of 1% is applied to the conductive paste of the present invention at an angular frequency of 1 Hz is not particularly limited, and is preferably 45° or more and 80° or less, and particularly preferably 45° or more and 78° or less. When the value of the phase difference δ of the conductive paste is within the above range, it is easy to form a thin, dense, and highly continuous terminal electrode.

[0118] For the conductive paste of the present invention, for example, a sample for evaluation test prepared by the following method can be used to calculate the electrode area ratio of the terminal electrode that appears later, the average value of the maximum thickness of the terminal electrode, and the average value of the minimum thickness of the terminal electrode. The sample for evaluation test can be prepared as follows: Prepare a rectangular parallelepiped-shaped laminated substrate with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, in which a dielectric layer containing barium titanate and an internal electrode layer containing nickel are laminated in multiple layers. At the end where the internal electrode of the laminated substrate is exposed, set the descending speed of the laminated substrate to 300 μm / s and the lifting speed to 100 μm / s, and coat the conductive paste by dip printing method. Then, keep it at 150 °C for 10 minutes in an air atmosphere. Then, in a nitrogen atmosphere, heat it at a heating rate of 50 °C / minute, and after reaching 700 °C or 720 °C, keep it for 15 minutes to form a terminal electrode. Thus, 20 electronic components with terminal electrodes are prepared. The 20 electronic components are respectively resin-embedded. In each electronic component, cut each electronic component in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a way that it passes through the central part of both end faces of each electronic component to expose the cross-section of each electronic component. Thus, a sample for evaluation test is prepared.

[0119] <Method for manufacturing electronic component>

[0120] The conductive paste of the present invention is suitable as a conductive paste for forming an electrode on an electrode-forming body (hereinafter also referred to as an electrode-forming body for electronic components) in the manufacture of electronic components, and is particularly suitable as a conductive paste for forming a terminal electrode on a laminated substrate for laminated electronic components.

[0121] Regarding a preferred method for manufacturing an electronic component using the conductive paste of the present invention, in a method for manufacturing an electronic component having a preparation process and an electrode formation process, the conductive paste of the present invention is used to form an electrode on the electrode-forming body for electronic components, wherein the preparation process prepares the electrode-forming body for electronic components, and the electrode formation process coats the conductive paste on the outer surface of the electrode-forming body for electronic components, and then fires the coated conductive paste to form an electrode. By using the conductive paste of the present invention in the method for manufacturing the electronic component, even when firing is performed at a low temperature in the electrode formation process, an electrode that is thin, dense, and has excellent continuity can be formed while maintaining high productivity. That is, according to the method for manufacturing the electronic component, even when firing is performed at a low temperature in the electrode formation process, an electronic component having an electrode that is thin, dense, and has excellent continuity can be manufactured while maintaining high productivity.

[0122] The preparation process is a process for preparing a body to be electrode-formed for an electronic component. The body to be electrode-formed for an electronic component refers to an object on which electrodes are formed in the manufacturing process of an electronic component. Examples of the body to be electrode-formed for an electronic component include a laminate for a multilayer electronic component including a plurality of ceramic layers and a plurality of internal electrode layers, a body to be cathode-formed for a solid electrolytic capacitor including an anode and a dielectric layer formed on the surface of the anode, and the like.

[0123] The electrode formation process is a process of applying a conductive paste on the outer surface of the body to be electrode-formed for an electronic component and firing the applied conductive paste to form electrodes. Examples of the method of applying the conductive paste include an impregnation printing method, a screen printing method, and a roll coating method. Among them, the impregnation printing method is preferred.

[0124] In the electrode formation process, the position, method, thickness of the electrodes, number of electrodes, type of metal constituting the electrodes, shape of the conductive powder used in electrode formation, etc. are appropriately selected according to the electronic component to be manufactured.

[0125] In the electrode formation process, after forming electrodes on the body to be electrode-formed for an electronic component, appropriate processes may be included according to the type of the electronic component. For example, in the case of a multilayer electronic component, in the electrode formation process, after forming electrodes at a given position on the multilayer substrate for an electronic component, a plating layer is formed on the surface of the electrodes.

[0126] Regarding a particularly preferred method for manufacturing an electronic component using the conductive paste of the present invention, in a method for manufacturing an electronic component having a laminate substrate preparation process and a terminal electrode formation process, the terminal electrodes are formed on the laminate substrate using the conductive paste of the present invention. In the laminate substrate preparation process, a laminate for a multilayer electronic component including a plurality of ceramic layers and a plurality of internal electrode layers is prepared. In the terminal electrode formation process, a conductive paste is applied to the exposed ends of the internal electrodes of the laminate substrate, and then the applied conductive paste is fired to form terminal electrodes. By using the conductive paste of the present invention in the method for manufacturing the electronic component, even when firing is performed at a low temperature in the terminal electrode formation process, it is possible to form thin, dense, and highly continuous terminal electrodes while maintaining high productivity. That is, according to the method for manufacturing the electronic component, even when firing is performed at a low temperature in the terminal electrode formation process, it is possible to manufacture an electronic component having thin, dense, and highly continuous terminal electrodes while maintaining high productivity.

[0127] The stacked substrate for a multilayer electronic component includes a plurality of ceramic layers and a plurality of internal electrode layers. In the stacked substrate for a multilayer electronic component, the ceramic layers and the internal electrode layers are alternately stacked. Examples of the stacked body for a multilayer electronic component include a stacked substrate for a multilayer ceramic capacitor, a stacked substrate for a multilayer ceramic inductor, and a stacked substrate for a piezoelectric actuator.

[0128] Examples of the forming material of the ceramic layer constituting the stacked substrate for a multilayer electronic component include barium titanate, strontium titanate, calcium titanate, barium zirconate, strontium zirconate, calcium zirconate, strontium calcium zirconate, etc.

[0129] Examples of the forming material of the internal electrode layer constituting the stacked substrate for a multilayer electronic component include any one of nickel, palladium, silver, copper, and gold, or an alloy containing one or more of them (for example, an alloy of silver and palladium, etc.).

[0130] In the terminal electrode forming step, the conductive paste of the present invention is applied to the exposed end portions of the internal electrodes of the stacked substrate for a multilayer electronic component, and the applied conductive paste is fired to form terminal electrodes. There is no particular limitation on the method of applying the conductive paste. For example, dipping printing method, screen printing method, roll coating method can be cited. Among them, the dipping printing method is preferred. It should be noted that after applying the conductive paste to the stacked substrate, it can also be fired after drying.

[0131] It should be noted that in this specification, both ends where the internal electrodes are exposed in the stacked substrate are referred to as "end portions", the surface where the internal electrodes are particularly exposed in the end portions is referred to as the "end face portion", and the outer edge portion of the end face portion in the end portions is referred to as the "corner portion". Generally, in the terminal electrode forming step, when applying the conductive paste to the end portions, the conductive paste is applied so as to cover the end face portion and the corner portion.

[0132] The size of the stacked substrate using the conductive paste of the present invention is not particularly limited. For example, it can be used for a stacked substrate for a multilayer ceramic capacitor of 2012 size, a stacked substrate for a multilayer ceramic capacitor of 1608 size, a stacked substrate for a multilayer ceramic capacitor of 1005 size, a stacked substrate for a multilayer ceramic capacitor of 0603 size, a stacked substrate for a multilayer ceramic capacitor of 0402 size, a stacked substrate for a multilayer ceramic capacitor of 0201 size. In particular, thinning of the terminal electrodes is required in small multilayer ceramic capacitors, and the conductive paste of the present invention can be preferably used in a stacked substrate for a multilayer ceramic capacitor of 1005 size, a stacked substrate for a multilayer ceramic capacitor of 0603 size, a stacked substrate for a multilayer ceramic capacitor of 0402 size, a stacked substrate for a multilayer ceramic capacitor of 0201 size.

[0133] The electrode area ratio of the terminal electrode of the multilayer electronic component obtained by the present invention is not particularly limited, preferably 90% or more, particularly preferably 99% or more. Thus, when plating the terminal electrode, it is easy to prevent the plating solution from invading the multilayer substrate. It should be noted that the electrode area ratio can be calculated, for example, by the following method. That is, a plurality of (e.g., 20) such electronic components are each resin-embedded, and in each electronic component, the electronic component is cut in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a manner as to pass through the central portions of both end faces of each electronic component, thereby exposing the cross-section of each electronic component. The cross-section is observed with a scanning electron microscope (e.g., 10 fields of view for each electronic component), and the ratio of the electrode area occupied in the observed fields of view can be calculated as the electrode area ratio.

[0134] As the maximum thickness of the terminal electrode measured by the method described below, it is preferably 40 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, further preferably 15 μm or less, and particularly preferably 10 μm or less. In addition, as the average value of the maximum thickness of the terminal electrode calculated by the method described below, it is preferably 40 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, further preferably 15 μm or less, and particularly preferably 10 μm or less. Thus, the size of the multilayer electronic component can be reduced. In addition, in a multilayer electronic component of a given size, the thinner the terminal electrode is made, the larger the size of the multilayer substrate can be, that is, the electrode area and the number of stacked layers can be increased, and thus the performance of the multilayer electronic component can be improved. It should be noted that the method for measuring the maximum thickness is not particularly limited. For example, the electronic component is resin-embedded, and the electronic component is cut in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a manner as to pass through the central portions of both end faces of the electronic component, thereby exposing the cross-section of the electronic component. The cross-section is observed with a scanning electron microscope. In this cross-section, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face portion of the multilayer substrate, the portion where the length of this perpendicular line is the largest can be measured as the maximum thickness. In addition, the method for calculating the average value of the maximum thickness is not particularly limited. For example, using a plurality of (e.g., 20) electronic components, the maximum thickness of the terminal electrode is measured respectively by the above-described method, and the maximum thickness is averaged, whereby the average value of the maximum thickness of the terminal electrode can be calculated.

[0135] The minimum thickness of the terminal electrode 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. In addition, the average value of the minimum thickness of the terminal electrode 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. Thereby, in the case of plating the terminal electrode, it is easy to prevent the plating solution from invading the laminated substrate. It should be noted that the method for measuring the minimum thickness is not particularly limited. For example, the electronic component is resin-embedded, and the electronic component is cut in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a way as to pass through the central portion of both end faces of the electronic component, thereby exposing the cross section of the electronic component. The cross section is observed with a scanning electron microscope. In this cross section, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face portion of the laminated substrate, the thickness of the portion where the length of the perpendicular line is the smallest and the thickness of the portion where the distance between the corner portion of the laminated substrate and the outer peripheral portion of the terminal electrode is the shortest are measured, and the thickness of the thinnest part is taken as the minimum thickness for measurement. In addition, the calculation method of the average value of the minimum thickness is not particularly limited. For example, by using a plurality of (e.g., 20) electronic components, the minimum thickness of the terminal electrode is measured respectively by the above method, and the minimum thickness is averaged, whereby the average value of the minimum thickness of the terminal electrode can be calculated.

[0136] Hereinafter, the present invention will be described based on specific examples, but the present invention is not limited thereto.

[0137] Examples

[0138] <Preparation of Conductive Powder>

[0139] First, prepare various spherical copper powders and spherical silver powders with different particle sizes, and adjust the particle size distribution and particle diameter by classification. Then, mix zirconia beads with a diameter of 0.1 mm, spherical copper powders, sec-butanol, and a given surface treatment agent (aliphatic amine), and use a bead mill to appropriately adjust the flow rate and number of passes to perform a pulverization treatment. Furthermore, perform a classification treatment as needed thereafter to adjust the particle size distribution and particle diameter, and obtain copper powders 1 to 22 and silver powder 1 described in Table 1. It should be noted that for copper powder 1, copper powder 3, and silver powder 1, the above-mentioned pulverization treatment is not performed. For copper powder 3 and silver powder 1, a surface treatment using a given surface treatment agent (aliphatic amine) is performed to obtain them. For the obtained copper powders 1 to 22 and silver powder 1, the major axis and minor axis of 500 copper particles (silver particles in the case of silver powder 1, and copper particles and silver particles in the case of mixed powder C) are measured by observation with a scanning electron microscope, and the average major axis and average minor axis are calculated. In addition, the conductive pastes prepared in Examples 1 to 16, 20 to 25 below are cast onto a PET film by a coater to form a coating film with a film thickness of 250 μm, and this coating film is dried under the conditions of an air atmosphere, 150 °C, and 10 minutes to form a dried film. The cross-section of this dried film is exposed by an ion milling device (manufactured by HITACHI HIGH-TECH Corporation, model: IM4000), and the cross-section of this dried film is observed with a scanning electron microscope (manufactured by HITACHI HIGH-TECH Corporation, model: SU-8020). 500 copper particles are randomly selected by this observation and the minor axis is measured, and the average thickness is calculated with this minor axis as the thickness. Based on the average major axis, average minor axis, and average thickness calculated above, the ratio of the average major axis to the average thickness and the ratio of the average major axis to the average minor axis are calculated. In addition, using a laser diffraction type particle size distribution measuring device (manufactured by HORIBA, LA-960), the cumulative 10% particle diameter D10, cumulative 50% particle diameter D50, and cumulative 90% particle diameter D90 on a volume basis are measured. Using these measured values, (D90 - D10) / D50 is calculated. It should be noted that the powder obtained by mixing copper powder 3 and copper powder 5 in a ratio of 20:80 by mass (used in Example 18 below) is used as mixed powder A, the powder obtained by mixing in a ratio of 45:55 (used in Example 19 below) is used as mixed powder B, and the powder obtained by mixing copper powder 5 and silver powder 1 in a ratio of 90:10 by mass (used in Example 17 below) is used as mixed powder C. For the "ratio of the average major axis to the average thickness", "ratio of the average major axis to the average minor axis", "D50", and "(D90 - D10) / D50" of the mixed powders (i.e., as the entire conductive powder), the above-mentioned method is used for measurement and calculation. The average thickness of mixed powders A to C is measured and calculated by the same method as the above-mentioned method except that the conductive pastes prepared in Examples 17 to 19 are used.Regarding the average thickness of silver powder 1, except for using silver powder 1 instead of copper powder 1, a conductive paste was prepared in the same manner as in Example 1. Except for using this conductive paste, measurements and calculations were performed in the same manner as the said method. These results are shown in Table 1.

[0140] [Table 1]

[0141] Conductive powder No. Average major axis X / average thickness Z Average major axis X / average minor axis Y D50 [μm] (D90 - D10) / D50 Copper powder 1 1.0 1.0 2.0 1.4 Copper powder 2 1.9 1.3 2.3 1.5 Copper powder 3 1.0 1.0 2.0 1.4 Copper powder 4 1.2 1.1 2.1 1.6 Copper powder 5 2.1 1.3 2.4 1.5 Copper powder 6 4.9 1.5 2.7 1.4 Copper powder 7 7.5 1.9 2.8 1.5 Copper powder 8 10.8 2.3 2.9 1.6 Copper powder 9 2.0 1.3 0.2 1.7 Copper powder 10 2.1 1.4 0.3 1.7 Copper powder 11 2.1 1.6 0.7 1.6 Copper powder 12 1.9 1.4 2.9 1.4 Copper powder 13 2.0 1.6 4.0 1.4 Copper powder 14 2.0 1.8 5.3 1.4 Copper powder 15 2.0 1.3 2.2 4.8 Copper powder 16 2.1 1.4 2.3 8.1 Copper powder 17 2.0 1.3 2.3 1.6 Copper powder 18 2.1 1.3 2.3 1.5 Copper powder 19 1.9 1.4 2.3 1.6 Copper powder 20 1.9 1.3 2.3 1.6 Copper powder 21 2.0 1.4 2.3 1.7 Copper powder 22 2.1 1.4 2.4 1.7 Silver powder 1 1.0 1.0 1.0 0.5 Mixed powder A 1.8 1.2 2.3 1.5 Mixed powder B 1.6 1.2 2.2 1.5 Mixed powder C 1.8 1.3 4.6 1.2

[0142] <Preparation of Glass Powder>

[0143] Prepare BaO-ZnO type glass (BaO: 30 mol%, ZnO: 27 mol%, B 2 O 3 : 25 mol%, SiO 2 : 7 mol%, CaO: 7 mol%, Al 2 O 3 : 4 mol%), and prepare glass powders 1 to 8 described in Table 2 by adjusting the particle size and particle size distribution through pulverization and classification. For the prepared glass powders, the cumulative 10% particle size D10 G , cumulative 50% particle size D50 G , and cumulative 90% particle size D90 G were measured by a laser diffraction type particle size distribution measuring device (manufactured by HORIBA, LA-960). Using these measured values, (D90 G - D10 G ) / D50 G was calculated. In addition, the glass transition temperature and softening point were measured using the said glass powders. In addition, the said glass powders were placed in a cylindrical container with an inner diameter of 5 mm, and a pressure of 3 MPa was applied axially for 10 seconds to form a cylindrical compact with a diameter of 5 mm and a height of 1 mm. The compact was placed on a copper plate with a surface roughness Ra of 100 nm in such a manner that the flat surface of the compact was in contact with the copper plate, and the compact was heated in a nitrogen atmosphere at a heating rate of 10 °C / min to 700 °C to measure the contact angle of the glass with respect to the copper plate when the glass constituting the compact melted. It should be noted that for glass powder 4, the contact angles at 680 °C and 720 °C were also measured, and the results were the same as the contact angle at 700 °C, and the contact angle was 50°.

[0144] [Table 2]

[0145] Glass powder No. <![CDATA[D50 G [μm]]]> <![CDATA[(D90 G -D10 G ) / D50 G > Contact angle [°] Glass transition temperature [℃] Softening point [℃] Glass powder 1 0.2 2.1 53 497 596 Glass powder 2 0.3 2.0 50 495 594 Glass powder 3 0.5 2.2 51 501 599 Glass powder 4 1.1 2.1 50 504 605 Glass powder 5 1.9 2.1 53 501 603 Glass powder 6 4.6 2.0 53 503 605 Glass powder 7 0.5 4.7 52 499 600 Glass powder 8 0.6 7.8 54 500 603

[0146] <Preparation of Conductive Paste>

[0147] The conductive powder, binder resin, and glass powder were blended at the blending ratios shown in Tables 3 to 6 to prepare a conductive paste. It should be noted that the amount of the surface treatment agent shown in the table represents the amount attached to the powder surface by surface treatment when preparing the conductive powder.

[0148] · 1 to 22 parts of copper powder, 1 part of silver powder

[0149] The ratio of the average major axis X to the average thickness Z, the ratio of the average major axis X to the average minor axis Y D50, and (D90 - D10) / D50 are shown in Table 1.

[0150] · 1 part of acrylic resin

[0151] Manufactured by MITSUBISHI CHEMICAL Corporation, model: Dianal MB - 2677, weight - average molecular weight: 700,000

[0152] · 1 part of acrylic resin 2

[0153] Manufactured by MITSUBISHI CHEMICAL Corporation, model: Dianal BR - 105, weight - average molecular weight: 50,000

[0154] · 1 to 8 parts of glass powder

[0155] D50 G 、(D90 G - D10G) / D50 G The contact angle with respect to the copper plate, softening point, and glass transition point are shown in Table 2.

[0156] (Examples 1 to 35, 41, 42)

[0157] The conductive powder shown in Table 1, the glass powder shown in Table 2, and acrylic resin 1 dissolved in terpineol were mixed at the blending ratios shown in Tables 3 to 6. Then, it was kneaded using a three - roll mill (manufactured by Inoue Seisakusho), and then diluted with terpineol to adjust the viscosity at 25°C and a shear rate of 4 s -1 to the values shown in Tables 3 to 6 to prepare a conductive paste. The prepared conductive paste was used for the following evaluations. The results are shown in Tables 3 to 6. It should be noted that the examples marked with "*" are outside the scope of the present invention.

[0158] (Examples 36 to 40)

[0159] The conductive powder shown in Table 1, the glass powder shown in Table 2, and acrylic resin 1 or acrylic resin 2 dissolved in terpineol were mixed at the blending ratios shown in Tables 3 to 6. Then, they were kneaded using a three-roll mill (manufactured by Inoue Seisakusho). Subsequently, they were diluted with terpineol and dipropylene glycol n-propyl ether as needed, and the viscosity and viscosity ratio at 25 °C and a shear rate of 4 s -1 were adjusted to the values shown in Table 6 to prepare a conductive paste. The prepared conductive paste was used for the following evaluations. The results are shown in Table 6.

[0160] (Example 43)

[0161] In this example, the conductive paste prepared in Example 5 was used. When evaluating the terminal electrode, as the laminated substrate, a laminated substrate formed by laminating a dielectric layer containing barium titanate and an internal electrode layer containing nickel in a substantially rectangular parallelepiped shape with a length of 0.4 mm, a width of 0.2 mm, and a height of 0.2 mm was used. Except for this, the terminal electrode was evaluated in the same manner as in Example 5.

[0162] [Table 3]

[0163]

[0164] [Table 4]

[0165]

[0166] [Table 5]

[0167]

[0168] [Table 6]

[0169]

[0170] <Physical Property Evaluation of Conductive Paste>

[0171] (Viscosity)

[0172] The viscosity of the conductive paste was measured using a rotational viscometer (manufactured by BROOKFIELD, model: HADV-II+Pro) at 25 °C and a shear rate of 4 s -1 under the conditions.

[0173] (Viscosity Ratio)

[0174] The viscosity of the conductive paste was measured using a rotational viscometer (manufactured by BROOKFIELD, model: HADV-II+Pro) at 25 °C, a shear rate of 0.4 s -1 and a shear rate of 40 s -1 under the conditions. The viscosity at a shear rate of 0.4 s-1 The viscosity ratio is calculated as the ratio of the viscosity at a shear rate of 40 s -1 to the viscosity at -1

[0175] (Phase difference)

[0176] Using a rheometer (manufactured by TA Instruments, model: AR2000), measurements were taken at 25 °C, an angular frequency of 1 Hz, and a strain of 1% using parallel plates with a diameter of 40 mm to obtain the phase difference value of the conductive paste.

[0177] (Evaluation test of terminal electrodes)

[0178] (Preparation of electronic components with terminal electrodes)

[0179] A laminated substrate was prepared, which was approximately cuboid in shape with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, and was laminated with a dielectric layer containing barium titanate and an internal electrode layer containing nickel in multiple layers. At the end where the internal electrode of the laminated substrate was exposed, the lowering speed of the laminated substrate was set to 300 μm / s and the lifting speed was set to 100 μm / s. After coating the conductive paste by the dip printing method, it was maintained for 10 minutes under the conditions of an air atmosphere and 150 °C. Then, in a nitrogen atmosphere, it was heated at a heating rate of 50 °C / minute. After reaching the temperatures recorded in Tables 3 to 6, it was maintained for 15 minutes to form terminal electrodes, and an electronic component with terminal electrodes was prepared.

[0180] (Preparation of samples for evaluation test)

[0181] In each example, 20 of the above-mentioned electronic components were prepared. Each electronic component was resin-embedded, and in each electronic component, it was cut in the stacking direction (the direction perpendicular to the dielectric layer and the internal electrode layer) in such a way that it passed through the central part of both end faces of each electronic component, thereby exposing the cross-section of each electronic component. Samples for evaluation test were prepared and the following evaluations were carried out.

[0182] (Density of terminal electrodes (electrode area ratio))

[0183] Using a scanning electron microscope, 200 fields of view in total, 10 fields of view for each sample, were observed for the above-mentioned samples for evaluation test, and the ratio of the electrode area occupied in the field of view was calculated as the electrode area ratio. The value of the electrode area ratio was evaluated based on the following evaluation criteria, and scores of 1 to 3 were given. A case where the score was 2 or more was considered qualified.

[0184] (Evaluation criteria)

[0185] 3: The electrode area ratio is 99% or more

[0186] 2: The electrode area ratio is 90% or more and less than 99%

[0187] 1: The electrode area ratio is less than 90%

[0188] (Fired film thickness of the terminal electrode)

[0189] The evaluation test sample is observed with a scanning electron microscope, and the thickness (maximum thickness) of the thickest part and the thickness (minimum thickness) of the thinnest part of the terminal electrode (fired film) are measured. The average value of the maximum thickness and the average value of the minimum thickness are calculated for each example. Based on the following evaluation criteria, the values of the average value of the maximum thickness and the average value of the minimum thickness are evaluated, and scores from 1 to 3 are given. A case with a score of 2 or more is considered qualified.

[0190] <Evaluation criteria>

[0191] 3: The average value of the maximum thickness ≤ 20 μm, and the average value of the minimum thickness ≥ 2.5 μm

[0192] 2: The average value of the maximum thickness ≤ 40 μm, and the average value of the minimum thickness ≥ 1.0 μm

[0193] (wherein, the case conforming to the said score 3 is not included.)

[0194] 1: The average value of the maximum thickness > 40 μm or the average value of the minimum thickness < 1.0 μm

[0195] Based on Figure 1 The method for measuring the fired film thickness is described.

[0196] Figure 1 It is a schematic diagram showing the evaluation test sample 10 obtained by forming the terminal electrode 4 on the laminated substrate 1 with a conductive paste.

[0197] In the cross-section of the evaluation test sample 10 observed with the scanning electron microscope, when a perpendicular line is drawn from the outer peripheral part 5 of the terminal electrode 4 to the end face part 3 of the laminated substrate 1, the length of the perpendicular line is set as D. The thickness of the part where D is the largest is measured, and the value of this thickness is set as the maximum thickness D max In addition, the thickness Da of the part where the value of D is the smallest and the thickness Db of the part where the distance between the corner part 2 of the laminated substrate 1 and the outer peripheral part 5 of the terminal electrode 4 is the shortest are measured, and the smaller value of Da and Db is taken as the minimum thickness D min It should be noted that in the cross-section of the evaluation test sample 10 observed with the scanning electron microscope, when there is a part where the laminated substrate 1 is exposed due to an opening or the like in the terminal electrode 4, the minimum thickness is "0 μm".

[0198] As can be seen from the embodiments, by using the conductive paste of the present invention, even when fired at a low temperature of 720 °C or lower, it is possible to form a thin, dense, and highly continuous terminal electrode while maintaining high productivity.

[0199] Symbol Explanation

[0200] 1 Laminated substrate

[0201] 2 Corner

[0202] 3 End face

[0203] 4 Terminal electrode

[0204] 5 Outer peripheral part

[0205] 10 Sample for evaluation test

[0206] D Length of the perpendicular line when drawing a perpendicular line from the outer peripheral part to the end face

[0207] Da Thickness of the part where the value of D is the smallest

[0208] Db Thickness of the part where the distance between the corner and the outer peripheral part is the shortest

[0209] D max Thickness of the part where D is the largest

[0210] D min Smaller value of Da and Db

Claims

1. A conductive paste containing a conductive powder mainly composed of copper, a glass powder, a binder resin, and an organic solvent, wherein, The volume-based cumulative 50% particle size D50 of the copper-based conductive powder in the laser diffraction particle size distribution measurement C is 0.3 μm or more and 4.5 μm or less, and the ratio of the average major axis X to the average minor axis Y is 1.0 or more and 3.0 or less, and the ratio of the average major axis X to the average thickness Z defined below is 1.1 or more and 9.0 or less. The cumulative 50% particle size D50 of the glass powder based on volume in the measurement of particle size distribution by laser diffraction G is 0.3 μm or more and 2.0 μm or less, the definition of the average thickness is as follows: The conductive paste containing the conductive powder mainly composed of copper is cast on a PET film by a coater to form a coating film with a film thickness of 250 μm, and the coating film is 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 is exposed by ion milling, and the cross-section of the dried film is observed with a scanning electron microscope. 500 conductive particles are randomly selected, and the average value of the thickness is obtained by measuring the short diameter as the thickness. The value of this average value is defined as the "average thickness". ” 2. The conductive paste according to claim 1, wherein, the conductive powder mainly composed of copper has an aliphatic amine on at least a part of its surface.

3. The conductive paste according to claim 2, wherein, relative to 100 parts by mass of the conductive powder mainly composed of copper, the aliphatic amine is 0.01 part by mass or more and 1.0 part by mass or less.

4. The conductive paste according to any one of claims 1 to 3, wherein, Set the cumulative 10% particle size by volume in the measurement of the glass powder's particle size distribution by laser diffraction as D10 G , and the cumulative 90% particle size as D90 G When, (D90 G - D10 G ) / D50 G is 7.5 or less.

5. The conductive paste according to any one of claims 1 to 4, wherein, The volume-based cumulative 10% particle size of the copper-based conductive powder in the laser diffraction particle size distribution measurement is defined as D10 C , and the cumulative 90% particle size is defined as D90 C When, (D90 C - D10 C ) / D50 C is 7.5 or less.

6. The conductive paste according to any one of claims 1 to 5, which satisfies at least any one of the following conditions: The ratio of the viscosity at a shear rate of 0.4 s -1 -1 at 25°C to the viscosity at a shear rate of 40 s -1 -1 at 25°C is 2.0 or more and 20.0 or less; and When a strain of 1% is applied to the conductive paste 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 45° or more and 80° or less.

7. The conductive paste according to any one of claims 1 to 6, which satisfies all of the following conditions: The electrode area ratio of the terminal electrode calculated by the following respective evaluation tests is 90% or more; The average value of the maximum thickness of the terminal electrode is 40 μm or less; and The average value of the minimum thickness of the terminal electrode is 1.0 μm or more, The electrode area ratio evaluation test of the terminal electrode is as follows: The evaluation test samples prepared by the method for preparing evaluation test samples described below are observed with a scanning electron microscope for 10 fields of view for each sample, and the ratio of the electrode area occupied in the observed fields of view is calculated as the electrode area ratio of the terminal electrode; The maximum thickness evaluation test of the terminal electrode is as follows: The evaluation test samples prepared by the method for preparing evaluation test samples described below are observed with a scanning electron microscope. In the evaluation test samples, when a perpendicular line is drawn from the outer peripheral part of the terminal electrode to the end face part of the laminated substrate, the part where the length of the perpendicular line is the largest is measured as the maximum thickness, and the maximum thicknesses of 20 electronic components with the maximum thickness measured are averaged, thereby calculating the average value of the maximum thickness of the terminal electrode; The minimum thickness evaluation test of the terminal electrode is as follows: The evaluation test samples prepared by the following method for preparing evaluation test samples are observed with a scanning electron microscope. In the evaluation test samples, when a perpendicular line is drawn from the outer peripheral portion of the terminal electrode to the end face portion of the laminated substrate, the thickness of the portion where the length of the perpendicular line becomes the minimum and the thickness of the portion where the distance between the corner portion of the laminated substrate and the outer peripheral portion of the terminal electrode becomes the shortest are measured, and the thickness of the thinnest part among them is measured as the minimum thickness. The average value of the minimum thickness of the 20 electronic components for which the minimum thickness has been measured is calculated to obtain the average value of the minimum thickness of the terminal electrode; The method for preparing the evaluation test samples is as follows: Prepare a rectangular parallelepiped-shaped laminated substrate with a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, which is laminated with a plurality of dielectric layers containing barium titanate and internal electrode layers containing nickel. At the exposed end of the internal electrode of the laminated substrate, set the lowering speed of the laminated substrate to 300 μm / s and the lifting speed to 100 μm / s, and coat the conductive paste by the dip printing method. Then, keep it in an air atmosphere at 150 °C for 10 minutes. Then, in a nitrogen atmosphere, heat it at a heating rate of 50 °C / minute, and after reaching 720 °C, keep it for 15 minutes to form a terminal electrode, thereby preparing 20 electronic components with terminal electrodes. The 20 electronic components are respectively resin-embedded, and in each electronic component, cut each electronic component in a direction passing through the central portion of the two end face portions and in the lamination direction, that is, in a direction perpendicular to the dielectric layer and the internal electrode layer, so as to expose the cross section of each electronic component, thereby preparing the evaluation test samples.

8. A method for manufacturing an electronic component, comprising: a laminated substrate preparation step of preparing a laminated substrate for a laminated electronic component including a plurality of ceramic layers and a plurality of internal electrode layers; and a terminal electrode formation step of coating a conductive paste on the exposed end of the internal electrode of the laminated substrate and then firing the coated conductive paste to form a terminal electrode, wherein the conductive paste is the conductive paste according to any one of claims 1 to 7.

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

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