WO2020158685A1 - Sn particles, conductive composition using the same, and method for producing sn particles - Google Patents

Sn particles, conductive composition using the same, and method for producing sn particles Download PDF

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Publication number
WO2020158685A1
WO2020158685A1 PCT/JP2020/002835 JP2020002835W WO2020158685A1 WO 2020158685 A1 WO2020158685 A1 WO 2020158685A1 JP 2020002835 W JP2020002835 W JP 2020002835W WO 2020158685 A1 WO2020158685 A1 WO 2020158685A1
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particles
mass
less
volume
plasma
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PCT/JP2020/002835
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French (fr)
Japanese (ja)
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服部　隆志
松山　敏和
晃祐 織田
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三井金属鉱業株式会社
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Priority to JP2020569624A priority Critical patent/JPWO2020158685A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/16—Metallic particles coated with a non-metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C13/00—Alloys based on tin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form

Definitions

  • the present invention relates to Sn particles, a conductive composition using the same, and a method for producing Sn particles.
  • a multilayer ceramic capacitor (MLCC) used in electronic devices generally includes an external electrode containing Cu and a plating layer containing Ni and Sn.
  • a conductive resin layer containing a metal powder such as Sn and a resin may be formed between the electrode and the plating layer for the purpose of relaxing external stress such as thermal shock and physical stress. ..
  • Mn is contained in an amount of 0.005% by mass or more and 0.1% by mass or less and Ge in an amount of 0.001% by mass or more and 0.1% by mass or less, and the balance
  • a paste using a solder alloy whose main component is Sn is described. It is also described in the same literature that this solder alloy can suppress the increase in the oxide film thickness and improve the fusion property.
  • Patent Document 2 describes a solder material including a solder layer made of a metal material having a Sn content of 40% or more, and a SnO film and a SnO 2 film that cover the surface of the solder layer. It is also described in the same document that this solder material can be used as a solder paste for a solder joint of an electronic component.
  • an object of the present invention is to provide Sn particles having a small particle size and excellent sinterability at low temperatures.
  • the present invention provides a Sn particle containing Sn and oxygen (O), 40 mass% or more of Sn is contained, 0.55 mass% or less of O is contained,
  • the present invention provides Sn particles having a ratio (mass %.g/m 2 ) of O content (mass %) to BET specific surface area (m 2 /g) of 0.40 or less.
  • the present invention also provides a conductive composition containing the Sn particles.
  • the present invention has a step of supplying Sn base powder to the plasma flame generated in the chamber to gasify the Sn base powder, and cooling the gasified Sn base powder to generate Sn particles.
  • the inside of the chamber is a reducing gas atmosphere or an inert gas atmosphere, and the pressure inside is lower than atmospheric pressure by 20 kPa or more and 40 kPa or less,
  • a method for producing Sn particles, wherein the ratio of plasma output to the amount of Sn mother powder supplied is 0.01 kW ⁇ min/g or more and 20 kW ⁇ min/g or less.
  • FIG. 1 is a schematic diagram showing an example of a DC plasma device for producing tin particles of the present invention.
  • the present invention will be described below based on its preferred embodiments.
  • the tin particles of the present invention (hereinafter, also referred to as “Sn particles”) contain tin (Sn) and oxygen (O) in a predetermined ratio, and the specific surface area and the oxygen content have a predetermined ratio. It has become.
  • the Sn particle contains Sn as its constituent metal.
  • the content of Sn in the Sn particles is preferably 40% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more.
  • the Sn particles may be an alloy containing Sn.
  • the Sn content is preferably in the same range as described above, but in the case of Sn-Bi alloy, the mechanical strength of the conductive film after sintering is decreased due to the low melting point of the alloy. From the viewpoint of preventing the decrease, the Sn content is preferably 30% by mass or more and less than 100% by mass.
  • the content of Sn is measured, for example, by a sample solution obtained by dissolving Sn particles in an acid such as an inorganic acid by plasma emission analysis by ICP (high frequency inductively coupled plasma). can do.
  • the Sn particles further contain O.
  • O content in the particles is extremely low.
  • the content of O in the Sn particles is, for example, an oxide of a metal that constitutes the Sn particles, such as Sn.
  • the O content may be at least one of SnO, SnO 2 and SnO 3 . It is preferable that these Sn oxides are present on the surface of the Sn particles and in the vicinity thereof, and that the inner region of the particles is a single crystal phase of Sn rather than the sites.
  • the content of O in the Sn particles is preferably 0.55% by mass or less, more preferably 0.50% by mass or less, from the viewpoint of further improving the sinterability at low temperature. It is more preferably 0.40% by mass or less.
  • the lower limit of the O content is preferably as small as possible, but it is preferably 0.05% by mass from the viewpoint of stability of particles in the air.
  • the O content can be measured using, for example, an oxygen analyzer ONH836 manufactured by LECO. Specifically, 0.1 g of a measurement sample is weighed in a graphite crucible and heated in a helium gas atmosphere. Carbon monoxide and carbon dioxide produced by the reaction of carbon and oxygen during heating were detected by a non-dispersion infrared absorption method, and the O content ratio (mass %) was calculated.
  • the Sn particles preferably have a ratio of O content (mass %) to BET specific surface area (m 2 /g) (unit: mass %.g/m 2 ) of 0.40 or less. , 0.30 or less is more preferable.
  • the lower limit of the ratio is preferably as small as possible, but it is preferably 0.01 from the viewpoint of improving stability in the atmosphere.
  • the BET specific surface area of the Sn particles is preferably 1 m 2 /g or more, more preferably 1.5 m 2 /g or more.
  • the upper limit of the BET specific surface area is preferably 5 m 2 /g, more preferably 4 m 2 /g. Since the size of the BET specific surface area and the small particle diameter are substantially correlated, the BET specific surface area within this range is advantageous in that the particle diameter of the Sn particles can be made sufficiently small. Is.
  • a nitrogen-helium mixed gas containing 30% by volume of nitrogen as an adsorbing gas and 70% by volume of helium as a carrier gas and a BET specific surface area measuring device (HM model-1210 manufactured by Mountech Co., Ltd.)can be measured in accordance with JIS R 1626 “Gas adsorption of fine ceramic powder: Method of measuring specific surface area by BET method”, “6.2 Flow method”, “(3.5) One-point method”.
  • the Sn particles may contain only Sn as a constituent metal, and Sn, Au, Ag, Cu, Si, Ni, Ti, Fe, Co, Cr, Mg, Al, Mn, Mo, W, Ta, It may contain an alloy in combination with one or more metal elements such as In, Zr, Nb, Ge, Zn, Bi and Sb.
  • Specific examples of the alloy contained in the Sn particles include Sn-Bi alloy, Sn-Ag alloy, Sn-Cu alloy, and Sn-Ag-Cu alloy.
  • the Sn-Ag-Cu alloy is more preferably used because it can be sufficiently sintered at a low temperature and can improve the conductivity and mechanical strength of the conductive film after sintering.
  • the Sn particles preferably contain only Sn as a constituent metal or an alloy in which Sn and at least one of Bi, Ag, and Cu are combined, and Sn, Ag, and Cu More preferably, it comprises an alloy. Note that it is permissible for the Sn particles to contain unavoidable impurities as long as the effects of the present invention are not impaired.
  • the Ag content is 0.1% by mass or more from the viewpoint of improving the mechanical strength of the film containing the Sn particles. Is preferable, and 2.5% by mass or more is more preferable.
  • the upper limit of the Ag content is preferably 4.0% by mass, and more preferably 3.5% by mass from the viewpoint of suppressing the corrosion of the connection target while maintaining good low-temperature sinterability. preferable.
  • the Cu content is preferably 0.1% by mass or more, and more preferably 0.3% by mass or more, from the viewpoint of suppressing the corrosion of the connection target.
  • the upper limit of the Cu content is preferably 1.0% by mass, and is preferably 0.75% by mass, from the viewpoint of improving the mechanical strength of the film while maintaining good low-temperature sinterability. More preferable.
  • the Sn particles have a specific particle diameter from the viewpoint of enabling the formation of a thin conductive film capable of realizing miniaturization and high performance of electronic devices.
  • the Sn particles have a volume cumulative particle diameter D SEM90 in a cumulative volume of 90% by volume measured by scanning electron microscope observation of preferably 2.0 ⁇ m or less, more preferably 1.5 ⁇ m or less. .. It is realistic that the lower limit value of the D SEM 90 is 0.3 ⁇ m.
  • the volume cumulative particle diameter D SEM50 at a cumulative volume of 50% by volume measured by scanning electron microscope observation is preferably 1.5 ⁇ m or less, and more preferably 1.0 ⁇ m or less.
  • the lower limit of the D SEM50 it is realistic that the lower limit is 0.2 ⁇ m.
  • the volume cumulative particle diameter D SEM10 at a cumulative volume of 10% by volume measured by scanning electron microscope observation is 0.7 ⁇ m or less. It is realistic that the lower limit of the D SEM 10 is 0.1 ⁇ m.
  • the paste when the Sn particles have a particle size distribution satisfying all the preferable ranges of the above-mentioned D SEM10 , D SEM50, and D SEM90 , when the Sn particles are used in the paste, the paste can be printed smoothly and uniformly. .. Further, the thickness of the film formed from the paste can be further reduced, and a conductive film which can realize miniaturization and high performance of electronic devices can be formed.
  • D SEM90 , D SEM50, and D SEM10 were obtained by randomly selecting 200 particles in which the particles do not overlap each other from the scanning electron microscope image of the Sn particles, and measuring the particle size (Haywood diameter). From the particle size, the volume when the particles are assumed to be spheres is calculated, and each particle size is obtained from the average value thereof.
  • the volume cumulative particle diameter D 50 at a cumulative volume of 50% by volume measured by the laser diffraction scattering particle size distribution measurement method is 0 from the viewpoint of enabling the formation of a thin conductive film that can realize miniaturization and high performance of electronic devices. It is preferably 0.3 ⁇ m or more and 2.5 ⁇ m or less, and more preferably 0.5 ⁇ m or more and 2.0 ⁇ m or less.
  • D 50 can be measured, for example, by the following method. That is, 0.1 g of a measurement sample and 50 mL of water are mixed and dispersed with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 1 minute. Then, the particle size distribution is measured by using a laser diffraction/scattering particle size distribution measuring device, for example, MT3300 EXII manufactured by Microtrac Bell.
  • an ultrasonic homogenizer manufactured by Nippon Seiki Seisakusho, US-300T
  • D 50 / D SEM 50 is the ratio of D 50 for D SEM 50 is preferably at 1.0 to 4.5, more preferably 1.0 to 4.0, 1 It is more preferably from 0.0 to 3.0.
  • D SEM50 represents the primary particle size of the particles
  • D 50 represents the secondary particle size of the particles. Since D 50 /D SEM50 is in the above range, the degree of aggregation of Sn particles is low, The proportion of primary particles is high. As a result, when the Sn particles are contained in the paste, the dispersibility of the Sn particles in the paste can be increased, and the surface of the applied paste can be smoothed to further reduce the electric resistance.
  • the primary particle refers to an object recognized as a minimum unit as a particle, judging from the geometrical shape on the outer shape
  • the secondary particle refers to an aggregate of a plurality of primary particles.
  • the shape of the Sn particles is not particularly limited, and various shapes such as spherical shape, flake shape, and polyhedral shape can be adopted. From the viewpoint of enhancing the dispersibility of Sn particles and enhancing the denseness when sintered, it is preferably spherical.
  • the term "spherical” as used herein means one having a circularity coefficient of 0.85 or more, more preferably 0.90 or more, based on the circularity coefficient measured by the following method. The circularity coefficient is obtained by randomly selecting 200 particles of Sn particles that do not overlap each other from the scanning electron microscope image of Sn particles, and letting the area of the two-dimensional projected image of the particles be S and the perimeter be L.
  • the circularity coefficient of the particles is calculated from the formula of 4 ⁇ S/L 2 , and the arithmetic mean value of the circularity coefficients of the respective particles is used as the circularity coefficient described above.
  • the upper limit of the circularity coefficient is preferably 1. The higher the circularity coefficient, the more spherical the particle is. It can be said that the shape is close to.
  • the Sn particles are surface-treated with a surface treatment agent.
  • a surface treatment agent examples include alcohol amines such as monoethanolamine, diethanolamine and triethanolamine, and organic acids such as oleic acid and stearic acid.
  • the content of carbon (C) in the Sn particles is, with or without surface treatment, relative to the mass of the Sn particles, It is preferably 1% by mass or less, more preferably 0.5% by mass or less, and the lower limit thereof is preferably 0.001% by mass.
  • the carbon content in the Sn particles can be measured using, for example, a carbon analyzer EMIA-920V manufactured by Horiba Ltd. 0.1 g of a measurement sample, 1.5 g of tungsten powder as a combustion improver, and 0.3 g of Sn powder are weighed in a magnetic crucible and heated in an oxygen gas atmosphere. Carbon monoxide and carbon dioxide produced by the reaction of carbon and oxygen in the sample during heating were detected by the non-dispersive infrared absorption method, and the carbon content ratio (mass %) was calculated. Such carbon content can be adjusted, for example, by subjecting a high-purity raw material to a direct-current thermal plasma method or a high-frequency plasma method.
  • the particle size is small and the O content in the particles is small, so that the sinterability at low temperature is excellent. Further, when the Sn particles are used as a conductive paste, the thickness of the film formed from the paste can be reduced, and as a result, the film containing the Sn particles is a thin film and is dense, and the electrode It has both a reduction in electric resistance and mechanical strength.
  • tin mother powder (hereinafter, also referred to as “Sn mother powder”) is subjected to a DC plasma method to generate Sn particles from the mother powder.
  • the present manufacturing method is a step of supplying Sn base powder to a plasma flame generated in a chamber to gasify the Sn base powder, and cooling the gasified base powder to generate Sn particles.
  • the Sn mother powder and the mother powder of the alloy component are supplied in the same ratio as the alloy composition of the target Sn particles, or the target Sn is obtained.
  • a mother powder of an Sn-containing alloy having the same alloy composition as the particles may be supplied.
  • the Sn mother powder, the mother powder of the alloy component, and the mother powder of the Sn-containing alloy are collectively referred to simply as “mother powder”.
  • the DC plasma device 1 includes a powder supply device 2, a chamber 3, a DC plasma torch 4, a recovery pot 5, a powder supply nozzle 6, a gas supply device 7, and a pressure adjusting device 8.
  • the mother powder passes from the powder supply device 2 through the powder supply nozzle 6 into the inside of the DC plasma torch 4.
  • Plasma gas is supplied to the DC plasma torch 4 from the gas supply device 7, and a plasma flame is generated.
  • the gasified mother powder is cooled and becomes a fine powder of Sn particles in the recovery pot 5. It is accumulated and collected inside.
  • the inside of the chamber 3 is controlled by the pressure adjusting device 8 so as to maintain a negative pressure relatively to the powder supply nozzle 6, thereby facilitating the supply of the mother powder to the DC plasma torch 4 and the plasma. It has a structure that stably generates a frame.
  • the apparatus shown in FIG. 1 is an example of a DC plasma apparatus, and the production of Sn particles of the present invention is not limited to this apparatus.
  • the chamber 3 has a reducing gas atmosphere containing hydrogen gas or the like, or an inert gas atmosphere containing nitrogen gas and argon gas. Is preferred. With such a configuration, the time from gasification of the mother powder to cooling is shortened, so that the particle growth of the Sn particles and the aggregation of the particles are suppressed, and the generated Sn particles are atomized. And the oxidation of the Sn particle surface is suppressed. In addition, by producing in a reducing gas atmosphere or an inert gas atmosphere, oxygen in the atmosphere is less likely to be mixed into the chamber, so that there is also an advantage that the oxidation of the generated Sn particle surface can be further suppressed.
  • a reducing gas/inert gas supply unit (not shown) is connected to the chamber 3 and the above-mentioned reducing gas or inert gas is supplied as plasma gas into the chamber 3.
  • a mixed gas of argon gas and nitrogen gas is used as the plasma gas
  • a larger vibration energy thermal energy
  • the nitrogen (diatomic molecule) gas can be imparted to the Sn mother powder by the nitrogen (diatomic molecule) gas.
  • the agglomerated state can be made uniform, so that particles with few coarse particles and a sharper particle size distribution can be obtained.
  • the ratio of the argon gas to the nitrogen gas in the plasma gas is the flow ratio of the argon gas:nitrogen gas from the viewpoint of obtaining particles having a sharp particle size distribution. It is preferably in the range of 99:1 to 10:90, and more preferably in the range of 95:5 to 60:40.
  • the ratio of the argon gas and the nitrogen gas is in the range of 99:1 to 55:45 in terms of the flow rate ratio of the argon gas:nitrogen gas, particularly 95: It is preferable to adjust the flow rate of the argon gas to be larger than that of the nitrogen gas, such as in the range of 5 to 55:45. With such a ratio, there is an advantage in that the decline of the plasma flame can be prevented.
  • the pressure inside the chamber 3 is controlled so that a negative pressure is maintained relatively more than the powder supply nozzle 6, so that the pressure at the powder supply nozzle 6 and the pressure inside the chamber 3 are controlled.
  • the differential pressure is preferably within a specific range.
  • the internal pressure of the chamber 3 is reduced to 50 kPa or more lower than the atmospheric pressure to make the negative pressure, so that the mother powder is sucked from the powder supply nozzle 6 to the chamber 3 side. For this reason, the amount of mother powder supplied to the DC plasma device was increased to improve the particle production efficiency.
  • the present inventor diligently studied a method for achieving both fine particle formation of Sn particles and suppression of surface oxidation while maintaining the production efficiency of Sn particles, and found that the pressure difference between the pressure inside the chamber and the atmospheric pressure was determined by the conventional technique. Surprisingly, it is possible to manufacture Sn particles in which the particle diameter is further reduced and the oxidation of the particle surface is suppressed by manufacturing the Sn particles in a negative pressure state that is smaller than the above, while maintaining the particle manufacturing efficiency. Found.
  • the pressure inside the chamber 3 is preferably lower than the atmospheric pressure by 20 kPa or more and 40 kPa or less, and more preferably 20 kPa or more and 35 kPa or less.
  • the negative pressure within such a range, when the Sn particles are formed from the gasified mother powder, the Sn growth generated by further suppressing the particle growth of the Sn particles and the agglomeration of the particles.
  • the particles can be efficiently made fine, and the oxidation of the surface of the Sn particles is further suppressed.
  • the inside of the chamber 3 is a reducing gas atmosphere or an inert gas atmosphere, it is more advantageous.
  • the pressure inside the chamber 3 can be appropriately controlled by, for example, the pressure adjusting device 8.
  • the cooling gas can be supplied by, for example, a cooling gas supply unit (not shown) connected to the side wall of the chamber 3.
  • a cooling gas for example, a reducing gas such as hydrogen gas or an inert gas such as nitrogen gas or argon gas can be used.
  • the mother powder used in the present production method is not particularly limited, but from the viewpoint of obtaining Sn particles whose surface oxidation is suppressed, it is preferable to use a mother powder containing a small amount of oxide.
  • the particle diameter D 50 of the mother powder is preferably 3.0 ⁇ m or more and 50 ⁇ m or less, more preferably 5.0 ⁇ m or more and 30 ⁇ m or less.
  • the feed rate of the mother powder is preferably 5 g/min or more and 200 g/min or less, and more preferably 10 g/min or more and 100 g/min or less.
  • the shape of the mother powder is not particularly limited, and examples thereof include a dendritic shape, a stick shape, a flake shape, a cubic shape, and a spherical shape. From the viewpoint of stabilizing the supply efficiency to the plasma torch, it is preferable to use spherical mother powder. Measurement of D 50 of the mother powder may be carried out in the same manner as the measurement of the D 50 of the above-mentioned Sn particles.
  • Whether or not the plasma frame is in a laminar flow state is determined by observing the plasma frame from the side where the frame width is thickest and the aspect ratio of the frame length to the frame width (hereinafter, frame aspect ratio) is 3 or less. It can be determined by whether or not the above. Specifically, if the frame aspect ratio is 3 or more, it can be determined that the flow is laminar, and if it is less than 3, it can be determined that the flow is turbulent.
  • the plasma output of the DC plasma device is preferably set to 2 kW or more and 100 kW or less, and more preferably 2 kW or more and 40 kW or less.
  • the gas flow rate of the plasma gas is preferably set to 0.1 L/min or more and 25 L/min or less, more preferably 0.5 L/min or more and 21 L/min or less.
  • the plasma output ratio is preferably 0.01 kW ⁇ min/g or more and 20 kW ⁇ min/g or less, and more preferably 0.05 kW ⁇ min/g or more and 15 kW ⁇ min/g or less.
  • the plasma gas flow rate with respect to the plasma output Ratio (unit: L/(min ⁇ kW)) is preferably 0.50 or more and 2.00 or less, more preferably 0.70 or more and 1.70 or less, and still more preferably 0.75 or more and 1.50 or less.
  • the Sn particles thus obtained are collected and collected in the recovery pot 5 as a fine powder which is an aggregate of the particles.
  • the recovered Sn particles may be used as they are, or may be classified in order to remove coarse agglomerated particles existing as contamination.
  • the classification may be performed by using an appropriate classifying device to separate the coarse powder and the fine powder so that the target particle size is centered.
  • ⁇ Sn particles are preferably used as a metal filler compounded in a conductive composition.
  • the conductive composition include a conductive paste and a conductive ink. These conductive compositions contain components such as Sn particles as a metal filler, a binder resin and an organic solvent.
  • the wiring composition of the printed wiring board can be formed, for example, by applying the conductive composition by a predetermined means. It can also be used as a via filling material in a printed wiring board or as an adhesive when surface-mounting an electronic device on the printed wiring board. Further, it can be used for forming electrodes of chip parts.
  • the Sn particles of the present invention have a small particle size and high sinterability at low temperatures, they can be used in small electronic components such as a multilayer ceramic capacitor (MLCC) that requires miniaturization and high performance. It can be suitably used for a conductive resin layer or the like.
  • MLCC multilayer ceramic capacitor
  • the flow rate of the plasma gas was 18.5 L/min.
  • the plasma output was 16.5 kW, and the ratio of the plasma gas flow rate to the plasma output was 1.12 (L/(min ⁇ kW)).
  • the ratio of plasma output to the amount of mother powder supplied was 0.47 kW ⁇ min/g.
  • the plasma flame had a flame aspect ratio of 4 and was in a laminar flow state.
  • the inside of the chamber 3 was made a nitrogen gas atmosphere, and the pressure inside the chamber 3 was set to be 30 kPa lower than the atmospheric pressure. Further, at the time of manufacturing, nitrogen gas at 25° C. was supplied as a cooling gas at a flow rate of 290 L/min. In this way, the target Sn particles were obtained.
  • the Sn content in the Sn particles of this example was 96.5% by mass.
  • Example 2 Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lowered by 20 kPa from the atmospheric pressure.
  • the Sn content in the Sn particles of this example was 96.5% by mass.
  • the Sn content in the Sn particles of this example was 100% by mass.
  • Example 1 Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lower than atmospheric pressure by 50 kPa and the flow rate of the cooling gas was 10 L/min. The Sn content in the Sn particles of this comparative example was 96.5% by mass.
  • Example 2 Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lowered by 50 kPa from the atmospheric pressure. The Sn content in the Sn particles of this comparative example was 96.5% by mass.
  • An alumina container was filled with the Sn particles of Examples and Comparative Examples, and the temperature was raised from room temperature (25° C.) to 300° C. at a heating rate of 10° C./min in a nitrogen gas atmosphere. Then, the temperature was lowered to room temperature, and the shrinkage ratio of the Sn particles after the temperature was lowered was confirmed. That is, an alumina container containing Sn particles after sintering was photographed from the upper surface direction, and the number of pixels on the bottom surface of the alumina container was determined using Image J as image processing software using the photographic data. Similarly, the number of pixels in a region where Sn particles after sintering were present was determined using Image J.
  • Example 4 Sn-Bi particles were produced in the same manner as in Example 4 except that the pressure inside the chamber 3 of Example 4 was lower than atmospheric pressure by 50 kPa.
  • the Sn content in the Sn particles of this comparative example was 42% by mass.
  • the Sn particles of the examples have a large specific surface area, and that D SEM90 can efficiently produce fine particles of about 1 ⁇ m.
  • the Sn particles of the example in which the differential pressure between the atmospheric pressure and the pressure inside the chamber 3 is in a suitable range has a smaller O content than the Sn particles of the comparative example, and the particles are sintered together. It turns out that it has excellent properties.
  • the Sn particles of the example since the D 50 /D SEM50 ratio is small, the particle distribution becomes sharp and the dispersibility is high, and a smooth and thin coating film is formed when a paste containing the particles is formed. be able to.
  • Sn particles having a small particle size and excellent in sinterability at low temperatures, and a conductive composition containing the particles.

Abstract

The Sn particles of the present invention contain greater than or equal to 40 mass% of Sn and less than or equal to 0.55 mass% of oxygen (O), and have a ratio (mass%・g/m2) of oxygen content (mass%) to BET specific surface area (m2/g) of less than or equal to 0.40. The Sn particles preferably include 0.1-4.0 mass%, inclusive, of Ag, and 0.1-1.0 mass%, inclusive, of Cu. The Sn particles also preferably contain greater than or equal to 0.05 mass% of oxygen. The BET specific surface area of the Sn particles is preferably greater than or equal to 1 m2/g. The Sn particles are preferably spherical. The present invention also pertains to a preferable method for producing the Sn particles.

Description

Ｓｎ粒子、それを用いた導電性組成物及びＳｎ粒子の製造方法Sn particles, conductive composition using the same, and method for producing Sn particles
　本発明は、Ｓｎ粒子、それを用いた導電性組成物及びＳｎ粒子の製造方法に関する。 The present invention relates to Sn particles, a conductive composition using the same, and a method for producing Sn particles.
　電子機器に用いられる積層セラミックコンデンサ（ＭＬＣＣ）は、一般的に、Ｃｕを含む外部電極と、Ｎｉ及びＳｎを含むメッキ層とを備えている。これに加えて、熱衝撃や物理的応力などの外的応力緩和の目的で、Ｓｎ等の金属粉及び樹脂を含む導電性樹脂層が、電極とメッキ層との間に形成されることがある。 A multilayer ceramic capacitor (MLCC) used in electronic devices generally includes an external electrode containing Cu and a plating layer containing Ni and Sn. In addition to this, a conductive resin layer containing a metal powder such as Sn and a resin may be formed between the electrode and the plating layer for the purpose of relaxing external stress such as thermal shock and physical stress. ..
　導電性樹脂層に用いられる材料として、例えば特許文献１には、Ｍｎを０．００５質量％以上０．１質量％以下、Ｇｅを０．００１質量％以上０．１質量％以下で含み、残部の主成分をＳｎとしたはんだ合金を用いたペーストが記載されている。このはんだ合金は、酸化膜厚の増加が抑制され、融合性を向上させることができることも同文献に記載されている。 As a material used for the conductive resin layer, for example, in Patent Document 1, Mn is contained in an amount of 0.005% by mass or more and 0.1% by mass or less and Ge in an amount of 0.001% by mass or more and 0.1% by mass or less, and the balance A paste using a solder alloy whose main component is Sn is described. It is also described in the same literature that this solder alloy can suppress the increase in the oxide film thickness and improve the fusion property.
　特許文献２には、Ｓｎの含有量が４０％以上である金属材料からなるはんだ層と、はんだ層の表面を被覆するＳｎＯ膜及びＳｎＯ２膜を備えたはんだ材料が記載されている。このはんだ材料は、はんだペーストとして、電子部品のはんだ継手に用いることができることも同文献に記載されている。 Patent Document 2 describes a solder material including a solder layer made of a metal material having a Sn content of 40% or more, and a SnO film and a SnO 2 film that cover the surface of the solder layer. It is also described in the same document that this solder material can be used as a solder paste for a solder joint of an electronic component.
ＵＳ　２０１７／２１６９７５　Ａ１US 2017/216975 A1 ＵＳ　２０１７／２５２８７１　Ａ１US 2017/252871 A1
　ところで近年、電子機器の小型化や高性能化に対応するため、導電性樹脂層の薄膜化が求められている。導電性樹脂層を薄膜化するためには、構成材料の一つであるＳｎ粒子の粒子径を小さくすることが望まれている。しかし、特許文献１及び２に記載のはんだ材料は、Ｓｎ粒子の粒子径が大きいため、導電性樹脂層の薄膜化に対応することができない。
　そこで、微細なＳｎ粒子を製造する方法として、直流熱プラズマ法（以下、「ＤＣプラズマ法」ともいう。）が用いられるが、現状の製造条件で得られるＳｎ粒子は、酸素（Ｏ）の含有量が高くなってしまい、低温での溶融性が十分なものとはならなかった。また、これに起因して、電極の電気抵抗の増大や機械的強度の低下を引き起こす可能性があった。 By the way, in recent years, in order to respond to downsizing and higher performance of electronic devices, thinning of the conductive resin layer is required. In order to reduce the thickness of the conductive resin layer, it is desired to reduce the particle size of Sn particles, which is one of the constituent materials. However, the solder materials described in Patent Documents 1 and 2 cannot cope with thinning of the conductive resin layer because the Sn particles have a large particle diameter.
Therefore, a direct current thermal plasma method (hereinafter, also referred to as “DC plasma method”) is used as a method for producing fine Sn particles, but the Sn particles obtained under the current production conditions contain oxygen (O). The amount became high, and the meltability at low temperature was not sufficient. Further, due to this, there is a possibility that the electrical resistance of the electrode may increase and the mechanical strength may decrease.
　したがって、本発明の課題は、粒子径が小さく、且つ低温での焼結性に優れたＳｎ粒子を提供することにある。 Therefore, an object of the present invention is to provide Sn particles having a small particle size and excellent sinterability at low temperatures.
　本発明は、Ｓｎと酸素（Ｏ）とを含むＳｎ粒子であって、
　前記Ｓｎを４０質量％以上含み、前記Ｏを０．５５質量％以下含み、
　ＢＥＴ比表面積（ｍ２／ｇ）に対するＯ含有量（質量％）の比（質量％・ｇ／ｍ２）が０．４０以下である、Ｓｎ粒子を提供するものである。 The present invention provides a Sn particle containing Sn and oxygen (O),
40 mass% or more of Sn is contained, 0.55 mass% or less of O is contained,
The present invention provides Sn particles having a ratio (mass %.g/m 2 ) of O content (mass %) to BET specific surface area (m 2 /g) of 0.40 or less.
　また本発明は、前記Ｓｎ粒子を含んでなる導電性組成物を提供するものである。 The present invention also provides a conductive composition containing the Sn particles.
　更に本発明は、チャンバー内に発生させたプラズマフレームにＳｎ母粉を供給して該Ｓｎ母粉をガス化させ、ガス化した前記Ｓｎ母粉を冷却してＳｎ粒子を生成させる工程を有し、
　前記チャンバーは、その内部が還元ガス雰囲気又は不活性ガス雰囲気であり、且つその内部の圧力が大気圧よりも２０ｋＰａ以上４０ｋＰａ以下低く、
　Ｓｎ母粉の供給量に対するプラズマ出力の比が、０．０１ｋＷ・ｍｉｎ／ｇ以上２０ｋＷ・ｍｉｎ／ｇ以下である、Ｓｎ粒子の製造方法を提供するものである。 Further, the present invention has a step of supplying Sn base powder to the plasma flame generated in the chamber to gasify the Sn base powder, and cooling the gasified Sn base powder to generate Sn particles. ,
The inside of the chamber is a reducing gas atmosphere or an inert gas atmosphere, and the pressure inside is lower than atmospheric pressure by 20 kPa or more and 40 kPa or less,
A method for producing Sn particles, wherein the ratio of plasma output to the amount of Sn mother powder supplied is 0.01 kW·min/g or more and 20 kW·min/g or less.
図１は、本発明のスズ粒子を製造するＤＣプラズマ装置の一例を示す模式図である。FIG. 1 is a schematic diagram showing an example of a DC plasma device for producing tin particles of the present invention.
　以下本発明を、その好ましい実施形態に基づき説明する。本発明のスズ粒子（以下、これを「Ｓｎ粒子」ともいう。）は、スズ（Ｓｎ）と酸素（Ｏ）とを所定の割合で含み、且つ比表面積と酸素含有量とが所定の比となっているものである。 The present invention will be described below based on its preferred embodiments. The tin particles of the present invention (hereinafter, also referred to as “Sn particles”) contain tin (Sn) and oxygen (O) in a predetermined ratio, and the specific surface area and the oxygen content have a predetermined ratio. It has become.
　Ｓｎ粒子は、その構成金属としてＳｎを含む。Ｓｎ粒子におけるＳｎの含有量は、４０質量％以上であることが好ましく、５０質量％以上であることがより好ましく、６０質量％以上であることが更に好ましい。Ｓｎの含有量を４０質量％以上とすることによって、コンデンサ等の電子素子を製造する際に、Ｓｎ粒子の融点を低く抑えて低温で焼結することができる。その結果、高温負荷に起因した素子の不具合を低減することができる。 The Sn particle contains Sn as its constituent metal. The content of Sn in the Sn particles is preferably 40% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more. By setting the content of Sn to 40% by mass or more, it is possible to suppress the melting point of Sn particles to be low and sinter at a low temperature when manufacturing an electronic element such as a capacitor. As a result, it is possible to reduce defects of the element due to the high temperature load.
　また、後述するように、Ｓｎ粒子は、Ｓｎを含む合金としてもよい。この場合のＳｎ含有量は、上述した範囲と同様であることが好ましいが、Ｓｎ－Ｂｉ合金である場合には、該合金の低い融点に起因した、焼結後の導電膜の機械的強度の低下を防止する観点から、Ｓｎ含有量は３０質量％以上１００質量％未満であることが好ましい。いずれの場合であっても、Ｓｎの含有量は、例えば、ＩＣＰ（高周波誘導結合プラズマ）によるプラズマ発光分析によって、Ｓｎ粒子を無機酸等の酸に溶解させて得られる試料溶液を分析対象として測定することができる。 Also, as described later, the Sn particles may be an alloy containing Sn. In this case, the Sn content is preferably in the same range as described above, but in the case of Sn-Bi alloy, the mechanical strength of the conductive film after sintering is decreased due to the low melting point of the alloy. From the viewpoint of preventing the decrease, the Sn content is preferably 30% by mass or more and less than 100% by mass. In any case, the content of Sn is measured, for example, by a sample solution obtained by dissolving Sn particles in an acid such as an inorganic acid by plasma emission analysis by ICP (high frequency inductively coupled plasma). can do.
　Ｓｎ粒子は、更にＯを含む。本発明のＳｎ粒子は、該粒子中のＯの含有量が極めて少ないことを特徴の一つとしている。Ｓｎ粒子におけるＯの含有態様は、例えばＳｎ等のＳｎ粒子を構成する金属の酸化物である。Ｓｎ粒子において、Ｓｎの酸化物を含む場合には、Ｏの含有態様は、ＳｎＯ、ＳｎＯ２及びＳｎＯ３のうち少なくとも一種であり得る。これらのＳｎ酸化物は、Ｓｎ粒子の表面及びその近傍の部位に存在しており、該部位よりも粒子の内部域は、Ｓｎの単結晶相になっていることが好ましい。 The Sn particles further contain O. One feature of the Sn particles of the present invention is that the O content in the particles is extremely low. The content of O in the Sn particles is, for example, an oxide of a metal that constitutes the Sn particles, such as Sn. When the Sn particles contain Sn oxide, the O content may be at least one of SnO, SnO 2 and SnO 3 . It is preferable that these Sn oxides are present on the surface of the Sn particles and in the vicinity thereof, and that the inner region of the particles is a single crystal phase of Sn rather than the sites.
　Ｓｎ粒子におけるＯの含有量は、低温での焼結性を一層優れたものとする観点から、０．５５質量％以下であることが好ましく、０．５０質量％以下であることがより好ましく、０．４０質量％以下であることが更に好ましい。一方で、Ｏの含有量の下限は少なければ少ないほど好ましいが、大気中での粒子の安定性の観点から、０．０５質量％であることが好ましい。 The content of O in the Sn particles is preferably 0.55% by mass or less, more preferably 0.50% by mass or less, from the viewpoint of further improving the sinterability at low temperature. It is more preferably 0.40% by mass or less. On the other hand, the lower limit of the O content is preferably as small as possible, but it is preferably 0.05% by mass from the viewpoint of stability of particles in the air.
　Ｏの含有量は、例えば、ＬＥＣＯ社製の酸素分析装置ＯＮＨ８３６を用いて測定することができる。詳細には、測定試料０．１ｇを黒鉛坩堝内に秤量し、ヘリウムガス雰囲気下で加熱する。加熱の際に炭素と酸素とが反応して生成した一酸化炭素及び二酸化炭素を非分散赤外線吸収法で検出し、Ｏの含有割合（質量％）を算出した。 The O content can be measured using, for example, an oxygen analyzer ONH836 manufactured by LECO. Specifically, 0.1 g of a measurement sample is weighed in a graphite crucible and heated in a helium gas atmosphere. Carbon monoxide and carbon dioxide produced by the reaction of carbon and oxygen during heating were detected by a non-dispersion infrared absorption method, and the O content ratio (mass %) was calculated.
　これに加えて、Ｓｎ粒子は、ＢＥＴ比表面積（ｍ２／ｇ）に対するＯ含有量（質量％）の比（単位：質量％・ｇ／ｍ２）が、０．４０以下であることが好ましく、０．３０以下であることがより好ましい。前記の比の下限は小さいほど好ましいが、大気での安定性を高める観点から、０．０１であることが好ましい。 In addition to this, the Sn particles preferably have a ratio of O content (mass %) to BET specific surface area (m 2 /g) (unit: mass %.g/m 2 ) of 0.40 or less. , 0.30 or less is more preferable. The lower limit of the ratio is preferably as small as possible, but it is preferably 0.01 from the viewpoint of improving stability in the atmosphere.
　Ｓｎ粒子におけるＢＥＴ比表面積は、１ｍ２／ｇ以上であることが好ましく、１．５ｍ２／ｇ以上であることがより好ましい。ＢＥＴ比表面積の上限としては、５ｍ２／ｇであることが好ましく、４ｍ２／ｇであることがより好ましい。ＢＥＴ比表面積の大きさと、粒子径の小ささとは概ね相関しているので、ＢＥＴ比表面積がこのような範囲にあることによって、Ｓｎ粒子の粒子径を十分に小さくすることができる点で有利である。 The BET specific surface area of the Sn particles is preferably 1 m 2 /g or more, more preferably 1.5 m 2 /g or more. The upper limit of the BET specific surface area is preferably 5 m 2 /g, more preferably 4 m 2 /g. Since the size of the BET specific surface area and the small particle diameter are substantially correlated, the BET specific surface area within this range is advantageous in that the particle diameter of the Sn particles can be made sufficiently small. Is.
　ＢＥＴ比表面積は、吸着ガスである窒素を３０容量％、キャリアガスであるヘリウムを７０容量％含有する窒素－ヘリウム混合ガスと、ＢＥＴ比表面積測定装置（株式会社マウンテック製、ＨＭ　ｍｏｄｅｌ－１２１０）とを用いて、ＪＩＳ　Ｒ　１６２６「ファインセラミックス粉体の気体吸着　ＢＥＴ法による比表面積の測定方法」の「６．２流動法」の「（３．５）一点法」に従って測定することができる。 As for the BET specific surface area, a nitrogen-helium mixed gas containing 30% by volume of nitrogen as an adsorbing gas and 70% by volume of helium as a carrier gas, and a BET specific surface area measuring device (HM model-1210 manufactured by Mountech Co., Ltd.) Can be measured in accordance with JIS R 1626 “Gas adsorption of fine ceramic powder: Method of measuring specific surface area by BET method”, “6.2 Flow method”, “(3.5) One-point method”.
　Ｓｎ粒子は、その構成金属としてＳｎのみを含んでいてもよく、Ｓｎと、Ａｕ、Ａｇ、Ｃｕ、Ｓｉ、Ｎｉ、Ｔｉ、Ｆｅ、Ｃｏ、Ｃｒ、Ｍｇ、Ａｌ、Ｍｎ、Ｍｏ、Ｗ、Ｔａ、Ｉｎ、Ｚｒ、Ｎｂ、Ｇｅ、Ｚｎ、Ｂｉ及びＳｂ等の金属元素の１種以上とを組み合わせた合金を含んでいてもよい。Ｓｎ粒子に含まれる合金の具体例としては、Ｓｎ－Ｂｉ合金、Ｓｎ－Ａｇ合金、Ｓｎ－Ｃｕ合金、Ｓｎ－Ａｇ－Ｃｕ合金等が挙げられる。これらのうち、Ｓｎ－Ａｇ－Ｃｕ合金は、低温での焼結を十分に行うことができるとともに、焼結後の導電膜の導電性及び機械的強度を向上できる点で更に好ましく用いられる。つまり、Ｓｎ粒子は、その構成金属として、Ｓｎのみを含むか、又はＳｎと、Ｂｉ、Ａｇ及びＣｕの少なくとも一種以上とを組み合わせた合金を含むことがより好ましく、Ｓｎと、Ａｇ及びＣｕとの合金を含むことが更に好ましい。なお、本発明の効果を損なわない範囲で、Ｓｎ粒子が不可避不純物を含有することは許容される。 The Sn particles may contain only Sn as a constituent metal, and Sn, Au, Ag, Cu, Si, Ni, Ti, Fe, Co, Cr, Mg, Al, Mn, Mo, W, Ta, It may contain an alloy in combination with one or more metal elements such as In, Zr, Nb, Ge, Zn, Bi and Sb. Specific examples of the alloy contained in the Sn particles include Sn-Bi alloy, Sn-Ag alloy, Sn-Cu alloy, and Sn-Ag-Cu alloy. Among these, the Sn-Ag-Cu alloy is more preferably used because it can be sufficiently sintered at a low temperature and can improve the conductivity and mechanical strength of the conductive film after sintering. That is, the Sn particles preferably contain only Sn as a constituent metal or an alloy in which Sn and at least one of Bi, Ag, and Cu are combined, and Sn, Ag, and Cu More preferably, it comprises an alloy. Note that it is permissible for the Sn particles to contain unavoidable impurities as long as the effects of the present invention are not impaired.
　Ｓｎ粒子の好ましい態様として、Ｓｎ粒子にＡｇ及びＣｕの双方を含む場合、Ａｇの含有量は、Ｓｎ粒子を含む膜の機械的強度の向上を図る観点から、０．１質量％以上であることが好ましく、２．５質量％以上であることがより好ましい。Ａｇの含有量の上限は、低温焼結性を良好なものとしつつ接続対象の溶食を抑制する観点から、４．０質量％であることが好ましく、３．５質量％であることがより好ましい。 As a preferable embodiment of the Sn particles, when the Sn particles include both Ag and Cu, the Ag content is 0.1% by mass or more from the viewpoint of improving the mechanical strength of the film containing the Sn particles. Is preferable, and 2.5% by mass or more is more preferable. The upper limit of the Ag content is preferably 4.0% by mass, and more preferably 3.5% by mass from the viewpoint of suppressing the corrosion of the connection target while maintaining good low-temperature sinterability. preferable.
　同様に、Ｃｕの含有量は、接続対象の溶食を抑制する観点から０．１質量％以上であることが好ましく、０．３質量％以上であることがより好ましい。Ｃｕの含有量の上限は、低温焼結性を良好なものとしつつ膜の機械的強度の向上を図る観点から、１．０質量％であることが好ましく、０．７５質量％であることがより好ましい。 Similarly, the Cu content is preferably 0.1% by mass or more, and more preferably 0.3% by mass or more, from the viewpoint of suppressing the corrosion of the connection target. The upper limit of the Cu content is preferably 1.0% by mass, and is preferably 0.75% by mass, from the viewpoint of improving the mechanical strength of the film while maintaining good low-temperature sinterability. More preferable.
　電子機器の小型化や高性能化を実現可能な薄い導電膜を形成できるようにする観点から、Ｓｎ粒子は、特定の粒子径を有していることも好ましい。詳細には、Ｓｎ粒子は、走査型電子顕微鏡観察によって測定された累積体積９０容量％における体積累積粒径ＤＳＥＭ９０が２．０μｍ以下であることが好ましく、１．５μｍ以下であることがより好ましい。ＤＳＥＭ９０の下限値としては、０．３μｍであることが現実的である。 It is also preferable that the Sn particles have a specific particle diameter from the viewpoint of enabling the formation of a thin conductive film capable of realizing miniaturization and high performance of electronic devices. Specifically, the Sn particles have a volume cumulative particle diameter D SEM90 in a cumulative volume of 90% by volume measured by scanning electron microscope observation of preferably 2.0 μm or less, more preferably 1.5 μm or less. .. It is realistic that the lower limit value of the D SEM 90 is 0.3 μm.
　同様の観点から、走査型電子顕微鏡観察によって測定された累積体積５０容量％における体積累積粒径ＤＳＥＭ５０が１．５μｍ以下であることが好ましく、１．０μｍ以下であることがより好ましい。ＤＳＥＭ５０の下限としては、０．２μｍであることが現実的である。 From the same viewpoint, the volume cumulative particle diameter D SEM50 at a cumulative volume of 50% by volume measured by scanning electron microscope observation is preferably 1.5 μm or less, and more preferably 1.0 μm or less. As a lower limit of the D SEM50 , it is realistic that the lower limit is 0.2 μm.
　また、走査型電子顕微鏡観察によって測定された累積体積１０容量％における体積累積粒径ＤＳＥＭ１０が０．７μｍ以下であることが好ましい。ＤＳＥＭ１０の下限としては、０．１μｍであることが現実的である。 Further, it is preferable that the volume cumulative particle diameter D SEM10 at a cumulative volume of 10% by volume measured by scanning electron microscope observation is 0.7 μm or less. It is realistic that the lower limit of the D SEM 10 is 0.1 μm.
　特に、Ｓｎ粒子が上述のＤＳＥＭ１０、ＤＳＥＭ５０及びＤＳＥＭ９０の好ましい範囲をすべて満たす粒度分布であることによって、Ｓｎ粒子をペーストに用いたときに、ペーストを平滑に且つ均一に印刷することができる。また、該ペーストから形成される膜の厚さを一層薄いものとすることができ、電子機器の小型化や高性能化を実現可能な導電膜を形成することができる。 In particular, when the Sn particles have a particle size distribution satisfying all the preferable ranges of the above-mentioned D SEM10 , D SEM50, and D SEM90 , when the Sn particles are used in the paste, the paste can be printed smoothly and uniformly. .. Further, the thickness of the film formed from the paste can be further reduced, and a conductive film which can realize miniaturization and high performance of electronic devices can be formed.
　ＤＳＥＭ９０、ＤＳＥＭ５０及びＤＳＥＭ１０は、Ｓｎ粒子の走査型電子顕微鏡像から、粒子どうしが重なり合っていないものを無作為に２００個選んで粒径（ヘイウッド径）を測定し、次いで、得られた粒径から、粒子が球であると仮定したときの体積を算出し、これらの平均値から各粒径を求める。 D SEM90 , D SEM50, and D SEM10 were obtained by randomly selecting 200 particles in which the particles do not overlap each other from the scanning electron microscope image of the Sn particles, and measuring the particle size (Haywood diameter). From the particle size, the volume when the particles are assumed to be spheres is calculated, and each particle size is obtained from the average value thereof.
　また、レーザー回折散乱式粒度分布測定法による累積体積５０容量％における体積累積粒径Ｄ５０は電子機器の小型化や高性能化を実現可能な薄い導電膜を形成できるようにする観点から、０．３μｍ以上２．５μｍ以下であることが好ましく、０．５μｍ以上２．０μｍ以下であることがより好ましい。 In addition, the volume cumulative particle diameter D 50 at a cumulative volume of 50% by volume measured by the laser diffraction scattering particle size distribution measurement method is 0 from the viewpoint of enabling the formation of a thin conductive film that can realize miniaturization and high performance of electronic devices. It is preferably 0.3 μm or more and 2.5 μm or less, and more preferably 0.5 μm or more and 2.0 μm or less.
　Ｄ５０は、例えば以下の方法で測定することができる。すなわち、０．１ｇの測定試料と水５０ｍＬとを混合し、超音波ホモジナイザ（日本精機製作所製、ＵＳ－３００Ｔ）で１分間分散させる。その後、レーザー回折散乱式粒度分布測定装置、例えばマイクロトラックベル製ＭＴ３３００　ＥＸＩＩを用いて粒度分布を測定する。 D 50 can be measured, for example, by the following method. That is, 0.1 g of a measurement sample and 50 mL of water are mixed and dispersed with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T) for 1 minute. Then, the particle size distribution is measured by using a laser diffraction/scattering particle size distribution measuring device, for example, MT3300 EXII manufactured by Microtrac Bell.
　Ｓｎ粒子は、ＤＳＥＭ５０に対するＤ５０の比であるＤ５０／ＤＳＥＭ５０が、１．０以上４．５以下であることが好ましく、１．０以上４．０以下であることがより好ましく、１．０以上３．０以下であることが更に好ましい。一般的に、ＤＳＥＭ５０は粒子の一次粒子径を表し、Ｄ５０は粒子の二次粒子径を表すところ、Ｄ５０／ＤＳＥＭ５０が上述した範囲にあることによって、Ｓｎ粒子の凝集度が低く、一次粒子の割合が高いこととなる。その結果、Ｓｎ粒子をペーストに含有したときに、ペースト中でのＳｎ粒子の分散性を高くできるとともに、塗布されたペースト表面を平滑にして、電気抵抗を一層低いものとすることができる。なお、一次粒子とは、外形上の幾何学的形態から判断して、粒子としての最小単位と認められる物体のことをいい、二次粒子とは複数個の一次粒子の凝集体をいう。 Sn particles, D 50 / D SEM 50 is the ratio of D 50 for D SEM 50 is preferably at 1.0 to 4.5, more preferably 1.0 to 4.0, 1 It is more preferably from 0.0 to 3.0. Generally, D SEM50 represents the primary particle size of the particles, and D 50 represents the secondary particle size of the particles. Since D 50 /D SEM50 is in the above range, the degree of aggregation of Sn particles is low, The proportion of primary particles is high. As a result, when the Sn particles are contained in the paste, the dispersibility of the Sn particles in the paste can be increased, and the surface of the applied paste can be smoothed to further reduce the electric resistance. In addition, the primary particle refers to an object recognized as a minimum unit as a particle, judging from the geometrical shape on the outer shape, and the secondary particle refers to an aggregate of a plurality of primary particles.
　Ｓｎ粒子の形状に特に制限はなく、例えば球状、フレーク状、多面体状など種々の形状を採用することができる。Ｓｎ粒子の分散性を高め、且つ焼結したときの緻密性を高める観点から、球状であることが好ましい。ここでいう球状とは、以下の方法で測定した円形度係数に基づき、好ましくは０．８５以上、更に好ましくは０．９０以上となるものをいう。円形度係数は、Ｓｎ粒子の走査型電子顕微鏡像から、粒子どうしが重なり合っていないものを無作為に２００個選び出し、粒子の二次元投影像の面積をＳとし、周囲長をＬとしたときに、粒子の円形度係数を４πＳ／Ｌ２の式から算出し、各粒子の円形度係数の算術平均値を上述した円形度係数とする。粒子の二次元投影像が真円である場合は粒子の円形度係数は１となるので、円形度係数の上限値は好ましくは１であり、円形度係数の数値が高いほど、粒子が真球に近い形状であるといえる。 The shape of the Sn particles is not particularly limited, and various shapes such as spherical shape, flake shape, and polyhedral shape can be adopted. From the viewpoint of enhancing the dispersibility of Sn particles and enhancing the denseness when sintered, it is preferably spherical. The term "spherical" as used herein means one having a circularity coefficient of 0.85 or more, more preferably 0.90 or more, based on the circularity coefficient measured by the following method. The circularity coefficient is obtained by randomly selecting 200 particles of Sn particles that do not overlap each other from the scanning electron microscope image of Sn particles, and letting the area of the two-dimensional projected image of the particles be S and the perimeter be L. The circularity coefficient of the particles is calculated from the formula of 4πS/L 2 , and the arithmetic mean value of the circularity coefficients of the respective particles is used as the circularity coefficient described above. When the two-dimensional projection image of a particle is a perfect circle, the particle has a circularity coefficient of 1. Therefore, the upper limit of the circularity coefficient is preferably 1. The higher the circularity coefficient, the more spherical the particle is. It can be said that the shape is close to.
　Ｓｎ粒子の取扱い性を高める観点から、Ｓｎ粒子は、表面処理剤によって表面処理が施されていることも好ましい。表面処理剤としては、例えばモノエタノールアミン、ジエタノールアミン、トリエタノールアミン等のアルコールアミン類や、オレイン酸、ステアリン酸等の有機酸類を用いることができる。 From the viewpoint of improving the handleability of the Sn particles, it is also preferable that the Sn particles are surface-treated with a surface treatment agent. Examples of the surface treatment agent that can be used include alcohol amines such as monoethanolamine, diethanolamine and triethanolamine, and organic acids such as oleic acid and stearic acid.
　Ｓｎ粒子の低温での十分な焼結性と導電性とを両立する観点から、Ｓｎ粒子中の炭素（Ｃ）の含有量は、表面処理の有無によらず、Ｓｎ粒子の質量に対して、好ましくは１質量％以下、更に好ましくは０．５質量％以下であり、またその下限は、好ましくは０．００１質量％である。 From the viewpoint of achieving both sufficient sinterability at low temperature of Sn particles and conductivity, the content of carbon (C) in the Sn particles is, with or without surface treatment, relative to the mass of the Sn particles, It is preferably 1% by mass or less, more preferably 0.5% by mass or less, and the lower limit thereof is preferably 0.001% by mass.
　Ｓｎ粒子中の炭素含有量は、例えば堀場製作所社製の炭素分析装置ＥＭＩＡ－９２０Ｖを用いて測定することができる。測定試料０．１ｇと、助燃剤としてタングステン粉１．５ｇと、Ｓｎ粉０．３ｇとを磁性坩堝内に秤量し、酸素ガス雰囲気化で加熱する。加熱の際に試料中の炭素と酸素とが反応して生成した一酸化炭素及び二酸化炭素を、非分散赤外線吸収法で検出し、炭素の含有割合（質量％）を算出した。このような炭素の含有量は、例えば高純度の原料を直流熱プラズマ法や高周波プラズマ法に供することによって調整することができる。 The carbon content in the Sn particles can be measured using, for example, a carbon analyzer EMIA-920V manufactured by Horiba Ltd. 0.1 g of a measurement sample, 1.5 g of tungsten powder as a combustion improver, and 0.3 g of Sn powder are weighed in a magnetic crucible and heated in an oxygen gas atmosphere. Carbon monoxide and carbon dioxide produced by the reaction of carbon and oxygen in the sample during heating were detected by the non-dispersive infrared absorption method, and the carbon content ratio (mass %) was calculated. Such carbon content can be adjusted, for example, by subjecting a high-purity raw material to a direct-current thermal plasma method or a high-frequency plasma method.
　以上の構成を有するＳｎ粒子によれば、粒子径が小さく、且つ該粒子におけるＯの含有量が少ないので、低温での焼結性に優れる。また、該Ｓｎ粒子を導電性ペーストとして用いたときに、該ペーストから形成される膜の厚みを薄くすることができ、その結果、Ｓｎ粒子を含む膜は薄膜でありながら緻密なものとなり、電極の電気抵抗の低減と、機械的強度とを兼ね備えたものとなる。 According to the Sn particles having the above structure, the particle size is small and the O content in the particles is small, so that the sinterability at low temperature is excellent. Further, when the Sn particles are used as a conductive paste, the thickness of the film formed from the paste can be reduced, and as a result, the film containing the Sn particles is a thin film and is dense, and the electrode It has both a reduction in electric resistance and mechanical strength.
　次に、Ｓｎ粒子の好適な製造方法について説明する。本製造方法は、スズ母粉（以下、「Ｓｎ母粉」ともいう。）をＤＣプラズマ法に付して、該母粉からＳｎ粒子を生成させるものである。詳細には、本製造方法は、チャンバー内に発生させたプラズマフレームにＳｎ母粉を供給して、Ｓｎ母粉をガス化させ、ガス化した該母粉を冷却してＳｎ粒子を生成させる工程を有する。Ｓｎ含有合金を含むＳｎ粒子を製造する場合には、目的とするＳｎ粒子の合金組成と同じとなるような比率でＳｎ母粉と合金成分の母粉とを供給するか、又は目的とするＳｎ粒子と同じ合金組成を有するＳｎ含有合金の母粉を供給すればよい。以下の説明では、Ｓｎ母粉、合金成分の母粉及びＳｎ含有合金の母粉を総称して、単に「母粉」ともいう。 Next, a suitable method for producing Sn particles will be described. In this production method, tin mother powder (hereinafter, also referred to as “Sn mother powder”) is subjected to a DC plasma method to generate Sn particles from the mother powder. Specifically, the present manufacturing method is a step of supplying Sn base powder to a plasma flame generated in a chamber to gasify the Sn base powder, and cooling the gasified base powder to generate Sn particles. Have. In the case of producing Sn particles containing an Sn-containing alloy, the Sn mother powder and the mother powder of the alloy component are supplied in the same ratio as the alloy composition of the target Sn particles, or the target Sn is obtained. A mother powder of an Sn-containing alloy having the same alloy composition as the particles may be supplied. In the following description, the Sn mother powder, the mother powder of the alloy component, and the mother powder of the Sn-containing alloy are collectively referred to simply as “mother powder”.
　本製造方法に好適に用いられるＤＣプラズマ装置を図１に示す。同図に示すように、ＤＣプラズマ装置１は、粉末供給装置２、チャンバー３、ＤＣプラズマトーチ４、回収ポット５、粉末供給ノズル６、ガス供給装置７及び圧力調整装置８を備えている。この装置においては、母粉は、粉末供給装置２から粉末供給ノズル６を通してＤＣプラズマトーチ４内部を通過する。ＤＣプラズマトーチ４には、プラズマガスがガス供給装置７から供給されプラズマフレームが発生する。また、ＤＣプラズマトーチ４で発生させたプラズマフレーム内で母粉がガス化されてチャンバー３に放出された後、ガス化された母粉が冷却され、Ｓｎ粒子の微粉末となって回収ポット５内に蓄積回収される。チャンバー３の内部は、圧力調整装置８によって粉末供給ノズル６よりも相対的に陰圧が保持されるように制御されており、母粉のＤＣプラズマトーチ４への供給を容易にするとともに、プラズマフレームを安定して発生する構造をとっている。なお図１に示す装置は、ＤＣプラズマ装置の一例であって、本発明のＳｎ粒子の製造はこの装置に限定されるものではない。 A DC plasma device preferably used in this manufacturing method is shown in FIG. As shown in the figure, the DC plasma device 1 includes a powder supply device 2, a chamber 3, a DC plasma torch 4, a recovery pot 5, a powder supply nozzle 6, a gas supply device 7, and a pressure adjusting device 8. In this device, the mother powder passes from the powder supply device 2 through the powder supply nozzle 6 into the inside of the DC plasma torch 4. Plasma gas is supplied to the DC plasma torch 4 from the gas supply device 7, and a plasma flame is generated. Further, after the mother powder is gasified in the plasma flame generated by the DC plasma torch 4 and discharged into the chamber 3, the gasified mother powder is cooled and becomes a fine powder of Sn particles in the recovery pot 5. It is accumulated and collected inside. The inside of the chamber 3 is controlled by the pressure adjusting device 8 so as to maintain a negative pressure relatively to the powder supply nozzle 6, thereby facilitating the supply of the mother powder to the DC plasma torch 4 and the plasma. It has a structure that stably generates a frame. The apparatus shown in FIG. 1 is an example of a DC plasma apparatus, and the production of Sn particles of the present invention is not limited to this apparatus.
　上述した構造を有するＤＣプラズマ装置を用いてＳｎ粒子を製造する場合、チャンバー３は、その内部が水素ガス等を含む還元ガス雰囲気であるか、又は窒素ガス及びアルゴンガス等を含む不活性ガス雰囲気であることが好ましい。このような構成とすることによって、母粉のガス化から冷却されるまでの時間が短縮されるので、Ｓｎ粒子の粒成長及び粒子どうしの凝集を抑制して、生成されるＳｎ粒子の微粒子化を達成できるとともに、Ｓｎ粒子表面の酸化が抑制される。また、還元ガス雰囲気又は不活性ガス雰囲気で製造することによって、大気中の酸素がチャンバー内へ混入することが少なくなるので、生成されるＳｎ粒子表面の酸化を一層抑制できるという利点もある。還元ガス雰囲気又は不活性ガス雰囲気は、例えば、還元ガス／不活性ガス供給部（図示せず）をチャンバー３に接続して、チャンバー３内にプラズマガスとして上述の還元ガス又は不活性ガスを供給することによって達成することができる。 When Sn particles are produced using the DC plasma device having the above-described structure, the chamber 3 has a reducing gas atmosphere containing hydrogen gas or the like, or an inert gas atmosphere containing nitrogen gas and argon gas. Is preferred. With such a configuration, the time from gasification of the mother powder to cooling is shortened, so that the particle growth of the Sn particles and the aggregation of the particles are suppressed, and the generated Sn particles are atomized. And the oxidation of the Sn particle surface is suppressed. In addition, by producing in a reducing gas atmosphere or an inert gas atmosphere, oxygen in the atmosphere is less likely to be mixed into the chamber, so that there is also an advantage that the oxidation of the generated Sn particle surface can be further suppressed. As the reducing gas atmosphere or the inert gas atmosphere, for example, a reducing gas/inert gas supply unit (not shown) is connected to the chamber 3 and the above-mentioned reducing gas or inert gas is supplied as plasma gas into the chamber 3. Can be achieved by
　特に、プラズマガスとしてアルゴンガスと窒素ガスとを混合したガスを使用すると、窒素（２原子分子）ガスによって、一層大きな振動エネルギー（熱エネルギー）をＳｎ母粉に付与することができ、そのことに起因して凝集状態を均一にできるので、粗粒が少なく、粒度分布がよりシャープな粒子を得ることができる。 In particular, when a mixed gas of argon gas and nitrogen gas is used as the plasma gas, a larger vibration energy (thermal energy) can be imparted to the Sn mother powder by the nitrogen (diatomic molecule) gas. As a result, the agglomerated state can be made uniform, so that particles with few coarse particles and a sharper particle size distribution can be obtained.
　プラズマガスとして、アルゴンガスと窒素ガスとの混合ガスを使用する場合、粒度分布のシャープな粒子を得る観点から、プラズマガスにおけるアルゴンガスと窒素ガスとの割合は、アルゴンガス：窒素ガスの流量比で９９：１～１０：９０の範囲であることが好ましく、９５：５～６０：４０の範囲であることが更に好ましい。また、目的とするＳｎ粒子の粒度分布をよりシャープにする観点からは、アルゴンガスと窒素ガスの割合は、アルゴンガス：窒素ガスの流量比で９９：１～５５：４５の範囲、特に９５：５～５５：４５の範囲のように、窒素ガスよりもアルゴンガスの流量の方が多い比率内で調整すること好ましい。このような比率であることによって、プラズマフレームの減退を防止できるという利点も奏される。 When a mixed gas of argon gas and nitrogen gas is used as the plasma gas, the ratio of the argon gas to the nitrogen gas in the plasma gas is the flow ratio of the argon gas:nitrogen gas from the viewpoint of obtaining particles having a sharp particle size distribution. It is preferably in the range of 99:1 to 10:90, and more preferably in the range of 95:5 to 60:40. Further, from the viewpoint of sharpening the particle size distribution of the target Sn particles, the ratio of the argon gas and the nitrogen gas is in the range of 99:1 to 55:45 in terms of the flow rate ratio of the argon gas:nitrogen gas, particularly 95: It is preferable to adjust the flow rate of the argon gas to be larger than that of the nitrogen gas, such as in the range of 5 to 55:45. With such a ratio, there is an advantage in that the decline of the plasma flame can be prevented.
　また、チャンバー３の内部は、その圧力が粉末供給ノズル６よりも相対的に陰圧が保持されるように制御されているところ、粉末供給ノズル６での圧力とチャンバー３の内部の圧力との差圧が特定の範囲であることが好ましい。従来のＤＣプラズマ装置による製造方法では、一般的に、チャンバー３の内部の圧力を大気圧よりも５０ｋＰａ以上低くして陰圧とすることによって、母粉を粉末供給ノズル６からチャンバー３側へ吸引しやすくして、ＤＣプラズマ装置への母粉の供給量を増加させて粒子の製造効率を高めていた。本発明者は、Ｓｎ粒子の製造効率を維持しつつ、Ｓｎ粒子の微粒子化と表面酸化の抑制とを両立する方法について鋭意検討したところ、チャンバー内部の圧力と大気圧との差圧を従来技術よりも小さくした陰圧の状態でＳｎ粒子を製造することによって、意外にも、粒子の製造効率を維持しながらも、粒子径が更に小さく、粒子表面の酸化が抑制されたＳｎ粒子を製造できることを見出した。 In addition, the pressure inside the chamber 3 is controlled so that a negative pressure is maintained relatively more than the powder supply nozzle 6, so that the pressure at the powder supply nozzle 6 and the pressure inside the chamber 3 are controlled. The differential pressure is preferably within a specific range. In the conventional manufacturing method using the DC plasma device, generally, the internal pressure of the chamber 3 is reduced to 50 kPa or more lower than the atmospheric pressure to make the negative pressure, so that the mother powder is sucked from the powder supply nozzle 6 to the chamber 3 side. For this reason, the amount of mother powder supplied to the DC plasma device was increased to improve the particle production efficiency. The present inventor diligently studied a method for achieving both fine particle formation of Sn particles and suppression of surface oxidation while maintaining the production efficiency of Sn particles, and found that the pressure difference between the pressure inside the chamber and the atmospheric pressure was determined by the conventional technique. Surprisingly, it is possible to manufacture Sn particles in which the particle diameter is further reduced and the oxidation of the particle surface is suppressed by manufacturing the Sn particles in a negative pressure state that is smaller than the above, while maintaining the particle manufacturing efficiency. Found.
　詳細には、チャンバー３の内部の圧力が、大気圧よりも２０ｋＰａ以上４０ｋＰａ以下低いことが好ましく、２０ｋＰａ以上３５ｋＰａ以下低いことがより好ましい。このような範囲の陰圧に制御されていることによって、ガス化した母粉からＳｎ粒子が形成される際に、Ｓｎ粒子の粒成長及び粒子どうしの凝集を一層抑制して、生成されるＳｎ粒子の微粒子化を効率よく達成できるとともに、Ｓｎ粒子表面の酸化が一層抑制される。特に、チャンバー３の内部が還元ガス雰囲気又は不活性ガス雰囲気であることによって、更に一層有利に奏される。チャンバー３内部の圧力は、例えば圧力調整装置８によって適宜制御することができる。 Specifically, the pressure inside the chamber 3 is preferably lower than the atmospheric pressure by 20 kPa or more and 40 kPa or less, and more preferably 20 kPa or more and 35 kPa or less. By controlling the negative pressure within such a range, when the Sn particles are formed from the gasified mother powder, the Sn growth generated by further suppressing the particle growth of the Sn particles and the agglomeration of the particles. The particles can be efficiently made fine, and the oxidation of the surface of the Sn particles is further suppressed. In particular, when the inside of the chamber 3 is a reducing gas atmosphere or an inert gas atmosphere, it is more advantageous. The pressure inside the chamber 3 can be appropriately controlled by, for example, the pressure adjusting device 8.
　母粉のガス化から冷却までの時間を一層短縮して、生成されるＳｎ粒子の微粒子化と、Ｓｎ粒子表面の酸化の低減とが両立したＳｎ粒子を効率よく製造する観点から、チャンバー３の内部に冷却用ガスを供給して、ガス化した母粉を冷却することが好ましい。冷却用ガスの供給は、例えばチャンバー３の側壁部に接続された冷却用ガス供給部（図示せず）によって行うことができる。冷却用ガスとしては、例えば水素ガス等の還元ガスや、窒素ガス及びアルゴンガス等の不活性ガスを用いることができる。冷却用ガスは、チャンバー３内部の圧力が上述した範囲の陰圧となっていることを条件として、例えば０℃以上３０℃以下の温度の冷却用ガスを、チャンバー３内部におけるプラズマフレームの先端近傍であり且つプラズマフレームの形成に干渉しない周囲に、１Ｌ／ｍｉｎ以上４００Ｌ／ｍｉｎ以下供給することができる。 From the viewpoint of efficiently producing Sn particles in which the time from the gasification of the mother powder to the cooling is further shortened, and the fine particles of the produced Sn particles and the reduction of the oxidation of the surface of the Sn particles are both efficiently produced, It is preferable to supply a cooling gas to the inside to cool the gasified mother powder. The cooling gas can be supplied by, for example, a cooling gas supply unit (not shown) connected to the side wall of the chamber 3. As the cooling gas, for example, a reducing gas such as hydrogen gas or an inert gas such as nitrogen gas or argon gas can be used. As for the cooling gas, for example, a cooling gas having a temperature of 0° C. or higher and 30° C. or lower is provided in the vicinity of the tip of the plasma flame inside the chamber 3, provided that the pressure inside the chamber 3 is a negative pressure within the above range. And 1 L/min or more and 400 L/min or less can be supplied to the surroundings that do not interfere with the formation of the plasma flame.
　本製造方法に用いられる母粉は、特に限定されるものではないが、表面の酸化が抑制されたＳｎ粒子を得る観点から、酸化物の含有量が少ない母粉を用いることが好ましい。母粉のプラズマ噴射性とコストの観点から、母粉の粒径Ｄ５０は、好ましくは３．０μｍ以上５０μｍ以下、更に好ましくは５．０μｍ以上３０μｍ以下である。得られるＳｎ粒子の製造効率の観点から、母粉の供給量は、５ｇ／ｍｉｎ以上２００ｇ／ｍｉｎ以下であることが好ましく、１０ｇ／ｍｉｎ以上１００ｇ／ｍｉｎ以下であることが更に好ましい。また、母粉の形状に特に制限はなく、例えば樹枝状、棒状、フレーク状、キュービック状、球状などが挙げられる。プラズマトーチへの供給効率を安定化させる観点から、球状の母粉を用いることが好ましい。母粉のＤ５０の測定は、上述したＳｎ粒子のＤ５０の測定と同様の方法で行うことができる。 The mother powder used in the present production method is not particularly limited, but from the viewpoint of obtaining Sn particles whose surface oxidation is suppressed, it is preferable to use a mother powder containing a small amount of oxide. From the viewpoint of the plasma sprayability of the mother powder and the cost, the particle diameter D 50 of the mother powder is preferably 3.0 μm or more and 50 μm or less, more preferably 5.0 μm or more and 30 μm or less. From the viewpoint of the production efficiency of the obtained Sn particles, the feed rate of the mother powder is preferably 5 g/min or more and 200 g/min or less, and more preferably 10 g/min or more and 100 g/min or less. The shape of the mother powder is not particularly limited, and examples thereof include a dendritic shape, a stick shape, a flake shape, a cubic shape, and a spherical shape. From the viewpoint of stabilizing the supply efficiency to the plasma torch, it is preferable to use spherical mother powder. Measurement of D 50 of the mother powder may be carried out in the same manner as the measurement of the D 50 of the above-mentioned Sn particles.
　ＤＣプラズマ装置を使用して母粉を加熱噴射する場合、プラズマガスを使用して、プラズマフレームが層流状態となるように調整することが好ましい。このように調整すれば、投入した母粉はプラズマ炎中で瞬時に蒸発気化し、プラズマフレーム内で十分なエネルギーを供給することができるため、サブミクロンオーダーの微粒子を首尾よく形成することができる。これに加えて、粗粒の母粉が残存しにくくなるという利点がある。 When heating and injecting mother powder using a DC plasma device, it is preferable to use plasma gas and adjust so that the plasma flame is in a laminar flow state. By adjusting in this way, the introduced mother powder is instantly vaporized and evaporated in the plasma flame, and sufficient energy can be supplied in the plasma flame, so that fine particles of submicron order can be successfully formed. .. In addition to this, there is an advantage that the coarse-grained mother powder is less likely to remain.
　プラズマフレームが層流状態であるか否かは、プラズマフレームを、フレーム幅が最も太く観察される側面から観察したときに、フレーム幅に対するフレーム長さの縦横比（以下、フレームアスペクト比）が３以上であるか否かによって判断することができる。具体的には、フレームアスペクト比が３以上であれば層流状態と判断することができ、３未満であれば乱流状態と判断することができる。 Whether or not the plasma frame is in a laminar flow state is determined by observing the plasma frame from the side where the frame width is thickest and the aspect ratio of the frame length to the frame width (hereinafter, frame aspect ratio) is 3 or less. It can be determined by whether or not the above. Specifically, if the frame aspect ratio is 3 or more, it can be determined that the flow is laminar, and if it is less than 3, it can be determined that the flow is turbulent.
　プラズマフレームが層流状態となるようにするためには、プラズマ出力とガス流量を調整することが有利である。詳細には、ＤＣプラズマ装置のプラズマ出力を好ましくは２ｋＷ以上１００ｋＷ以下、更に好ましくは２ｋＷ以上４０ｋＷ以下に設定する。また、プラズマガスのガス流量に関しては、好ましくは０．１Ｌ／ｍｉｎ以上２５Ｌ／ｍｉｎ以下、更に好ましくは０．５Ｌ／ｍｉｎ以上２１Ｌ／ｍｉｎ以下に設定する。 ▽It is advantageous to adjust the plasma output and gas flow rate so that the plasma flame becomes laminar. Specifically, the plasma output of the DC plasma device is preferably set to 2 kW or more and 100 kW or less, and more preferably 2 kW or more and 40 kW or less. The gas flow rate of the plasma gas is preferably set to 0.1 L/min or more and 25 L/min or less, more preferably 0.5 L/min or more and 21 L/min or less.
　プラズマフレーム内で十分な熱エネルギーを母粉に供給し、サブミクロンオーダーの微粒子を首尾よく形成することに加えて、粗粒の母粉を残存しにくくするという観点から、母粉の供給量に対するプラズマ出力の比は、好ましくは０．０１ｋＷ・ｍｉｎ／ｇ以上２０ｋＷ・ｍｉｎ／ｇ以下であり、更に好ましくは０．０５ｋＷ・ｍｉｎ／ｇ以上１５ｋＷ・ｍｉｎ／ｇ以下である。 In addition to supplying sufficient heat energy to the mother powder in the plasma flame to successfully form submicron-order fine particles, it is difficult to leave coarse mother powder The plasma output ratio is preferably 0.01 kW·min/g or more and 20 kW·min/g or less, and more preferably 0.05 kW·min/g or more and 15 kW·min/g or less.
　特に、プラズマフレームを層流状態に安定的に保ちつつ、母粉のガス化に必要な流速を確実に得る観点から、上述の範囲のプラズマ出力及びガス流量を保ちつつ、プラズマ出力に対するプラズマガス流量の比（単位：Ｌ／（ｍｉｎ・ｋＷ））を、好ましくは０．５０以上２．００以下、より好ましくは０．７０以上１．７０以下、更に好ましくは０．７５以上１．５０以下に設定する。 In particular, from the viewpoint of reliably obtaining the flow rate required for gasification of the mother powder while stably maintaining the plasma flame in the laminar flow state, while maintaining the plasma output and the gas flow rate in the above range, the plasma gas flow rate with respect to the plasma output Ratio (unit: L/(min·kW)) is preferably 0.50 or more and 2.00 or less, more preferably 0.70 or more and 1.70 or less, and still more preferably 0.75 or more and 1.50 or less. Set.
　このようにして得られたＳｎ粒子は、該粒子の集合体である微粉末となって回収ポット５内に蓄積回収される。回収されたＳｎ粒子は、そのままでも用いてもよく、コンタミネーションとして存在する粗大凝集粒子の除去を行うために分級してもよい。分級は、適切な分級装置を用いて、目的とする粒度が中心となるように、粗粉や微粉を分離するようにすればよい。 The Sn particles thus obtained are collected and collected in the recovery pot 5 as a fine powder which is an aggregate of the particles. The recovered Sn particles may be used as they are, or may be classified in order to remove coarse agglomerated particles existing as contamination. The classification may be performed by using an appropriate classifying device to separate the coarse powder and the fine powder so that the target particle size is centered.
　Ｓｎ粒子は、導電性組成物に配合される金属フィラーとして好適に用いられる。導電性組成物としては、例えば導電ペーストや導電インクなどが挙げられる。これらの導電性組成物は、金属フィラーとしてのＳｎ粒子、バインダ樹脂及び有機溶媒等の成分を含むものである。導電性組成物は、例えばこれを所定の手段によって塗布することで、プリント配線基板の配線回路を形成することができる。またプリント配線基板中のビア充填用材料や、プリント配線基板に電子デバイスを表面実装するときの接着剤として用いることもできる。更に、チップ部品の電極形成に用いることもできる。特に、本発明のＳｎ粒子は、粒子径が小さく、且つ低温での焼結性の高いものであるので、小型化や高性能化が要求される積層セラミックコンデンサ（ＭＬＣＣ）等の小型電子部品の導電性樹脂層等に好適に用いることができる。 ∙ Sn particles are preferably used as a metal filler compounded in a conductive composition. Examples of the conductive composition include a conductive paste and a conductive ink. These conductive compositions contain components such as Sn particles as a metal filler, a binder resin and an organic solvent. The wiring composition of the printed wiring board can be formed, for example, by applying the conductive composition by a predetermined means. It can also be used as a via filling material in a printed wiring board or as an adhesive when surface-mounting an electronic device on the printed wiring board. Further, it can be used for forming electrodes of chip parts. In particular, since the Sn particles of the present invention have a small particle size and high sinterability at low temperatures, they can be used in small electronic components such as a multilayer ceramic capacitor (MLCC) that requires miniaturization and high performance. It can be suitably used for a conductive resin layer or the like.
　以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲は、かかる実施例に制限されない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the invention is not limited to such embodiments.
〔実施例１〕
　図１に示す構造のＤＣプラズマ装置１を用いて、以下のとおりＳｎ粒子を製造した。粉末供給装置２から粉末供給ノズル６を通して、母粉としてＳｎ－Ａｇ－Ｃｕ母粉（Ｓｎ：９６．５質量％、Ａｇ：３．０質量％、Ｃｕ：０．５質量％、粒径Ｄ５０＝１３μｍ、球状粒子）を３５ｇ／ｍｉｎの供給量で導入した。これとともに、プラズマガスとしてアルゴンガスと窒素ガスとの混合ガス（流量比として、アルゴンガス：窒素ガス＝７６：２４）をプラズマフレームの内部に供給した。プラズマガスの流量は１８．５Ｌ／ｍｉｎとした。プラズマ出力は１６．５ｋＷであり、プラズマ出力に対するプラズマガス流量の比は１．１２（Ｌ／（ｍｉｎ・ｋＷ））であった。また、母粉の供給量に対するプラズマ出力の比は０．４７ｋＷ・ｍｉｎ／ｇであった。プラズマフレームはフレームアスペクト比が４であり、層流状態であった。 [Example 1]
Sn particles were manufactured as follows using the DC plasma device 1 having the structure shown in FIG. Sn—Ag—Cu mother powder (Sn: 96.5% by mass, Ag: 3.0% by mass, Cu: 0.5% by mass, particle diameter D 50) as a mother powder from the powder supplying device 2 through the powder supplying nozzle 6. =13 μm, spherical particles) were introduced at a supply rate of 35 g/min. At the same time, a mixed gas of argon gas and nitrogen gas (a flow rate ratio of argon gas:nitrogen gas=76:24) was supplied to the inside of the plasma flame as the plasma gas. The flow rate of the plasma gas was 18.5 L/min. The plasma output was 16.5 kW, and the ratio of the plasma gas flow rate to the plasma output was 1.12 (L/(min·kW)). The ratio of plasma output to the amount of mother powder supplied was 0.47 kW·min/g. The plasma flame had a flame aspect ratio of 4 and was in a laminar flow state.
　チャンバー３の内部は窒素ガス雰囲気とし、チャンバー３内部の圧力は大気圧よりも３０ｋＰａ低くした。また、製造時において、冷却用ガスとして２５℃の窒素ガスを２９０Ｌ／ｍｉｎの流量で供給した。このようにして、目的とするＳｎ粒子を得た。本実施例のＳｎ粒子におけるＳｎ含有量は９６．５質量％であった。 The inside of the chamber 3 was made a nitrogen gas atmosphere, and the pressure inside the chamber 3 was set to be 30 kPa lower than the atmospheric pressure. Further, at the time of manufacturing, nitrogen gas at 25° C. was supplied as a cooling gas at a flow rate of 290 L/min. In this way, the target Sn particles were obtained. The Sn content in the Sn particles of this example was 96.5% by mass.
〔実施例２〕
　チャンバー３の内部の圧力を、大気圧よりも２０ｋＰａ低くした他は、実施例１と同様にＳｎ粒子を製造した。本実施例のＳｎ粒子におけるＳｎ含有量は９６．５質量％であった。 [Example 2]
Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lowered by 20 kPa from the atmospheric pressure. The Sn content in the Sn particles of this example was 96.5% by mass.
〔実施例３〕
　母粉としてＳｎ母粉（Ｓｎ：１００質量％、粒径Ｄ５０＝１５μｍ、球状粒子）を用いた他は、実施例１と同様にＳｎ粒子を得た。本実施例のＳｎ粒子におけるＳｎ含有量は１００質量％であった。 [Example 3]
Sn particles were obtained in the same manner as in Example 1 except that Sn mother powder (Sn: 100% by mass, particle diameter D 50 =15 μm, spherical particles) was used as the mother powder. The Sn content in the Sn particles of this example was 100% by mass.
〔比較例１〕
　チャンバー３の内部の圧力を、大気圧よりも５０ｋＰａ低くし、冷却用ガスの流量を１０Ｌ／ｍｉｎとした他は、実施例１と同様にＳｎ粒子を製造した。本比較例のＳｎ粒子におけるＳｎ含有量は９６．５質量％であった。 [Comparative Example 1]
Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lower than atmospheric pressure by 50 kPa and the flow rate of the cooling gas was 10 L/min. The Sn content in the Sn particles of this comparative example was 96.5% by mass.
〔比較例２〕
　チャンバー３の内部の圧力を、大気圧よりも５０ｋＰａ低くした他は、実施例１と同様にＳｎ粒子を製造した。本比較例のＳｎ粒子におけるＳｎ含有量は９６．５質量％であった。 [Comparative Example 2]
Sn particles were produced in the same manner as in Example 1 except that the pressure inside the chamber 3 was lowered by 50 kPa from the atmospheric pressure. The Sn content in the Sn particles of this comparative example was 96.5% by mass.
〔比較例３〕
　母粉としてＳｎ母粉（Ｓｎ：１００質量％、粒径Ｄ５０＝１５μｍ、球状粒子）を１１ｇ／ｍｉｎの供給量で導入し、チャンバー３の内部の圧力を大気圧よりも５０ｋＰａ低くし、冷却用ガスの流量を３０Ｌ／ｍｉｎとした他は、実施例１と同様にＳｎ粒子を得た。なお、本比較例では、母粉の供給量に対するプラズマ出力の比は１．５ｋＷ・ｍｉｎ／ｇであった。本比較例のＳｎ粒子におけるＳｎ含有量は１００質量％であった。 [Comparative Example 3]
As a mother powder, Sn mother powder (Sn: 100% by mass, particle diameter D 50 =15 μm, spherical particles) was introduced at a supply rate of 11 g/min, and the pressure inside the chamber 3 was reduced to 50 kPa below atmospheric pressure and cooled. Sn particles were obtained in the same manner as in Example 1 except that the flow rate of the working gas was 30 L/min. In this comparative example, the ratio of plasma output to the amount of mother powder supplied was 1.5 kW·min/g. The Sn content in the Sn particles of this comparative example was 100% by mass.
　〔粒子物性の評価〕
　実施例及び比較例のＳｎ粒子について、ＤＳＥＭ１０、ＤＳＥＭ５０、ＤＳＥＭ９０、Ｄ５０、ＢＥＴ比表面積、Ｏ含有量、Ｃ含有量及び円形度係数を上述の方法に従って、それぞれ測定した。結果を表１に示す。 [Evaluation of physical properties of particles]
For the Sn particles of Examples and Comparative Examples, D SEM10 , D SEM50 , D SEM90 , D 50 , BET specific surface area, O content, C content, and circularity coefficient were measured according to the methods described above. The results are shown in Table 1.
〔焼結性の評価〕
　アルミナ容器に実施例及び比較例のＳｎ粒子を満たし、窒素ガス雰囲気下で室温（２５℃）から３００℃まで１０℃／ｍｉｎの昇温速度で昇温した。その後、室温まで降温して、降温した後のＳｎ粒子の収縮率を確認した。すなわち、焼結後のＳｎ粒子を含んだアルミナ容器を上面方向から写真撮影し、当該写真データを用いて、アルミナ容器底面におけるピクセル数を画像処理ソフトとしてＩｍａｇｅ　Ｊを用いて求めた。同様に、焼結後のＳｎ粒子が存在する領域におけるピクセル数をＩｍａｇｅ　Ｊを用いて求めた。アルミナ容器底面のピクセル数をＰ１とし、焼結後のＳｎ粒子の存在領域のピクセル数をＰ２としたときの収縮率（％）を以下の式によって算出した。収縮率が高いほど溶融性が高く、焼結性に優れることを意味する。
　　収縮率（％）＝（Ｐ１－Ｐ２）×１００／Ｐ１ [Evaluation of sinterability]
An alumina container was filled with the Sn particles of Examples and Comparative Examples, and the temperature was raised from room temperature (25° C.) to 300° C. at a heating rate of 10° C./min in a nitrogen gas atmosphere. Then, the temperature was lowered to room temperature, and the shrinkage ratio of the Sn particles after the temperature was lowered was confirmed. That is, an alumina container containing Sn particles after sintering was photographed from the upper surface direction, and the number of pixels on the bottom surface of the alumina container was determined using Image J as image processing software using the photographic data. Similarly, the number of pixels in a region where Sn particles after sintering were present was determined using Image J. When the number of pixels on the bottom surface of the alumina container is P1 and the number of pixels on the area where Sn particles exist after sintering is P2, the shrinkage ratio (%) was calculated by the following formula. Higher shrinkage means higher meltability and better sinterability.
Shrinkage rate (%)=(P1-P2)×100/P1
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
〔実施例４〕
　実施例１で用いたＳｎ－Ａｇ－Ｃｕ母粉に代えて、Ｓｎ－Ｂｉ母粉（Ｓｎ：４２質量％、Ｂｉ：５８質量％、粒径Ｄ５０＝１３μｍ、球状粒子）を３０ｇ／ｍｉｎの供給量で導入した。また、プラズマ出力を１３．１ｋＷに変更し、プラズマ出力に対するプラズマガス流量の比を１．４１（Ｌ／（ｍｉｎ・ｋＷ））とした。さらに、母粉の供給量に対するプラズマ出力の比を０．４４ｋＷ・ｍｉｎ／ｇとした。これに加えて、冷却用ガスの流量を１３０Ｌ／ｍｉｎとした、これらの条件以外は実施例１と同様にして、Ｓｎ－Ｂｉ粒子を製造した。本実施例のＳｎ粒子におけるＳｎ含有量は４２質量％であった。 [Example 4]
Instead of the Sn—Ag—Cu base powder used in Example 1, Sn—Bi base powder (Sn: 42% by mass, Bi: 58% by mass, particle diameter D 50 =13 μm, spherical particles) of 30 g/min was used. Introduced in supply. Further, the plasma output was changed to 13.1 kW and the ratio of the plasma gas flow rate to the plasma output was 1.41 (L/(min·kW)). Further, the ratio of plasma output to the amount of mother powder supplied was 0.44 kW·min/g. In addition to this, Sn-Bi particles were produced in the same manner as in Example 1 except that the cooling gas flow rate was 130 L/min. The Sn content in the Sn particles of this example was 42 mass %.
〔比較例４〕
　実施例４のチャンバー３の内部の圧力を大気圧よりも５０ｋＰａ低くした以外は、実施例４と同様にして、Ｓｎ－Ｂｉ粒子を製造した。本比較例のＳｎ粒子におけるＳｎ含有量は４２質量％であった。 [Comparative Example 4]
Sn-Bi particles were produced in the same manner as in Example 4 except that the pressure inside the chamber 3 of Example 4 was lower than atmospheric pressure by 50 kPa. The Sn content in the Sn particles of this comparative example was 42% by mass.
〔評価〕
　実施例４及び比較例４のＳｎ－Ｂｉ粒子について、上述と同様にして粒子物性及び焼結性の評価を行った。結果を表２に示す。 [Evaluation]
The Sn—Bi particles of Example 4 and Comparative Example 4 were evaluated for particle properties and sinterability in the same manner as described above. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１及び表２に示すように、実施例のＳｎ粒子は、比表面積が大きく、また、ＤＳＥＭ９０が１μｍ程度の微粒子を効率よく製造できることが判る。また、大気圧とチャンバー３の内部の圧力との差圧を好適な範囲とした実施例のＳｎ粒子は、比較例のＳｎ粒子と比較して、Ｏの含有量が少なく、粒子どうしの焼結性に優れることが判る。また、実施例のＳｎ粒子によれば、Ｄ５０／ＤＳＥＭ５０の比が小さいので、粒子分布がシャープとなり分散性が高く、該粒子を含むペーストとしたときに、平滑且つ薄い塗膜を形成することができる。 As shown in Tables 1 and 2, it is understood that the Sn particles of the examples have a large specific surface area, and that D SEM90 can efficiently produce fine particles of about 1 μm. In addition, the Sn particles of the example in which the differential pressure between the atmospheric pressure and the pressure inside the chamber 3 is in a suitable range has a smaller O content than the Sn particles of the comparative example, and the particles are sintered together. It turns out that it has excellent properties. In addition, according to the Sn particles of the example, since the D 50 /D SEM50 ratio is small, the particle distribution becomes sharp and the dispersibility is high, and a smooth and thin coating film is formed when a paste containing the particles is formed. be able to.
　本発明によれば、粒子径が小さく、且つ低温での焼結性に優れたＳｎ粒子及び該粒子を含む導電性組成物が提供される。
  According to the present invention, there are provided Sn particles having a small particle size and excellent in sinterability at low temperatures, and a conductive composition containing the particles.

Claims (10)

  1. 　Ｓｎと酸素（Ｏ）とを含むＳｎ粒子であって、
    　前記Ｓｎを４０質量％以上含み、前記Ｏを０．５５質量％以下含み、
    　ＢＥＴ比表面積（ｍ２／ｇ）に対するＯ含有量（質量％）の比（質量％・ｇ／ｍ２）が０．４０以下である、Ｓｎ粒子。     A Sn particle containing Sn and oxygen (O),
    40 mass% or more of Sn is contained, 0.55 mass% or less of O is contained,
    Sn particles having a ratio (mass %.g/m 2 ) of O content (mass %) to BET specific surface area (m 2 /g) of 0.40 or less.
  2. 　前記Ｏを０．０５質量％以上含む、請求項１に記載のＳｎ粒子。 The Sn particles according to claim 1, wherein the content of O is 0.05% by mass or more.
  3. 　Ａｕ、Ａｇ、Ｃｕ、Ｓｉ、Ｎｉ、Ｔｉ、Ｆｅ、Ｃｏ、Ｃｒ、Ｍｇ、Ａｌ、Ｍｎ、Ｍｏ、Ｗ、Ｔａ、Ｉｎ、Ｚｒ、Ｎｂ、Ｇｅ、Ｚｎ、Ｂｉ及びＳｂの少なくとも一種の金属を更に含む、請求項１又は２に記載のＳｎ粒子。 Further, at least one metal selected from Au, Ag, Cu, Si, Ni, Ti, Fe, Co, Cr, Mg, Al, Mn, Mo, W, Ta, In, Zr, Nb, Ge, Zn, Bi and Sb. The Sn particle according to claim 1 or 2, which comprises:
  4. 　Ａｇを０．１質量％以上４．０質量％以下含み、Ｃｕを０．１質量％以上１．０質量％以下含む、請求項１ないし３のいずれか一項に記載のＳｎ粒子。 The Sn particles according to any one of claims 1 to 3, containing 0.1 mass% or more and 4.0 mass% or less of Ag, and 0.1 mass% or more and 1.0 mass% or less of Cu.
  5. 　走査型電子顕微鏡観察によって測定された累積体積９０容量％における体積累積粒径ＤＳＥＭ９０が２．０μｍ以下である、請求項１ないし４のいずれか一項に記載のＳｎ粒子。 The Sn particles according to any one of claims 1 to 4, wherein a volume cumulative particle diameter D SEM90 at a cumulative volume of 90% by volume measured by scanning electron microscope observation is 2.0 µm or less.
  6. 　ＢＥＴ比表面積が１ｍ２／ｇ以上である、請求項１ないし５のいずれか一項に記載のＳｎ粒子。 The Sn particles according to any one of claims 1 to 5, having a BET specific surface area of 1 m 2 /g or more.
  7. 　球状である、請求項１ないし６のいずれか一項に記載のＳｎ粒子。 The Sn particles according to any one of claims 1 to 6, which are spherical.
  8. 　走査型電子顕微鏡観察によって測定された累積体積５０容量％における体積累積粒径ＤＳＥＭ５０に対する、レーザー回折散乱式粒度分布測定法による累積体積５０容量％における体積累積粒径Ｄ５０の比Ｄ５０／ＤＳＥＭ５０が、１．０以上４．５以下である、請求項１ないし７のいずれか一項に記載のＳｎ粒子。 Ratio D 50 /D of volume cumulative particle diameter D 50 at cumulative volume of 50 volume% by laser diffraction scattering type particle size distribution measurement method to volume cumulative particle diameter D SEM50 at cumulative volume of 50 volume% measured by scanning electron microscope observation. The Sn particles according to any one of claims 1 to 7, wherein SEM50 is 1.0 or more and 4.5 or less.
  9. 　請求項１ないし８のいずれか一項に記載のＳｎ粒子を含んでなる導電性組成物。 A conductive composition comprising the Sn particles according to any one of claims 1 to 8.
  10. 　チャンバー内に発生させたプラズマフレームにＳｎ母粉を供給して該Ｓｎ母粉をガス化させ、ガス化した前記Ｓｎ母粉を冷却してＳｎ粒子を生成させる工程を有し、
    　前記チャンバーは、その内部が還元ガス雰囲気又は不活性ガス雰囲気であり、且つその内部の圧力が大気圧よりも２０ｋＰａ以上４０ｋＰａ以下低く、
    　Ｓｎ母粉の供給量に対するプラズマ出力の比が、０．０１ｋＷ・ｍｉｎ／ｇ以上２０ｋＷ・ｍｉｎ／ｇ以下である、Ｓｎ粒子の製造方法。
          A step of supplying Sn base powder to a plasma flame generated in the chamber to gasify the Sn base powder, and cooling the gasified Sn base powder to generate Sn particles;
    The inside of the chamber is a reducing gas atmosphere or an inert gas atmosphere, and the pressure inside is lower than atmospheric pressure by 20 kPa or more and 40 kPa or less,
    A method for producing Sn particles, wherein the ratio of the plasma output to the supply amount of Sn mother powder is 0.01 kW·min/g or more and 20 kW·min/g or less.
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