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WO2024195068A1 - Silver microparticles - Google Patents

Silver microparticles Download PDF

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Publication number
WO2024195068A1
WO2024195068A1 PCT/JP2023/011346 JP2023011346W WO2024195068A1 WO 2024195068 A1 WO2024195068 A1 WO 2024195068A1 JP 2023011346 W JP2023011346 W JP 2023011346W WO 2024195068 A1 WO2024195068 A1 WO 2024195068A1
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WO
WIPO (PCT)
Prior art keywords
silver
particles
gas
particle size
less
Prior art date
Application number
PCT/JP2023/011346
Other languages
French (fr)
Japanese (ja)
Inventor
志織 末安
周 渡邉
Original Assignee
日清エンジニアリング株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日清エンジニアリング株式会社 filed Critical 日清エンジニアリング株式会社
Priority to PCT/JP2023/011346 priority Critical patent/WO2024195068A1/en
Publication of WO2024195068A1 publication Critical patent/WO2024195068A1/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
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/12—Making metallic powder or suspensions thereof using physical processes starting from gaseous material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • 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

Definitions

  • the present invention relates to silver microparticles that are used for bonding semiconductor elements, high-frequency devices, light-emitting diodes, semiconductor lasers, etc. to substrates, etc., or for wiring, etc.
  • power semiconductor elements using wide band gap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide, or diamond are being developed.
  • Power semiconductor elements have a lower on-resistance than semiconductor elements using Si or GaAs, can be switched at high speed, and can be made smaller.
  • power semiconductor elements have high heat resistance and can operate at high temperatures of 250 to 300°C.
  • Solder has been used conventionally to bond semiconductor elements to substrates and the like.
  • power semiconductor elements have a higher operating temperature than conventional semiconductor elements using Si or GaAs, and when solder is used for bonding, the elements must be used at a temperature at which the solder does not melt.
  • solder is used for bonding, the power semiconductor elements are subject to restrictions on their use.
  • bonding materials are also required to be able to be used at high temperatures.
  • Patent Document 1 describes bonding of SiC semiconductor elements using eutectic AuGe solder.
  • Patent Document 2 describes a thermally conductive paste as a joining material that contains low-temperature sinterable silver fine particles and a thermosetting binder, in which the thermosetting binder is composed of (B1) at least one epoxy resin selected from the group consisting of phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and C1-C4 alkyl substituted derivatives thereof, and (B2) at least one curing agent selected from the group consisting of a cationic polymerization initiator, an amine-based curing agent, and an acid anhydride curing agent, and in which the thermosetting binder is present in an amount of 2 to 7 parts by mass per 100 parts by mass of the silver fine particles.
  • the thermosetting binder is composed of (B1) at least one epoxy resin selected from the group consisting of phthalic
  • the object of the present invention is to provide silver microparticles that suppress volumetric shrinkage and have high electrical conductivity.
  • one aspect of the present invention provides fine silver particles having a particle size of 0.1 ⁇ m or more and 1 ⁇ m or less as measured by the BET method, a volume resistivity of 10 ⁇ cm or less after being fired in the form of a pellet in air at a temperature of 150° C. for 1 hour, and a volume shrinkage rate of less than 5%.
  • the content of particles having a particle size of less than 0.1 ⁇ m is preferably 40% or less by volume. It is more preferable that the content of particles having a particle size of less than 0.1 ⁇ m is 35% or less by volume, and further more preferable that the content of particles having a particle size of less than 0.1 ⁇ m is 5% or less by volume.
  • the present invention provides silver microparticles that suppress volumetric shrinkage and have high electrical conductivity.
  • FIG. 1 is a schematic diagram showing an example of a usage form of the silver fine particles of the present invention.
  • FIG. 1 is a schematic diagram showing an example of an apparatus for producing fine silver particles of the present invention.
  • 1 is a graph showing the particle size distribution of fine silver particles in Examples 1 and 2 of the present invention.
  • FIG. 2 is a schematic diagram showing an SEM image of the silver fine particles of Example 1 of the present invention.
  • FIG. 2 is a schematic diagram showing an SEM image of the silver fine particles of Example 2 of the present invention.
  • FIG. 1 is a schematic diagram showing an SEM image of conventional silver fine particles.
  • the silver microparticles have a particle size measured by the BET method of 0.1 ⁇ m or more and 1 ⁇ m or less, and after being fired in the form of a pellet in air at a temperature of 150° C. for 1 hour, the volume resistivity is 10 ⁇ cm or less, and the volume shrinkage rate is less than 5%.
  • the atmosphere refers to an atmosphere generally called air.
  • the atmosphere is also called the air atmosphere.
  • the composition of air is 78.08 vol% nitrogen, 20.95 vol% oxygen, 0.93 vol% argon, and 0.03 vol% carbon dioxide. Note that a general measurement error is allowed for the composition of air.
  • the content of particles having a particle size of less than 0.1 ⁇ m is preferably 40% or less by volume.
  • the content of particles having a particle size of less than 0.1 ⁇ m is 35% or less by volume, and it is even more preferable that the content of particles having a particle size of less than 0.1 ⁇ m is 5% or less by volume.
  • the lower limit of the content of particles having a particle size of less than 0.1 ⁇ m is 0% by volume.
  • the particle size of the silver particles is preferably 100 to 400 nm, and more preferably 200 to 400 nm, because this reduces the volumetric shrinkage rate after baking in the pellet state in the atmosphere (i.e., in air) at a temperature of 150° C. for 1 hour.
  • the particle size of the silver particles measured by the BET method is the average particle size measured by the BET method, which is calculated from the specific surface area on the assumption that the particles are spherical.
  • the silver fine particles are not dispersed in a solvent or the like, but exist alone without the presence of a solvent, etc. Therefore, when using silver fine particles, a fired body can be obtained using only the silver fine particles. Furthermore, when silver particles are used in combination with a solvent, the combination of silver particles and a solvent is not particularly limited, and there is a high degree of freedom in the selection of the solvent.
  • the volume resistivity is preferably 9 ⁇ cm or less, more preferably 8 ⁇ cm or less, and most preferably 7 ⁇ cm or less.
  • the lower limit of the volume resistivity is 1.47 ⁇ cm.
  • the volumetric shrinkage is preferably 3% or less, more preferably 1% or less, and most preferably 0%.
  • the lower limit of the volumetric shrinkage is 0%.
  • it is preferable that the content of silver particles having a particle size of less than 0.1 ⁇ m is 40% or less by volume, since this suppresses the occurrence of cracks after firing.
  • the content of particles having a particle size of less than 0.1 ⁇ m in the silver microparticles is determined from a volume-based particle size distribution obtained by acquiring a scanning electron microscope (SEM) image of the silver microparticles and performing image analysis on the SEM image.
  • SEM scanning electron microscope
  • the content of particles having a particle size of less than 0.1 ⁇ m is determined as a percentage of the total volume of the silver microparticles.
  • the silver particles are formed into a cylindrical pellet, which is placed in an electric furnace and fired in the atmosphere at a temperature of 150° C. for one hour.
  • the pellets are prepared by pressing the silver particles at a pressure of 127 MPa for 10 seconds using a press.
  • the volume resistivity is a value obtained by measuring the pellets by the four-terminal method.
  • a measuring device such as Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation is used.
  • the volumetric shrinkage rate was calculated by forming a cylindrical pellet from the silver fine particles using a press machine as described above, holding the silver fine particles at a pressure of 127 MPa for 10 seconds, measuring the thickness and diameter of the cylindrical pellet with a vernier caliper, and calculating the volume of the pellet before and after firing.
  • the silver microparticles have a particle size of 0.1 ⁇ m or more and 1 ⁇ m or less as measured by the BET method, and have a volume resistivity of 10 ⁇ cm or less after being fired in the form of pellets in the air at a temperature of 150° C. for 1 hour, and a volume shrinkage rate of less than 5%, thereby suppressing volume shrinkage and providing high electrical conductivity.
  • the silver microparticles have a higher melting point and superior heat resistance than solder, etc. Therefore, when the silver microparticles are used as a bonding material, it is possible to provide a material with excellent electrical conductivity while satisfying heat resistance.
  • the particles will all have a large particle size, which is preferable because it further suppresses volume shrinkage after firing of the silver microparticles.
  • FIG. 1 is a schematic diagram showing an example of a form of use of the silver fine particles of the present invention.
  • the silver particles are used, for example, for bonding a substrate 50 and a power semiconductor element 52 shown in Fig. 1.
  • the silver particles are used for die attachment.
  • the silver particles constitute a joint 54 that joins the substrate 50 and the power semiconductor element 52.
  • the joint 54 is formed by baking the silver particles in air, for example, at a temperature of 150° C. for one hour.
  • the joint 54 joins the substrate 50 and the power semiconductor element 52, and physically fixes the substrate 50 and the power semiconductor element 52 together.
  • the silver microparticles have a higher melting point and higher heat resistance than solder and resin.
  • the silver microparticles have a volume resistivity of 10 ⁇ cm or less and a volume shrinkage rate of less than 5% after being baked in the form of pellets at a temperature of 150° C. for 1 hour in the atmosphere. Therefore, even if a temperature change occurs due to the operation of the power semiconductor element 52, the volume fluctuation of the joint 54 is small, and the occurrence of cracks is suppressed. This maintains the bond and provides high durability.
  • the silver microparticles have a low volume resistivity after baking, and therefore have excellent thermal conductivity, and the joint 54 can efficiently conduct the heat generated by the power semiconductor element 52 to the substrate 50.
  • the substrate 50 is, for example, a ceramic substrate such as Si 3 N 4 on which copper wiring is provided.
  • the power semiconductor element 52 is a semiconductor element using a semiconductor such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide, or diamond.
  • the silver particles can be used not only for bonding to the power semiconductor element 52 but also for bonding to high-frequency devices, light-emitting diodes, semiconductor lasers, etc. As described above, the silver particles have excellent thermal conductivity and are suitable for bonding to objects that generate a large amount of heat or have a high operating temperature. In addition to bonding, the silver particles can also be used for various wiring such as signal wiring and conductive wiring.
  • FIG. 2 is a schematic diagram showing an example of an apparatus for producing fine silver particles of the present invention.
  • the above-mentioned fine silver particles can be obtained by the fine silver particle manufacturing apparatus 10 shown in FIG. 2 (hereinafter simply referred to as the manufacturing apparatus 10).
  • the manufacturing apparatus 10 includes a plasma torch 12 that generates a thermal plasma flame, a material supply device 14 that supplies raw powder of silver particles into the plasma torch 12, a chamber 16 that functions as a cooling tank for generating primary silver particles 15, a cyclone 19 that removes coarse particles having a particle size equal to or larger than an arbitrarily specified particle size from the primary silver particles 15, and a recovery section 20 that recovers secondary silver particles 18 having a desired particle size classified by the cyclone 19.
  • the chamber 16 and the cyclone 19 are connected by a connection pipe 21a.
  • the cyclone 19 and the recovery section 20 are also connected by a connection pipe 21b that is connected to an inner pipe 19e.
  • the manufacturing apparatus 10 further includes a supply section 40 that supplies a surface treatment agent to the primary silver particles 15 or the secondary silver particles 18 .
  • the primary silver particles 15 and the secondary silver particles 18 are both particulate bodies in the process of producing the particles of the present invention.
  • the particles obtained by surface-treating the primary silver particles 15 or the secondary silver particles 18, i.e., the surface-treated silver particles 30, are the particles of the present invention.
  • various devices described in, for example, JP 2007-138287 A can be used.
  • silver powder is used as a raw material for producing the fine particles.
  • the average particle size of the silver powder is appropriately set so that it can be easily evaporated in the thermal plasma flame.
  • the average particle size of the silver powder is measured using a laser diffraction method and is, for example, 100 ⁇ m or less, preferably 50 ⁇ m or less, and more preferably 15 ⁇ m or less.
  • the plasma torch 12 is composed of a quartz tube 12a and a high-frequency oscillation coil 12b that surrounds it.
  • a supply tube 14a (described later) is provided in the center of the upper part of the plasma torch 12 for supplying fine particle raw material powder into the plasma torch 12.
  • a plasma gas supply port 12c is formed on the periphery (on the same circumference) of the supply tube 14a, and the plasma gas supply port 12c is ring-shaped.
  • a power source (not shown) that generates a high-frequency voltage is connected to the high-frequency oscillation coil 12b. When a high-frequency voltage is applied to the high-frequency oscillation coil 12b, a thermal plasma flame 24 is generated.
  • the raw material (not shown) is evaporated by the thermal plasma flame 24, becoming a gas-phase mixture.
  • the plasma torch 12 is a processing section that uses a gas-phase method to turn the raw material into a gas-phase mixture.
  • the plasma gas supply unit 22 supplies plasma gas into the plasma torch 12.
  • the plasma gas supply unit 22 is connected to the plasma gas supply port 12c via piping 22a.
  • the plasma gas supply unit 22 is provided with a supply amount adjustment unit such as a valve for adjusting the supply amount.
  • the plasma gas is supplied from the plasma gas supply unit 22 through the ring-shaped plasma gas supply port 12c into the plasma torch 12 in the directions indicated by arrows P and S.
  • the plasma gas used is, for example, a mixed gas of hydrogen gas and argon gas.
  • hydrogen gas and argon gas are stored in the plasma gas supply unit 22.
  • Hydrogen gas and argon gas are supplied from the plasma gas supply unit 22 through the piping 22a and the plasma gas supply port 12c into the plasma torch 12 in the directions indicated by the arrows P and S. It is noted that only argon gas may be supplied in the direction indicated by the arrow P.
  • a plasma gas appropriate for the silver particles it is not essential to use a mixed gas as the plasma gas as described above, and a single type of gas may be used as the plasma gas.
  • the temperature of the thermal plasma flame 24 must be higher than the boiling point of the raw material powder. On the other hand, the higher the temperature of the thermal plasma flame 24, the easier it is for the raw material powder to become in a gaseous state, so this is preferable, but the temperature is not particularly limited.
  • the temperature of the thermal plasma flame 24 can be set to 6000°C, and theoretically it is thought to reach about 10000°C.
  • the pressure atmosphere in the plasma torch 12 is preferably equal to or lower than atmospheric pressure.
  • the pressure atmosphere is not particularly limited, but is, for example, 0.5 to 100 kPa.
  • the outside of the quartz tube 12a is surrounded by a concentric tube (not shown), and cooling water is circulated between this tube and the quartz tube 12a to water-cool the quartz tube 12a and prevent the quartz tube 12a from becoming too hot due to the thermal plasma flame 24 generated inside the plasma torch 12.
  • the material supply device 14 is connected to the upper part of the plasma torch 12 via a supply pipe 14a.
  • the material supply device 14 supplies raw material into a thermal plasma flame 24 in the plasma torch 12.
  • the material supply device 14 is not particularly limited as long as it can supply the raw material into the thermal plasma flame 24.
  • the raw material is supplied into the thermal plasma flame 24 in a particulate dispersed state.
  • the material supply device 14 that supplies silver powder in powder form can be, as described above, for example, the one disclosed in JP 2007-138287 A.
  • the material supply device 14 has, for example, a storage tank (not shown) for storing the raw material, a screw feeder (not shown) for transporting a fixed amount of the raw material, a dispersion section (not shown) for dispersing the raw material transported by the screw feeder into primary particles before it is finally sprayed, and a carrier gas supply source (not shown).
  • the gas supply unit 28 supplies a temperature control gas containing an inert gas, for example, into the connecting pipe 21 a or the connecting pipe 21 b.
  • the gas supply unit 28 supplies the temperature control gas containing an inert gas to the silver primary particles 15 or the silver secondary particles 18.
  • the gas supply unit 28 includes, for example, a valve 28a, and a first gas supply pipe 28b and a second gas supply pipe 28c connected to the valve 28a.
  • the first gas supply pipe 28b is connected to the connecting pipe 21a
  • the second gas supply pipe 28c is connected to the connecting pipe 21b.
  • the gas supply unit 28 further includes a pressure applying device (not shown), such as a compressor or a blower, that applies extrusion pressure to the temperature adjustment gas supplied to the first gas supply pipe 28b or the second gas supply pipe 28c.
  • the gas supply unit 28 also includes a storage unit (not shown) for storing a temperature adjusting gas, and a pressure control valve for controlling the amount of gas supplied.
  • the temperature adjusting gas is, for example, argon gas. The gas temperature can be adjusted to a desired temperature by the temperature adjusting gas supplied from the gas supply unit 28 into the connecting pipe 21a or the connecting pipe 21b.
  • the chamber 16 is provided with a cyclone 19 for classifying the primary silver particles 15 into the desired particle size.
  • the cyclone 19 is provided with an inlet pipe 19a for supplying the primary particles 15 from the chamber 16, a cylindrical outer tube 19b connected to the inlet pipe 19a and located at the top of the cyclone 19, a truncated cone section 19c that continues downward from the bottom of the outer tube 19b and has a gradually decreasing diameter, a coarse particle recovery chamber 19d connected to the bottom of the truncated cone section 19c for recovering coarse particles having a particle size equal to or larger than the desired particle size, and an inner tube 19e connected to the recovery section 20 described later and protruding from the outer tube 19b.
  • the chamber 16 and the inlet pipe 19a are connected by a connecting pipe 21a, and the primary particles 15 move to the cyclone 19 through the connecting pipe 21a.
  • the connecting pipe 21a is a transport path for the primary particles 15.
  • fine particles that are more affected by the drag force than the centrifugal force are discharged together with the ascending flow on the inner wall of the truncated cone portion 19c through the inner pipe 19e and the connecting pipe 21b to the outside of the cyclone 19.
  • a negative pressure (suction force) is generated from the collection section 20, which will be described in detail later, through the inner tube 19e and the connecting tube 21b.
  • This negative pressure causes the fine particles separated from the swirling airflow to be sucked in as indicated by the symbol U, and is sent to the collection section 20 through the inner tube 19e and the connecting tube 21b.
  • a recovery section 20 for recovering silver microparticles 30 having a desired nanometer-order particle size is provided on the extension of inner tube 19e, which is the outlet of the airflow in cyclone 19.
  • Recovery section 20 includes recovery chamber 20a, filter 20b provided in recovery chamber 20a, and vacuum pump 29 connected via a tube provided below recovery chamber 20a. Silver microparticles 30 sent from cyclone 19 are sucked by vacuum pump 29 and drawn into recovery chamber 20a, where they are collected while remaining on the surface of filter 20b.
  • the number of cyclones used is not limited to one, and may be two or more.
  • the supply unit 40 supplies the surface treatment agent St to the silver particles in the chamber 16, downstream of the first gas supply pipe 28b in the connecting pipe 21a, or downstream of the second gas supply pipe 28c in the connecting pipe 21b.
  • the chamber 16 side with respect to the connecting pipe 21a is referred to as the upstream side
  • the cyclone 19 side is referred to as the downstream side.
  • the supply unit 40 has, for example, a valve 41, and a first supply pipe 41a, a second supply pipe 41b, and a third supply pipe 41c connected to the valve 41.
  • the first supply pipe 41a is connected to the side surface 16b of the chamber 16.
  • the second supply pipe 41b is connected to the connecting pipe 21a downstream of the first gas supply pipe 28b, and the third supply pipe 41c is connected to the connecting pipe 21b downstream of the second gas supply pipe 28c.
  • the first supply pipe 41a is connected, for example, at a height equal to or lower than the position where the connecting pipe 21a is connected in the chamber 16.
  • the surface treatment agent St is supplied into the chamber 16 from the inner wall 16a of the chamber 16 through the first supply pipe 41a.
  • the connection position of the second supply pipe 41b to the connection pipe 21a is designated as P1
  • the connection position of the third supply pipe 41c to the connection pipe 21b is designated as P2 .
  • the connection position P2 of the third supply pipe 41c is downstream of the connection position P1 of the second supply pipe 41b.
  • the supply unit 40 supplies the surface treatment agent St to the primary silver particles 15 in the chamber 16, the primary silver particles 15 passing through the connection pipe 21a, or the secondary silver particles 18 passing through the connection pipe 21b.
  • the supply unit 40 supplies the surface treatment agent St in a temperature range suitable for the surface treatment agent St.
  • the surface treatment agent St adheres to the primary silver particles 15 or the secondary silver particles 18, the primary silver particles 15 or the secondary silver particles 18 are surface-treated, and fusion of the silver particles is prevented, thereby obtaining silver particles 30.
  • the method of supplying the surface treatment agent St by the supply unit 40 is not particularly limited, and an example thereof is a method in which the surface treatment agent St is made into droplets and sprayed onto the secondary fine silver particles 18 .
  • the surface treatment agent St is supplied in a suitable temperature range.
  • the suitable temperature range is a temperature range in which the surface treatment agent St can play a role in preventing the fusion of the silver fine particles. Therefore, as long as the fusion of the silver fine particles can be prevented, the surface treatment agent St may be introduced from a temperature range in which the surface treatment agent St is denatured, or from a temperature range in which the surface treatment agent St is not denatured.
  • the surface condition of the surface-treated fine particles can be examined, for example, by using an FT-IR (Fourier transform infrared spectrophotometer).
  • the temperature range capable of preventing the fusion of the silver fine particles is a temperature range in which the primary fine particles 15 can be covered with the organic matter produced by the denaturation of the surface treatment agent St or with the surface treatment agent St.
  • the temperature range in which the surface treatment agent St does not denature is a temperature range determined based on the temperature measured by simultaneous differential thermal analysis-thermogravimetry (TG-DTA).
  • the temperature range in which the surface treatment agent St does not denature is a temperature range in which the weight loss rate of the surface treatment agent St is 50% by mass or less in simultaneous differential thermal and thermogravimetric measurements, more preferably 30% by mass or less, and even more preferably 10% by mass or less.
  • STA7200 product name manufactured by Hitachi High-Tech Science Corporation is used.
  • the surface treatment agent St is not particularly limited, but may be, for example, an organic acid alone or an organic acid solution, an organic substance having an amine group, or a solution of an organic substance having an amine group.
  • the organic acid is in a liquid state when used, it is not necessary to dissolve the organic acid in a solvent as in an aqueous solution, and the organic acid can be used alone.
  • a surface treatment agent St other than an organic acid such as an acidic substance, a basic substance, a natural resin, or a synthetic resin, is used, it can be used alone as long as it is in a liquid state when used, similarly to the organic acid.
  • An example of an organic substance having an amine group is dodecylamine.
  • the dispersant for example, a dispersant having only an amine group is used.
  • the following dispersants can be used.
  • the amine value of the dispersant is preferably 10 or more and 100 or less, and more preferably 10 or more and 60 or less.
  • Dispersants having only amine groups include, for example, DISPERBYK-102, DISPERBYK-160, DISPERBYK-161, DISPERBYK-162, DISPERBYK-2163, DISPERBYK-2164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-2000, DISPERBYK-2050, DISPERBYK-2150, DISPERBYK-2155, DISPERBYK-LPN6919, DISPERBYK-LPN21116, DISPERBYK-LPN 21234, DISPERBYK-9075, DISPERBYK-9077 (all manufactured by BYK-Chemie); EFKA 4015, EFKA 4020, EFKA 4046, EFKA 4047, EFKA 4050, EFKA 4055, EFKA 4060, EFKA 4080, EFKA 4300, EFKA 4
  • polymeric dispersants having amine groups include DISPERBYK-142, DISPERBYK-145, DISPERBYK-2001, DISPERBYK-2010, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-9076, and Anti-Terra-205 (all manufactured by BYK-Chemie); SOLSPERSE 24000 (manufactured by Lubrizol Corporation); AJISPER (registered trademark) PB821, AJISPER PB880, and AJISPER PB881 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.).
  • Organic solvent is not particularly limited and can be appropriately selected according to the purpose.
  • examples of the organic solvent include alcohols such as methanol, ketones such as acetone, alkyl halides, amides such as formamide, sulfoxides such as dimethyl sulfoxide, heterocyclic compounds, hydrocarbons, esters such as ethyl acetate, and ethers. These may be used alone or in combination of two or more.
  • organic acid which is an acidic substance
  • an aqueous solution using pure water as a solvent is sprayed from the supply unit 40.
  • the organic acid is preferably water-soluble and has a low boiling point, and is preferably composed only of C, O, and H.
  • organic acids examples include L-ascorbic acid (C 6 H 8 O 6 ), formic acid (CH 2 O 2 ), glutaric acid (C 5 H 8 O 4 ), succinic acid (C 4 H 6 O 4 ), oxalic acid (C 2 H 2 O 4 ), DL-tartaric acid (C 4 H 6 O 6 ), lactose monohydrate, maltose monohydrate, maleic acid (C 4 H 4 O 4 ), D-mannite (C 6 H 14 O 6 ), citric acid (C 6 H 8 O 7 ), malic acid (C 4 H 6 O 5 ), malonic acid (C 3 H 4 O 4 ), and aliphatic carboxylic acids. It is preferable to use at least one of the above organic acids.
  • the spray gas for turning the aqueous solution of the organic acid into droplets is, for example, argon gas, but is not limited to argon gas, and an inert gas such as nitrogen gas can be used.
  • a sensor may be provided to measure the temperature of the transport path of the silver primary particles 15 or the silver secondary particles 18.
  • the temperature measurement result of this sensor is used to determine whether or not the temperature range is suitable for the surface treatment agent St.
  • the temperature measurement result is output to, for example, the supply unit 40.
  • the supply unit 40 can determine whether or not the temperature range is suitable for the surface treatment agent St based on the temperature measurement result of the transport path of the silver primary particles 15 or the silver secondary particles 18 by the sensor.
  • the flow rate of the temperature adjustment gas supplied from the gas supply unit 28 is changed.
  • the sensor is preferably provided upstream of the connection position P1 of the connecting pipe 21a of the second supply pipe 41b. For this reason, the sensor is provided, for example, in the connecting pipe 21a.
  • the sensor is not particularly limited in configuration as long as it can measure temperature, but it is preferable that the measurement time is short. For this reason, the sensor may be, for example, a resistance thermometer, a radiation thermometer, an infrared radiation temperature sensor, a thermistor, or the like.
  • raw powder of silver particles for example, silver powder having an average particle size of 15 ⁇ m or less is fed into the material supply device 14 .
  • argon gas and hydrogen gas are used as the plasma gas, and a high-frequency voltage is applied to the high-frequency oscillation coil 12 b to generate a thermal plasma flame 24 in the plasma torch 12 .
  • the silver powder is gas-transported using, for example, argon gas as a carrier gas, and is supplied via the supply pipe 14a into the thermal plasma flame 24 in the plasma torch 12.
  • the supplied silver powder evaporates in the thermal plasma flame 24 to become a gas-phase mixture, and primary silver particles 15 are generated from the gas-phase mixture in the chamber 16 without using a cooling gas.
  • the primary silver particles 15 obtained in the chamber 16 pass through the connecting pipe 21a and are blown together with the airflow from the inlet pipe 19a of the cyclone 19 along the inner peripheral wall of the outer cylinder 19b, whereby the airflow flows along the inner peripheral wall of the outer cylinder 19b as indicated by the arrow T in Fig. 2, forming a swirling flow and descending.
  • the balance between the centrifugal force and the drag force means that the coarse particles cannot ride on the ascending flow, and so they descend along the side surface of the truncated cone portion 19c and are collected in the coarse particle collection chamber 19d.
  • the fine particles that are more affected by the drag force than the centrifugal force are discharged from the inner wall of the truncated cone portion 19c together with the ascending flow at the inner wall of the truncated cone portion 19c, to the outside of the cyclone 19.
  • the discharged secondary silver particles 18 are sucked in the direction indicated by the symbol U in FIG. 1 by the negative pressure (suction force) from the recovery section 20 by the vacuum pump 29, and pass through the inner tube 19e and the connection tube 21b.
  • a temperature adjusting gas is supplied from the gas supply unit 28 through the first gas supply pipe 28b or the second gas supply pipe 28c into the connecting pipe 21a or the connecting pipe 21b to cool the silver primary particles 15 or the silver secondary particles 18.
  • the surface treatment agent St is further supplied from the supply unit 40 to the chamber 16, the connecting pipe 21a or the connecting pipe 21b in the form of, for example, a spray to the silver primary particles 15 or the silver secondary particles 18, so that the silver primary particles 15 or the silver secondary particles 18 are surface-treated.
  • the surface-treated primary silver particles 15 or secondary silver particles 18, i.e., silver particles 30, are sent to the recovery section 20, and the silver particles 30 are recovered by the filter 20b of the recovery section 20. In this manner, silver particles are obtained.
  • the internal pressure in the cyclone 19 is preferably equal to or lower than atmospheric pressure.
  • the particle diameter of the silver microparticles 30 is specified to any particle diameter on the order of nanometers depending on the purpose.
  • the primary silver particles are formed using a thermal plasma flame as a heat source, but the primary silver particles can also be formed using other gas phase methods. Therefore, as long as the gas phase method is used, it is not limited to using a thermal plasma flame, and for example, a manufacturing method in which the primary silver particles are formed by a flame method may be used.
  • the manufacturing method of the primary silver particles using a thermal plasma flame is called a thermal plasma method.
  • the flame method is a method of synthesizing fine particles by passing a raw material containing silver through a flame using a flame as a heat source.
  • the raw material containing silver is supplied to a flame, silver particles are generated in the flame, and the growth of the silver particles is suppressed to obtain primary silver particles 15.
  • a surface treatment agent St is supplied to the primary silver particles 15 or the secondary silver particles 18 to produce silver fine particles.
  • the same surface treatment agent as that used in the thermal plasma method can be used.
  • the present invention is basically configured as described above.
  • the silver microparticles of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiment, and various improvements and modifications may of course be made within the scope of the gist of the present invention.
  • the fine silver particles of the present invention will now be described in more detail.
  • the silver fine particles of Examples 1 to 3 and conventional silver fine particles were produced.
  • the silver fine particles of Examples 1 to 3 and conventional silver fine particles were produced using a production apparatus 10 shown in Fig. 2.
  • the production conditions are as follows.
  • Example 1 silver powder having an average particle size of 15 ⁇ m was used as the raw material powder.
  • the average particle size of the silver powder was measured using a particle size distribution meter.
  • the particle size distribution meter used was MT3300 manufactured by Microtrack Bell Co., Ltd.
  • the conditions for producing the silver particles were a constant input power to the plasma of 18 kW and a fixed pressure inside the plasma torch of 60 kPa.
  • Argon gas was used as the carrier gas, and the flow rate of the argon gas was set to 5 liters/minute (standard condition conversion).
  • Argon gas and hydrogen gas were used as plasma gases, with the flow rate of the argon gas being 200 liters/minute (based on standard conditions) and the flow rate of the hydrogen gas being 5 liters/minute (based on standard conditions).
  • Argon gas was used as the temperature adjusting gas, and the flow rate of the argon gas was set to 240 liters/minute (standard state conversion).
  • citric acid was used as the organic acid. Pure water was used as the solvent, and an aqueous solution containing citric acid (citric acid concentration: 3.76 W/W%) was sprayed onto the primary fine particles of silver using a spray gas from the second supply pipe 41b (see FIG. 2) connected to the side surface 16b of the chamber 16.
  • Argon gas was used as the spray gas.
  • Example 2 was the same as Example 1 except for the following points.
  • the pressure inside the plasma torch was fixed at 85 kPa, and the flow rate of the argon gas, which was the temperature adjusting gas, was set to 15 liters/minute (standard state conversion).
  • Example 3 was the same as Example 2 except for the following: Example 3 did not use a temperature adjustment gas.
  • the input power to the plasma was kept constant at 14 kW, and the pressure inside the plasma torch was fixed at 40 kPa.
  • Argon gas was used as the carrier gas, and the flow rate of the argon gas was set to 5 liters/minute (standard condition conversion).
  • Argon gas and hydrogen gas were used as plasma gases, with the flow rate of the argon gas being 170 liters/minute (based on standard conditions) and the flow rate of the hydrogen gas being 5 liters/minute (based on standard conditions).
  • Argon gas and methane gas were used as cooling gases.
  • the flow rate of argon gas was set to 300 liters/minute (standard state conversion), and the flow rate of methane gas was set to 5.7 liters/minute (standard state conversion).
  • no temperature adjusting gas was supplied, and no organic acid was used.
  • FIG. 1 is a graph showing the particle size distribution of the silver microparticles of Examples 1 and 2 of the present invention.
  • the particle size distribution of the silver microparticles shown in Figure 3 shows the particle size distribution obtained on a volume basis.
  • reference numeral 62 indicates the cumulative distribution of particle diameters in Example 1
  • reference numeral 63 indicates the frequency distribution of particle diameters in Example 1.
  • the particle diameter measured by the BET method was 192 nm.
  • Example 3 has a low content of particles having a particle size of less than 0.1 ⁇ m (100 nm).
  • the volume resistivity before sintering was formed into a cylindrical pellet, and the volume resistivity and volume shrinkage rate after sintering in the atmosphere (i.e., in air) at a temperature of 150° C. for 1 hour were measured.
  • the results are shown in Table 1 below.
  • the composition of the atmosphere (air) was as described above.
  • Table 1 below also shows the particle sizes and the volumetric content of particles with a particle size of less than 0.1 ⁇ m (100 nm) in Examples 1 to 3.
  • the above-mentioned "conventional fine silver particles” are referred to as "conventional example.”
  • the silver particles were first pressed into a cylindrical pellet at a pressure of 127 MPa for 10 seconds using a press.
  • the pellets were placed in an electric furnace and fired in the air (atmosphere) at a temperature of 150° C. for 1 hour.
  • volume shrinkage rate 100 - ((volume after firing / volume before firing) x 100) The density was measured as follows.
  • the thickness and diameter of the cylindrical pellet before firing were measured with a vernier caliper, the mass of the pellet was measured with an electronic balance, and the density of the cylindrical pellet before firing was calculated from the volume and mass of the cylindrical pellet.
  • the thickness and diameter of the cylindrical pellet after firing were measured with a vernier caliper, the mass of the pellet was measured with an electronic balance, and the density of the cylindrical pellet after firing was calculated from the volume and mass of the cylindrical pellet after firing.
  • Fig. 4 is a schematic diagram showing an SEM image of the silver fine particles of Example 1 of the present invention
  • Fig. 5 is a schematic diagram showing an SEM image of the silver fine particles of Example 2 of the present invention
  • Fig. 6 is a schematic diagram showing an SEM image of conventional silver fine particles. 4 to 6, the silver microparticles in Examples 1 and 2 have a larger particle size than the conventional silver microparticles, and there are fewer particles with a smaller particle size. It has also been confirmed that Example 3 has a larger particle size than the conventional silver microparticles, and there are fewer particles with a smaller particle size. As shown in Table 1, the silver microparticles of Examples 1 to 3, after being molded into cylindrical pellets and fired in air at a temperature of 150°C for 1 hour, had lower volume resistivity and lower volume shrinkage rates than conventional silver microparticles.
  • Silver microparticle manufacturing equipment REFERENCE SIGNS LIST 12 plasma torch 12a quartz tube 12b high frequency oscillation coil 12c plasma gas supply port 14 material supply device 14a supply tube 15 primary fine particles 16 chamber 16a inner wall 16b side surface 18 secondary fine particles 19 cyclone 19a inlet tube 19b outer cylinder 19c truncated cone portion 19d coarse particle recovery chamber 19e inner tube 20 recovery section 20a recovery chamber 20b filter 21a, 21b connecting tube 22 plasma gas supply section 22a piping 24 thermal plasma flame 28 gas supply section 28a valve 28b first gas supply tube 28c second gas supply tube 29 vacuum pump 30 silver fine particles 40 supply section 41 valve 41a first supply tube 41b: second supply pipe; 41c: third supply pipe; 50: substrate; 52: power semiconductor element; 54: joint; St: surface treatment agent

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Abstract

Provided are silver microparticles that exhibit suppressed volumetric shrinkage and high conductivity. The particle size of the silver microparticles, as measured by the BET method, is 0.1-1 μm, and after being fired in the form of pellets in an atmosphere at a temperature of 150℃ for one hour, the volume resistivity of the silver microparticles is no more than 10 μΩ·cm and the volumetric shrinkage ratio thereof is less than 5%.

Description

銀微粒子Silver particles
　本発明は、半導体素子、高周波デバイス、発光ダイオード又は半導体レーザー等と基板等との接合、又は配線等に用いられる銀微粒子に関する。 The present invention relates to silver microparticles that are used for bonding semiconductor elements, high-frequency devices, light-emitting diodes, semiconductor lasers, etc. to substrates, etc., or for wiring, etc.
　現在、炭化珪素（ＳｉＣ）、窒化ガリウム（ＧａＮ）、酸化ガリウム、又はダイヤモンド等のワイドバンドギャップ半導体を用いたパワー半導体素子が開発されている。パワー半導体素子は、Ｓｉ又はＧａＡｓを用いた半導体素子に比べてオン抵抗が低く、高速スイッチイングさせることが可能であり、小型化もできる。しかもパワー半導体素子は、耐熱性が高く２５０～３００℃の高温でも動作が可能である。
　半導体素子と基板等との接合には、従来からはんだが利用されている。しかしながら、パワー半導体素子は、動作温度が従来のＳｉ又はＧａＡｓを用いた半導体素子に比べて高く、はんだを用いた接合では、はんだが融解しない温度で使用する必要がある。はんだを接合に用いた場合、パワー半導体素子は使用に制約を受ける。このように、接合材料についても高い温度で使用できることが要求されている。 Currently, power semiconductor elements using wide band gap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide, or diamond are being developed. Power semiconductor elements have a lower on-resistance than semiconductor elements using Si or GaAs, can be switched at high speed, and can be made smaller. Moreover, power semiconductor elements have high heat resistance and can operate at high temperatures of 250 to 300°C.
Solder has been used conventionally to bond semiconductor elements to substrates and the like. However, power semiconductor elements have a higher operating temperature than conventional semiconductor elements using Si or GaAs, and when solder is used for bonding, the elements must be used at a temperature at which the solder does not melt. When solder is used for bonding, the power semiconductor elements are subject to restrictions on their use. Thus, bonding materials are also required to be able to be used at high temperatures.
　例えば、特許文献１には、共晶ＡｕＧｅはんだを用いて、ＳｉＣ半導体素子を接合することが記載されている。
　はんだ以外に、接合材料として、特許文献２に、低温焼結性銀微粒子及び熱硬化型バインダを含み、熱硬化型バインダが、（Ｂ１）フタル酸ジグリシジルエステル、テトラヒドロフタル酸ジグリシジルエステル、ヘキサヒドロフタル酸ジグリシジルエステル及びそれらのＣ１～Ｃ４アルキル置換体からなる群より選択される少なくとも１種のエポキシ樹脂、並びに（Ｂ２）カチオン重合開始剤、アミン系硬化剤及び酸無水物硬化剤からなる群より選択される少なくとも１種の硬化剤からなり、銀微粒子１００質量部に対して、熱硬化型バインダが２～７質量部である熱伝導性ペーストが記載されている。 For example, Patent Document 1 describes bonding of SiC semiconductor elements using eutectic AuGe solder.
In addition to solder, Patent Document 2 describes a thermally conductive paste as a joining material that contains low-temperature sinterable silver fine particles and a thermosetting binder, in which the thermosetting binder is composed of (B1) at least one epoxy resin selected from the group consisting of phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and C1-C4 alkyl substituted derivatives thereof, and (B2) at least one curing agent selected from the group consisting of a cationic polymerization initiator, an amine-based curing agent, and an acid anhydride curing agent, and in which the thermosetting binder is present in an amount of 2 to 7 parts by mass per 100 parts by mass of the silver fine particles.
特許第５８５６３１４号公報Patent No. 5856314 特許第６３４３０４１号公報Patent No. 6343041
　上述のように、特許文献１のようにＡｕＧｅはんだを用いた場合、熱膨張係数が大きく、パワー半導体素子の動作に伴う温度変化により体積が変動してクラック等が生じ、十分な接合状態が維持できない。また、ＡｕＧｅはんだは、銅又は銀等に比べて融点が低く、耐熱性も十分ではない。
　特許文献２のように熱硬化型バインダを含有する場合、体積収縮率は小さくできるが、体積抵抗値が大きく、導電性が十分ではない。
　このように、接合材料として、耐熱性を満足しつつ、導電性が優れたものがないが現状である。 As described above, when AuGe solder is used as in Patent Document 1, the thermal expansion coefficient is large, and the volume fluctuates due to temperature changes accompanying the operation of the power semiconductor element, causing cracks and the like, making it impossible to maintain a sufficient bonding state. In addition, AuGe solder has a lower melting point than copper or silver, and does not have sufficient heat resistance.
When a thermosetting binder is contained as in Patent Document 2, the volume shrinkage rate can be reduced, but the volume resistivity is high and the electrical conductivity is insufficient.
Thus, at present, there is no bonding material that satisfies heat resistance and has excellent electrical conductivity.
　本発明の目的は、体積収縮を抑制し、かつ導電性が高い銀微粒子を提供することにある。 The object of the present invention is to provide silver microparticles that suppress volumetric shrinkage and have high electrical conductivity.
　上述の目的を達成するために、本発明の一態様は、ＢＥＴ法により測定された粒径が０．１μｍ以上１μｍ以下であり、ペレットの状態で大気中において温度１５０℃で１時間焼成した後の体積抵抗値が１０μΩ・ｃｍ以下、かつ体積収縮率が５％未満である、銀微粒子を提供するものである。
　粒径が０．１μｍ未満の粒子の含有割合が、体積基準で４０％以下であることが好ましい。なお、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で３５％以下であることがより好ましく、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で５％以下であることがさらに好ましい。 In order to achieve the above-mentioned object, one aspect of the present invention provides fine silver particles having a particle size of 0.1 μm or more and 1 μm or less as measured by the BET method, a volume resistivity of 10 μΩ·cm or less after being fired in the form of a pellet in air at a temperature of 150° C. for 1 hour, and a volume shrinkage rate of less than 5%.
The content of particles having a particle size of less than 0.1 μm is preferably 40% or less by volume. It is more preferable that the content of particles having a particle size of less than 0.1 μm is 35% or less by volume, and further more preferable that the content of particles having a particle size of less than 0.1 μm is 5% or less by volume.
　本発明によれば、体積収縮を抑制し、かつ導電性が高い銀微粒子を提供できる。 The present invention provides silver microparticles that suppress volumetric shrinkage and have high electrical conductivity.
本発明の銀微粒子の利用形態の一例を示す模式図である。FIG. 1 is a schematic diagram showing an example of a usage form of the silver fine particles of the present invention. 本発明の銀微粒子の製造装置の一例を示す模式図である。FIG. 1 is a schematic diagram showing an example of an apparatus for producing fine silver particles of the present invention. 本発明の実施例１、２の銀微粒子の粒度分布を示すグラフである。1 is a graph showing the particle size distribution of fine silver particles in Examples 1 and 2 of the present invention. 本発明の実施例１の銀微粒子のＳＥＭ像を示す模式図である。FIG. 2 is a schematic diagram showing an SEM image of the silver fine particles of Example 1 of the present invention. 本発明の実施例２の銀微粒子のＳＥＭ像を示す模式図である。FIG. 2 is a schematic diagram showing an SEM image of the silver fine particles of Example 2 of the present invention. 従来の銀微粒子のＳＥＭ像を示す模式図である。FIG. 1 is a schematic diagram showing an SEM image of conventional silver fine particles.
　以下に、添付の図面に示す好適実施形態に基づいて、本発明の銀微粒子を詳細に説明する。
　なお、以下に説明する図は、本発明を説明するための例示的なものであり、以下に示す図に本発明が限定されるものではない。
　以下、銀微粒子について説明する。 The silver particles of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.
It should be noted that the drawings described below are illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below.
The silver particles will now be described.
［銀微粒子］
　銀微粒子は、ＢＥＴ法により測定された粒径が０．１μｍ以上１μｍ以下であり、ペレットの状態で大気中において温度１５０℃で１時間焼成した後の体積抵抗値が１０μΩ・ｃｍ以下、かつ体積収縮率が５％未満である。
　本発明において、大気中とは、一般に空気中と呼ばれる雰囲気のことである。大気中のことを、大気雰囲気ともいう。空気の組成は、窒素７８．０８体積％、酸素２０．９５体積％、アルゴン０．９３体積％、二酸化炭素０．０３体積％である。なお、空気の組成に対して一般的な測定誤差は許容される。
　粒径が０．１μｍ未満の粒子の含有割合が、体積基準で４０％以下であることが好ましい。なお、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で３５％以下であることがより好ましく、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で５％以下であることがさらに好ましい。また、粒径が０．１μｍ未満の粒子の含有割合の下限値は、体積基準で０％である。
　また、銀微粒子の粒径は、ペレットの状態で大気中（すなわち、空気中）において温度１５０℃で１時間焼成した後の体積収縮率が小さくなることから、１００～４００ｎｍが好ましく、２００ｎｍ～４００ｎｍがさらに好ましい。
　銀微粒子のＢＥＴ法により測定された粒径とは、ＢＥＴ法を用いて測定された平均粒子径である。ＢＥＴ法では、粒子が球形であることを仮定して比表面積から算出している。
　銀微粒子は、溶媒内等に分散されている状態ではなく、溶媒等がない銀微粒子単独で存在する。このため、銀微粒子を利用する場合、銀微粒子だけで焼成体を得ることができる。
　また、銀微粒子を溶媒と組み合わせて使用する場合、銀微粒子と溶媒との組合せも特に限定されるものではなく、溶媒の選択の自由度が高い。 [Silver particles]
The silver microparticles have a particle size measured by the BET method of 0.1 μm or more and 1 μm or less, and after being fired in the form of a pellet in air at a temperature of 150° C. for 1 hour, the volume resistivity is 10 μΩ·cm or less, and the volume shrinkage rate is less than 5%.
In the present invention, the atmosphere refers to an atmosphere generally called air. The atmosphere is also called the air atmosphere. The composition of air is 78.08 vol% nitrogen, 20.95 vol% oxygen, 0.93 vol% argon, and 0.03 vol% carbon dioxide. Note that a general measurement error is allowed for the composition of air.
The content of particles having a particle size of less than 0.1 μm is preferably 40% or less by volume. It is more preferable that the content of particles having a particle size of less than 0.1 μm is 35% or less by volume, and it is even more preferable that the content of particles having a particle size of less than 0.1 μm is 5% or less by volume. The lower limit of the content of particles having a particle size of less than 0.1 μm is 0% by volume.
The particle size of the silver particles is preferably 100 to 400 nm, and more preferably 200 to 400 nm, because this reduces the volumetric shrinkage rate after baking in the pellet state in the atmosphere (i.e., in air) at a temperature of 150° C. for 1 hour.
The particle size of the silver particles measured by the BET method is the average particle size measured by the BET method, which is calculated from the specific surface area on the assumption that the particles are spherical.
The silver fine particles are not dispersed in a solvent or the like, but exist alone without the presence of a solvent, etc. Therefore, when using silver fine particles, a fired body can be obtained using only the silver fine particles.
Furthermore, when silver particles are used in combination with a solvent, the combination of silver particles and a solvent is not particularly limited, and there is a high degree of freedom in the selection of the solvent.
　体積抵抗値としては、９μΩ・ｃｍ以下であることが好ましく、８μΩ・ｃｍ以下であることがより好ましく、７μΩ・ｃｍ以下であることが最も好ましい。また、体積抵抗値の下限値は、１．４７μΩ・ｃｍである。
　また、体積収縮率としては、３％以下であることが好ましく、１％以下であることがより好ましく、０％であることが最も好ましい。また、体積収縮率の下限値は、０％である。
　また、銀微粒子は、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で４０％以下であると、焼成後にクラックが発生することが抑制されるため、好ましい。
　銀微粒子において、粒径が０．１μｍ未満の粒子の含有割合は、銀微粒子のＳＥＭ（走査電子顕微鏡）像を取得し、ＳＥＭ像を画像解析することによって得られた体積基準の粒度分布から求める。すなわち、粒径が０．１μｍ未満の粒子の含有割合は、銀微粒子全体の体積に対する割合として求められる。 The volume resistivity is preferably 9 μΩ·cm or less, more preferably 8 μΩ·cm or less, and most preferably 7 μΩ·cm or less. The lower limit of the volume resistivity is 1.47 μΩ·cm.
The volumetric shrinkage is preferably 3% or less, more preferably 1% or less, and most preferably 0%. The lower limit of the volumetric shrinkage is 0%.
In addition, it is preferable that the content of silver particles having a particle size of less than 0.1 μm is 40% or less by volume, since this suppresses the occurrence of cracks after firing.
The content of particles having a particle size of less than 0.1 μm in the silver microparticles is determined from a volume-based particle size distribution obtained by acquiring a scanning electron microscope (SEM) image of the silver microparticles and performing image analysis on the SEM image. In other words, the content of particles having a particle size of less than 0.1 μm is determined as a percentage of the total volume of the silver microparticles.
　焼成については、銀微粒子を円筒状のペレットに成形し、ペレットを電気炉内に設置し、大気中において温度１５０℃で１時間焼成する。
　ペレットは、銀微粒子をプレス機を用いて、圧力１２７ＭＰａで１０秒間保持して作製する。
　体積抵抗値は、ペレットを用いて四端子法にて測定して得られた値である。例えば、測定装置には三菱化学株式会社製ロレスタEP(MCP-T360)が用いられる。焼成の前後でペレットの体積抵抗値を測定することにより、焼成後の体積抵抗値の変化を測定できる。 For the firing, the silver particles are formed into a cylindrical pellet, which is placed in an electric furnace and fired in the atmosphere at a temperature of 150° C. for one hour.
The pellets are prepared by pressing the silver particles at a pressure of 127 MPa for 10 seconds using a press.
The volume resistivity is a value obtained by measuring the pellets by the four-terminal method. For example, a measuring device such as Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation is used. By measuring the volume resistivity of the pellets before and after firing, the change in the volume resistivity after firing can be measured.
　体積収縮率は、銀微粒子を、上述のようにプレス機を用いて、圧力１２７ＭＰａで１０秒間保持して円筒状のペレットを作製し、円筒状のペレットの厚みと直径をノギスにて測定し、焼成前後のペレットの体積から算出した値である。体積収縮率は、下記式により得られる。また、ペレットの焼成には電気炉を用いる。
体積収縮率（％）＝１００－（（焼成後の体積／焼成前の体積）×１００） The volumetric shrinkage rate was calculated by forming a cylindrical pellet from the silver fine particles using a press machine as described above, holding the silver fine particles at a pressure of 127 MPa for 10 seconds, measuring the thickness and diameter of the cylindrical pellet with a vernier caliper, and calculating the volume of the pellet before and after firing. The volumetric shrinkage rate is calculated using the following formula. An electric furnace is used to fire the pellets.
Volume shrinkage rate (%) = 100 - ((volume after firing / volume before firing) x 100)
　銀微粒子は、ＢＥＴ法により測定された粒径が０．１μｍ以上１μｍ以下であり、ペレットの状態で大気中において温度１５０℃で１時間焼成した後の体積抵抗値が１０μΩ・ｃｍ以下、かつ体積収縮率が５％未満であることにより、体積収縮を抑制し、かつ導電性が高い。また、銀微粒子は、はんだ等に比べて融点が高く、耐熱性も優れる。このため、銀微粒子を接合材料に用いた場合、耐熱性を満足しつつ、導電性が優れたものとすることができる。
　また、粒径が０．１μｍ未満の粒子の含有割合が、体積基準で４０％以下であると、粒径が大きなものが揃うため、銀微粒子の焼成後に、体積が収縮することを更に抑制できるため、好ましい。 The silver microparticles have a particle size of 0.1 μm or more and 1 μm or less as measured by the BET method, and have a volume resistivity of 10 μΩ·cm or less after being fired in the form of pellets in the air at a temperature of 150° C. for 1 hour, and a volume shrinkage rate of less than 5%, thereby suppressing volume shrinkage and providing high electrical conductivity. In addition, the silver microparticles have a higher melting point and superior heat resistance than solder, etc. Therefore, when the silver microparticles are used as a bonding material, it is possible to provide a material with excellent electrical conductivity while satisfying heat resistance.
Furthermore, if the content of particles with a particle size of less than 0.1 μm is 40% or less on a volume basis, the particles will all have a large particle size, which is preferable because it further suppresses volume shrinkage after firing of the silver microparticles.
　図１は本発明の銀微粒子の利用形態の一例を示す模式図である。
　銀微粒子は、例えば、図１に示す基板５０とパワー半導体素子５２との接合に利用される。銀微粒子は、ダイアタッチメントに利用される。
　銀微粒子は、基板５０とパワー半導体素子５２とを接合する接合部５４を構成する。接合部５４は、銀微粒子を、例えば、温度１５０℃で１時間、大気中で焼成することにより形成される。接合部５４により、基板５０とパワー半導体素子５２とが接合され、基板５０とパワー半導体素子５２とが物理的に固定される。
　銀微粒子は、融点が、はんだ及び樹脂に比して高く耐熱性が高い。また、銀微粒子は、上述のようにペレットの状態で大気中において温度１５０℃で１時間焼成した後の体積抵抗値が１０μΩ・ｃｍ以下、かつ体積収縮率が５％未満である。このことから、パワー半導体素子５２の動作に伴い温度変化が生じても接合部５４は体積変動が小さく、クラックの発生等が抑制される。これにより、接合が維持され、高い耐久性も得られる。また、銀微粒子は、焼成後の体積抵抗値が低いため、熱伝導性も優れ、接合部５４により、パワー半導体素子５２で発生した熱を基板５０に効率良く伝導できる。
　基板５０は、例えば、Ｓｉ３Ｎ４等のセラミックス基板に銅配線が設けられたものである。
　パワー半導体素子５２は、例えば、炭化珪素（ＳｉＣ）、窒化ガリウム（ＧａＮ）、酸化ガリウム、又はダイヤモンド等の半導体を用いた半導体素子である。
　なお、銀微粒子は、パワー半導体素子５２との接合に限定されるものではなく、高周波デバイス、発光ダイオード又は半導体レーザー等の接合にも利用できる。銀微粒子は、上述のように熱伝導性が優れており、発熱量が多いもの、動作温度が高いものとの接合に好適である。
　また、銀微粒子は、接合以外に、信号配線、及び導電配線等の各種の配線にも利用できる。 FIG. 1 is a schematic diagram showing an example of a form of use of the silver fine particles of the present invention.
The silver particles are used, for example, for bonding a substrate 50 and a power semiconductor element 52 shown in Fig. 1. The silver particles are used for die attachment.
The silver particles constitute a joint 54 that joins the substrate 50 and the power semiconductor element 52. The joint 54 is formed by baking the silver particles in air, for example, at a temperature of 150° C. for one hour. The joint 54 joins the substrate 50 and the power semiconductor element 52, and physically fixes the substrate 50 and the power semiconductor element 52 together.
The silver microparticles have a higher melting point and higher heat resistance than solder and resin. As described above, the silver microparticles have a volume resistivity of 10 μΩ·cm or less and a volume shrinkage rate of less than 5% after being baked in the form of pellets at a temperature of 150° C. for 1 hour in the atmosphere. Therefore, even if a temperature change occurs due to the operation of the power semiconductor element 52, the volume fluctuation of the joint 54 is small, and the occurrence of cracks is suppressed. This maintains the bond and provides high durability. In addition, the silver microparticles have a low volume resistivity after baking, and therefore have excellent thermal conductivity, and the joint 54 can efficiently conduct the heat generated by the power semiconductor element 52 to the substrate 50.
The substrate 50 is, for example, a ceramic substrate such as Si 3 N 4 on which copper wiring is provided.
The power semiconductor element 52 is a semiconductor element using a semiconductor such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide, or diamond.
The silver particles can be used not only for bonding to the power semiconductor element 52 but also for bonding to high-frequency devices, light-emitting diodes, semiconductor lasers, etc. As described above, the silver particles have excellent thermal conductivity and are suitable for bonding to objects that generate a large amount of heat or have a high operating temperature.
In addition to bonding, the silver particles can also be used for various wiring such as signal wiring and conductive wiring.
［銀微粒子の製造方法］
　次に、銀微粒子の製造方法の一例について、図２に基づいて説明するが、本発明の銀微粒子の製造方法は、図２に示す銀微粒子の製造装置を用いた製造方法に限定されない。
　図２は本発明の銀微粒子の製造装置の一例を示す模式図である。
　図２に示す銀微粒子の製造装置１０（以下、単に製造装置１０という）により、上述の銀微粒子を得ることができる。 [Method of manufacturing silver particles]
Next, an example of a method for producing fine silver particles will be described with reference to FIG. 2. However, the method for producing fine silver particles of the present invention is not limited to a production method using the fine silver particle production apparatus shown in FIG.
FIG. 2 is a schematic diagram showing an example of an apparatus for producing fine silver particles of the present invention.
The above-mentioned fine silver particles can be obtained by the fine silver particle manufacturing apparatus 10 shown in FIG. 2 (hereinafter simply referred to as the manufacturing apparatus 10).
　製造装置１０は、熱プラズマ炎を発生させるプラズマトーチ１２と、銀微粒子の原料粉末をプラズマトーチ１２内へ供給する材料供給装置１４と、銀の１次微粒子１５を生成させるための冷却槽としての機能を有するチャンバ１６と、銀の１次微粒子１５から任意に規定された粒径以上の粒径を有する粗大粒子を除去するサイクロン１９と、サイクロン１９により分級された所望の粒径を有する銀の２次微粒子１８を回収する回収部２０とを有する。チャンバ１６とサイクロン１９とは接続管２１ａにより接続されている。また、サイクロン１９と回収部２０とは、内管１９ｅに接続された接続管２１ｂにより接続されている。
　製造装置１０は、さらに、銀の１次微粒子１５又は銀の２次微粒子１８に表面処理剤を供給する供給部４０とを有する。
　銀の１次微粒子１５及び銀の２次微粒子１８は、いずれも本発明の微粒子の製造途中の微粒子体である。銀の１次微粒子１５又は銀の２次微粒子１８を表面処理して得られたもの、すなわち、表面処理された銀微粒子３０が本発明の微粒子である。
　材料供給装置１４、チャンバ１６、サイクロン１９、回収部２０については、例えば、特開２００７－１３８２８７号公報の各種装置を用いることができる。 The manufacturing apparatus 10 includes a plasma torch 12 that generates a thermal plasma flame, a material supply device 14 that supplies raw powder of silver particles into the plasma torch 12, a chamber 16 that functions as a cooling tank for generating primary silver particles 15, a cyclone 19 that removes coarse particles having a particle size equal to or larger than an arbitrarily specified particle size from the primary silver particles 15, and a recovery section 20 that recovers secondary silver particles 18 having a desired particle size classified by the cyclone 19. The chamber 16 and the cyclone 19 are connected by a connection pipe 21a. The cyclone 19 and the recovery section 20 are also connected by a connection pipe 21b that is connected to an inner pipe 19e.
The manufacturing apparatus 10 further includes a supply section 40 that supplies a surface treatment agent to the primary silver particles 15 or the secondary silver particles 18 .
The primary silver particles 15 and the secondary silver particles 18 are both particulate bodies in the process of producing the particles of the present invention. The particles obtained by surface-treating the primary silver particles 15 or the secondary silver particles 18, i.e., the surface-treated silver particles 30, are the particles of the present invention.
For the material supply device 14, chamber 16, cyclone 19, and recovery section 20, various devices described in, for example, JP 2007-138287 A can be used.
　本実施形態において、微粒子の製造には、原料として、例えば、銀の粉末が用いられる。
　銀の粉末は、熱プラズマ炎中で容易に蒸発するように、その平均粒径が適宜設定される。銀の粉末の平均粒径は、レーザー回折法を用いて測定されたものであり、例えば、１００μｍ以下であり、好ましくは５０μｍ以下、さらに好ましくは１５μｍ以下である。 In this embodiment, for example, silver powder is used as a raw material for producing the fine particles.
The average particle size of the silver powder is appropriately set so that it can be easily evaporated in the thermal plasma flame. The average particle size of the silver powder is measured using a laser diffraction method and is, for example, 100 μm or less, preferably 50 μm or less, and more preferably 15 μm or less.
　プラズマトーチ１２は、石英管１２ａと、その外側を取り巻く高周波発振用コイル１２ｂとで構成されている。プラズマトーチ１２の上部には微粒子の原料粉末をプラズマトーチ１２内に供給するための後述する供給管１４ａがその中央部に設けられている。プラズマガス供給口１２ｃが、供給管１４ａの周辺部（同一円周上）に形成されており、プラズマガス供給口１２ｃはリング状である。高周波発振用コイル１２ｂには高周波電圧を発生する電源（図示せず）が接続されている。高周波発振用コイル１２ｂに高周波電圧が印加されると熱プラズマ炎２４が発生する。熱プラズマ炎２４により、原料（図示せず）が蒸発し、気相状態の混合物になる。プラズマトーチ１２が、気相法を用いて原料を気相状態の混合物にする処理部である。 The plasma torch 12 is composed of a quartz tube 12a and a high-frequency oscillation coil 12b that surrounds it. A supply tube 14a (described later) is provided in the center of the upper part of the plasma torch 12 for supplying fine particle raw material powder into the plasma torch 12. A plasma gas supply port 12c is formed on the periphery (on the same circumference) of the supply tube 14a, and the plasma gas supply port 12c is ring-shaped. A power source (not shown) that generates a high-frequency voltage is connected to the high-frequency oscillation coil 12b. When a high-frequency voltage is applied to the high-frequency oscillation coil 12b, a thermal plasma flame 24 is generated. The raw material (not shown) is evaporated by the thermal plasma flame 24, becoming a gas-phase mixture. The plasma torch 12 is a processing section that uses a gas-phase method to turn the raw material into a gas-phase mixture.
　プラズマガス供給部２２は、プラズマガスをプラズマトーチ１２内に供給するものである。プラズマガス供給部２２は配管２２ａを介してプラズマガス供給口１２ｃに接続されている。プラズマガス供給部２２は図示はしないが供給量を調整するためのバルブ等の供給量調整部が設けられている。プラズマガスは、プラズマガス供給部２２からリング状のプラズマガス供給口１２ｃを経て、矢印Ｐで示す方向と矢印Ｓで示す方向からプラズマトーチ１２内に供給される。 The plasma gas supply unit 22 supplies plasma gas into the plasma torch 12. The plasma gas supply unit 22 is connected to the plasma gas supply port 12c via piping 22a. Although not shown, the plasma gas supply unit 22 is provided with a supply amount adjustment unit such as a valve for adjusting the supply amount. The plasma gas is supplied from the plasma gas supply unit 22 through the ring-shaped plasma gas supply port 12c into the plasma torch 12 in the directions indicated by arrows P and S.
　プラズマガスには、例えば、水素ガスとアルゴンガスとの混合ガスが用いられる。この場合、プラズマガス供給部２２に、水素ガスと、アルゴンガスとが貯蔵される。プラズマガス供給部２２から水素ガス、及びアルゴンガスが配管２２ａを介してプラズマガス供給口１２ｃを経て、矢印Ｐで示す方向と矢印Ｓで示す方向からプラズマトーチ１２内に供給される。なお、矢印Ｐで示す方向にはアルゴンガスだけを供給してもよい。
　また、プラズマガスには、銀微粒子に応じたものが用いられるため、上述のようにプラズマガスに混合ガスを用いることは必須ではなく、プラズマガスとしては１種のガスでもよい。
　高周波発振用コイル１２ｂに高周波電圧が印加されると、プラズマトーチ１２内で熱プラズマ炎２４が発生する。 The plasma gas used is, for example, a mixed gas of hydrogen gas and argon gas. In this case, hydrogen gas and argon gas are stored in the plasma gas supply unit 22. Hydrogen gas and argon gas are supplied from the plasma gas supply unit 22 through the piping 22a and the plasma gas supply port 12c into the plasma torch 12 in the directions indicated by the arrows P and S. It is noted that only argon gas may be supplied in the direction indicated by the arrow P.
Furthermore, since a plasma gas appropriate for the silver particles is used, it is not essential to use a mixed gas as the plasma gas as described above, and a single type of gas may be used as the plasma gas.
When a high-frequency voltage is applied to the high-frequency oscillation coil 12 b , a thermal plasma flame 24 is generated within the plasma torch 12 .
　熱プラズマ炎２４の温度は、原料粉末の沸点よりも高い必要がある。一方、熱プラズマ炎２４の温度が高いほど、容易に原料粉末が気相状態となるので好ましいが、特に温度は限定されるものではない。例えば、熱プラズマ炎２４の温度を６０００℃とすることもできるし、理論上は１００００℃程度に達するものと考えられる。
　また、プラズマトーチ１２内における圧力雰囲気は、大気圧以下であることが好ましい。ここで、大気圧以下の雰囲気については、特に限定されないが、例えば、０．５～１００ｋＰａである。 The temperature of the thermal plasma flame 24 must be higher than the boiling point of the raw material powder. On the other hand, the higher the temperature of the thermal plasma flame 24, the easier it is for the raw material powder to become in a gaseous state, so this is preferable, but the temperature is not particularly limited. For example, the temperature of the thermal plasma flame 24 can be set to 6000°C, and theoretically it is thought to reach about 10000°C.
The pressure atmosphere in the plasma torch 12 is preferably equal to or lower than atmospheric pressure. The pressure atmosphere is not particularly limited, but is, for example, 0.5 to 100 kPa.
　なお、石英管１２ａの外側は、同心円状に形成された管（図示されていない）で囲まれており、この管と石英管１２ａとの間に冷却水を循環させて石英管１２ａを水冷し、プラズマトーチ１２内で発生した熱プラズマ炎２４により石英管１２ａが高温になりすぎるのを防止している。 The outside of the quartz tube 12a is surrounded by a concentric tube (not shown), and cooling water is circulated between this tube and the quartz tube 12a to water-cool the quartz tube 12a and prevent the quartz tube 12a from becoming too hot due to the thermal plasma flame 24 generated inside the plasma torch 12.
　材料供給装置１４は、供給管１４ａを介してプラズマトーチ１２の上部に接続されている。材料供給装置１４は、原料をプラズマトーチ１２内の熱プラズマ炎２４中に供給するものである。
　材料供給装置１４は、原料を熱プラズマ炎２４中に供給することができれば、特に限定されるものではなく、例えば、原料を粒子状に分散させた状態で熱プラズマ炎２４中に供給する。 The material supply device 14 is connected to the upper part of the plasma torch 12 via a supply pipe 14a. The material supply device 14 supplies raw material into a thermal plasma flame 24 in the plasma torch 12.
The material supply device 14 is not particularly limited as long as it can supply the raw material into the thermal plasma flame 24. For example, the raw material is supplied into the thermal plasma flame 24 in a particulate dispersed state.
　原料が粉末の場合、例えば、銀の粉末を、粉末の形態で供給する材料供給装置１４としては、上述のように、例えば、特開２００７－１３８２８７号公報に開示されているものを用いることができる。この場合、材料供給装置１４は、例えば、原料を貯蔵する貯蔵槽（図示せず）と、原料を定量搬送するスクリューフィーダ（図示せず）と、スクリューフィーダで搬送された原料が最終的に散布される前に、これを一次粒子の状態に分散させる分散部（図示せず）と、キャリアガス供給源（図示せず）とを有する。 When the raw material is a powder, for example, the material supply device 14 that supplies silver powder in powder form can be, as described above, for example, the one disclosed in JP 2007-138287 A. In this case, the material supply device 14 has, for example, a storage tank (not shown) for storing the raw material, a screw feeder (not shown) for transporting a fixed amount of the raw material, a dispersion section (not shown) for dispersing the raw material transported by the screw feeder into primary particles before it is finally sprayed, and a carrier gas supply source (not shown).
　キャリアガス供給源から押出し圧力がかけられたキャリアガスとともに原料は供給管１４ａを介してプラズマトーチ１２内の熱プラズマ炎２４中へ供給される。
　材料供給装置１４は、原料の凝集を防止し、分散状態を維持したまま、原料をプラズマトーチ１２内に散布することができるものであれば、その構成は特に限定されるものではない。キャリアガスには、例えば、アルゴンガス等の不活性ガスが用いられる。キャリアガス流量は、例えば、フロート式流量計等の流量計を用いて制御することができる。また、キャリアガスの流量値とは、流量計の目盛り値のことである。 The raw material is supplied together with carrier gas under extrusion pressure from a carrier gas supply source through a supply pipe 14a into a thermal plasma flame 24 in the plasma torch 12.
The configuration of the material supply device 14 is not particularly limited as long as it can prevent the raw material from agglomerating and can disperse the raw material into the plasma torch 12 while maintaining the raw material in a dispersed state. For example, an inert gas such as argon gas is used as the carrier gas. The flow rate of the carrier gas can be controlled using a flow meter such as a float type flow meter. The flow rate value of the carrier gas refers to the scale value of the flow meter.
　チャンバ１６は、プラズマトーチ１２の下方に隣接して設けられており、チャンバ１６内で、冷却ガスを用いることなく、上述の気相状態の混合物から、微粒子体である銀の１次微粒子１５が生成される。チャンバ１６は冷却槽として機能するものである。なお、冷却ガスは、急冷ガスとも呼ばれるものであり、アルゴンガス等が用いられる。 The chamber 16 is provided adjacent to and below the plasma torch 12, and within the chamber 16, primary silver particles 15, which are fine particles, are generated from the gaseous mixture described above without using a cooling gas. The chamber 16 functions as a cooling tank. The cooling gas is also called a quenching gas, and argon gas or the like is used.
　気体供給部２８は、例えば、接続管２１ａ内又は接続管２１ｂ内に、不活性ガスを含む温度調整ガスを供給するものである。気体供給部２８は、銀の１次微粒子１５又は銀の２次微粒子１８に不活性ガスを含む温度調整ガスを供給する。
　気体供給部２８は、例えば、バルブ２８ａと、バルブ２８ａに接続された第１の気体供給管２８ｂと第２の気体供給管２８ｃとを有する。第１の気体供給管２８ｂは接続管２１ａに接続され、第２の気体供給管２８ｃは接続管２１ｂに接続されている。
　バルブ２８ａを切換えることにより第１の気体供給管２８ｂ又は第２の気体供給管２８ｃのいずれかに温度調整ガスが供給され、接続管２１ａ内又は接続管２１ｂ内に温度調整ガスが供給される。 The gas supply unit 28 supplies a temperature control gas containing an inert gas, for example, into the connecting pipe 21 a or the connecting pipe 21 b. The gas supply unit 28 supplies the temperature control gas containing an inert gas to the silver primary particles 15 or the silver secondary particles 18.
The gas supply unit 28 includes, for example, a valve 28a, and a first gas supply pipe 28b and a second gas supply pipe 28c connected to the valve 28a. The first gas supply pipe 28b is connected to the connecting pipe 21a, and the second gas supply pipe 28c is connected to the connecting pipe 21b.
By switching the valve 28a, the temperature regulating gas is supplied to either the first gas supply pipe 28b or the second gas supply pipe 28c, and the temperature regulating gas is supplied into the connecting pipe 21a or the connecting pipe 21b.
　気体供給部２８は、さらに第１の気体供給管２８ｂ又は第２の気体供給管２８ｃに供給する温度調整ガスに押出し圧力をかけるコンプレッサ、又はブロア等の圧力付与装置（図示せず）を有する。
　また、気体供給部２８は、温度調整ガスを貯蔵する貯蔵部（図示せず）と、ガス供給量を制御する圧力制御弁とを有する。温度調整ガスは、例えば、アルゴンガスである。
　気体供給部２８から接続管２１ａ内又は接続管２１ｂ内に供給される温度調整ガスにより、所望のガス温度に調整することができる。 The gas supply unit 28 further includes a pressure applying device (not shown), such as a compressor or a blower, that applies extrusion pressure to the temperature adjustment gas supplied to the first gas supply pipe 28b or the second gas supply pipe 28c.
The gas supply unit 28 also includes a storage unit (not shown) for storing a temperature adjusting gas, and a pressure control valve for controlling the amount of gas supplied. The temperature adjusting gas is, for example, argon gas.
The gas temperature can be adjusted to a desired temperature by the temperature adjusting gas supplied from the gas supply unit 28 into the connecting pipe 21a or the connecting pipe 21b.
　図２に示すように、チャンバ１６には、銀の１次微粒子１５を所望の粒径で分級するためのサイクロン１９が設けられている。このサイクロン１９は、チャンバ１６から１次微粒子１５を供給する入口管１９ａと、この入口管１９ａと接続され、サイクロン１９の上部に位置する円筒形状の外筒１９ｂと、この外筒１９ｂ下部から下側に向かって連続し、かつ、径が漸減する円錐台部１９ｃと、この円錐台部１９ｃ下側に接続され、上述の所望の粒径以上の粒径を有する粗大粒子を回収する粗大粒子回収チャンバ１９ｄと、後に詳述する回収部２０に接続され、外筒１９ｂに突設される内管１９ｅとを備えている。チャンバ１６と入口管１９ａとは接続管２１ａにより接続されており、１次微粒子１５は接続管２１ａを通ってサイクロン１９に移動する。接続管２１ａは１次微粒子１５の搬送路である。 As shown in FIG. 2, the chamber 16 is provided with a cyclone 19 for classifying the primary silver particles 15 into the desired particle size. The cyclone 19 is provided with an inlet pipe 19a for supplying the primary particles 15 from the chamber 16, a cylindrical outer tube 19b connected to the inlet pipe 19a and located at the top of the cyclone 19, a truncated cone section 19c that continues downward from the bottom of the outer tube 19b and has a gradually decreasing diameter, a coarse particle recovery chamber 19d connected to the bottom of the truncated cone section 19c for recovering coarse particles having a particle size equal to or larger than the desired particle size, and an inner tube 19e connected to the recovery section 20 described later and protruding from the outer tube 19b. The chamber 16 and the inlet pipe 19a are connected by a connecting pipe 21a, and the primary particles 15 move to the cyclone 19 through the connecting pipe 21a. The connecting pipe 21a is a transport path for the primary particles 15.
　サイクロン１９の入口管１９ａから、１次微粒子１５を含んだ気流が、外筒１９ｂ内周壁に沿って吹き込まれ、これにより、この気流が図２中に矢印Ｔで示すように外筒１９ｂの内周壁から円錐台部１９ｃ方向に向かって流れることで下降する旋回流が形成される。
　そして、上述の下降する旋回流が反転し、上昇流になったとき、遠心力と抗力のバランスにより、粗大粒子は、上昇流にのることができず、円錐台部１９ｃ側面に沿って下降し、粗大粒子回収チャンバ１９ｄで回収される。また、遠心力よりも抗力の影響をより受けた微粒子は、円錐台部１９ｃ内壁での上昇流とともに内管１９ｅ及び接続管２１ｂを経てサイクロン１９外に排出される。 An airflow containing the primary fine particles 15 is blown from the inlet pipe 19a of the cyclone 19 along the inner wall of the outer cylinder 19b, and as a result, this airflow flows from the inner wall of the outer cylinder 19b toward the truncated cone portion 19c as shown by the arrow T in Figure 2, forming a downward swirling flow.
When the descending swirling flow reverses and becomes an ascending flow, the coarse particles cannot ride on the ascending flow due to the balance between the centrifugal force and the drag force, and so they descend along the side surface of the truncated cone portion 19c and are collected in the coarse particle collection chamber 19d. Furthermore, fine particles that are more affected by the drag force than the centrifugal force are discharged together with the ascending flow on the inner wall of the truncated cone portion 19c through the inner pipe 19e and the connecting pipe 21b to the outside of the cyclone 19.
　また、内管１９ｅ及び接続管２１ｂを通して、後に詳述する回収部２０から負圧（吸引力）が生じるようになっている。そして、この負圧（吸引力）によって、上述の旋回する気流から分離した微粒子が、符号Ｕで示すように吸引され、内管１９ｅ及び接続管２１ｂを通して回収部２０に送られるようになっている。 Also, a negative pressure (suction force) is generated from the collection section 20, which will be described in detail later, through the inner tube 19e and the connecting tube 21b. This negative pressure (suction force) causes the fine particles separated from the swirling airflow to be sucked in as indicated by the symbol U, and is sent to the collection section 20 through the inner tube 19e and the connecting tube 21b.
　サイクロン１９内の気流の出口である内管１９ｅの延長上に所望のナノメートルオーダの粒径を有する銀微粒子３０を回収する回収部２０が設けられている。回収部２０は、回収室２０ａと、回収室２０ａ内に設けられたフィルター２０ｂと、回収室２０ａ内下方に設けられた管を介して接続された真空ポンプ２９とを備える。サイクロン１９から送られた銀微粒子３０は、真空ポンプ２９で吸引されることにより、回収室２０ａ内に引き込まれ、フィルター２０ｂの表面で留まった状態にされて回収される。
　なお、上述の製造装置１０において、使用するサイクロンの個数は、１つに限定されず、２つ以上でもよい。 A recovery section 20 for recovering silver microparticles 30 having a desired nanometer-order particle size is provided on the extension of inner tube 19e, which is the outlet of the airflow in cyclone 19. Recovery section 20 includes recovery chamber 20a, filter 20b provided in recovery chamber 20a, and vacuum pump 29 connected via a tube provided below recovery chamber 20a. Silver microparticles 30 sent from cyclone 19 are sucked by vacuum pump 29 and drawn into recovery chamber 20a, where they are collected while remaining on the surface of filter 20b.
In addition, in the above-mentioned manufacturing apparatus 10, the number of cyclones used is not limited to one, and may be two or more.
　供給部４０は、チャンバ１６内、接続管２１ａにおける第１の気体供給管２８ｂの下流、又は接続管２１ｂにおける第２の気体供給管２８ｃの下流で、銀の微粒子に表面処理剤Ｓｔを供給するものである。ここで、接続管２１ａに対してチャンバ１６側を上流側といい、サイクロン１９側を下流側という。
　供給部４０は、例えば、バルブ４１と、バルブ４１に接続された第１供給管４１ａと第２供給管４１ｂと第３供給管４１ｃとを有する。第１供給管４１ａがチャンバ１６の側面１６ｂに接続されている。第２供給管４１ｂが接続管２１ａに第１の気体供給管２８ｂの下流で接続され、第３供給管４１ｃが接続管２１ｂに第２の気体供給管２８ｃの下流で接続されている。第１供給管４１ａは、例えば、チャンバ１６において、接続管２１ａが接続された位置と同程度か、又はそれ以下の高さに接続されている。表面処理剤Ｓｔは第１供給管４１ａを経てチャンバ１６の内側壁１６ａからチャンバ１６内に供給される。
　第２供給管４１ｂの接続管２１ａにおける接続位置をＰ１とし、第３供給管４１ｃの接続管２１ｂにおける接続位置をＰ２とする。第３供給管４１ｃの接続位置Ｐ２は、第２供給管４１ｂの接続位置Ｐ１よりも下流にある。
　供給部４０は、チャンバ１６内の銀の１次微粒子１５、接続管２１ａを通る銀の１次微粒子１５又は接続管２１ｂを通る銀の２次微粒子１８に表面処理剤Ｓｔを供給する。
　供給部４０は、表面処理剤Ｓｔに適する温度領域で、表面処理剤Ｓｔを供給するものである。銀の１次微粒子１５又は銀の２次微粒子１８に表面処理剤Ｓｔが付着し、銀の１次微粒子１５又は銀の２次微粒子１８が表面処理されて、銀微粒子の融着が防止されて、銀微粒子３０が得られる。
　供給部４０による表面処理剤Ｓｔの供給方法は、特に限定されるものではなく、例えば、表面処理剤Ｓｔを液滴化して銀の２次微粒子１８に噴霧する方法が例示される。 The supply unit 40 supplies the surface treatment agent St to the silver particles in the chamber 16, downstream of the first gas supply pipe 28b in the connecting pipe 21a, or downstream of the second gas supply pipe 28c in the connecting pipe 21b. Here, the chamber 16 side with respect to the connecting pipe 21a is referred to as the upstream side, and the cyclone 19 side is referred to as the downstream side.
The supply unit 40 has, for example, a valve 41, and a first supply pipe 41a, a second supply pipe 41b, and a third supply pipe 41c connected to the valve 41. The first supply pipe 41a is connected to the side surface 16b of the chamber 16. The second supply pipe 41b is connected to the connecting pipe 21a downstream of the first gas supply pipe 28b, and the third supply pipe 41c is connected to the connecting pipe 21b downstream of the second gas supply pipe 28c. The first supply pipe 41a is connected, for example, at a height equal to or lower than the position where the connecting pipe 21a is connected in the chamber 16. The surface treatment agent St is supplied into the chamber 16 from the inner wall 16a of the chamber 16 through the first supply pipe 41a.
The connection position of the second supply pipe 41b to the connection pipe 21a is designated as P1 , and the connection position of the third supply pipe 41c to the connection pipe 21b is designated as P2 . The connection position P2 of the third supply pipe 41c is downstream of the connection position P1 of the second supply pipe 41b.
The supply unit 40 supplies the surface treatment agent St to the primary silver particles 15 in the chamber 16, the primary silver particles 15 passing through the connection pipe 21a, or the secondary silver particles 18 passing through the connection pipe 21b.
The supply unit 40 supplies the surface treatment agent St in a temperature range suitable for the surface treatment agent St. The surface treatment agent St adheres to the primary silver particles 15 or the secondary silver particles 18, the primary silver particles 15 or the secondary silver particles 18 are surface-treated, and fusion of the silver particles is prevented, thereby obtaining silver particles 30.
The method of supplying the surface treatment agent St by the supply unit 40 is not particularly limited, and an example thereof is a method in which the surface treatment agent St is made into droplets and sprayed onto the secondary fine silver particles 18 .
　上述のように、表面処理剤Ｓｔは適する温度領域で供給される。適する温度領域とは、表面処理剤Ｓｔが、銀微粒子の融着を防ぐ役割を果たすことができる温度領域である。したがって、銀微粒子の融着を防ぐことができれば、表面処理剤Ｓｔが変性する温度領域から導入してもよく、表面処理剤Ｓｔが変性しない温度領域から導入してもよい。
　なお、表面処理された微粒子の表面状態は、例えば、ＦＴ－ＩＲ（フーリエ変換赤外分光光度計）を用いて調べることができる。 As described above, the surface treatment agent St is supplied in a suitable temperature range. The suitable temperature range is a temperature range in which the surface treatment agent St can play a role in preventing the fusion of the silver fine particles. Therefore, as long as the fusion of the silver fine particles can be prevented, the surface treatment agent St may be introduced from a temperature range in which the surface treatment agent St is denatured, or from a temperature range in which the surface treatment agent St is not denatured.
The surface condition of the surface-treated fine particles can be examined, for example, by using an FT-IR (Fourier transform infrared spectrophotometer).
　上述の銀微粒子の融着を防ぐ役割を果たすことができる温度領域とは１次微粒子１５を表面処理剤Ｓｔの変性で生じた有機物もしくは表面処理剤Ｓｔで被覆できる温度領域である。上述の表面処理剤Ｓｔが変性しない温度領域とは、示差熱―熱重量同時測定（ＴＧ－ＤＴＡ）により測定した温度を基に決定される温度領域のことである。
　上述の表面処理剤Ｓｔが変性しない温度領域は、表面処理剤Ｓｔの示差熱―熱重量同時測定において、重量減少割合が５０質量％以下である温度領域とする。重量減少割合は、より好ましくは３０質量％以下であり、さらに好ましくは１０質量％以下である。
　なお、示差熱―熱重量同時測定には、株式会社日立ハイテクサイエンスのＳＴＡ７２００（商品名）が用いられる。 The temperature range capable of preventing the fusion of the silver fine particles is a temperature range in which the primary fine particles 15 can be covered with the organic matter produced by the denaturation of the surface treatment agent St or with the surface treatment agent St. The temperature range in which the surface treatment agent St does not denature is a temperature range determined based on the temperature measured by simultaneous differential thermal analysis-thermogravimetry (TG-DTA).
The temperature range in which the surface treatment agent St does not denature is a temperature range in which the weight loss rate of the surface treatment agent St is 50% by mass or less in simultaneous differential thermal and thermogravimetric measurements, more preferably 30% by mass or less, and even more preferably 10% by mass or less.
For the simultaneous differential thermal and thermogravimetric measurements, STA7200 (product name) manufactured by Hitachi High-Tech Science Corporation is used.
　表面処理剤Ｓｔは、特に限定されるものではないが、例えば、有機酸単体及び有機酸溶液、並びにアミン基を有する有機物及びアミン基を有する有機物の溶液である。
　また、有機酸が使用状態で液状であれば必ずしも水溶液のように、有機酸を溶媒に溶解させる必要はなく、有機酸を単体で使用することもできる。有機酸以外の酸性物質、塩基性物質、天然樹脂及び合成樹脂等の表面処理剤Ｓｔを使用する場合でも、有機酸と同様であり、使用状態で液状であれば単体で使用することができる。
　アミン基を有する有機物は、例えば、ドデシルアミンである。 The surface treatment agent St is not particularly limited, but may be, for example, an organic acid alone or an organic acid solution, an organic substance having an amine group, or a solution of an organic substance having an amine group.
In addition, if the organic acid is in a liquid state when used, it is not necessary to dissolve the organic acid in a solvent as in an aqueous solution, and the organic acid can be used alone. Even when a surface treatment agent St other than an organic acid, such as an acidic substance, a basic substance, a natural resin, or a synthetic resin, is used, it can be used alone as long as it is in a liquid state when used, similarly to the organic acid.
An example of an organic substance having an amine group is dodecylamine.
（分散剤単体及び分散剤溶液）
　分散剤は、例えば、アミン基のみを有する分散剤等が用いられる。分散剤には、以下のものを用いることができる。分散剤がアミン基を有する場合、分散剤のアミン価は、１０以上１００以下が好ましく、１０以上６０以下がより好ましい。 (Dispersant alone and dispersant solution)
As the dispersant, for example, a dispersant having only an amine group is used. The following dispersants can be used. When the dispersant has an amine group, the amine value of the dispersant is preferably 10 or more and 100 or less, and more preferably 10 or more and 60 or less.
　アミン基のみを有する分散剤としては、例えば、ＤＩＳＰＥＲＢＹＫ－１０２、ＤＩＳＰＥＲＢＹＫ－１６０、ＤＩＳＰＥＲＢＹＫ－１６１、ＤＩＳＰＥＲＢＹＫ－１６２、ＤＩＳＰＥＲＢＹＫ－２１６３、ＤＩＳＰＥＲＢＹＫ－２１６４、ＤＩＳＰＥＲＢＹＫ－１６６、ＤＩＳＰＥＲＢＹＫ－１６７、ＤＩＳＰＥＲＢＹＫ－１６８、ＤＩＳＰＥＲＢＹＫ－２０００、ＤＩＳＰＥＲＢＹＫ－２０５０、ＤＩＳＰＥＲＢＹＫ－２１５０、ＤＩＳＰＥＲＢＹＫ－２１５５、ＤＩＳＰＥＲＢＹＫ－ＬＰＮ６９１９、ＤＩＳＰＥＲＢＹＫ－ＬＰＮ２１１１６、ＤＩＳＰＥＲＢＹＫ－ＬＰＮ２１２３４、ＤＩＳＰＥＲＢＹＫ－９０７５、ＤＩＳＰＥＲＢＹＫ－９０７７（以上、ビックケミー社製）；ＥＦＫＡ　４０１５、ＥＦＫＡ　４０２０、ＥＦＫＡ　４０４６、ＥＦＫＡ　４０４７、ＥＦＫＡ　４０５０、ＥＦＫＡ　４０５５、ＥＦＫＡ　４０６０、ＥＦＫＡ　４０８０、ＥＦＫＡ　４３００、ＥＦＫＡ　４３３０、ＥＦＫＡ　４３４０、ＥＦＫＡ　４４００、ＥＦＫＡ　４４０１、ＥＦＫＡ　４４０２、ＥＦＫＡ　４４０３、ＥＦＫＡ　４８００（以上、ＢＡＳＦ社製）；アジスパー（登録商標）ＰＢ７１１（味の素ファインテクノ株式会社製）等が挙げられる。 Dispersants having only amine groups include, for example, DISPERBYK-102, DISPERBYK-160, DISPERBYK-161, DISPERBYK-162, DISPERBYK-2163, DISPERBYK-2164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-2000, DISPERBYK-2050, DISPERBYK-2150, DISPERBYK-2155, DISPERBYK-LPN6919, DISPERBYK-LPN21116, DISPERBYK-LPN 21234, DISPERBYK-9075, DISPERBYK-9077 (all manufactured by BYK-Chemie); EFKA 4015, EFKA 4020, EFKA 4046, EFKA 4047, EFKA 4050, EFKA 4055, EFKA 4060, EFKA 4080, EFKA 4300, EFKA 4330, EFKA 4340, EFKA 4400, EFKA 4401, EFKA 4402, EFKA 4403, EFKA 4800 (all manufactured by BASF); AJISPER (registered trademark) PB711 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), etc.
　アミン基を有する高分子分散剤としては、例えば、ＤＩＳＰＥＲＢＹＫ－１４２、ＤＩＳＰＥＲＢＹＫ－１４５、ＤＩＳＰＥＲＢＹＫ－２００１、ＤＩＳＰＥＲＢＹＫ－２０１０、ＤＩＳＰＥＲＢＹＫ－２０２０、ＤＩＳＰＥＲＢＹＫ－２０２５、ＤＩＳＰＥＲＢＹＫ－９０７６、Ａｎｔｉ－Ｔｅｒｒａ－２０５（以上、ビックケミー社製）；ＳＯＬＳＰＥＲＳＥ　２４０００（ルーブリゾール株式会社製）；アジスパー（登録商標）ＰＢ８２１、アジスパーＰＢ８８０、アジスパーＰＢ８８１（以上、味の素ファインテクノ株式会社製）等を挙げることができる。 Examples of polymeric dispersants having amine groups include DISPERBYK-142, DISPERBYK-145, DISPERBYK-2001, DISPERBYK-2010, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-9076, and Anti-Terra-205 (all manufactured by BYK-Chemie); SOLSPERSE 24000 (manufactured by Lubrizol Corporation); AJISPER (registered trademark) PB821, AJISPER PB880, and AJISPER PB881 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.).
（有機溶媒）
　有機溶媒は、特に制限はなく、目的に応じて適宜選択することができる。有機溶媒としては、例えば、メタノール等のアルコール類、アセトン等のケトン類、アルキルハライド類、ホルムアミド等のアミド類、ジメチルスルホキシド等のスルホキシド類、ヘテロ環化合物、炭化水素類、酢酸エチル等のエステル類、及びエーテル類等が挙げられる。これらは、１種を単独で使用してもよく、２種以上のもの組み合わせてもよい。 (Organic solvent)
The organic solvent is not particularly limited and can be appropriately selected according to the purpose. Examples of the organic solvent include alcohols such as methanol, ketones such as acetone, alkyl halides, amides such as formamide, sulfoxides such as dimethyl sulfoxide, heterocyclic compounds, hydrocarbons, esters such as ethyl acetate, and ethers. These may be used alone or in combination of two or more.
（有機酸単体及び有機酸溶液）
　表面処理剤に酸性物質である有機酸を用いる場合、例えば、溶媒に純水を用いて水溶液として、供給部４０から噴霧する。この場合、有機酸は、水溶性であり、かつ低沸点であることが好ましく、有機酸はＣ、Ｏ及びＨだけで構成されていることが好ましい。有機酸としては、例えば、Ｌ－アスコルビン酸（Ｃ６Ｈ８Ｏ６）、ギ酸（ＣＨ２Ｏ２）、グルタル酸（Ｃ５Ｈ８Ｏ４）、コハク酸（Ｃ４Ｈ６Ｏ４）、シュウ酸（Ｃ２Ｈ２Ｏ４）、ＤＬ－酒石酸（Ｃ４Ｈ６Ｏ６）、ラクトース一水和物、マルトース一水和物、マレイン酸（Ｃ４Ｈ４Ｏ４）、Ｄ－マンニット（Ｃ６Ｈ１４Ｏ６）、クエン酸（Ｃ６Ｈ８Ｏ７）、リンゴ酸（Ｃ４Ｈ６Ｏ５）、マロン酸（Ｃ３Ｈ４Ｏ４）及び脂肪族カルボン酸等を用いることができる。上述の有機酸のうち、少なくとも１種を用いることが好ましい。
　有機酸の水溶液を液滴化する噴霧ガスは、例えば、アルゴンガスが用いられるが、アルゴンガスに限定されるものではなく、窒素ガス等の不活性ガスを用いることができる。 (Organic acid alone and organic acid solution)
When an organic acid, which is an acidic substance, is used as the surface treatment agent, for example, an aqueous solution using pure water as a solvent is sprayed from the supply unit 40. In this case, the organic acid is preferably water-soluble and has a low boiling point, and is preferably composed only of C, O, and H. Examples of organic acids that can be used include L-ascorbic acid (C 6 H 8 O 6 ), formic acid (CH 2 O 2 ), glutaric acid (C 5 H 8 O 4 ), succinic acid (C 4 H 6 O 4 ), oxalic acid (C 2 H 2 O 4 ), DL-tartaric acid (C 4 H 6 O 6 ), lactose monohydrate, maltose monohydrate, maleic acid (C 4 H 4 O 4 ), D-mannite (C 6 H 14 O 6 ), citric acid (C 6 H 8 O 7 ), malic acid (C 4 H 6 O 5 ), malonic acid (C 3 H 4 O 4 ), and aliphatic carboxylic acids. It is preferable to use at least one of the above organic acids.
The spray gas for turning the aqueous solution of the organic acid into droplets is, for example, argon gas, but is not limited to argon gas, and an inert gas such as nitrogen gas can be used.
　銀の１次微粒子１５又は銀の２次微粒子１８の搬送路の温度を計測するセンサ（図示せず）を有してもよい。このセンサの温度の計測結果は、表面処理剤Ｓｔに適する温度領域であるか否かの判定に利用される。この場合、温度の計測結果は、例えば、供給部４０に出力される。供給部４０では、センサによる、銀の１次微粒子１５又は銀の２次微粒子１８の搬送路の温度の計測結果に基づき、表面処理剤Ｓｔに適する温度領域であるか否かを判定することができる。銀の１次微粒子１５又は銀の２次微粒子１８の搬送路の温度が、表面処理剤Ｓｔに適さない温度領域の場合、例えば、気体供給部２８から供給される温度調整ガスの流量を変更する。
　上述のように、センサの温度の計測結果は、表面処理剤Ｓｔに適する温度領域であるか否かの判定に用いられるため、センサは、第２供給管４１ｂの接続管２１ａにおける接続位置Ｐ１よりも上流に設けることが好ましい。このため、センサは、例えば、接続管２１ａに設けられる。
　センサは温度を計測できれば、その構成は特に限定されるものではないが、計測時間が短いことが好ましい。このため、センサには、例えば、抵抗温度計、放射温度計、赤外放射温度センサ、及びサーミスタ等を用いることができる。 A sensor (not shown) may be provided to measure the temperature of the transport path of the silver primary particles 15 or the silver secondary particles 18. The temperature measurement result of this sensor is used to determine whether or not the temperature range is suitable for the surface treatment agent St. In this case, the temperature measurement result is output to, for example, the supply unit 40. The supply unit 40 can determine whether or not the temperature range is suitable for the surface treatment agent St based on the temperature measurement result of the transport path of the silver primary particles 15 or the silver secondary particles 18 by the sensor. When the temperature of the transport path of the silver primary particles 15 or the silver secondary particles 18 is in a temperature range that is not suitable for the surface treatment agent St, for example, the flow rate of the temperature adjustment gas supplied from the gas supply unit 28 is changed.
As described above, since the measurement result of the temperature of the sensor is used to determine whether or not the temperature range is suitable for the surface treatment agent St, the sensor is preferably provided upstream of the connection position P1 of the connecting pipe 21a of the second supply pipe 41b. For this reason, the sensor is provided, for example, in the connecting pipe 21a.
The sensor is not particularly limited in configuration as long as it can measure temperature, but it is preferable that the measurement time is short. For this reason, the sensor may be, for example, a resistance thermometer, a radiation thermometer, an infrared radiation temperature sensor, a thermistor, or the like.
　次に、上述の製造装置１０を用いた銀微粒子の製造方法の一例について説明する。
　まず、銀微粒子の原料粉末として、例えば、平均粒子径が１５μｍ以下の銀の粉末を材料供給装置１４に投入する。
　プラズマガスに、例えば、アルゴンガス及び水素ガスを用い、高周波発振用コイル１２ｂに高周波電圧を印加し、プラズマトーチ１２内に熱プラズマ炎２４を発生させる。
　次に、キャリアガスとして、例えば、アルゴンガスを用いて銀の粉末を気体搬送し、供給管１４ａを介してプラズマトーチ１２内の熱プラズマ炎２４中に供給する。供給された銀の粉末は、熱プラズマ炎２４中で蒸発して気相状態の混合物となり、チャンバ１６内で、冷却ガスを用いることなく、気相状態の混合物から銀の１次微粒子１５が生成される。 Next, an example of a method for producing silver particles using the above-mentioned production apparatus 10 will be described.
First, as raw powder of silver particles, for example, silver powder having an average particle size of 15 μm or less is fed into the material supply device 14 .
For example, argon gas and hydrogen gas are used as the plasma gas, and a high-frequency voltage is applied to the high-frequency oscillation coil 12 b to generate a thermal plasma flame 24 in the plasma torch 12 .
Next, the silver powder is gas-transported using, for example, argon gas as a carrier gas, and is supplied via the supply pipe 14a into the thermal plasma flame 24 in the plasma torch 12. The supplied silver powder evaporates in the thermal plasma flame 24 to become a gas-phase mixture, and primary silver particles 15 are generated from the gas-phase mixture in the chamber 16 without using a cooling gas.
　そして、チャンバ１６内で得られた銀の１次微粒子１５は、接続管２１ａを通りサイクロン１９の入口管１９ａから、気流とともに外筒１９ｂの内周壁に沿って吹き込まれ、これにより、この気流が図２の矢印Ｔに示すように外筒１９ｂの内周壁に沿って流れることにより、旋回流を形成して下降する。そして、上述の下降する旋回流が反転し、上昇流になったとき、遠心力と抗力のバランスにより、粗大粒子は、上昇流にのることができず、円錐台部１９ｃ側面に沿って下降し、粗大粒子回収チャンバ１９ｄで回収される。また、遠心力よりも抗力の影響をより受けた微粒子は、円錐台部１９ｃ内壁での上昇流とともに内壁からサイクロン１９外に排出される。
　排出された銀の２次微粒子１８は、真空ポンプ２９による回収部２０からの負圧（吸引力）によって、図１中、符号Ｕに示す方向に吸引されて内管１９ｅ及び接続管２１ｂを通過する。 The primary silver particles 15 obtained in the chamber 16 pass through the connecting pipe 21a and are blown together with the airflow from the inlet pipe 19a of the cyclone 19 along the inner peripheral wall of the outer cylinder 19b, whereby the airflow flows along the inner peripheral wall of the outer cylinder 19b as indicated by the arrow T in Fig. 2, forming a swirling flow and descending. When the descending swirling flow reverses and becomes an ascending flow, the balance between the centrifugal force and the drag force means that the coarse particles cannot ride on the ascending flow, and so they descend along the side surface of the truncated cone portion 19c and are collected in the coarse particle collection chamber 19d. Furthermore, the fine particles that are more affected by the drag force than the centrifugal force are discharged from the inner wall of the truncated cone portion 19c together with the ascending flow at the inner wall of the truncated cone portion 19c, to the outside of the cyclone 19.
The discharged secondary silver particles 18 are sucked in the direction indicated by the symbol U in FIG. 1 by the negative pressure (suction force) from the recovery section 20 by the vacuum pump 29, and pass through the inner tube 19e and the connection tube 21b.
　銀の１次微粒子１５又は銀の２次微粒子１８が接続管２１ａ内又は接続管２１ｂ内を通過する際、気体供給部２８から温度調整ガスが、第１の気体供給管２８ｂ又は第２の気体供給管２８ｃを通り接続管２１ａ内又は接続管２１ｂ内に供給されて、銀の１次微粒子１５又は銀の２次微粒子１８が冷却される。温度調整ガスにより、銀の１次微粒子１５又は銀の２次微粒子１８を表面処理剤に適する温度領域とした後、さらに、供給部４０からチャンバ１６内、接続管２１ａ内又は接続管２１ｂ内に、表面処理剤Ｓｔが銀の１次微粒子１５又は銀の２次微粒子１８に、例えば、噴霧等の形態で供給されて、銀の１次微粒子１５又は銀の２次微粒子１８が表面処理される。
　表面処理された銀の１次微粒子１５又は銀の２次微粒子１８、すなわち、銀微粒子３０が回収部２０に送られ、回収部２０のフィルター２０ｂで銀微粒子３０が回収される。このようにして、銀微粒子が得られる。 When the silver primary particles 15 or the silver secondary particles 18 pass through the connecting pipe 21a or the connecting pipe 21b, a temperature adjusting gas is supplied from the gas supply unit 28 through the first gas supply pipe 28b or the second gas supply pipe 28c into the connecting pipe 21a or the connecting pipe 21b to cool the silver primary particles 15 or the silver secondary particles 18. After the silver primary particles 15 or the silver secondary particles 18 are brought into a temperature range suitable for the surface treatment agent by the temperature adjusting gas, the surface treatment agent St is further supplied from the supply unit 40 to the chamber 16, the connecting pipe 21a or the connecting pipe 21b in the form of, for example, a spray to the silver primary particles 15 or the silver secondary particles 18, so that the silver primary particles 15 or the silver secondary particles 18 are surface-treated.
The surface-treated primary silver particles 15 or secondary silver particles 18, i.e., silver particles 30, are sent to the recovery section 20, and the silver particles 30 are recovered by the filter 20b of the recovery section 20. In this manner, silver particles are obtained.
　銀微粒子３０が回収部２０に回収されるとき、サイクロン１９内の内圧は、大気圧以下であることが好ましい。また、銀微粒子３０の粒径は、目的に応じて、ナノメートルオーダの任意の粒径が規定される。
　なお、本発明では、熱源に熱プラズマ炎を用いて銀の１次微粒子を形成しているが、他の気相法を用いて銀の１次微粒子を形成することもできる。このため、気相法であれば、熱プラズマ炎を用いることに限定されるものではなく、例えば、火炎法により、銀の１次微粒子を形成する製造方法でもよい。なお、熱プラズマ炎を用いた１次微粒子の製造方法を熱プラズマ法という。 When the silver microparticles 30 are collected in the collection section 20, the internal pressure in the cyclone 19 is preferably equal to or lower than atmospheric pressure. In addition, the particle diameter of the silver microparticles 30 is specified to any particle diameter on the order of nanometers depending on the purpose.
In the present invention, the primary silver particles are formed using a thermal plasma flame as a heat source, but the primary silver particles can also be formed using other gas phase methods. Therefore, as long as the gas phase method is used, it is not limited to using a thermal plasma flame, and for example, a manufacturing method in which the primary silver particles are formed by a flame method may be used. The manufacturing method of the primary silver particles using a thermal plasma flame is called a thermal plasma method.
　ここで、火炎法とは、火炎を熱源として用い，銀を含む原料を火炎に通すことにより微粒子を合成する方法である。火炎法では、銀を含む原料を、火炎に供給し火炎の中で銀粒子を生成させて銀粒子の成長を抑制して銀の１次微粒子１５を得る。さらに、表面処理剤Ｓｔを、銀の１次微粒子１５又は銀の２次微粒子１８に供給して、銀微粒子を製造する。
　なお、火炎法においても、表面処理剤は、上述の熱プラズマ法と同じものを用いることができる。 Here, the flame method is a method of synthesizing fine particles by passing a raw material containing silver through a flame using a flame as a heat source. In the flame method, the raw material containing silver is supplied to a flame, silver particles are generated in the flame, and the growth of the silver particles is suppressed to obtain primary silver particles 15. Furthermore, a surface treatment agent St is supplied to the primary silver particles 15 or the secondary silver particles 18 to produce silver fine particles.
In the flame method, the same surface treatment agent as that used in the thermal plasma method can be used.
　本発明は、基本的に以上のように構成されるものである。以上、本発明の銀微粒子について詳細に説明したが、本発明は上述の実施形態に限定されず、本発明の主旨を逸脱しない範囲において、種々の改良又は変更をしてもよいのはもちろんである。 The present invention is basically configured as described above. The silver microparticles of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiment, and various improvements and modifications may of course be made within the scope of the gist of the present invention.
　以下、本発明の銀微粒子について、より具体的に説明する。
　本実施例においては、実施例１～３の銀微粒子及び従来の銀微粒子を製造した。実施例１～３の銀微粒子及び従来の銀微粒子の製造には図２に示す製造装置１０を用いた。以下に製造条件を示す。 The fine silver particles of the present invention will now be described in more detail.
In this example, the silver fine particles of Examples 1 to 3 and conventional silver fine particles were produced. The silver fine particles of Examples 1 to 3 and conventional silver fine particles were produced using a production apparatus 10 shown in Fig. 2. The production conditions are as follows.
　実施例１では原料粉末に、平均粒子径１５μｍの銀の粉末を用いた。銀の粉体の平均粒径は粒度分布計で測定した値である。粒度分布計にはマイクロトラック・ベル株式会社製ＭＴ３３００を用いた。
　なお、銀微粒子の製造条件は、プラズマへの入力を１８ｋＷ一定として、プラズマトーチ内圧力は６０ｋＰａに固定した。
　キャリアガスにアルゴンガスを用いた。アルゴンガスの流量を５リットル／分（標準状態換算）とした。
　プラズマガスにアルゴンガスと水素ガスとを用いた。アルゴンガスの流量を２００リットル／分（標準状態換算）とし、水素ガスの流量を５リットル／分（標準状態換算）とした。
　温度調整ガスにアルゴンガスを用いた。アルゴンガスの流量を２４０リットル／分(標準状態換算)とした。
　実施例１では、有機酸にクエン酸を用いた。溶媒に純水を用い、クエン酸を含む水溶液（クエン酸の濃度３．７６Ｗ／Ｗ％）を、噴霧ガスを用いて、チャンバ１６の側面１６ｂに接続された第２供給管４１ｂ（図２参照）から銀の１次微粒子に噴霧した。噴霧ガスにアルゴンガスを用いた。 In Example 1, silver powder having an average particle size of 15 μm was used as the raw material powder. The average particle size of the silver powder was measured using a particle size distribution meter. The particle size distribution meter used was MT3300 manufactured by Microtrack Bell Co., Ltd.
The conditions for producing the silver particles were a constant input power to the plasma of 18 kW and a fixed pressure inside the plasma torch of 60 kPa.
Argon gas was used as the carrier gas, and the flow rate of the argon gas was set to 5 liters/minute (standard condition conversion).
Argon gas and hydrogen gas were used as plasma gases, with the flow rate of the argon gas being 200 liters/minute (based on standard conditions) and the flow rate of the hydrogen gas being 5 liters/minute (based on standard conditions).
Argon gas was used as the temperature adjusting gas, and the flow rate of the argon gas was set to 240 liters/minute (standard state conversion).
In Example 1, citric acid was used as the organic acid. Pure water was used as the solvent, and an aqueous solution containing citric acid (citric acid concentration: 3.76 W/W%) was sprayed onto the primary fine particles of silver using a spray gas from the second supply pipe 41b (see FIG. 2) connected to the side surface 16b of the chamber 16. Argon gas was used as the spray gas.
　実施例２は、実施例１に比して、以下のこと以外は、実施例１と同じとした。
　実施例２では、プラズマトーチ内圧力を８５ｋＰａに固定した。また、温度調整ガスのアルゴンガスの流量を１５リットル／分(標準状態換算)とした。 Example 2 was the same as Example 1 except for the following points.
In Example 2, the pressure inside the plasma torch was fixed at 85 kPa, and the flow rate of the argon gas, which was the temperature adjusting gas, was set to 15 liters/minute (standard state conversion).
　実施例３は、実施例２に比して、以下のこと以外は、実施例２と同じとした。実施例３は、温度調整ガスを用いなかった。 Example 3 was the same as Example 2 except for the following: Example 3 did not use a temperature adjustment gas.
　従来の銀微粒子では、プラズマへの入力を１４ｋＷ一定として、プラズマトーチ内圧力は４０ｋＰａに固定した。
　キャリアガスにアルゴンガスを用いた。アルゴンガスの流量を５リットル／分（標準状態換算）とした。
　プラズマガスにアルゴンガスと水素ガスとを用いた。アルゴンガスの流量を１７０リットル／分（標準状態換算）とし、水素ガスの流量を５リットル／分（標準状態換算）とした。
　冷却ガスにアルゴンガスとメタンガスを用いた。アルゴンガスの流量を３００リットル／分（標準状態換算）とし、メタンガスの流量を５．７リットル／分(標準状態換算)とした。
　なお、従来の銀微粒子では、温度調整用ガスを供給せず、また、有機酸を用いなかった。 For the conventional silver microparticles, the input power to the plasma was kept constant at 14 kW, and the pressure inside the plasma torch was fixed at 40 kPa.
Argon gas was used as the carrier gas, and the flow rate of the argon gas was set to 5 liters/minute (standard condition conversion).
Argon gas and hydrogen gas were used as plasma gases, with the flow rate of the argon gas being 170 liters/minute (based on standard conditions) and the flow rate of the hydrogen gas being 5 liters/minute (based on standard conditions).
Argon gas and methane gas were used as cooling gases. The flow rate of argon gas was set to 300 liters/minute (standard state conversion), and the flow rate of methane gas was set to 5.7 liters/minute (standard state conversion).
In addition, in the conventional silver fine particles, no temperature adjusting gas was supplied, and no organic acid was used.
　実施例１～３について、得られた銀微粒子のＳＥＭ像を得た。ＳＥＭ像は株式会社日立ハイテクノロジーズ製Ｒｅｇｕｌｕｓ８２２０を用いて取得した。
　実施例１～３の銀微粒子のＳＥＭ像を、それぞれ画像解析して粒度分布を算出した。その結果を図３に示す。図３は本発明の実施例１、２の銀微粒子の粒度分布を示すグラフである。図３に示す銀微粒子の粒度分布は、体積基準で得られた粒度分布を示す。
　図３において、符号６２は実施例１の粒径の累積分布を示し、符号６３は実施例１の粒径の頻度分布を示す。実施例１はＢＥＴ法による粒径が１９２ｎｍであった。
　符号６４は実施例２の粒径の累積分布を示し、符号６５は実施例２の粒径の頻度分布を示す。実施例２はＢＥＴ法による粒径が３５６ｎｍであった。また、実施例３はＢＥＴ法による粒径が３８６ｎｍであった。実施例１～３の銀微粒子のＢＥＴ法による粒径の測定には、株式会社マウンテック製Ｍａｃｓｏｒｂ　ＨＭ－１２０８を用いた。
　実施例１～３の銀微粒子において、粒径が０．１μｍ未満の粒子の含有割合は、まず、銀微粒子のＳＥＭ像を画像解析して体積基準での粒度分布を求めた。次に、体積基準での粒度分布から、銀微粒子について、粒径が０．１μｍ（１００ｎｍ）未満の粒子の含有割合を求めた。
　図３に示すように実施例１、２は、粒径が０．１μｍ（１００ｎｍ）未満の粒子の含有割合が少ない。なお、実施例３も、粒径が０．１μｍ（１００ｎｍ）未満の粒子の含有割合が少ないことを確認している。 SEM images of the obtained silver fine particles were obtained for Examples 1 to 3. The SEM images were obtained using a Regulus 8220 manufactured by Hitachi High-Technologies Corporation.
The SEM images of the silver microparticles of Examples 1 to 3 were each subjected to image analysis to calculate the particle size distribution. The results are shown in Figure 3. Figure 3 is a graph showing the particle size distribution of the silver microparticles of Examples 1 and 2 of the present invention. The particle size distribution of the silver microparticles shown in Figure 3 shows the particle size distribution obtained on a volume basis.
3, reference numeral 62 indicates the cumulative distribution of particle diameters in Example 1, and reference numeral 63 indicates the frequency distribution of particle diameters in Example 1. In Example 1, the particle diameter measured by the BET method was 192 nm.
Reference numeral 64 denotes the cumulative distribution of particle sizes in Example 2, and reference numeral 65 denotes the frequency distribution of particle sizes in Example 2. The particle size measured by the BET method in Example 2 was 356 nm. The particle size measured by the BET method in Example 3 was 386 nm. Macsorb HM-1208 manufactured by Mountech Co., Ltd. was used to measure the particle sizes of the silver fine particles in Examples 1 to 3 by the BET method.
In the silver microparticles of Examples 1 to 3, the content of particles having a particle diameter of less than 0.1 μm was determined by first performing image analysis of SEM images of the silver microparticles to determine the particle size distribution on a volume basis. Next, the content of particles having a particle diameter of less than 0.1 μm (100 nm) was determined for the silver microparticles from the particle size distribution on a volume basis.
3, the content of particles having a particle size of less than 0.1 μm (100 nm) is low in Examples 1 and 2. It has also been confirmed that Example 3 has a low content of particles having a particle size of less than 0.1 μm (100 nm).
　実施例１～３及び従来の銀微粒子について、円筒状のペレットに成形して焼成前の体積抵抗値と、大気中（すなわち、空気中）において温度１５０℃で１時間焼成した後の体積抵抗値と体積収縮率を測定した。その結果、下記表１に示す。なお、大気（空気）の組成は、上述の通りである。
　下記表１には、実施例１～３の粒径、及び粒径が０．１μｍ（１００ｎｍ）未満の粒子の体積基準の含有割合も示す。なお、下記表１では、上述の「従来の銀微粒子」を「従来例」とした。
　体積抵抗値の測定においては、まず、銀微粒子をプレス機を用いて、圧力１２７ＭＰａで１０秒間保持して円筒状のペレットを作製した。測定装置に三菱化学株式会社製ロレスタＥＰ（ＭＣＰ－Ｔ３６０）を用い、四端子法にて、焼成前後のペレットの体積抵抗値を測定した。
　なお、ペレットは、電気炉内に設置し、大気中（大気雰囲気）において温度１５０℃で１時間焼成した。 For the silver fine particles of Examples 1 to 3 and the conventional fine particles, the volume resistivity before sintering was formed into a cylindrical pellet, and the volume resistivity and volume shrinkage rate after sintering in the atmosphere (i.e., in air) at a temperature of 150° C. for 1 hour were measured. The results are shown in Table 1 below. The composition of the atmosphere (air) was as described above.
Table 1 below also shows the particle sizes and the volumetric content of particles with a particle size of less than 0.1 μm (100 nm) in Examples 1 to 3. In Table 1 below, the above-mentioned "conventional fine silver particles" are referred to as "conventional example."
In measuring the volume resistivity, the silver particles were first pressed into a cylindrical pellet at a pressure of 127 MPa for 10 seconds using a press. A measuring device, Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation, was used to measure the volume resistivity of the pellet before and after firing by a four-terminal method.
The pellets were placed in an electric furnace and fired in the air (atmosphere) at a temperature of 150° C. for 1 hour.
　体積収縮率の測定においては、まず、銀微粒子をプレス機を用いて、圧力１２７ＭＰａで１０秒間保持して円筒状のペレットを作製した。円筒状のペレットの厚みと直径をノギスにて測定して、焼成前の体積を得た。焼成後についても、円筒状のペレットの厚みと直径をノギスにて測定して、焼成後の体積を得た。焼成前後のペレットの体積から体積収縮率を算出した。体積収縮率の算出には下記式を用いた。なお、ペレットは、電気炉内に設置し、大気中において温度１５０℃で１時間焼成した。
体積収縮率（％）＝１００－（（焼成後の体積／焼成前の体積）×１００）
　なお、密度については、以下のようにして測定した。焼成前の円筒状のペレットの厚みと直径をノギスにて測定し、ペレットの質量を電子天秤にて測定し、円筒状のペレットの体積と質量とから、焼成前の円筒状のペレットの密度を算出した。また、焼成後の円筒状のペレットの厚みと直径をノギスにて測定し、ペレットの質量を電子天秤にて測定し、焼成後の円筒状のペレットの体積と質量とから、焼成後の円筒状のペレットの密度を算出した。 In measuring the volumetric shrinkage rate, first, the silver fine particles were pressed with a press machine and held at a pressure of 127 MPa for 10 seconds to produce a cylindrical pellet. The thickness and diameter of the cylindrical pellet were measured with a vernier caliper to obtain the volume before firing. After firing, the thickness and diameter of the cylindrical pellet were also measured with a vernier caliper to obtain the volume after firing. The volumetric shrinkage rate was calculated from the pellet volumes before and after firing. The following formula was used to calculate the volumetric shrinkage rate. The pellet was placed in an electric furnace and fired in air at a temperature of 150°C for 1 hour.
Volume shrinkage rate (%) = 100 - ((volume after firing / volume before firing) x 100)
The density was measured as follows. The thickness and diameter of the cylindrical pellet before firing were measured with a vernier caliper, the mass of the pellet was measured with an electronic balance, and the density of the cylindrical pellet before firing was calculated from the volume and mass of the cylindrical pellet. The thickness and diameter of the cylindrical pellet after firing were measured with a vernier caliper, the mass of the pellet was measured with an electronic balance, and the density of the cylindrical pellet after firing was calculated from the volume and mass of the cylindrical pellet after firing.
　図４は本発明の実施例１の銀微粒子のＳＥＭ像を示す模式図であり、図５は本発明の実施例２の銀微粒子のＳＥＭ像を示す模式図である。図６は従来の銀微粒子のＳＥＭ像を示す模式図である。
　図４～図６に示すように、実施例１、２の銀微粒子は、従来の銀微粒子よりも粒径が大きく、かつ粒径が小さいものが少ない。なお、実施例３も、従来の銀微粒子よりも粒径が大きく、かつ粒径が小さいものが少ないことを確認している。
　表１に示すように、実施例１～３の銀微粒子は、円筒状のペレットに成形して大気中において温度１５０℃で１時間焼成した後では、従来の銀微粒子に比して、体積抵抗値が小さく、かつ体積収縮率も小さい。 Fig. 4 is a schematic diagram showing an SEM image of the silver fine particles of Example 1 of the present invention, and Fig. 5 is a schematic diagram showing an SEM image of the silver fine particles of Example 2 of the present invention. Fig. 6 is a schematic diagram showing an SEM image of conventional silver fine particles.
4 to 6, the silver microparticles in Examples 1 and 2 have a larger particle size than the conventional silver microparticles, and there are fewer particles with a smaller particle size. It has also been confirmed that Example 3 has a larger particle size than the conventional silver microparticles, and there are fewer particles with a smaller particle size.
As shown in Table 1, the silver microparticles of Examples 1 to 3, after being molded into cylindrical pellets and fired in air at a temperature of 150°C for 1 hour, had lower volume resistivity and lower volume shrinkage rates than conventional silver microparticles.
　１０　銀微粒子の製造装置（製造装置）
　１２　プラズマトーチ
　１２ａ　石英管
　１２ｂ　高周波発振用コイル
　１２ｃ　プラズマガス供給口
　１４　材料供給装置
　１４ａ　供給管
　１５　１次微粒子
　１６　チャンバ
　１６ａ　内側壁
　１６ｂ　側面
　１８　２次微粒子
　１９　サイクロン
　１９ａ　入口管
　１９ｂ　外筒
　１９ｃ　円錐台部
　１９ｄ　粗大粒子回収チャンバ
　１９ｅ　内管
　２０　回収部
　２０ａ　回収室
　２０ｂ　フィルター
　２１ａ、２１ｂ　接続管
　２２　プラズマガス供給部
　２２ａ　配管
　２４　熱プラズマ炎
　２８　気体供給部
　２８ａ　バルブ
　２８ｂ　第１の気体供給管
　２８ｃ　第２の気体供給管
　２９　真空ポンプ
　３０　銀微粒子
　４０　供給部
　４１　バルブ
　４１ａ　第１供給管
　４１ｂ　第２供給管
　４１ｃ　第３供給管
　５０　基板
　５２　パワー半導体素子
　５４　接合部
　Ｓｔ　表面処理剤 10. Silver microparticle manufacturing equipment (manufacturing equipment)
REFERENCE SIGNS LIST 12 plasma torch 12a quartz tube 12b high frequency oscillation coil 12c plasma gas supply port 14 material supply device 14a supply tube 15 primary fine particles 16 chamber 16a inner wall 16b side surface 18 secondary fine particles 19 cyclone 19a inlet tube 19b outer cylinder 19c truncated cone portion 19d coarse particle recovery chamber 19e inner tube 20 recovery section 20a recovery chamber 20b filter 21a, 21b connecting tube 22 plasma gas supply section 22a piping 24 thermal plasma flame 28 gas supply section 28a valve 28b first gas supply tube 28c second gas supply tube 29 vacuum pump 30 silver fine particles 40 supply section 41 valve 41a first supply tube 41b: second supply pipe; 41c: third supply pipe; 50: substrate; 52: power semiconductor element; 54: joint; St: surface treatment agent

Claims (2)

  1. 　ＢＥＴ法により測定された粒径が０．１μｍ以上１μｍ以下であり、
    　ペレットの状態で大気中において温度１５０℃で１時間焼成した後の体積抵抗値が１０μΩ・ｃｍ以下、かつ体積収縮率が５％未満である、銀微粒子。     The particle size measured by the BET method is 0.1 μm or more and 1 μm or less,
    Fine silver particles having a volume resistivity of 10 μΩ·cm or less and a volume shrinkage rate of less than 5% after being fired in the form of pellets in air at a temperature of 150° C. for 1 hour.
  2. 　粒径が０．１μｍ未満の粒子の含有割合が、体積基準で４０％以下である、請求項１に記載の銀微粒子。 The silver microparticles according to claim 1, in which the content of particles having a particle size of less than 0.1 μm is 40% or less by volume.
PCT/JP2023/011346 2023-03-23 2023-03-23 Silver microparticles WO2024195068A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013159805A (en) * 2012-02-02 2013-08-19 Toda Kogyo Corp Method for producing silver microparticle, silver microparticle produced by the method for producing silver microparticle, and conductive paste containing the silver microparticle
JP2013159804A (en) * 2012-02-02 2013-08-19 Toda Kogyo Corp Silver microparticle, method for producing same, and conductive paste, conductive film and electronic device containing silver microparticle
WO2019146412A1 (en) * 2018-01-26 2019-08-01 日清エンジニアリング株式会社 Silver fine particle production method and silver fine particles
WO2021100559A1 (en) * 2019-11-18 2021-05-27 日清エンジニアリング株式会社 Fine particle production device and fine particle production method
JP2023057992A (en) * 2021-10-12 2023-04-24 日清エンジニアリング株式会社 Silver micro-particle

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013159805A (en) * 2012-02-02 2013-08-19 Toda Kogyo Corp Method for producing silver microparticle, silver microparticle produced by the method for producing silver microparticle, and conductive paste containing the silver microparticle
JP2013159804A (en) * 2012-02-02 2013-08-19 Toda Kogyo Corp Silver microparticle, method for producing same, and conductive paste, conductive film and electronic device containing silver microparticle
WO2019146412A1 (en) * 2018-01-26 2019-08-01 日清エンジニアリング株式会社 Silver fine particle production method and silver fine particles
WO2021100559A1 (en) * 2019-11-18 2021-05-27 日清エンジニアリング株式会社 Fine particle production device and fine particle production method
JP2023057992A (en) * 2021-10-12 2023-04-24 日清エンジニアリング株式会社 Silver micro-particle

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