Silver microparticles

Abstract

Provided are silver microparticles having large volume shrinkage and high conductivity. The silver microparticles have a particle diameter of 0.1 [mu] m or more and 1 [mu] m or less as measured by a BET method, a volume resistance value of 15 [mu] Omega.cm or less after being fired for 1 hour in a particulate state in a nitrogen atmosphere at a temperature of 100 DEG C, and a volume shrinkage of 5% or more.

Description

Technical Field

[0001] The present invention relates to silver microparticles used for bonding semiconductor elements, high-frequency devices, light-emitting diodes, semiconductor lasers, etc., to substrates, etc. Background Art

[0002] Currently, power semiconductor devices using wide bandgap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide or diamond are being developed. Compared with semiconductor devices using Si or GaAs, power semiconductor devices have lower on-resistance, can switch at high speed, and can be miniaturized. In addition, power semiconductor devices have high heat resistance and can operate even at high temperatures of 250 to 300°C.

[0003] The conventional technology for joining semiconductor elements to substrates, etc. uses solder. However, the operating temperature of power semiconductor elements is higher than that of conventional semiconductor elements using Si or GaAs. When joining using solder, the temperature at which the solder does not melt must be used. When solder is used in joining, the use of power semiconductor elements is restricted. Thus, the joining material is also required to be usable at a relatively high temperature.

[0004] As a bonding material other than solder, Patent Document 1 describes a thermally conductive paste comprising low-temperature sintering silver particles and a thermosetting adhesive, wherein the thermosetting adhesive is composed of (B1) at least one epoxy resin selected from the group consisting of diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate and C1-C4 alkyl substituted forms thereof, and (B2) at least one hardener selected from the group consisting of a cationic polymerization initiator, an amine hardener and an acid anhydride hardener, and the amount of the thermosetting adhesive is 2 to 7 parts by mass relative to 100 parts by mass of the silver particles.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6343041 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] When a thermosetting binder is contained as in Patent Document 1, the volume shrinkage is small.

[0010] Nowadays, not only a single semiconductor element is bonded to a substrate, but also multiple semiconductor elements of different sizes are bonded to one substrate at the same time. When bonding multiple semiconductor elements of different sizes, the distances from the substrate to the semiconductor element with a lower thickness and the semiconductor element with a higher thickness are different. When a bonding material with a smaller volume shrinkage rate is used as described in Patent Document 1, the substrate cannot be uniformly bonded to the multiple semiconductor elements, and a sufficient bonding state cannot be maintained. When bonding multiple semiconductor elements with different distances to the substrate, the volume shrinkage of the bonding material must be adjusted according to the distance from the semiconductor element to the substrate. The sufficient bonding state between the substrate and the multiple semiconductor elements cannot be maintained only with a bonding material with a smaller volume shrinkage. Such bonding materials must be materials with a larger volume shrinkage. In addition, the bonding material preferably has excellent conductivity.

[0011] An object of the present invention is to provide silver microparticles having large volume shrinkage and high conductivity.

[0012] Means for solving technical problems

[0013] In order to achieve the above-mentioned purpose, one embodiment of the present invention provides a silver microparticle, whose particle size measured by the BET method is greater than 0.1 μm and less than 1 μm, and whose volume resistance value after being sintered in a pellet state at a temperature of 100°C in a nitrogen environment for 1 hour is less than 15 μΩ·cm, and whose volume shrinkage is greater than 5%.

[0014] The present invention provides silver microparticles having a particle size of 0.1 μm or more and 1 μm or less as measured by the BET method, a volume resistance of 10 μΩ·cm or less after being sintered in a nitrogen environment at 150° C. for 1 hour, and a volume shrinkage of 10% or more.

[0015] The present invention provides silver microparticles having a particle size of 0.1 μm or more and 1 μm or less as measured by the BET method, a volume resistance of 10 μΩ·cm or less after being sintered in the air at 150° C. for 1 hour in a particle state, and a volume shrinkage of 5% or more.

[0016] Preferably, the surface is coated with an aliphatic amine.

[0017] Preferably, the aliphatic amine has 10-18 carbon atoms.

[0018] Effects of the Invention

[0019] According to the present invention, silver fine particles having a large volume yield and high conductivity can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic diagram showing an example of the utilization form of the silver microparticles of the present invention.

[0021] Figure 2 This is a schematic diagram showing another example of the utilization form of the silver microparticles of the present invention.

[0022] Figure 3 This is a schematic diagram showing an example of a production apparatus for silver microparticles of the present invention.

[0023] Figure 4 This is a schematic diagram showing a SEM image of silver microparticles in Example 1 of the present invention.

[0024] Figure 5 This is a schematic diagram showing a SEM image of silver microparticles in Example 2 of the present invention.

[0025] Reference numerals

[0026] 10 silver microparticle manufacturing device (manufacturing device) 12 plasma torch 12a quartz tube

[0027] 12b High frequency oscillation coil 12c Plasma gas supply port 14 Material supply device 14a Supply pipe

[0028] 15 1st particle 16 chamber 16a inner wall 16b side 18 2nd particle 19 cyclone

[0029] 19a Inlet pipe 19b Outer cylinder 19c Cone portion 19d Coarse particle recovery chamber 19e Inner tube

[0030] 20 Recovery unit 20a Recovery chamber 20b Filter 21a, 21b Connection pipe 22 Plasma gas supply unit

[0031] 22a Pipe 24 Thermal plasma flame 28 Gas supply unit 28a Valve 28b First gas supply pipe

[0032] 28c Second gas supply pipe 29 Vacuum pump 30 Silver particles 40 Supply unit 41 Valve 41a First supply pipe 41b 2nd supply pipe 41c 3rd supply pipe 50 substrate 52 power semiconductor element 53 semiconductor element

[0033] 54St surface treatment agent for joint part DETAILED DESCRIPTION

[0034] Hereinafter, the silver microparticles of the present invention will be described in detail based on preferred embodiments shown in the drawings.

[0035] In addition, the drawings described below are examples for explaining the present invention, and the present invention is not limited to the drawings shown below.

[0036] Next, silver microparticles will be described.

[0037] [First example of silver microparticles]

[0038] The particle size of the silver particles measured by the BET method is 0.1 μm or more and 1 μm or less, and the volume resistance value after sintering in a particle state at 100° C. in a nitrogen atmosphere for 1 hour is 15 μΩ·cm or less, and the volume shrinkage is 5% or more.

[0039] Furthermore, in the present invention, the so-called nitrogen environment refers to an environment in which nitrogen with a purity of 99.99 (nitrogen 99.99 volume %) is always circulated, and it can be said that the oxygen concentration is an environment of 100 volume ppm or less. Therefore, in the nitrogen environment, the oxygen concentration can be set to 100 volume ppm or less, or the gas or its decomposition product that does not react with silver, such as rare gases, can be mixed in the nitrogen. The oxygen concentration can be measured using, for example, a low-concentration oxygen analyzer PS-820-L manufactured by Iijima Electronics Co., Ltd.

[0040] The particle size of the silver microparticles is preferably 100 to 400 nm, more preferably 300 to 400 nm, in order to improve workability during dispersion and reduce the volume shrinkage after calcining in a particle state at 100° C. for 1 hour in a nitrogen atmosphere.

[0041] The volume resistance value is 15 μΩ·cm or less, preferably 10 μΩ·cm or less, and more preferably 8 μΩ·cm or less. The lower limit of the volume resistance value is 1.47 μΩ·cm.

[0042] The volume shrinkage rate is 5% or more, preferably 6% or more.

[0043] In addition, the upper limit of the volume shrinkage is 40%.

[0044] The particle size of silver microparticles measured by the BET method is an average particle size measured by the BET method. The BET method is to calculate the specific surface area based on the assumption that the particles are spherical.

[0045] The silver particles are not dispersed in a solvent, etc., but exist alone as silver particles without a solvent, etc. Therefore, when using silver particles, a sintered body can be obtained only with the silver particles.

[0046] Furthermore, when silver fine particles and a solvent are used in combination, the combination of the silver fine particles and the solvent is not particularly limited, and the degree of freedom in selecting the solvent is high.

[0047] For the firing, the silver fine particles were formed into cylindrical particles, and the particles were placed in an electric furnace and fired at 100° C. for 1 hour in a nitrogen atmosphere.

[0048] The particles were produced by pressing silver microparticles at a pressure of 127 MPa for 10 seconds using a press.

[0049] The volume resistivity is a value measured by a four-terminal method using particles. For example, the measuring device used is Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation. By measuring the volume resistivity of the particles before and after sintering, the change in the volume resistivity after sintering can be measured.

[0050] Volumetric shrinkage is to use the above-mentioned pressing machine with silver microparticles, keep 10 seconds with pressure 127MPa and make cylindrical particles, measure the thickness and diameter of cylindrical particles with caliper, and the value calculated by the volume of particles before and after firing.Volume shrinkage is obtained by following formula.In addition, the firing of particles uses electric furnace.

[0051] Volume shrinkage (%) = 100 - ((volume after firing / volume before firing) × 100)

[0052] The particle size of the silver particles measured by the BET method is 0.1 μm or more and 1 μm or less. The volume resistance value after sintering at 100°C in a nitrogen environment for 1 hour is 15 μΩ·cm or less, and the volume shrinkage is 5% or more, thereby the volume shrinkage is large and the conductivity is high. In addition, the silver particles have a higher melting point than solder and the like, and are also excellent in heat resistance. Therefore, when silver particles are used as bonding materials, heat resistance can be met and conductivity is excellent.

[0053] [Second example of silver microparticles]

[0054] The particle size of the silver particles measured by the BET method is 0.1 μm or more and 1 μm or less, and the volume resistance value after sintering in a particle state at 150° C. in a nitrogen atmosphere for 1 hour is 10 μΩ·cm or less, and the volume shrinkage is 10% or more.

[0055] In addition, due to the operability during dispersion and the volume shrinkage of the particles after calcination at 150°C for 1 hour in a nitrogen environment, the particle size of the silver particles is preferably 100 to 600 nm, more preferably 300 to 600 nm, further preferably 300 to 500 nm, and most preferably 300 to 400 nm.

[0056] The volume resistance value is 10 μΩ·cm or less, preferably 7 μΩ·cm or less, and more preferably 4 μΩ·cm or less. The lower limit of the volume resistance value is 1.47 μΩ·cm.

[0057] The volume shrinkage is 10% or more, preferably 13% or more, and more preferably 15% or more. The upper limit of the volume shrinkage is 40%.

[0058] The particle size of the silver microparticles measured by the BET method is as described above.

[0059] Regarding the firing, the silver fine particles were formed into cylindrical particles, and the particles were placed in an electric furnace and fired at 150° C. for 1 hour in a nitrogen atmosphere.

[0060] The particles were produced by pressing silver microparticles at a pressure of 127 MPa for 10 seconds using a press.

[0061] The volume resistivity is a value measured by a four-terminal method using pellets. For example, a measurement device using Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation is used to measure the volume resistivity of the pellets before and after sintering, and the change in the volume resistivity after sintering can be measured.

[0062] Volumetric shrinkage is to use the above-mentioned pressing machine with silver microparticles, keep 10 seconds with pressure 127MPa and make cylindrical particles, measure the thickness and diameter of cylindrical particles with caliper, and the value calculated by the volume of particles before and after firing.Volume shrinkage is obtained by following formula.In addition, the firing of particles uses an electric furnace.

[0063] Volume shrinkage (%) = 100 - ((volume after firing / volume before firing) × 100)

[0064] The particle size of silver particles measured by the BET method is 0.1 μm or more and 1 μm or less. After being sintered at 150°C in a nitrogen environment for 1 hour, the volume resistance value is 10 μΩ·cm or less, and the volume shrinkage rate is 10% or more. The volume shrinkage is large and the conductivity is high. In addition, silver particles have a higher melting point than solder and other materials, and are also excellent in heat resistance. Therefore, in bonding

[0065] When silver microparticles are used as the material, heat resistance can be satisfied while excellent conductivity can be achieved.

[0066] [Third example of silver microparticles]

[0067] The silver particles have a particle size of 0.1 μm to 1 μm as measured by the BET method, a volume resistance of 10 μΩ·cm or less after being sintered in the particle state at 150° C. in the air for 1 hour, and a volume shrinkage of 5% or more.

[0068] In the present invention, the atmosphere generally refers to the environment in the air. The atmosphere refers to the atmospheric environment. The composition of air is 78.08 volume % nitrogen, 20.95 volume % oxygen, 0.93 volume % argon, and 0.03 volume % carbon dioxide. The general measurement error is allowed for the composition of air.

[0069] In addition, due to the operability during dispersion and the volume shrinkage of the particles after calcination at a temperature of 150° C. for 1 hour in the atmosphere (atmospheric environment), the particle size of the silver particles is preferably 100 to 600 nm, more preferably 300 to 600 nm, further preferably 300 to 500 nm, and most preferably 300 to 400 nm.

[0070] The volume resistance value is preferably 8 μΩ·cm or less, more preferably 7 μΩ·cm or less, and most preferably 5 μΩ·cm or less. The lower limit of the volume resistance value is 1.47 μΩ·cm.

[0071] The volume shrinkage is 5% or more, preferably 6% or more, and more preferably 7% or more. The upper limit of the volume shrinkage is 40%.

[0072] The particle size of the silver microparticles measured by the BET method is as described above.

[0073] Regarding the firing, the silver fine particles were formed into cylindrical particles, and the particles were placed in an electric furnace and fired at a temperature of 150° C. for 1 hour in the atmosphere.

[0074] The particles were produced by pressing silver microparticles at a pressure of 127 MPa for 10 seconds using a press.

[0075] The volume resistivity is a value measured by a four-terminal method using pellets. For example, the measurement device is Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation, and by measuring the volume resistivity of the pellets before and after sintering, the change in the volume resistivity after sintering can be measured.

[0076] Volumetric shrinkage is to use silver microparticles as above-mentioned press, keep 10 seconds and make cylindrical particles with pressure 127MPa, measure the thickness and diameter of cylindrical particles with caliper, and the value calculated by the volume of particles before and after firing.Volume shrinkage is obtained by following formula.In addition, the firing of particles uses electric furnace.

[0077] Volume shrinkage (%) = 100 - ((volume after firing / volume before firing) × 100)

[0078] The particle size of the silver particles measured by the BET method is 0.1 μm or more and 1 μm or less. The volume resistance value after sintering at 150°C in the air for 1 hour in the state of particles is 10 μΩ·cm or less, and the volume shrinkage rate is 5% or more, thereby the volume shrinkage is large and the conductivity is high. In addition, the silver particles have a higher melting point than solder and the like, and are also excellent in heat resistance. Therefore, when silver particles are used as bonding materials, heat resistance can be met and conductivity is excellent.

[0079] The silver microparticles are preferably coated with aliphatic amine on their surfaces.

[0080] For example, aliphatic amine exists as a surface coating of silver microparticles. In order to increase the volume shrinkage and improve the conductivity, the aliphatic amine preferably has 10 to 18 carbon atoms, and more preferably has 12 to 16 carbon atoms.

[0081] Examples of the aliphatic amine include dodecylamine and hexadecylamine. Dodecylamine and hexadecylamine have a linear structure.

[0082] The presence or absence of surface coating and the composition of the silver microparticles can be investigated using, for example, FT-IR (Fourier transform infrared spectrometer).

[0083] [Application forms of silver particles]

[0084] Figure 1 This is a schematic diagram showing an example of the utilization form of the silver microparticles of the present invention. Figure 2 This is a schematic diagram showing another example of the utilization form of the silver microparticles of the present invention.

[0085] Silver microparticles are used, for example, Figure 1 The substrate 50 is shown bonded to the power semiconductor element 52. Silver particles are used for die attach.

[0086] The silver particles constitute a joint 54 that joins the substrate 50 and the power semiconductor 52. The joint 54 is formed by firing the silver particles at a temperature of, for example, 100° C. or 150° C. in a nitrogen atmosphere or in the air for 1 hour. The substrate 50 and the power semiconductor 52 are joined by the joint 54, and the substrate 50 and the power semiconductor 52 are physically fixed.

[0087] In addition, we also use Figure 2 The illustrated bonding of one substrate 50 and a plurality of semiconductor elements. Figure 2 3 semiconductor elements 53 are shown in the figure. The three semiconductor elements 53 have different heights. The three semiconductor elements 53 are bonded to the substrate 50 via a bonding portion 54 .

[0088] Silver particles have a higher melting point and higher heat resistance than solder and resin. In addition, the volume resistance of the silver particles after being sintered at 100°C in a nitrogen environment for 1 hour in the particle state as described above is less than 15 μΩ·cm, and the volume shrinkage is more than 5%, for example, less than 40%.

[0089] Furthermore, the volume resistance of the silver particles after being fired in a particle state at 150° C. in a nitrogen atmosphere for 1 hour is 10 μΩ·cm or less, and the volume shrinkage is 10% or more, for example, 40% or less.

[0090] Furthermore, the volume resistance of the silver fine particles after being fired in the air at 150° C. for 1 hour in a particle state is 10 μΩ·cm or less, and the volume shrinkage is 5% or more, for example, 40% or less.

[0091] Based on these, even if the temperature changes with the operation of the power semiconductor element 52, the volume change of the joint 54 is small, and the occurrence of cracks is suppressed. In this way, the joint can be maintained and high durability can be obtained. In addition, since the volume resistance value of the silver particles after firing is low, the thermal conductivity is also excellent. Through the joint 54, the heat generated by the power semiconductor 52 can be efficiently conducted to the substrate 50.

[0092] In addition, if Figure 2 As shown, when multiple semiconductor elements of different sizes are joined, the distances from the semiconductor element with short thickness and the semiconductor element with tall thickness to the substrate 50 are different. Since the silver particles of the present invention have a large volume shrinkage rate, even when the substrate 50 is pressurized to join the semiconductor element with short thickness, excessive pressure will not be applied to the semiconductor element with tall thickness.

[0093] In the above Figure 2 In the case where three semiconductor elements 53 of different heights are bonded to one substrate 50 as shown, when they are pressurized and bonded to one substrate at the same time, silver particles with a large volume shrinkage rate are used as bonding material in the narrow area between the semiconductor element 53 and the substrate 50, and bonding material with a smaller volume shrinkage rate is used in the wider area. As a result, the multiple semiconductor elements 53 can be uniformly pressurized and sufficient bonding can be maintained.

[0094] The substrate 50 is a ceramic substrate such as Si 3 N 4 on which a copper circuit is provided.

[0095] The power semiconductor element 52 uses a semiconductor element such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide, or diamond. The semiconductor element 53 uses a semiconductor element of a general silicon substrate. In addition, the semiconductor element 53 can also be a power semiconductor element. In addition, the silver particles are not limited to the bonding with the power semiconductor element 52 or the semiconductor element 53, and can also be used for bonding with high-frequency devices, light-emitting diodes or semiconductor lasers. As mentioned above, the silver particles have excellent thermal conductivity and are suitable for bonding with those with a large heat generation and a high operating temperature.

[0096] In addition to bonding, silver microparticles can also be used for various wirings such as signal wiring and conductive wiring.

[0097] [Method for producing silver microparticles]

[0098] Next, an example of a method for producing silver microparticles is described based on Figure 3 However, the method for producing silver microparticles of the present invention is not limited to using Figure 3 The manufacturing method of the silver microparticle manufacturing device 10 shown.

[0099] Figure 3 This is a schematic diagram showing an example of a production apparatus for silver microparticles of the present invention.

[0100] pass Figure 3 The silver microparticle production device 10 shown (hereinafter, simply referred to as the production device 10) can obtain the above-mentioned silver microparticles.

[0101] The manufacturing device 10 includes a plasma torch 12 for generating a hot plasma flame, a material supply device 14 for supplying a raw material 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 for removing coarse particles having a particle size larger than an arbitrary predetermined particle size from the primary silver particles 15, and a recovery unit 20 for recovering 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 connecting pipe 21a. The cyclone 19 and the recovery unit 20 are connected by a connecting pipe 21b connected to an inner pipe 19e.

[0102] The manufacturing apparatus 10 further includes a supply unit 40 that supplies a surface treatment agent to the primary silver particles 15 or the secondary silver particles 18 .

[0103] The primary silver particles 15 and the secondary silver particles 18 are both particles in the process of manufacturing the particles of the present invention. The primary silver particles 15 or the secondary silver particles 18 are surface treated, that is, the surface treated silver particles 30 are the silver particles of the present invention. The silver particles 30 are the particles whose surfaces are coated with aliphatic amine.

[0104] For the material supply device 14 , the chamber 16 , the cyclone 19 , and the recovery unit 20 , for example, various devices disclosed in Japanese Patent Application Laid-Open No. 2007-138287 can be used.

[0105] In the present embodiment, the fine particles are produced using, for example, silver powder as a raw material.

[0106] The average particle size of the silver powder is appropriately set so as to 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.

[0107] The plasma torch 12 is composed of a quartz tube 12a and a high-frequency oscillation coil 12b surrounding the outside thereof. A supply pipe 14a described later is provided in the central portion of the upper portion of the plasma torch 12 in order to supply the raw material powder of the microparticles into the plasma torch 12. A plasma gas supply port 12c is formed on the outer periphery (on the same circumference) of the supply pipe 14a, and the plasma gas supply port 12c is annular. A power supply (not shown) for generating a high-frequency voltage is connected to the high-frequency oscillation coil 12b. If a high-frequency voltage is applied to the high-frequency oscillation coil 12b, a hot plasma flame 24 is generated. The hot plasma flame 24 evaporates the raw material (not shown) to form a mixture in a gas phase. The plasma torch 12 is a processing unit that uses a gas phase method to convert the raw material into a mixture in a gas phase.

[0108] 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 a pipe 22a, and the plasma gas supply unit 22 is provided with a supply amount adjustment unit such as a valve (not shown) for adjusting the supply amount. The plasma gas is supplied from the plasma gas supply unit 22 through the annular plasma gas supply port 12c to the plasma torch 12 in the direction indicated by the arrow P and the direction indicated by the arrow S.

[0109] Plasma gas may be a mixed gas of hydrogen and argon, for example. In this case, hydrogen and argon are stored in the plasma gas supply unit 22. From the plasma gas supply unit 22, hydrogen and argon are supplied to the plasma torch 12 from the direction indicated by the arrow P and the direction indicated by the arrow S via the pipe 22a through the plasma gas supply port 12c. In addition, only argon may be supplied in the direction indicated by the arrow P.

[0110] In addition, in order to cope with the silver microparticles, the plasma gas as described above does not necessarily need to be a mixed gas, and the plasma gas may be a single gas.

[0111] When a high-frequency voltage is applied to the high-frequency oscillation coil 12 b , a hot plasma flame 24 is generated in the plasma torch 12 .

[0112] The temperature of the hot 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 hot plasma flame 24, the easier it is for the raw material powder to be in a gas phase, which is preferred, but the temperature is not particularly limited. For example, the temperature of the hot plasma flame 24 can be set to 6000°C, and it is considered that it can reach about 10000°C in theory.

[0113] In addition, the pressure environment in the plasma torch 12 is preferably equal to or lower than atmospheric pressure. Here, the pressure environment equal to or lower than atmospheric pressure is not particularly limited, but is, for example, 0.5 to 100 kPa.

[0114] Furthermore, the outer side of the quartz tube 12a is surrounded by a concentric tube (not shown), and cooling water is circulated between the tube and the quartz tube 12a to water-cool the quartz tube 12a to prevent the hot plasma flame 24 generated in the plasma torch 12 from causing the quartz tube 12a to be too hot.

[0115] 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 a raw material to the hot plasma flame 24 in the plasma torch 12.

[0116] The material supply device 14 is not particularly limited as long as it can supply the raw material to the thermal plasma flame 24 , and for example, the raw material is dispersed in particles and supplied to the thermal plasma flame 24 .

[0117] When the raw material is a powder, for example, as the material supply device 14 for supplying silver powder in a powder state, as described above, for example, the one disclosed in Japanese Patent Application Laid-Open No. 2007-138287 can be used. In this case, the material supply device 14 includes, for example, a storage tank (not shown) for storing the raw material, a screw feeder (not shown) for quantitatively conveying the raw material, and a dispersion unit (not shown) for dispersing the raw material conveyed by the screw feeder into a primary particle state before finally dispersing it, and a carrier gas supply source (not shown).

[0118] The raw material is supplied to the hot plasma flame 24 in the plasma torch 12 through the supply pipe 14 a together with the carrier gas to which the pressure is applied from the carrier gas supply source.

[0119] The material supply device 14 is not particularly limited in its configuration as long as it can prevent the raw material from agglomerating and maintain the raw material in a dispersed state and can spread the raw material into the plasma torch 12. The carrier gas can use an inert gas such as argon. The flow rate of the carrier gas can be controlled using a flow meter such as a float flow meter. In addition, the so-called flow rate value of the carrier gas is the scale value of the flow meter.

[0120] The chamber 16 is disposed adjacent to the lower portion of the plasma torch 12, and the primary particles 15 of silver particles are generated from the above-mentioned gas phase mixture without using cooling gas in the chamber 16. In addition, the chamber 16 functions as a cooling tank. The cooling gas is also called a quenching gas, and argon gas or the like can be used.

[0121] The gas supply unit 28 supplies a temperature-adjusting gas containing an inert gas, for example, into the connection pipe 21 a or the connection pipe 21 b . The gas supply unit 28 supplies a temperature-adjusting gas containing an inert gas to the primary silver particles 15 or the secondary silver particles 18 .

[0122] 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 connection pipe 21a, and the second gas supply pipe 28c is connected to the connection pipe 21b.

[0123] The temperature-adjusting gas can be supplied to either the first gas supply pipe 28b or the second gas supply pipe 28b by the switching valve 28a, and the temperature-adjusting gas can be supplied to either the connecting pipe 21a or the connecting pipe 21b.

[0124] The gas supply unit 28 further includes a compressor or a pressure imparting device (not shown) such as a blower for applying extrusion pressure to the temperature-adjusting gas supplied to the first gas supply pipe 28b or the second gas supply pipe 28c, and also includes a storage unit (not shown) for storing the temperature-adjusting gas and a pressure control valve for controlling the gas supply amount. The temperature-adjusting gas is, for example, argon gas.

[0125] The temperature of the gas can be adjusted to a desired temperature by supplying the temperature-adjusting gas from the gas supply unit 28 into the connecting pipe 21 a or the connecting pipe 21 b .

[0126] like Figure 3 As shown, a cyclone 19 is provided in the chamber 16 for classifying the primary particles 15 of silver into a desired particle size. The cyclone 19 includes an inlet pipe 19a for supplying the primary particles 15 from the chamber 16, a cylindrical outer cylinder 19b connected to the inlet pipe 19a and located at the upper part of the cyclone 19, a truncated cone portion 19c which is continuous from the lower part of the outer cylinder 19b toward the lower side and whose diameter gradually decreases, a coarse particle recovery chamber 19d connected to the lower side of the truncated cone 19c and recovering coarse particles having a particle size greater than the above-mentioned desired particle size, and an inner tube 19e connected to a recovery unit 20 described in detail later and protruding from the outer cylinder 19b. The chamber 16 and the inlet pipe 19a are connected by a connecting pipe 21a, and the primary particles 15 are moved to the cyclone 19 through the connecting pipe 21a. The connecting pipe 21a is a conveying path for the primary particles 15.

[0127] The inlet pipe 19a of the cyclone 19 blows an airflow containing the primary particles 15 along the inner peripheral wall of the outer cylinder 19b, whereby the airflow is Figure 3 As shown by arrow T, the liquid forms a descending swirling flow by flowing from the inner peripheral wall of the outer cylinder 19b toward the truncated cone portion 19c.

[0128] Next, when the descending swirling flow is reversed to become an ascending flow, due to the balance between centrifugal force and resistance, the coarse particles cannot ride on the ascending flow, and fall along the side of the truncated cone portion 19c, and are recovered by the coarse particle recovery chamber 19d. In addition, the fine particles, which are more affected by resistance than centrifugal force, are discharged to the outside of the cyclone 19 through the inner pipe 19e and the connecting pipe 21b together with the ascending flow on the inner wall of the truncated cone portion 19c.

[0129] In addition, negative pressure (attractive force) is generated from the recovery unit 20 described in detail later through the inner tube 19e and the connecting tube 21b. Then, the microparticles separated from the above-mentioned swirling airflow are attracted in a manner represented by symbol U by the negative pressure (attractive force) and sent to the recovery unit 20 through the inner tube 19e and the connecting tube 21b.

[0130] A recovery unit 20 for recovering silver particles 30 having a desired nanometer-level particle size is provided on an extension of an inner tube 19e at an airflow outlet in the cyclone 19. The recovery unit 20 includes a recovery chamber 20a, a filter 20b provided in the recovery chamber 20a, and a vacuum pump 29 connected via a pipe provided at the bottom of the recovery chamber 20a. The silver particles 30 transported from the cyclone 19 are sucked by the vacuum pump 29, introduced into the recovery chamber 20a, and recovered in a state of residing on the surface of the filter 20b.

[0131] Furthermore, in the above-mentioned production apparatus 10, the number of cyclones used is not limited to one, and may be two or more, or no cyclone may be used.

[0132] The supply unit 40 is a component that supplies the surface treatment agent St to the silver particles, downstream of the first gas supply pipe 28b of the connecting pipe 21a, or downstream of the second gas supply pipe 28c of the connecting pipe 21b, in the chamber 16. The silver particles whose surfaces are coated with aliphatic amines are formed by the surface treatment agent St. Here, the chamber 16 side is referred to as the upstream side, and the cyclone 19 side is referred to as the downstream side with respect to the connecting pipe 21a.

[0133] The supply unit 40 includes, 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 to the same level as the position where the connecting pipe 21a is connected, or is connected to a height below the position in the chamber 16. The surface treatment agent St is supplied from the inner side wall 16a of the chamber 16 to the chamber 16 via the first supply pipe 41a.

[0134] The connection position of the second supply pipe 41b in the connection pipe 21a is P1, and the connection position of the third supply pipe 41c in the connection pipe 21b is P2. The connection position P2 of the third supply pipe 41c is located downstream of the connection position P1 of the second supply pipe 41b.

[0135] 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 tube 21 a , or the secondary silver particles 18 passing through the connection tube 21 b .

[0136] The supply unit 40 supplies the surface treatment agent St at a temperature range suitable for the surface treatment agent St. The surface treatment agent St is attached to the primary silver particles 15 or the secondary silver particles 18, so that the primary silver particles 15 or the secondary silver particles 18 are subjected to surface treatment to form silver particles whose surfaces are coated with aliphatic amines. In this way, the melting of the silver particles is prevented, and the silver particles 30 are obtained.

[0137] 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 of converting the surface treatment agent St into droplets and spraying the droplets onto the secondary silver particles 18 .

[0138] As described above, the surface treatment agent St is supplied in an appropriate temperature range. The so-called appropriate temperature range is a temperature range in which the surface treatment agent St can play a role in preventing the melting of silver microparticles. However, as long as the melting of silver microparticles can be prevented, the surface treatment agent St can be introduced from a temperature range that denatures the surface treatment agent St, or it can be introduced from a temperature range that does not denature the surface treatment agent St.

[0139] Furthermore, the surface state of the surface-treated fine particles can be investigated using, for example, FT-IR (Fourier transform infrared spectrometer).

[0140] The temperature range that can prevent the silver particles from melting is a temperature range in which the primary particles 15 can be coated with organic matter or surface treatment agent by the denaturation of the surface treatment agent St. The temperature range that does not denature the surface treatment agent St is a temperature range determined based on the temperature measured by differential thermal-thermogravimetric simultaneous measurement (TG-DTA).

[0141] The temperature range in which the surface treatment agent St is not denatured is a temperature range in which the weight reduction ratio is 50% by mass or less in the differential thermal-thermogravimetric simultaneous measurement of the surface treatment agent St. The weight reduction ratio is more preferably 30% by mass or less, and further preferably 10% by mass or less.

[0142] In addition, the differential thermal-thermogravimetric simultaneous measurement was performed using STA7200 (trade name) manufactured by Hitachi High-Tech Science Co., Ltd.

[0143] For example, aliphatic amine is used as the surface treatment agent St. If the aliphatic amine is in a liquid state when used, it is not necessarily necessary to be dissolved in a solvent like an aqueous solution, and it can also be used as a monomer.

[0144] The aliphatic amine preferably has 10 to 18 carbon atoms, and more preferably 12 to 16 carbon atoms. Examples of the aliphatic amine include dodecylamine and hexadecylamine. Dodecylamine and hexadecylamine have a linear structure.

[0145] As dodecylamine, for example, the product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (Product No. 123-00246) can be used.

[0146] As hexadecylamine, for example, the product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (Product No. 038-07162) can be used.

[0147] In addition, the surface treatment agent St may contain an organic solvent.

[0148] (Organic Solvent)

[0149] The organic solvent is not particularly limited and can be appropriately selected according to the purpose. As the organic solvent, for example, alcohols such as methanol and ethanol, ketones such as acetone, amides such as alkyl halides, formamides, sulfoxides such as dimethyl sulfoxide, heterocyclics, hydrocarbons, esters such as ethyl acetate, and ethers can be used. One of these can be used alone, or two or more can be combined.

[0150] A sensor (not shown) for measuring the temperature of the transport path of the primary silver particles 15 or the secondary silver particles 18 may be provided, and the temperature measurement result of the sensor may be used to determine whether the temperature is in a temperature zone 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 may determine whether the temperature is in a temperature zone suitable for the surface treatment agent St based on the result of measuring the temperature of the transport path of the primary silver particles 15 or the secondary silver particles 18 using the sensor. In the case where the temperature of the transport path of the primary silver particles 15 or the secondary silver particles 18 is not suitable for the temperature zone of the surface treatment agent St, for example, the flow rate of the temperature adjustment gas supplied from the gas supply unit 28 is changed.

[0151] As described above, since the temperature measurement result of the sensor is used to determine whether the temperature is in a suitable temperature range for the surface treatment agent St, the sensor is preferably provided upstream of the connection position P1 of the connection pipe 21a of the second supply pipe 41b. Therefore, the sensor is provided in the connection pipe 21a, for example.

[0152] The sensor is not particularly limited in configuration as long as it can measure temperature, but the shorter the measuring time, the better. Therefore, the sensor may be, for example, a resistance thermometer, a radiation thermometer, an infrared temperature sensor, or a thermistor.

[0153] Next, an example of a method for producing silver microparticles using the above-mentioned production apparatus 10 will be described.

[0154] First, as raw material powder of silver fine particles, for example, silver powder having an average particle size of 15 μm or less is fed into the material supply device 14 .

[0155] As the plasma gas, for example, argon gas and hydrogen gas are used, and a high-frequency voltage is applied to the high-frequency oscillation coil 12 b to generate a hot plasma flame 24 in the plasma torch 12 .

[0156] Next, the silver powder is transported by gas using, for example, argon gas as a carrier gas, and supplied to the hot plasma flame 24 in the plasma torch 12 through the supply pipe 14a. The supplied silver powder evaporates in the hot plasma flame 24 to become a mixture in a gas phase, and in the chamber 16, primary silver particles 15 are generated from the mixture in a gas phase without using a cooling gas.

[0157] Next, the primary silver particles 15 obtained in the chamber 16 are blown into the inlet pipe 19a of the cyclone 19 through the connecting pipe 21a, along the inner peripheral wall of the outer cylinder 19b together with the air flow, thereby the air flow is as follows: Figure 3As shown by the arrow, it flows along the inner wall of the outer cylinder 19b, forming a swirling flow and descending. Then, when the descending swirling flow is reversed and becomes an ascending flow, due to the balance between centrifugal force and resistance, the coarse particles cannot ride on the ascending flow, but descend along the side of the truncated cone portion 19c and are recovered by the coarse particle recovery chamber 19d. In addition, the fine particles, which are more affected by resistance than centrifugal force, are discharged from the inner wall of the truncated cone portion 19c together with the ascending flow to the outside of the cyclone 19.

[0158] The discharged silver secondary particles 18 are attracted to the negative pressure (attractive force) generated by the vacuum pump 29 from the recovery unit 20. Figure 3 The direction indicated by the symbol U passes through the inner tube 19e and the connecting tube 21b.

[0159] When the primary silver particles 15 or the secondary silver particles 18 pass through the connecting tube 21a or the connecting tube 21b, the temperature adjustment gas from the gas supply unit 28 is supplied to the connecting tube 21a or the connecting tube 21b through the first gas supply pipe 28b or the second gas supply pipe 28c to cool the primary silver particles 15 or the secondary silver particles 18. After the primary silver particles 15 or the secondary silver particles 18 are set to a temperature range suitable for the surface treatment agent by the temperature adjustment gas, the surface treatment agent St is supplied to the primary silver particles 15 or the secondary silver particles 18 in the form of spray, for example, from the supply unit 40 in the chamber 16, the connecting tube 21a or the connecting tube 21b to perform surface treatment on the primary silver particles 15 or the secondary silver particles 18.

[0160] The surface-treated primary silver particles 15 or secondary silver particles 18, that is, silver particles 30, are sent to the recovery unit 20, and the silver particles 30 are recovered by the filter 20b of the recovery unit 20. In this way, silver particles are obtained.

[0161] When the silver microparticles 30 are recovered in the recovery unit 20, the internal pressure in the cyclone 19 is preferably equal to or lower than the atmospheric pressure. The particle size of the silver microparticles 30 can be set to any particle size of the nanometer order according to the purpose.

[0162] Furthermore, in the present invention, a thermal plasma flame is used as a heat source to form the primary particles of silver, but other gas phase methods may be used to form the primary particles of silver. Therefore, as long as it is a gas phase method, it is not limited to the method of manufacturing the primary particles of silver using a thermal plasma flame, and it is also possible to form the primary particles of silver using, for example, a flame method. Furthermore, the method of manufacturing the primary particles using a thermal plasma flame is called a thermal plasma method.

[0163] Here, the so-called 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, a raw material containing silver is supplied to a flame, silver particles are generated in the flame, and primary fine particles 15 of silver are obtained. Furthermore, a surface treatment agent St is supplied to the primary fine particles 15 of silver or the secondary fine particles 18 of silver to produce silver fine particles.

[0164] In the flame method, the same surface treatment agent as that in the thermal plasma method can be used.

[0165] The present invention is basically constituted as above. The above is a detailed description of the silver microparticles of the present invention, but the present invention is not limited to the above-mentioned embodiments, and various improvements or changes can be made within the scope of the present invention.

[0166] [Example 1]

[0167] Hereinafter, the silver microparticles of the present invention will be described in more detail.

[0168] In the first embodiment, silver particles of Examples 1 and 2 and silver particles of Comparative Example 1 were prepared. The silver particles of Examples 1 and 2 and the silver particles of Comparative Example 1 were prepared using Figure 3 The manufacturing apparatus 10 shown is shown below. The manufacturing conditions are shown below.

[0169] (Example 1)

[0170] 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 is a value measured by a particle size distribution meter. The particle size distribution meter used was MT3300 manufactured by Microtrac BEL Co., Ltd.

[0171] In addition, the production conditions of silver microparticles were such that the output of plasma was fixed at 18 kW and the pressure in the plasma torch was fixed at 60 kPa.

[0172] Argon gas was used as the carrier gas, and the flow rate of argon gas was set to 5 liters / minute (converted to standard state).

[0173] Argon and hydrogen were used as plasma gases. The flow rate of argon was set to 200 liters / minute (converted to standard conditions), and the flow rate of hydrogen was set to 5 liters / minute (converted to standard conditions).

[0174] Argon gas was used as the temperature adjustment gas, and the flow rate of the argon gas was set to 380 liters / minute (converted to standard state).

[0175] In Example 1, dodecylamine was used as the surface treatment agent. Ethanol was used as the solvent, and a solution containing dodecylamine (dodecylamine concentration: 10.0 W / W%) was supplied from the third supply pipe 41c (refer to Figure 3) is sprayed onto primary silver particles. Argon gas is used as the spraying gas.

[0176] Furthermore, dodecylamine was produced by Fujifilm Wako Pure Chemical Industries, Ltd. (product number 123-00246), and ethanol was produced by Junsei Chemical Co., Ltd. (product number 17065-1283).

[0177] (Example 2)

[0178] In Example 2, compared with Example 1, the difference is that hexadecylamine is used as the surface treatment agent. In Example 2, ethanol is used as the solvent, and a solution containing hexadecylamine (hexadecylamine concentration 10.0 W / W%) is supplied from the third supply pipe 41c (refer to Figure 3 ) is sprayed on primary particles of silver. Argon gas is used as the spraying gas.

[0179] In Example 2, the flow rate of argon gas used as the temperature adjustment gas was set to 500 liters / minute (converted to standard conditions).

[0180] Hexadecylamine was manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (Product No. 038-07162), and ethanol was manufactured by Junsei Chemical Co., Ltd. (Product No. 17065-1283).

[0181] (Comparative Example 1)

[0182] In Comparative Example 1, in addition to the difference in the surface treatment agent, the surface treatment agent is supplied from the second supply pipe 41b (refer to Figure 3 ) Except for the different supply and temperature adjustment gas flow rates, the present invention is the same as Example 1.

[0183] Comparative Example 1 used citric acid. Pure water was used as the solvent, and an aqueous solution containing citric acid (citric acid concentration: 3.76 W / W%) was supplied from the second supply pipe 41b (refer to Figure 3 ) The primary fine particles of silver were sprayed. Argon gas was used as the spray gas.

[0184] The flow rate of argon gas as the temperature adjustment gas was set to 500 liters / minute (converted under standard conditions).

[0185] SEM images were obtained for the silver particles of Examples 1 and 2. The SEM images were obtained using Regulus 8220 manufactured by Hitachi High-Technologies Co., Ltd. The SEM image of the silver particles of Example 1 is shown in FIG. Figure 4 The SEM image of the silver particles of Example 2 is shown in Figure 5 .

[0186] The particle sizes of the silver particles of Examples 1 and 2 and the silver particles of Comparative Example 1 were measured by the BET method using Macsorb HM-1208 manufactured by Mountech Corporation.

[0187] The volume resistance value of the cylindrical particles before firing, and the volume resistance value and volume shrinkage after firing at 100° C. for 1 hour in a nitrogen atmosphere were measured for the silver particles of Examples 1 and 2 and the silver particles of Comparative Example 1. The results are shown in Table 1 below.

[0188] The nitrogen atmosphere was a state where nitrogen gas with a purity of 99.99 (nitrogen 99.99 volume %) was always flowing, and the oxygen concentration was 100 volume ppm or less. The oxygen concentration was measured using a low concentration oxygen analyzer PS-820-L manufactured by Iijima Electronics Co., Ltd.

[0189] In the measurement of volume resistance, first, silver particles were pressed at a pressure of 127 MPa for 10 seconds to produce cylindrical particles. The measurement device used was Loresta EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation, and the volume resistance of the particles before and after sintering was measured by a four-probe method.

[0190] Then, the pellets were placed in an electric furnace and fired at 100° C. for 1 hour in a nitrogen atmosphere.

[0191] In the determination of volume shrinkage, first, the silver particles are pressed by a press machine and kept at a pressure of 127 MPa for 10 seconds to make cylindrical particles. The thickness and diameter of the cylindrical particles are measured with a caliper, and the volume shrinkage is calculated from the volume of the particles before and after firing. The volume shrinkage is calculated using the following formula. In addition, the particles are placed in an electric furnace and fired at a temperature of 100°C for 1 hour in a nitrogen environment.

[0192] Volume shrinkage (%) = 100 - ((volume after firing / volume before firing) × 100)

[0193] In addition, the density is measured as follows. The thickness and diameter of the cylindrical particles before firing are measured with a caliper, the mass of the particles is measured with an electronic balance, and the density of the cylindrical particles before firing is calculated from the volume and mass of the cylindrical particles. In addition, the thickness and diameter of the cylindrical particles after firing are measured with a caliper, the mass of the particles is measured with an electronic balance, and the density of the cylindrical particles after firing is calculated from the volume and mass of the cylindrical particles after firing.

[0194] [Table 1]

[0195]

[0196] As shown in Table 1, the particle size of the silver particles of Examples 1 and 2 is larger than that of the silver particles of Comparative Example 1. The silver particles of Examples 1 and 2 were formed into cylindrical particles and sintered at 100°C for 1 hour in a nitrogen environment. Compared with the silver particles of Comparative Example 1, the volume resistivity was smaller and the volume shrinkage was larger.

[0197] [Example 2]

[0198] In the second embodiment, silver particles of Examples 10 to 13 and silver particles of Comparative Example 10 were manufactured. The silver particles of Examples 10 to 13 and silver particles of Comparative Example 10 were manufactured using the following method: Figure 3 The manufacturing apparatus 10 is shown below. The manufacturing conditions are shown below.

[0199] (Example 10)

[0200] Example 10 is the same as Example 1 of Example 1.

[0201] (Example 11)

[0202] Example 11 is the same as Example 1 except that the pressure in the plasma torch is 85 kPa, the concentration of dodecylamine is 1.5 W / W%, and the flow rate of argon gas as the temperature adjustment gas is 150 L / min (converted to standard state).

[0203] (Example 12)

[0204] Example 12 is the same as Example 2 of Example 1.

[0205] (Example 13)

[0206] Example 13 is the same as Example 2 of Example 1 except that the pressure in the plasma torch is 85 kPa and the concentration of hexadecylamine is 1.5 W / W%.

[0207] (Comparative Example 10)

[0208] Comparative Example 10 is the same as Comparative Example 1 of the first embodiment.

[0209] In the second example, SEM images (not shown) were obtained for the silver particles of Examples 10 to 13. The SEM images were obtained using Regulus 8220 manufactured by Hitachi High-Technologies Co., Ltd. The silver particles of Examples 10 to 13 were confirmed to be similar to those described above. Figure 4 The SEM images and Figure 5 The silver microparticles of Example 2 shown are the same.

[0210] The particle sizes of the silver particles of Examples 10 to 13 and the silver particles of Comparative Example 10 were measured by the BET method using Macsorb HM-1208 manufactured by Mountech Corporation.

[0211] In the second embodiment, similarly to the first embodiment, the volume resistance value of the silver particles of Examples 10 to 13 and the silver particles of Comparative Example 10 before firing and the volume resistance value and volume shrinkage after firing at 150° C. for 1 hour in a nitrogen atmosphere were measured. The results are shown in the following Table 2. In addition, the nitrogen atmosphere was the same as in the first embodiment.

[0212] The volume resistivity was measured in the same manner as in the first embodiment. The density was also measured in the same manner as in the first embodiment.

[0213] Furthermore, the pellets were placed in an electric furnace and fired at 150° C. for 1 hour in a nitrogen atmosphere.

[0214] The volume shrinkage was measured in the same manner as in the first embodiment. The pellets were placed in an electric furnace and fired at 150° C. in a nitrogen atmosphere until the pellets were calcined for 1 h.

[0215] [Table 2]

[0216]

[0217] As shown in Table 2, the silver particles of Examples 10 to 13 have a larger particle size than the silver particles of Comparative Example 10. The silver particles of Examples 10 to 13 were formed into cylindrical particles and fired at 150° C. for 1 hour in a nitrogen atmosphere. Compared with the silver particles of Comparative Example 10, they had both low volume resistance and large volume shrinkage.

[0218] [Example 3]

[0219] In the third embodiment, silver particles of Examples 20 to 25 and silver particles of Comparative Examples 20 to 22 were produced. The silver particles of Examples 20 to 25 and the silver particles of Comparative Examples 20 to 22 were produced using Figure 3 The manufacturing apparatus 10 is shown below. The manufacturing conditions are shown below.

[0220] (Example 20)

[0221] Example 20 is the same as Example 1 of Example 1.

[0222] (Example 21)

[0223] Example 21 is the same as Example 1 except that the pressure inside the plasma torch is 85 kPa, the concentration of dodecylamine is 0.5 W / W%, and the flow rate of argon gas as the temperature adjustment gas is 150 L / min (converted to standard state).

[0224] (Example 22)

[0225] Example 22 is the same as Example 11 of Example 2.

[0226] (Example 23)

[0227] Example 23 is the same as Example 2 of Example 1.

[0228] (Example 24)

[0229] Example 24 is the same as Example 2 of Example 1 except that the pressure inside the plasma torch is 85 kPa, the concentration of hexadecylamine is 0.5 W / W%, and the flow rate of argon gas for temperature adjustment is 150 L / min (converted to standard state).

[0230] (Example 25)

[0231] Example 25 is the same as Example 13 of Example 2.

[0232] (Comparative Example 20)

[0233] Comparative Example 20 is different from Example 1 in that the cooling gas and the surface treatment agent are different, and the surface treatment agent is supplied from the first supply pipe 41a (see Figure 3 ) is the same as Example 1 except that the temperature adjustment gas is not used.

[0234] Argon and methane were used as cooling gases. The argon flow rate was 800 liters / minute (converted to standard conditions), and the methane flow rate was 1 liter / minute (converted to standard conditions). In Comparative Example 20, 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 18.8 W / W%) was sprayed from the first supply pipe 41a (refer to Figure 3 ) The primary fine particles of silver were sprayed. Argon gas was used as the spray gas.

[0235] (Comparative Example 21)

[0236] Comparative Example 21 is different from Comparative Example 20 except that no cooling gas is used, the citric acid concentration is 3.76 W / W%, and the surface treatment agent is supplied from the second supply pipe 41a (refer to Figure 3 ) is the same as Comparative Example 20 except for the aspect of supplying and using the temperature regulating gas.

[0237] The flow rate of argon gas used as the temperature adjustment gas was 240 liters / minute (converted under standard conditions).

[0238] (Comparative Example 22)

[0239] Comparative Example 22 is the same as Comparative Example 21 except that the pressure in the plasma torch is 85 kPa and the flow rate of the temperature adjustment gas is different.

[0240] The flow rate of argon gas used as the temperature adjustment gas was 15 liters / minute (converted under standard conditions).

[0241] In the third example, SEM images (not shown) were obtained for the silver particles of Examples 20 to 25. The SEM images were obtained using Regulus 8220 manufactured by Hitachi High-Technologies Co., Ltd. The silver particles of Examples 20 to 25 were confirmed to be similar to those described above. Figure 4 The SEM images and Figure 5 The silver microparticles of Example 2 shown are the same.

[0242] The particle sizes of the silver particles of Examples 20 to 25 and the silver particles of Comparative Examples 20 to 22 were measured by the BET method using Macsorb HM-1208 manufactured by Mountech Corporation.

[0243] In the third embodiment, similar to the first embodiment, the volume resistance value of the silver particles of Examples 20 to 25 and the silver particles of Comparative Examples 20 to 22 before firing and the volume resistance value and volume shrinkage after firing at 150° C. for 1 hour in the atmosphere (i.e., in air) were measured. The results are shown in the following Table 3. In addition, the composition of the atmosphere (air) is as described above.

[0244] The volume resistivity was measured in the same manner as in the first embodiment. The density was also measured in the same manner as in the first embodiment.

[0245] Then, the pellets were placed in an electric furnace and fired at 150° C. for 1 hour in the atmosphere.

[0246] The volume shrinkage was measured in the same manner as in the first embodiment. The pellets were placed in an electric furnace and fired at 150° C. for 1 hour in the atmosphere.

[0247] [Table 3]

[0248]

[0249] As shown in Table 3, the particle size of the silver particles of Examples 20 to 25 is slightly larger than that of the silver particles of Comparative Examples 20 to 22. The silver particles of Examples 20 to 25 are formed into cylindrical particles and fired at 150° C. for 1 hour in an atmospheric environment. Compared with the silver particles of Comparative Examples 20 to 22, they have both low volume resistance and large volume shrinkage.

Claims

1. A silver microparticle, characterized in that: The particle size measured by the BET method is 0.1 μm or more and 1 μm or less, the volume resistance value after sintering in a particle state at 100° C. in a nitrogen atmosphere for 1 hour is 15 μΩ·cm or less, and the volume shrinkage is 5% or more.

2. A silver microparticle, characterized in that: The particle size measured by the BET method is 0.1 μm or more and 1 μm or less, the volume resistance value after sintering in a particle state at 150° C. in a nitrogen atmosphere for 1 hour is 10 μΩ·cm or less, and the volume shrinkage is 10% or more.

3. A silver microparticle, characterized in that: The particle size measured by the BET method is 0.1 μm or more and 1 μm or less, the volume resistance value after calcining in the state of particles at 150° C. in the air for 1 hour is 10 μΩ·cm or less, and the volume shrinkage is 5% or more.

4. The silver microparticles according to any one of claims 1 to 3, characterized in that Its surface is coated with aliphatic amine.

5. The silver microparticles according to claim 4, characterized in that The aliphatic amine has 10 to 18 carbon atoms.

Images