JP2006241549A - Spherical metal tin fine powder and method and device for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal tin fine powder having a fine particle diameter, comprising no coarse grains, and suitable as electrically conductive particles for electrically conductive paste and electrically conductive resin in a multilayer wiring board, and to provide a method and a device for efficiently producing the metal tin fine powder. <P>SOLUTION: Metal tin fine particles are produced by a plasma process, and the metal tin fine particles are carried while controlling the temperature of a carrier gas by a cooling chamber 5, and are collected into an organic solvent, or are contacted with the gas in an organic solvent 6 in a coating chamber 4 while being carried, and, after coating the surface of each fine particle with the organic solvent, are recovered in a recovery chamber 2. The obtained metal tin fine powder is spherical, has the average particle diameter of 0.4 to 2 μm and the maximum particle diameter of ≤5 μm, and has a uniform particle diameter and has excellent dispersibility, and the surface of each particle is coated with the organic solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fine metal tin powder suitable as conductive particles for conductive paste and conductive resin used for a multilayer wiring board such as an IC substrate, and a manufacturing method and manufacturing apparatus thereof.

  Conventionally, powders of low melting point metals such as silver, copper and tin have been used as conductive particles for conductive pastes and conductive resins for multilayer wiring boards such as IC boards. As a method for producing these metal powders, a dry method such as an atomizing method or an arc plasma method and a wet reduction method are generally known.

  In particular, metal powder for conductive paste is required to have a fine particle size and no coarse particles with the recent fine pitch of multilayer wiring boards and the like. However, a metal powder produced by a general water atomization method has a wide particle size distribution, and it is difficult to obtain a spherical powder when the average particle size is 5 μm or less. On the other hand, according to the gas atomization method using an inert gas as the spray medium, although spherical powder is obtained, the average particle size becomes as large as about 10 μm and cannot be used as a conductive paste for fine wiring.

  Recently, fine particles having an average particle diameter of 5 μm or less can be produced by improving the water atomization method. However, in order to obtain a fine powder having a particle size suitable for a conductive paste for fine wiring, for example, an average particle size of 2 μm, it is necessary to classify from a wide particle size distribution. Even in the water atomization method improved in this way, it is necessary to apply a classification method in the subsequent step technically, and the classification efficiency is about 10%, so that the manufacturing cost is high and there is an economical problem. .

  It is also known to produce metal powder using the arc plasma method (Japanese Patent No. 1146170). However, the fine particles produced by the arc plasma method tend to agglomerate very quickly immediately after the production due to the high temperature of the plasma gas. (H. Toku, O.W. Bende, A.C. Doring, A.C. de Cruz, P.K. Kiyohara and A.L. Silva, “KONA”, 21, (2003), 163 -177). When such fine particles agglomerated in the shape of grapes are used as conductive particles for conductive pastes or conductive resins, there is a problem that the aggregated fine particles become coarse during sintering and cause voids and cracks. .

On the other hand, metal particles having a particle size of 1 μm or less can be produced by a general wet reduction method. However, aggregation is likely to occur, and a spherical powder having a good particle shape cannot be obtained. For this reason, a method of reducing the amount while adding a protective agent to suppress aggregation is used (Japanese Patent Laid-Open No. 2003-306707). According to this improved wet reduction method, fine metal powder having an average particle size of 0.1 μm or less can be obtained. However, since the particle size is small, the bulk density is low. However, there was a problem that good conductivity could not be obtained because of the remaining protective agent.
Japanese Patent No. 1146170 JP 2003-306707 A H. Toku, O.W. Bende, A.C. Doring, A.C. de Cruz, P.K. Kiyohara and A.L. Silva, "KONA", 21, (2003), 163-177

  In view of the above-described conventional circumstances, the present invention has a fine spherical metal tin powder that is fine and does not include coarse particles, and is suitable as a conductive particle for a conductive paste or a conductive resin of a multilayer wiring board, and It aims at providing the method and manufacturing apparatus which manufacture the spherical metal tin fine powder efficiently.

  As a result of intensive studies on a method for producing metal tin fine powders for conductive pastes and conductive resins, the present inventors pay attention to a plasma method suitable for producing metal fine particles having a spherical shape and a suitable particle size. In addition, it was found that by collecting the surface of the metal fine particles obtained by coating with an organic solvent and recovering the spherical metal tin fine powder having a fine particle size and no coarse particles, and having good dispersibility, the present invention Has been completed.

  That is, the spherical metallic tin fine powder provided by the present invention is composed of spherical metallic tin fine particles, the average particle diameter is 0.4-2 μm, the maximum particle diameter is 5 μm or less, the particle diameter is uniform and dispersible. The spherical fine particle surface is coated with an organic solvent.

  In addition, the method for producing the spherical metal tin fine powder of the present invention includes collecting the produced metal tin fine particles in an organic solvent, or carrying the produced metal tin fine particles with a carrier gas while conveying the produced metal tin fine particles with a carrier gas. It is contacted, and the surface of spherical fine particles is covered with an organic solvent and recovered.

  Further, the apparatus for producing the spherical metal tin fine powder of the present invention is an apparatus for producing the metal tin fine powder by the plasma method, comprising an evaporation chamber having a cathode and an anode equipped with a tin raw material, and the produced metal tin. A recovery chamber for recovering the fine particles, and a temperature control means provided in a transport pipe that communicates the evaporation chamber and the recovery chamber. The recovery chamber stores an organic solvent for collecting metal tin fine particles, or An organic solvent gas for coating metal tin fine particles is supplied to a coating chamber provided upstream.

  According to the present invention, the surface of fine particles produced is covered with an organic solvent and collected by using the plasma method, so that aggregation of fine particles can be prevented even with a low melting point metal tin, and the particle size is reduced. A spherical metal tin fine powder that is uniform and does not contain coarse particles and has excellent dispersibility can be efficiently produced.

  Moreover, the spherical metal tin fine powder has excellent oxidation resistance because the surface of the fine particles is coated with an organic solvent, and the residual organic matter can be obtained by using terpineol, which is a constituent component of a conductive paste, as an organic solvent for coating. There is an advantage that the solvent does not become an impurity during the production of the conductive paste. Moreover, since this spherical metal tin fine powder has a small average particle size of 0.4 to 2 μm and does not include coarse particles exceeding 5 μm, it is a conductive paste and conductive resin conductive particles that require a fine wiring pitch. In particular, it can be suitably used as conductive particles of a conductive paste for through holes.

  The spherical metallic tin fine powder of the present invention is produced by a plasma method in a non-oxidizing atmosphere. In the production of powder by the plasma method, fine particles are produced by melting and evaporating a raw material to be heated at a high temperature of plasma. In general, arc plasma is used, and the raw material to be heated is melted and evaporated by the arc plasma generated between the cathode and the anode (the heated raw material side) to produce powder.

  By melting and evaporating the tin raw material by the plasma method, metal tin fine particles having a particle size suitable for a conductive paste or the like having a spherical shape and a fine wiring pitch, specifically, an average particle size of 0. Metal tin fine particles having a small particle size of 4 to 2 μm and a maximum particle size of 5 μm or less and containing no coarse particles can be produced. If the average particle size exceeds 2 μm or the maximum particle size exceeds 5 μm, it will be difficult to apply to a conductive paste for fine wiring pitch, and if the average particle size is less than 0.4 μm, aggregation of fine particles occurs. This is because it becomes easier.

  When the tin raw material is melted and evaporated, a non-oxidizing gas is used as the arc plasma gas in order to prevent the oxidation reaction of tin. In general, an inert gas such as argon is used. However, if hydrogen gas is mixed with an inert gas, the oxidation rate of tin can be improved simultaneously with the prevention of tin oxidation. However, if the amount of hydrogen gas mixed in increases, the generated metal tin fine particles tend to aggregate. Therefore, it is particularly desirable to prevent the aggregation by controlling the temperature during the transportation of the fine particles.

  In addition, the particle size and dispersibility of the metal tin fine particles vary depending on the atmospheric temperature and carrier gas temperature during the production of the fine particles. The smaller the current during production and the lower the ambient temperature, and the lower the carrier gas temperature, the finer the particles of the fine particles. The diameter is reduced and the dispersibility is improved. For example, fine particles having a particle size of 0.4 μm are fused at about 100 ° C., and when the particle size is 2 μm, they are fused at about 160 ° C. to easily grow into large particles or easily aggregate. Therefore, for example, while the produced fine particles are conveyed with the carrier gas, the particle diameter and dispersibility of the obtained metal tin fine particles are brought to a desired preferable range by adjusting the temperature of the carrier gas to a temperature lower than the above temperature. It is possible to adjust.

  Furthermore, in the present invention, the surface of the spherical metal tin fine particles generated by the plasma method is coated with an organic solvent and recovered. For example, the produced metal tin fine particles are collected in an organic solvent, and the organic solvent is separated by filtration, evaporation or the like, and the metal tin fine powder whose surface is coated with the organic solvent is recovered. In addition, while the produced metal tin fine particles are conveyed by a carrier gas, the metal tin fine powder can be recovered after contacting the surface with the gas of the organic solvent to cover the surface.

  In general, fine metal particles have high surface activity, and tin is a low melting point metal, so that grain growth and aggregation are likely to occur. However, in the present invention, the temperature of the carrier gas is appropriately controlled between the generation and recovery of metal tin fine particles, and the surface of the fine particles is covered with an organic solvent for recovery, thereby suppressing grain growth and aggregation. be able to. Further, since it is not exposed to the atmosphere from the generation of fine particles to the surface coating with an organic solvent and recovery, even highly active fine particles can prevent contamination such as oxidation.

  As the organic solvent used for the surface coating of the metal tin fine particles, aromatic solvents, alcohols, esters, ketones and other organic solvents such as terpineol, dihydroterpineol, ethyl cellosolve, butyl cellosolve, ethyl carbitol, Examples thereof include butyl carbitol, or acetates thereof, pentanediol alkyl ether, dibutyl phthalate, and γ-butyrolactone.

  In particular, if an organic solvent usually used for conductive paste such as terpineol is used for surface coating, it remains when the conductive paste is produced with metal tin fine powder surface-coated with the organic solvent. The organic solvent is extremely advantageous because it does not become an impurity.

  Next, the apparatus for producing spherical metal tin fine powder according to the present invention will be described in detail with reference to FIG. This apparatus includes an evaporation chamber 1 for melting and evaporating tin raw material by arc plasma, a recovery chamber 2 for recovering generated metal tin fine particles, a transport pipe 3 communicating between the evaporation chamber 1 and the recovery chamber 2, and a recovery chamber. 2 is provided with a coating chamber 4 provided in the transfer pipe 3 on the upstream side, and a temperature adjusting cooling chamber 5 provided in the transfer pipe 3 at the outlet of the evaporation chamber 1. An organic solvent 6 is placed in the coating chamber 4, and the organic solvent 6 is evaporated by a heater 7 to be gasified.

  The evaporation chamber 1 includes a DC arc cathode 8a and an anode 8b, and a tin raw material 10 is attached to the anode 8b. Tin ingot or tin powder is used as the tin raw material 10 and is supplied continuously and quantitatively at a rate of 1 to 10 g / min in batch production and in mass production. While supplying the arc plasma gas and the carrier gas from the gas supply port 9 to the evaporation chamber 1, arc discharge is performed between the cathode 8 a and the anode 8 b to melt and evaporate the tin raw material 10 to generate fine metal tin particles. In general, argon and hydrogen are used as the arc plasma gas and the carrier gas, and are mixed and supplied separately at a total flow rate of 10 to 200 liters / minute.

  Tin fine particles generated in the evaporation chamber 1 are sent to the coating chamber 4 through the transfer pipe 3 by the transfer gas. At this time, if the atmospheric temperature and carrier gas temperature during the production of the fine particles are high, the tin fine particles are likely to aggregate and become large particles. Further, since the transport pipe 3 is heated by the high-temperature transport gas (argon + hydrogen) and gradually rises in temperature, aggregation is more likely to occur. Therefore, the temperature of the carrier gas is adjusted by cooling in the cooling chamber 5 in which cooling water or the like is flowed while measuring the temperature with a thermocouple (not shown) installed in the carrier pipe 3.

  The tin fine particles entering the coating chamber 4 come into contact with the gas of the organic solvent 6 evaporated by the heater 7, so that the surface is coated with the organic solvent. Tin fine particles having an organic solvent coating layer formed on the surface thereof are further transported to the recovery chamber 2 by the carrier gas, settled and deposited, and recovered as metal tin fine powder 11. In the apparatus shown in FIG. 1, a coating chamber 4 for coating with an organic solvent gas is provided. Instead of the coating chamber 4, an organic solvent is stored in the recovery chamber 2, and tin fine particles are contained in the organic solvent. The organic solvent can be coated on the surface of the tin fine particles also by collecting and collecting the.

[Example 1]
1 using an active arc plasma fine powder production apparatus (ARC-IE, manufactured by Hosokawa Micron Co., Ltd.) (however, the coating chamber 4 is not provided), and a metal tin base as a tin raw material 10 for the anode 8b. About 60 g of gold was attached. By supplying a direct current between the anode 8b and the cathode 8a (tungsten + 2% thorium) while flowing an argon gas of 70 liters / minute and hydrogen of 10 liters / minute, an arc discharge is performed at a current of 200 A and a voltage of 30 V. Gold was melted and evaporated. The produced tin fine particles were introduced into the collection chamber 2 by a carrier gas controlled at 80 ° C., and collected in terpineol stored in the collection chamber 2 to collect fine metal tin powder.

  A scanning electron microscope (SEM) photograph of the metal tin fine powder collected and dried is shown in FIG. According to the laser diffraction method, the particle size distribution of the metal tin fine powder was D10 = 0.14 μm, D50 = 0.49 μm, D90 = 0.94 μm, D100 = 2.31 μm. Moreover, the average particle diameter calculated | required from the SEM photograph of FIG. 2 was D50 = 0.41 micrometer. From this result, it can be seen that a fine metal tin powder having a spherical shape and no coarse particles, that is, no coarse particles of 5 μm or more and excellent dispersibility was obtained.

[Example 2]
Using the production apparatus of FIG. 1 (installing the coating chamber 4), the tin raw material was melted and evaporated under the same conditions as in Example 1, and the generated tin fine particles were brought into contact with the terpineol gas in the coating chamber 4, and then the recovery chamber. 2 was collected to collect fine metal tin powder. At that time, the flow rates of the arc plasma gas and the carrier gas were 30 liters / minute of argon gas and 3 liters / minute of hydrogen.

  According to the laser diffraction method, the particle size distribution of the recovered metal tin fine powder was D10 = 0.13 μm, D50 = 0.53 μm, D90 = 1.00 μm, D100 = 1.94 μm. Further, from observation of the SEM photograph, coarse particles of 5 μm or more were not present. From this result, it can be seen that a fine metal tin powder having a spherical shape and no coarse particles, that is, no coarse particles of 5 μm or more and excellent dispersibility was obtained.

[Example 3]
Metal tin fine powder was produced and recovered by the same method as in Example 2 using the production apparatus of FIG. At that time, the flow rates of the arc plasma gas and the carrier gas were 50 liters / minute of argon gas and 10 liters / minute of hydrogen.

  According to the laser diffraction method, the particle size distribution of the recovered metal tin fine powder was D10 = 0.13 μm, D50 = 0.98 μm, D90 = 1.80 μm, D100 = 3.89 μm. Further, from observation of the SEM photograph, coarse particles of 5 μm or more were not present. From this result, it can be seen that a fine metal tin powder having a spherical shape and no coarse particles, that is, no coarse particles of 5 μm or more and excellent dispersibility was obtained.

[Conventional example]
Using the same active arc plasma fine powder production apparatus as above, about 60 g of metal tin metal was attached to the anode as a tin raw material. The metal tin ingot was melted and evaporated by arc discharge at a current of 150 A and a voltage of 30 V while flowing argon gas of 80 liters / minute. The produced tin fine particles were directly introduced into the recovery chamber by the carrier gas and recovered. In order to make aggregation less likely to occur, an argon gas atmosphere containing no hydrogen was used at a low current, and the gas flow rate was the same as in Example 1.

  A scanning electron microscope (SEM) photograph of the collected metal tin fine powder is shown in FIG. Although this metal tin fine powder had a primary particle size of 0.5 μm or less as observed by SEM, sintering between the primary particles proceeded to form a grape-like aggregate. The particle size distribution determined by the laser diffraction method was D10 = 0.69 μm, D50 = 3.29 μm, D90 = 14.8 μm, and D100 = 37.0 μm.

It is a schematic sectional drawing which shows one specific example of the metal tin fine powder manufacturing apparatus by this invention. It is a scanning electron micrograph of the metal tin fine powder of this invention. It is a scanning electron micrograph of metal tin fine powder by a normal plasma method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Evaporation chamber 2 Collection | recovery chamber 3 Conveyance pipe | tube 4 Coating | covering chamber 5 Cooling chamber 6 Organic solvent 7 Heater 8a Cathode 8b Anode 9 Gas supply port 10 Tin raw material 11 Metal tin fine powder

Claims (3)

  It is composed of spherical metallic tin particles, has an average particle size of 0.4-2 μm, a maximum particle size of 5 μm or less, a uniform particle size, excellent dispersibility, and the fine particle surface is coated with an organic solvent. Spherical metal tin fine powder characterized by   A method for producing metal tin fine powder by a plasma method, wherein the produced metal tin fine particles are collected in an organic solvent, or the produced metal tin fine particles are brought into contact with an organic solvent gas while being carried by a carrier gas. A method for producing fine spherical metal tin powder, wherein the surface of spherical fine particles is covered with an organic solvent and collected. An apparatus for producing metal tin fine powder by a plasma method, comprising an evaporation chamber having a cathode and an anode equipped with a tin raw material, a recovery chamber for recovering the produced metal tin fine particles, and a transport that connects the evaporation chamber and the recovery chamber A temperature adjusting means provided in the tube, and the organic solvent for collecting the metal tin fine particles is stored in the recovery chamber, or the organic solvent gas for coating the metal tin fine particles is provided in the coating chamber provided upstream of the recovery chamber. An apparatus for producing fine spherical metal tin powder, wherein: