JP2005105365A - Electrically conductive powder material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically conductive powder material composed of nickel or a nickel alloy, and in which the formation of a surface oxide film can be suppressed even it is fired in a nonreducing atmosphere, and to provide its production method. <P>SOLUTION: In the method of producing the electrically conductive powder material, an Ni particle-dispersed solution in which Ni particles 1 are dispersed in an organic solvent is made misty, and is fed into a core tube together with gaseous H<SB>2</SB>and gaseous Ar. Then, in the core tube, heating is performed at 200 to 600°C first and the surfaces of the Ni particles 1 are reduced to remove a surface oxide film. Heating is performed at 600 to 1,100°C next, by which the organic solvent is caused to undergo dehydrogenation reaction to form a C-covered layer 2a composed of graphite on the surfaces of the Ni particles. The average thickness of the C-covered layer 2a is 5 to 30 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive powder material that is contained in a mounting material for electronic components such as a conductive paste, a conductive adhesive, and an anisotropic conductive sheet, and that imparts conductivity to the mounting material for these electronic components, and a method for manufacturing the same. .

  In mounting materials for electronic components such as conductive pastes, conductive adhesives and anisotropic conductive sheets for connecting substrates, electronic components, wirings, etc. (hereinafter also simply referred to as mounting materials), a mother made of resin, etc. A conductive powder material having conductivity is added to the material. This conductive powder material includes metal particles composed of metals such as Ag, Pd, Cu, Ni, alloy particles composed of alloys such as Ag—Pd alloys and Cu—Ag based on these metals, and styrene and divinyl. There are metal composite resin particles and the like in which a metal such as Au or Ni is plated on the surface of a powder made of a heat resistant resin such as benzene.

  Such a mounting material is solidified by being fired after being applied or adhered to a substrate or an electronic component. At this time, the firing temperature is limited by the heat resistance performance of the substrate and the electronic component. For example, when this mounting material is used for a rigid substrate such as glass epoxy, the upper limit of the firing temperature is about 260 ° C., and when used for a membrane substrate made of polyimide, polyethylene terephthalate, etc. The upper limit of the firing temperature is about 180 to 220 ° C.

  At such a low firing temperature, metal particles, alloy particles or metal composite resin particles (hereinafter collectively referred to as metal particles) that are conductive powder materials do not sinter and fuse with each other. The conductivity of a mounting material such as a conductive adhesive or an anisotropic conductive sheet is realized by contact between metal particles. Therefore, the metal particles added to these mounting materials are required to have low resistance, low resistance increase due to thermal shock and mechanical stress, and excellent migration resistance. Is done. In addition, the shape of these metal particles is preferably a flat flake shape that allows a large contact area between the particles. Moreover, there are various particle sizes in the range of 0.1 to several hundreds of μm, and they are properly used according to the purpose.

  Ag (silver) is widely used as a material for forming metal particles (see, for example, Patent Document 1). This is because Ag has a low specific resistance value and does not cause a problem of contact failure due to surface oxidation. In addition, Cu (copper) and Ag—Cu alloys, which have the second lowest resistivity after Ag, are widely used as materials for forming the metal particles (see, for example, Patent Documents 2 to 5).

  However, Ag and Cu have a problem that migration is likely to occur. In the future, electronic components will be mounted at high density, and the wiring width and spacing (L / S) in the electronic component will be reduced to about several tens to 10 μm. It becomes more and more important. For this reason, the electroconductive powder material which was excellent in the migration resistance replaced with Ag and Cu is calculated | required. Further, Cu has a problem that its surface is easily oxidized and oxidation is promoted by thermal shock, so that reliability as a mounting material is lacking.

  For this reason, it is conceivable to use Ni or a Ni alloy (hereinafter collectively referred to as Ni) as a material for forming the above-described metal particles. Although Ni has a higher specific resistance value than Ag, it is a material that is unlikely to cause migration, so it can be expected as a next-generation conductive material suitable for high-density mounting.

JP 2001-234152 A JP 2003-068140 A Japanese Patent Laid-Open No. 11-007830 Japanese Patent Laid-Open No. 7-073730 JP-A-10-162647

  However, the conventional techniques described above have the following problems. Since a surface oxide film is easily formed in the atmosphere in the Ni particles, when using a mounting material such as a conductive paste containing Ni particles, the surface oxide film of the Ni particles is removed and the Ni particles are removed. In order to promote the metal bonding between them and reduce the connection resistance, it is necessary to reduce and sinter the mounting material in hydrogen gas. As a result, there are problems that the processing cost and equipment cost of baking increase and the handling becomes difficult.

  The present invention has been made in view of such problems, and is made of nickel or a nickel alloy, and a conductive powder material capable of suppressing the formation of a surface oxide film even when fired in a non-reducing atmosphere, and its manufacture It aims to provide a method.

  In the conductive powder material according to the present invention, the conductive powder material contained in the mounting material for electronic components has an average thickness of 5 to 5 that is made of particles made of nickel or a nickel alloy and made of carbon and covers the surface of the particles. And a covering layer of 30 nm.

  In the present invention, since the particles are formed of nickel or a nickel alloy, the migration resistance of the mounting material is improved when the particles are contained in the electronic component mounting material. Moreover, since the coating layer made of carbon is formed on the surface of the particles, it is possible to suppress the oxidation of the surface of the particles, and the mounting material for electronic parts is fired in a non-reducing atmosphere such as in the air and in an inert gas. can do.

  The method for producing a conductive powder material according to the present invention includes a reduction step in which the surface of particles made of nickel or a nickel alloy is reduced to remove a surface oxide film, and the surface of the particles whose surface has been reduced is made of carbon and has an average thickness. And a coating step of coating a coating layer having a thickness of 5 to 30 nm.

  In addition, the method for producing a conductive powder material according to the present invention includes a supply step of supplying a nickel particle dispersion solution in which particles made of nickel or a nickel alloy are dispersed in an organic solvent into a reducing atmosphere in a mist form. The reduction step is a step of heating the mist-like nickel particle dispersion solution to a temperature of 200 to 600 ° C. in the reducing atmosphere, and the coating step includes the particles whose surface has been reduced and the organic solvent. It is preferably a step of depositing carbon on the surface of the particles by heating to a temperature of 600 to 1100 ° C. in a non-oxidizing atmosphere. Thereby, the electroconductive powder material which concerns on this invention can be manufactured efficiently.

  Further, the supplying step is a step of supplying the mist-like nickel particle dispersion solution together with a reducing gas into the core tube and circulating the inside of the core tube, and the reducing step is performed in an upstream portion of the core tube. The covering step may be performed at a downstream portion of the core tube, and the particles may be collected at a downstream end portion of the core tube. Thereby, the conductive powder material according to the present invention can be continuously and efficiently manufactured with simple equipment.

  According to the present invention, a conductive powder material that can be fired in a non-reducing atmosphere such as in the air and in an inert gas when it is contained in a packaging material for electronic components, and that provides good migration resistance. Can be obtained. Thereby, high-density mounting of electronic components can be performed at low cost.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. First, a first embodiment of the present invention will be described. 1A and 1B are cross-sectional views showing a conductive powder material according to the present embodiment, FIG. 1A shows a material in which the C coating layer is made of graphite, and FIG. 1B shows an amorphous material in which the C coating layer is amorphous. The material which consists of carbon is shown. As shown to Fig.1 (a) and (b), in the electroconductive powder material which concerns on this embodiment, the Ni particle 1 which consists of nickel or a nickel alloy is provided. Further, a C coating layer 2 a made of graphite or a C coating layer 2 b made of amorphous carbon is formed on the surface of the Ni particles 1, and the C coating layer 2 b covers the Ni particles 1. The C coating layer 2a made of graphite is formed in a layer shape, and its average thickness is 5 to 30 nm. The C coating layer 2b made of amorphous carbon is formed in a lump shape, and the surface of the Ni particles 1 is partially exposed. The average thickness of the C coating layer 2b is 5 to 30 nm. Depending on the production conditions, the C coating layer becomes graphite, becomes amorphous carbon, or both coexist. The Ni particles 1 and the C coating layer 2a or 2b form C-coated Ni particles that are conductive powder materials according to this embodiment. The shape of the C-coated Ni particles is spherical or flat flaky, and the average diameter is, for example, 200 nm.

  For example, the C-coated Ni particles are added to a paste containing an organic solvent and a binder to form a conductive paste. Then, this conductive paste is applied between members to be connected, for example, a substrate, an electronic component, or wiring, and baked in the atmosphere or in an inert gas. Thereby, the applied conductive paste is solidified. At this time, the C-coated Ni particles come into contact with each other in the conductive paste to form a current path, whereby conductivity can be imparted to the conductive paste. As a result, the aforementioned members can be connected to each other. The same applies to the case where a conductive adhesive and an anisotropic conductive sheet are used as the mounting material. Hereinafter, the reason for the numerical limitation in the constituent requirements of the present invention will be described.

Average thickness of coating layer: 5 to 30 nm
By forming the C coating layer on the surface of the Ni particles, oxidation of the surface of the Ni particles can be suppressed. In addition, a surface oxide film is easily formed on the surface of the Ni particles by the atmosphere, but the thickness of the surface oxide film is extremely thin, less than 5 nm. For this reason, if the average thickness of the coating layer is 5 nm or more, even if a surface oxide film is formed on the exposed portion of Ni that is not covered by the C coating layer on the surface of the Ni particles, the conductive powder materials are in contact with each other. In this case, the coating layers come into contact with each other, and the conductivity of the mounting material is ensured. On the other hand, the specific resistance value of carbon (C) is about 1 × 10 ^{−3 to} 1 × 10 ⁻⁴ Ω · cm, which is 10 times compared to the specific resistance value of metal that is 1 × 10 ⁻⁵ Ω · cm or less. About high. For this reason, when the thickness of the coating layer exceeds 30 nm, the resistance of the mounting material increases. Therefore, the average thickness of the coating layer needs to be 5 to 30 nm.

  In this embodiment, since the particles are made of Ni, the migration resistance is good. In addition, since a coating layer made of graphite having a thickness of 5 to 30 nm is formed on the surface of the Ni particles, formation of a surface oxide film on the surface of the Ni particles is suppressed. For this reason, when the C-coated Ni particles of the present embodiment are contained in a mounting material such as a conductive paste, a conductive adhesive, and an anisotropic conductive sheet, the mounting material is baked in a non-reducing atmosphere, for example, in the atmosphere or Even if it is performed in an inert gas, the conductivity of the mounting material can be ensured. Further, even if the mounting material is exposed to a high temperature atmosphere, the resistance of the mounting material does not increase, the thermal shock resistance is high, and the connection reliability is high.

  Next, a second embodiment of the present invention will be described. The present embodiment is a method for producing a conductive powder material according to the first embodiment described above. FIG. 2 is a diagram showing an apparatus for producing C-coated Ni particles in the present embodiment. As shown in FIG. 2, an ultrasonic bath 11 is provided in the production apparatus 10 for C-coated Ni particles, and a pressure-resistant sealed raw material container 12 is immersed in the ultrasonic bath 11. A Ni particle dispersion solution 13 is held in the sealed raw material container 12. The Ni particle dispersion solution 13 is, for example, a solution in which Ni particles 1 (see FIG. 1), an organic solvent, and a dispersant are mixed.

In addition, a dispersing agent is a surfactant for mutually dispersing Ni particles 1 so that they do not aggregate with each other, for example, sodium hexametaphosphate. The organic solvent is a raw material for precipitating carbon (graphite or amorphous carbon) on the surface of the Ni particles 1 by a dehydrogenation reaction, as will be described later, and is a C _x H _y O _z system such as tetrahydrofuran (THF). A solvent or a C _x H _y solvent such as benzene, toluene or hexane is used.

  Further, one end of the pressurized gas introduction tube 14 is inserted into the sealed raw material container 12 so as not to be immersed in the Ni particle dispersion solution 13, and a flow meter 15 is provided in the middle of the pressurized gas introduction tube 14. Is provided. Thereby, the pressurized gas for applying a pressure to the Ni particle dispersion solution 13 is introduced into the ultrasonic bath 12. The pressurized gas is an inert gas, for example, Ar gas.

On the other hand, one end of the outlet pipe 16 is inserted into the sealed raw material container 12 so as to be immersed in the Ni particle dispersion solution 13, and an atomizer 17 is connected to the other end of the outlet pipe 16. An atomizing gas introduction pipe 18 is connected to the atomizer 17, and a flow meter 19 is provided in the middle of the atomizing gas introduction pipe 18. As a result, the Ni particle dispersion solution 13 and the atomizing gas are supplied to the atomizer 17. The atomizer 17 is supplied with the Ni particle dispersion solution 13 and the atomizing gas, and ejects the Ni particle dispersion solution 13 in a mist form. The atomizing gas is a reducing gas that is mixed with the Ni particle dispersion solution 13 at the tip of the atomizer 17 to reduce the surface of the Ni particles, and is a mixed gas of inert gas and H ₂ gas, for example, Ar gas and H _2. It is a mixed gas with gas.

  Further, the upper end of the core tube 20 is connected to the jet port 17 a of the atomizer 17. The core tube 20 is a tube whose tube axis extends in the vertical direction and whose upper end and lower end are opened. An electric furnace A is provided around the upper portion of the core tube 20, that is, the upstream portion, and an electric furnace B is provided around the lower portion of the core tube 20, that is, the downstream portion. A filter 21 is connected to the lower end of 20.

  Next, a method for producing C-coated Ni particles will be described. As shown in FIG. 2, first, the Ni particle dispersion solution 13 is injected into the sealed raw material container 12 of the manufacturing apparatus 10. Then, by operating the ultrasonic bath 11, the Ni particles are dispersed in the Ni particle dispersion solution 13. At this stage, a surface oxide film is formed on the surface of the Ni particles.

  Next, Ar gas is introduced into the sealed source container 12 as a pressurized gas through the pressurized gas introduction pipe 14. At this time, the flow rate of Ar gas is adjusted by the flow meter 15. As a result, the Ni particle dispersion solution 13 in the sealed raw material container 12 is pushed out to the outlet pipe 16 by the pressurized gas and supplied to the atomizer 17. In addition, since the supply rate of the Ni particle dispersion solution 13 is controlled by the flow rate of the pressurized gas, the sealed raw material container 12 has pressure resistance.

On the other hand, a mixed gas of Ar gas and H ₂ gas is supplied to the atomizer 17 as an atomizing gas through the atomizing gas introduction pipe 18. At this time, the flow rate of the atomizing gas is adjusted by the flow meter 19. As a result, the atomizer 17 converts the Ni particle dispersion solution 13 into a mist form with the atomizing gas to form the raw material mist 22 and ejects it from the ejection port 17a. Thereby, the raw material mist 22 is supplied to the upper end portion of the core tube 20. In the reactor core tube 20, the raw material mist 22 descends slowly and flows through the reactor core tube 20 from the upper end portion to the lower end portion. Thus, the raw material mist 22 is first heated by the electric furnace A and then heated by the electric furnace B. The inside of the furnace tube 20 is a reducing atmosphere, and the pressure is, for example, atmospheric pressure.

Then, the electric furnace A heats the raw material mist 22 and the atomizing gas descending in the furnace core tube 20 to a temperature of 200 to 600 ° C. As a result, a reduction reaction represented by the following chemical formula (1) occurs between the surface oxide film (NiO) of the Ni particles and the H ₂ gas in the atomizing gas, and the NiO film formed on the surface of the Ni particles becomes Ni. Reduced.
NiO + H ₂ → Ni + H ₂ O (1)

Next, the electric furnace B heats the raw material mist 22 and the atomizing gas descending in the furnace core tube 20 to a temperature of 600 to 1100 ° C. Thereby, Ni particle | grains play the role of a catalyst and an organic solvent raise | generates the dehydrogenation reaction shown to following Chemical formula (2) or (3). That is, if the organic solvent is a C _x H _y solvents, reaction occurs represented by the following chemical formula (2), if the organic solvent is a C _x H _y O _z type solvent, the reaction represented by the following chemical formula (3) Occur. As a result, C dissolves in the Ni particles.
_{Ni + C x H y → Ni} + xC + (y / 2) H 2 (2)
_{Ni + C x H y O z} → Ni + xC + (y / 2-z) H 2 + zH 2 O (3)

  Next, when the Ni particles are cooled, C (graphite or carbon) is deposited on the surfaces of the Ni particles. Thereby, a C coating layer is formed on the surface of the Ni particles, and C coated Ni particles are formed. The raw material mist 22 passes through the core tube 20 and reaches the filter 21, and the C-coated Ni particles are separated from the raw material mist 22 by the filter 21 and collected.

  Hereinafter, the reason for the numerical limitation in each constituent requirement of the present invention will be described.

Heating temperature in the reduction process: 200 to 600 ° C
When the heating temperature in the reduction step is less than 200 ° C., the reduction reaction represented by the chemical formula (1) may not occur. On the other hand, the higher the heating temperature, the shorter the reaction time, and hence the shorter the core tube, and therefore the higher the heating temperature is preferable. However, when the heating temperature exceeds 600 ° C., the chemical formula (2) or (3 The dehydrogenation reaction of the organic solvent shown in FIG. For example, when the reaction represented by the chemical formula (3) occurs, H ₂ O is generated, and the H ₂ O partial pressure in the atmosphere increases. As a result, the reaction represented by the chemical formula (1) does not easily proceed to the right. For this reason, in order to smoothly advance the reduction reaction represented by the chemical formula (1), the reaction represented by the chemical formula (3) should not occur. Therefore, the heating temperature in the reduction step is preferably 200 to 600 ° C.

Heating temperature in the coating process: 600 to 1100 ° C.
When the heating temperature in the coating step is less than 600 ° C., the dehydrogenation reaction of the organic solvent represented by the chemical formulas (2) and (3) does not occur. On the other hand, the higher the heating temperature, the shorter the reaction time and thus the shorter the core tube, so the higher the heating temperature is preferable. However, when the heating temperature exceeds 1100 ° C., the following chemical formula (4 The thermal decomposition reaction of the organic solvent shown in FIG. As a result, part of the carbon precipitates in the gas phase to form soot and does not precipitate on the surface of the Ni particles. Accordingly, the heating temperature in the coating step is preferably 600 to 1100 ° C. The processing time required in the coating process varies depending on the heating temperature, furnace length, gas pressure, etc. In this embodiment, for example, when the heating temperature is 1000 ° C., the processing time is 1 minute or more. A C coating layer was formed on the surface of the Ni particles.
_{Ni + C x H y → Ni} + zC + C p H q + C r H s (4)

  In the present embodiment, Ni particles having an oxide film formed on the surface are removed by a reduction reaction, and subsequently, the surface of the Ni particles from which the oxide film has been removed by a dehydrogenation reaction of an organic solvent. By depositing C, C-coated Ni particles can be produced. In addition, the reduction process is performed in the upper part of one furnace core tube, that is, the part surrounded by the electric furnace A, and the covering process is performed in the lower part, that is, the part surrounded by the electric furnace B, thereby efficiently using simple equipment. C-coated Ni particles can be produced.

In the present embodiment, although using Ar gas as a pressurized gas, the present invention is not limited thereto, the pressurized gas may be any inert gas containing no O ₂ gas, N ₂ gas or He gas or the like may be used. In the present embodiment uses a mixed gas of Ar gas and H ₂ gas as the atomizing gas, the present invention is not limited to this, the atomizing gas may be any reducing gas, eg, N ₂ A mixed gas of gas and H ₂ gas, a mixed gas of He gas and H ₂ gas, or the like may be used.

  Hereinafter, the effect of the embodiment of the present invention will be specifically described in comparison with a comparative example that deviates from the scope of claims. C-coated Ni particles were produced by the method described in the second embodiment. The manufacturing conditions are shown in Table 1.

  The sample of the C-coated Ni particles produced in this way was subjected to morphology observation and measurement of the thickness of the C coating layer. Moreover, the electroconductive paste containing this sample was produced and the electroconductivity was evaluated.

(1) Form observation Among the above-mentioned samples, a sample manufactured at a heating temperature of the electric furnace B of 700 ° C. and a sample manufactured at 1200 ° C. were observed by SEM (Scanning Electron Microscope). FIG. 3A is an SEM photograph showing a sample manufactured at a heating temperature of the electric furnace B of 700 ° C., and FIG. 3B is an SEM photograph showing a sample manufactured at a heating temperature of the electric furnace B of 1200 ° C.

  As shown in FIGS. 3A and 3B, when the heating temperature of the electric furnace B is 700 ° C., only spherical C-coated Ni particles are observed, whereas the heating temperature of the electric furnace B is In the case of 1200 ° C., a considerable amount of carbon crystals were observed in addition to the C-coated Ni particles. This is considered to be because when the heating temperature of the electric furnace B was 1200 ° C., the decomposition reaction of the organic solvent occurred in the gas phase, and C was generated and mixed as soot.

(2) Thickness measurement of C coating layer Moreover, C content was analyzed about the sample which made the heating temperature of the electric furnace B 700-1100 degreeC, and the thickness of C coating layer was estimated from the analysis result. As a result, the tendency that the thickness of the C coating layer increases as the heating temperature of the electric furnace B is increased. When the heating temperature of the electric furnace B is 700 ° C., the thickness of the C coating layer is 5 When the heating temperature was 1100 ° C., the thickness of the C coating layer was 20 to 30 nm.

(3) Conductivity evaluation Further, with respect to a sample in which the heating temperature of the electric furnace B was set to 700 ° C. and a C coating layer was formed, and a sample in which an untreated C coating layer was not formed, these samples were treated with an organic solvent and a binder. A conductive paste was prepared by adding to the containing paste. Then, this conductive paste was printed on a substrate with a squeegee to form a strip-shaped test pattern. Then, the conductive paste after printing, the atmosphere, respectively fired in a N ₂ gas and H ₂ gas, to measure the resistivity. Table 2 shows conditions for producing the conductive paste, printing conditions, and firing conditions.

  FIG. 4 is a graph showing the influence of the firing atmosphere on the conductivity of the conductive paste, with the horizontal axis representing the firing atmosphere of the conductive paste and the vertical axis representing the measured resistivity of the conductive paste after firing. FIG. In FIG. 4, a specific resistance value of infinity (∞) indicates that the specific resistance is too large and exceeds the measurement range of the measuring apparatus.

As shown in FIG. 4, in the conductive paste containing untreated Ni particles in which the C coating layer is not formed, conductivity is obtained only when baked in H ₂ gas. _In the case of firing in ₂ gases, conductivity was not obtained. On the other hand, the conductive paste containing the C-coated Ni particles with the C coating layer formed is sufficient even when baked under any conditions in air, N ₂ gas, or H ₂ gas. Conductivity could be obtained.

As shown in FIG. 4, in the conductive paste using C-coated Ni particles, the specific resistance value was about 1 × 10 ⁻⁴ Ω · cm under any firing condition. It is possible to obtain a resistivity of 10 ⁻⁵ Ω · cm level by optimizing the above.

(A) And (b) is sectional drawing which shows the electroconductive powder material which concerns on the 1st Embodiment of this invention, (a) shows the material in which C coating layer consists of graphite, (b) is C coating | coated. A material whose layer is made of amorphous carbon is shown. It is a figure which shows the manufacturing apparatus of the C covering Ni particle in the 2nd Embodiment of this invention. (A) is a drawing-substituting photograph showing a sample manufactured with the heating temperature of the electric furnace B being 700 ° C., and (b) is a drawing-substituting photograph showing a sample manufactured with the heating temperature of the electric furnace B being 1200 ° C. ( SEM photograph: 10000 times magnification). It is a graph which shows the influence which the baking atmosphere has on the electroconductivity of a conductive paste, taking the baking atmosphere of a conductive paste on a horizontal axis, and taking the measured value of the specific resistance of the conductive paste after baking on a vertical axis | shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Ni particle 2a, 2b; C coating layer 10; Manufacturing apparatus 11; Ultrasonic bath 12; Sealed-type raw material container 13; Ni particle dispersion solution 14; Pressurized gas introduction pipe 15; Flowmeter 16; 17a; Outlet 18; Atomized gas introduction pipe 19; Flow meter 20; Furnace core pipe 21; Filter 22; Raw material mist A, B; Electric furnace

Claims (4)

The conductive powder material contained in the mounting material for electronic parts has particles made of nickel or a nickel alloy and a coating layer made of carbon and having an average thickness of 5 to 30 nm covering the surface of the particles. Characteristic conductive powder material. A reduction step of removing the surface oxide film by reducing the surface of particles made of nickel or a nickel alloy, and a coating step of covering the surface of the particles whose surface has been reduced with a coating layer made of carbon and having an average thickness of 5 to 30 nm And a method for producing a conductive powder material. A supply step of supplying a nickel particle dispersion solution in which particles of nickel or a nickel alloy are dispersed in an organic solvent into a reducing atmosphere in a mist state, and the reducing step includes the mist type in the reducing atmosphere. The nickel particle dispersion solution is heated to a temperature of 200 to 600 ° C., and the coating step includes heating the particles whose surface has been reduced and the organic solvent to a temperature of 600 to 1100 ° C. in a non-oxidizing atmosphere. The method for producing a conductive powder material according to claim 2, wherein carbon is deposited on the surface of the particles. The supplying step is a step of supplying the mist-like nickel particle dispersion solution together with a reducing gas into the core tube and circulating the inside of the core tube, and the reducing step is performed in an upstream portion of the core tube, The method for producing a conductive powder material according to claim 3, wherein the covering step is performed at a downstream portion of the core tube, and the particles are collected at a downstream end portion of the core tube.

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