Conductive filler, method for manufacturing conductive filler, and conductive paste

Patent metadata

Field	Value
Publication number	US-10639713-B2
Application number	US-201515104745-A
Country	US
Kind code	B2
Filing date	Mar 3, 2015
Priority date	Mar 5, 2014
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

There is provided conductive paste excellent in electro-conductivity and thermal conductivity. Conductive paste comprising conductive filler being composite particles including copper powder and nanosize precipitates which are disposed on the surface of the copper powder and composed of at least one kind of transition metal belonging to the group 8 to group 10 of the periodic table or a compound of the transition metal, and a binder resin.

First claim

The invention claimed is:

1. A conductive filler comprising:
composite particles comprising copper powder and nanosize precipitates which are placed on the surface of the copper powder,
wherein the nanosize precipitates are composed of at least one kind of transition metal selected from the group consisting of iron, ruthenium, osmium, hassium, cobalt, rhodium, iridium, meitnerium, nickel, palladium, platinum, and darmstadtium, or a compound of at least one kind of transition metal selected from the group consisting of iron, ruthenium, osmium, hassium, cobalt, rhodium, iridium, meitnerium, nickel, palladium, platinum, and darmstadtium,
the average particle diameter of the copper powder lies within the range of 1.0 μm to 25 μm, and
the nanosize precipitates are particles and the particle diameter of the particle of the nanosize precipitate is less than or equal to 100 nm, and
wherein the transition metal is cobalt.

2. The conductive filler according to claim 1 , wherein the nanosize precipitates exist also in the inside of the copper powder.

3. The conductive filler according to claim 1 , wherein the content of the transition metal or the compound of the transition metal lies within the range of 0.1 to 6.0% by weight in 100% by weight of the composite particles.

4. The conductive filler according to claim 1 , wherein the compound of the transition metal is at least one among an oxide of the transition metal and a carbide of the transition metal.

5. The conductive filler according to claim 4 , wherein the compound of the transition metal is at least one among cobalt oxide and cobalt carbide.

6. The conductive filler according to claim 1 , wherein the copper powder is composed of pure copper.

7. A conductive paste comprising the conductive filler according to claim 1 and a binder resin.

8. The conductive paste according to claim 7 , wherein the binder resin is at least one kind of resin selected from the group consisting of an epoxy resin, a polyester resin, a urethane resin, a phenol resin and an imide resin.

9. The conductive paste according to claim 7 , wherein the binder resin in an amount of 10 to 35 parts by weight relative to 100 parts by weight of the conductive filler is included.

10. The conductive paste according to claim 7 being an electrically conductive paste.

11. The conductive paste according to claim 7 , being thermally conductive paste.

12. The conductive paste according to claim 7 , further comprising a hardener selected from the group consisting of an amine-based epoxy hardener, an acid anhydride-based epoxy hardener, an isocyanate-based hardener, and an imidazole-based hardener.

13. The conductive paste according to claim 7 , further comprising an inorganic filling material selected from the group consisting of silica and calcium carbonate.

14. A method for manufacturing conductive filler according to claim 1 , comprising the steps of:
preparing composite metal powder comprising copper and at least one kind of transition metal belonging to the group 8 to group 10 of the periodic table or a compound of the transition metal which constitutes the material of nanosize precipitates;
bringing a carbon source into contact with the surface of the composite metal powder to allow carbon to attach to the surface of the composite metal powder;
subjecting the composite metal powder to a heat treatment to allow nanosize precipitates to precipitate on the surface of the composite metal powder; and
removing at least some of carbon attaching to the surface of the composite metal powder to obtain conductive filler being composite particles.

15. The method for manufacturing conductive filler according to claim 14 , wherein the step of preparing composite metal powder is performed by an atomizing method.

16. The method for manufacturing conductive filler according to claim 14 , further comprising the step of allowing the composite metal powder to be added and mixed with a sintering inhibitor before the step of subjecting the composite metal powder to a heat treatment.

17. The method for manufacturing conductive filler according to claim 14 , wherein the step of bringing a carbon source into contact with the surface of the composite metal powder is performed by bringing a carbon-containing gas into contact with the composite metal powder at 250 to 400° C.

18. The method for manufacturing conductive filler according to claim 14 , wherein the heat treatment is performed at 400° C. to 700° C. under an inert gas atmosphere.

19. The method for manufacturing conductive filler according to claim 14 , wherein the step of removing at least some of carbon attaching to the surface of the composite metal powder to obtain conductive filler is performed by mixing the composite metal powder and a binder resin until at least some of carbon attaching to the surface of the composite metal powder is removed away.

20. The method for manufacturing conductive filler according to claim 19 , wherein the mixing of the composite metal powder and the binder resin is performed by being kneaded for 20 minutes to 1 hour.

21. The method for manufacturing conductive filler according to claim 14 , further comprising the step of bringing a carbon source into contact with the surface of the composite metal powder by a CVD method to allow a carbon allotrope to grow out from the surface of the composite metal powder; and the high-temperature heat treatment step of subjecting the composite metal powder having the carbon allotrope grown out from the surface thereof, to a heat treatment at 650° C. to 950° C. under an inert gas atmosphere, after the step of subjecting the composite metal powder to a heat treatment,
wherein the carbon allotrope is removed together with the carbon attaching to the surface of the composite metal powder.

22. The conductive filler according to claim 1 , wherein the average particle diameter of the copper powder lies within the range of 3.0 μm to 25 μm.

Assignees

• Sekisui Chemical Co Ltd

Inventors

• Ohnishi Shigekatsu

Classifications

• C08K2201/001

  Conductive additives · CPC title

• H01B1/02

  mainly consisting of metals or alloys · CPC title

• B22F2301/10

  Copper · CPC title

• B22F2302/10

  Carbide · CPC title

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title