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US-12623281-B2 - Oxide-containing copper fine particles, method for producing same, and method for producing sintered compact using oxide-containing copper fine particles

US12623281B2US 12623281 B2US12623281 B2US 12623281B2US-12623281-B2

Abstract

Disclosed is oxide-containing copper fine particles including Cu 64 O and optionally Cu 2 O and coated with a carboxylic acid, wherein a mass ratio of Cu 64 O to a total mass of Cu, Cu 64 O and Cu 2 O is 0.5 to 2.0% by mass.

Inventors

  • Tetsu Yonezawa

Assignees

  • NATIONAL UNIVERSITY CORPORATION HOKKAIDO UNIVERSITY

Dates

Publication Date
20260512
Application Date
20210826
Priority Date
20200828

Claims (20)

  1. 1 . Oxide-containing copper fine particles comprising Cu 64 O and optionally Cu 2 O and coated with a carboxylic acid, wherein a mass ratio of Cu 64 O to a total mass of Cu, Cu 64 O and Cu 2 O is 0.5 to 2.0% by mass.
  2. 2 . The oxide-containing copper fine particles according to claim 1 , wherein a mass ratio of Cu 2 O to the total mass of Cu, Cu 64 O and Cu 2 O is 0% by mass or more and less than 0.5% by mass.
  3. 3 . The oxide-containing copper fine particles according to claim 1 , wherein a mass ratio of Cu 2 O to the total mass of Cu, Cu 64 O and Cu 2 O is 0.5 to 2.0% by mass.
  4. 4 . A method for producing the oxide-containing copper fine particles according to claim 1 , wherein the method comprises: preparing copper fine particles; coating the copper fine particles with a carboxylic acid; and adding the copper fine particles coated with the carboxylic acid to a dispersing medium and dispersing the copper fine particles by using a bead mill or a high-pressure wet type atomizer.
  5. 5 . The method according to claim 4 , wherein the dispersing is performed under an inert gas atmosphere.
  6. 6 . The method according to claim 4 , wherein the dispersing is performed under a normal air atmosphere.
  7. 7 . The method according to claim 4 , wherein a rotation speed of an agitator of the bead mill is 1000 rpm or more and less than 3000 rpm.
  8. 8 . A method for producing a copper fine particle sintered compact, wherein the method comprises heating the oxide-containing copper fine particles according to claim 1 to 100° C. to 200° C. under an inert gas atmosphere.
  9. 9 . The method according to claim 8 , wherein the inert gas comprises N 2 .
  10. 10 . The method according to claim 9 , wherein the inert gas is mixed with less than 4% by volume of H 2 .
  11. 11 . A method for producing the oxide-containing copper fine particles according to claim 2 , wherein the method comprises: preparing copper fine particles; coating the copper fine particles with a carboxylic acid; and adding the copper fine particles coated with the carboxylic acid to a dispersing medium and dispersing the copper fine particles by using a bead mill or a high-pressure wet type atomizer under an inert gas atmosphere.
  12. 12 . The method according to claim 11 , wherein a rotation speed of an agitator of the bead mill is 1000 rpm or more and less than 3000 rpm.
  13. 13 . A method for producing the oxide-containing copper fine particles according to claim 3 , wherein the method comprises: preparing copper fine particles; coating the copper fine particles with a carboxylic acid; and adding the copper fine particles coated with the carboxylic acid to a dispersing medium and dispersing the copper fine particles by using a bead mill or a high-pressure wet type atomizer under a normal air atmosphere.
  14. 14 . The method according to claim 13 , wherein a rotation speed of an agitator of the bead mill is 1000 rpm or more and less than 3000 rpm.
  15. 15 . A method for producing a copper fine particle sintered compact, wherein the method comprises heating the oxide-containing copper fine particles according to claim 2 to 100° C. to 200° C. under an inert gas atmosphere.
  16. 16 . The method according to claim 15 , wherein the inert gas comprises N 2 .
  17. 17 . A method for producing a copper fine particle sintered compact, wherein the method comprises heating the oxide-containing copper fine particles according to claim 3 to 100° C. to 200° C. under an inert gas atmosphere.
  18. 18 . The oxide-containing copper fine particles according to claim 1 , wherein the carboxylic acid comprises at least one compound selected from the group consisting of aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, aromatic carboxylic acids, and terpene-based carboxylic acids.
  19. 19 . The oxide-containing copper fine particles according to claim 1 , wherein Cu 64 O is present on a surface of the oxide-containing copper fine particles.
  20. 20 . Oxide-containing copper fine particles comprising Cu 64 O and Cu 2 O and coated with a carboxylic acid, wherein a mass ratio of Cu 64 O to a total mass of Cu, Cu 64 O and Cu 2 O is 0.5 to 2.0% by mass.

Description

TECHNICAL FIELD The present disclosure relates to oxide-containing copper fine particles, a method for producing the same, and a method for producing a sintered compact using the oxide-containing copper fine particles. BACKGROUND ART In recent years, in the manufacture of printed circuit boards, as a clean technique that requires neither exposure to light nor etching, which have been conventionally used, and that does not emit harmful chemical substances, a technique called printable electronics that directly forms fine wiring by inkjet or printing has attracted attention. The fine wiring is mainly obtained by heating and sintering metal fine particles. The metal fine particles are required to be sintered at a temperature 250 to lower than 350° C., for example, from the viewpoint of heat resistance of a substrate or the like. At present, silver fine particles, which can be sintered at a low temperature, are often used, but silver fine particles are expensive and there is a concern about the influence of a wiring short circuit due to ion migration. As a substitute for silver fine particles, copper fine particles, which are inexpensive and have high resistance to ion migration, have attracted attention, but copper fine particles have a problem that it is difficult to sinter them at a low temperature, so that they have not been used practically. On the other hand, the present inventors have made it possible to sinter copper fine particles at 200° C. or lower by any of two-steps heating (Patent Document 1), introduction of a copper complex ink (Patent Document 2), and incorporation of cuprous oxide (Cu2O) into copper fine particles (Patent Document 3). CONVENTIONAL ART DOCUMENT Patent Document Patent Document 1: JP 2015-214722 APatent Document 2: JP 2017-1978 APatent Document 3: WO 2019/106739 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in Patent Document 1, two-steps heating (oxidation treatment and reduction treatment) is required, whereas in Patent Document 2, it is necessary to prepare, in addition to copper fine particles (copper powder), an additional copper material (copper complex). In both the cases, many steps are required. In Patent Document 3, it is necessary to perform sintering under high vacuum, and batch processing is required for taking in and out of a vacuum facility, so that productivity is lowered. The present invention has been made in view of such a situation, and an object thereof is to provide copper fine particles from which a sintered compact that exhibits sufficient conductivity can be obtained by one-step heating at 200° C. or lower under normal pressure (or a pressure not lower than normal pressure) without requiring two-steps heating or an additional copper material, a method for producing the copper fine particles, and a method for producing a sintered compact using the copper fine particles. Means for Solving the Problems An aspect 1 of the present invention is directed to oxide-containing copper fine particles including Cu64O and optionally Cu2O and coated with a carboxylic acid, wherein a mass ratio of Cu64O to a total mass of Cu, Cu64O and Cu2O is 0.5 to 2.0% by mass. An aspect 2 of the present invention is directed to the oxide-containing copper fine particles according to the aspect 1, wherein a mass ratio of Cu2O to the total mass of Cu, Cu64O and Cu2O is 0% by mass or more and less than 0.5% by mass. An aspect 3 of the present invention is directed to the oxide-containing copper fine particles according to the aspect 1, wherein a mass ratio of Cu2O to the total mass of Cu, Cu64O and Cu2O is 0.5 to 2.0% by mass. An aspect 4 of the present invention is directed to a method for producing the oxide-containing copper fine particles according to any one of the aspects 1 to 3, wherein the method includes:preparing copper fine particles;coating the copper fine particles with a carboxylic acid; andadding the copper fine particles coated with the carboxylic acid to a dispersing medium and dispersing the copper fine particles by using a bead mill or a high-pressure wet type atomizer. An aspect 5 of the present invention is directed to the method according to the aspect 4, wherein the dispersing is performed under an inert gas atmosphere. An aspect 6 of the present invention is directed to the method according to the aspect 4, wherein the dispersing is performed under a normal air atmosphere. An aspect 7 of the present invention is directed to the method according to any one of the aspects 4 to 6, wherein a rotation speed of an agitator of the bead mill is 1000 rpm or more and less than 3000 rpm. An aspect 8 of the present invention is directed to a method for producing a copper fine particle sintered compact, wherein the method includes heating the oxide-containing copper fine particles according to any one of the aspects 1 to 3 to 100° C. to 200° C. under an inert gas atmosphere. An aspect 9 of the present invention is directed to the method according