Copper powder and method for producing copper powder

Abstract

The copper powder has a surface covered with an organic substance and satisfies the following conditions: (1) in detection of the organic substance on the surface of the copper powder by GC-MS, detected is a predetermined organic substance described herein; (2) in detection of the organic substance on the surface of the copper powder by LC-MS, detected is a predetermined organic substance described herein; (3) in measurement of the thermal shrinkage ratio of a green compact of the copper powder, a temperature at which the thermal shrinkage ratio is 1% is 230° C. or lower; and (4) in measurement of the thermal shrinkage ratio of the green compact of the copper powder, a temperature difference between a temperature at which the thermal shrinkage ratio in an inert atmosphere is 3% and a temperature at which the thermal shrinkage ratio in a reducing atmosphere is 3% is smaller than 10° C.

1 . Copper powder having an average particle diameter of 250 nm or less and having a surface covered with an organic substance, the copper powder satisfying all the following conditions (1) to (4):
 (1) in detection of the organic substance on the surface of the copper powder by gas chromatography-mass spectrometry, detected is one or more selected from the group consisting of   H(—O—CH 2 —CH 2 ) n —OH (where n is an integer of 1 or more and 4 or less),   HOOC—CH 2 (—O—CH 2 —CH 2 ) m —OH (where m is an integer of 1 or more and 3 or less),   HOOC—CH 2 (—O—CH 2 —CH 2 ) l —O—CH 2 —COOH (where l is 1 or 2),   H(—C 3 H 6 O) s —OH (where s is an integer of 1 or more and 4 or less),   HOOC—CH(CH 3 )(—C 3 H 6 O) t —OH (where t is an integer of 1 or more and 3 or less), and   HOOC—CH(CH 3 )(—C 3 H 6 O) u —O—CH(CH 3 )—COOH (where u is 1 or 2);   (2) in detection of the organic substance on the surface of the copper powder by liquid chromatography-mass spectrometry, detected is a chain organic substance having a molecular weight of 200 or more and 1,000 or less and having, at each terminal of the molecule, one selected from the group consisting of a carboxy group (—COOH), a hydroxy group (—OH), an amino group (—NH 2 ), an aldehyde group (—CHO), a nitro group (—NO 2 ), a thiol group (—SH), a sulfo group (—SO 3 H[[HH]]), a phosphate group (—PO 4 H 2 ), a cyan group (—CN), a chloro group (—Cl), a bromo group (—Br), and an iodo group (—I), which are each a functional group capable of being coordinated with a copper ion;   (3) in measurement of a thermal shrinkage ratio when a green compact obtained by pressure-molding the copper powder is heated from 25° C. in an inert atmosphere on the basis of the thickness of the green compact at 25° C., a temperature at which the thermal shrinkage ratio is 1% is 230° C. or lower; and   (4) in measurement of a thermal shrinkage ratio when a green compact obtained by pressure-molding the copper powder is heated from 25° C. in an inert atmosphere and in a reducing atmosphere on the basis of the thickness of the green compact at 25° C., a temperature difference between a temperature at which the thermal shrinkage ratio in the inert atmosphere is 3% and a temperature at which the thermal shrinkage ratio in the reducing atmosphere is 3% is smaller than 10° C.   
     
     
         2 . The copper powder according to  claim 1 , the average particle diameter being 200 nm or less. 
     
     
         3 . The copper powder according to  claim 1 , the average particle diameter being 150 mm or less. 
     
     
         4 . A method for producing the copper powder according to  claim 1 , the method comprising
 mixing copper oxide powder with a polyol solvent having a boiling point of 230° C. or lower to which the chain organic substance is added, to obtain copper oxide powder slurry, and heating the copper oxide powder slurry at 230° C. or lower.   
     
     
         5 . The method for producing the copper powder according to  claim 4 , the chain organic substance being added in an amount of 0.005% by mass or more and 10% by mass or less relative to a total amount of copper contained in the copper oxide powder. 
     
     
         6 . The method for producing the copper powder according to  claim 4 , the polyol solvent having a boiling point of 230° C. or lower being one or more selected from the group consisting of ethylene glycol (boiling point: 196° C.), propylene glycol (boiling point: 188° C.), 1,3-propanediol (boiling point: 214° C.), 1,2-butanediol (boiling point: 194° C.), 1,3-butanediol (boiling point: 207° C.), 1,4-butanediol (boiling point: 228° C.), 1,2-pentanediol (boiling point: 210° C.), and 1,2-hexanediol (boiling point: 223° C.). 
     
     
         7 . A method for producing the copper powder according to  claim 1 , the method comprising
 mixing copper powder having an average particle diameter of 250 nm or less and not satisfying at least any of the conditions (3) and (4) with a polyol solvent having a boiling point of 250° C. or higher to which the chain organic substance is added, to obtain copper powder slurry, and heat-treating the copper powder slurry at 230° C. or higher.   
     
     
         8 . The method for producing the copper powder according to  claim 7 , the chain organic substance being added in an amount of 0.005% by mass or more and 10% by mass or less relative to a total amount of copper contained in the copper powder to be heat-treated. 
     
     
         9 . The method for producing the copper powder according to  claim 7 , the polyol solvent having a boiling point of 250° C. or higher being one or more selected from the group consisting of triethylene glycol (boiling point: 287° C.), tetraethylene glycol (boiling point: 327° C.), and polyethylene glycol having an average molecular weight of 200 or more and 600 or less (boiling point: approximately 300° C.). 
     
     
         10 . The method for producing the copper powder according to  claim 7 , a temperature of the heat-treating being 250° C. or higher. 
     
     
         11 . The method for producing the copper powder according to  claim 7 , a temperature of the heat-treating being 270° C. or higher.