| CPC C25C 1/12 (2013.01) [C22C 9/00 (2013.01)] | 8 Claims |
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1. A method for producing high-purity electrolytic copper, comprising:
Preparing a copper electrolyte using copper sulfate;
adding a first additive (A) containing an aromatic ring of a hydrophobic group and a polyoxyalkylene group of a hydrophilic group, a second additive (B) formed of polyvinyl alcohols, and a third additive (C) formed of tetrazoles to the copper electrolyte; and
performing copper electrolysis by setting a concentration of the first additive (A) to be 10 mg/L to 500 mg/L, a concentration of the second additive (B) to be 1 mg/L to 100 mg/L, a concentration of the third additive (C) to be 0.01 mg/L to 5 mg/L, a concentration ratio (B/A) of the second additive (B) to the first additive (A) to be 0.1 to 0.8, and a concentration ratio (C/A) of the third additive (C) to the first additive (A) to be greater than 0 and 0.7 or less, and controlling a current density and a bath temperature to produce electrolytic copper in which a concentration of Ag is less than 0.2 mass ppm, a concentration of S is less than 0.1 mass ppm, a concentration of all impurities is less than 0.2 mass ppm, and an area ratio of crystal grains having an average crystal grain misorientation (referred to as a GOS value) exceeding 2.5º is 10% or less, wherein
the third additive (C) is one or more of the tetrazoles selected from a group consisting of 5-methyl-1H-tetrazole and 5-phenyl-1H-tetrazole.
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