Method of producing copper foil for fine wiring

A method of producing a copper foil for fine wiring, comprising

• treating a copper foil as a cathode by electrolysis in a plating bath (A) containing (1) copper ions, (2) metal ions of at least one metal selected from the group consisting of tungsten and molybdenum, (3) metal ions of at least one metal selected from the group consisting of nickel, cobalt, iron and zinc and (4) 1 to 100 mg/l of chloronium ions, at a current density lower than a limiting current density of the plating bath (A), to form on a bonding surface of the copper foil a composite metal layer comprising (I) copper, (II) at least one metal selected from the group consisting of tungsten and molybdenum and (III) at least one metal selected from the group consisting of nickel, cobalt, iron and zinc;
• and
• forming a roughened layer comprising copper on the composite metal layer by carrying out electrolysis in a plating bath (B) containing copper ions at a current density not lower than a limiting current density of the plating bath (B) to form a dendritic copper electrodeposition layer and then carrying out subsequent electrolysis at a current density lower than the limiting current density of the plating bath (B) to form nodular copper.