Abstract: The invention relates to an electrolytic copper alloy foil having large mechanical strength in an ordinary state and showing resistant to heat deterioration even when it is heated to 300° C. or more. That electrolytic copper alloy foil, which contains tungsten copper, preferably incorporates tungsten into copper foil as a copper alloy, has a tensile strength at ordinary temperature of 650 MPa, has a tensile strength after heat treatment at 300° C. for 1 hour of 450 MPa or more, and has a conductivity of 80% or more. Further preferably, the electrolytic copper foil has an elongation at ordinary temperature of 2.5% or more and an elongation after treatment at 300° C. for 1 hour of 3.5% or more. The electrolytic copper foil is produced by adding a thiourea compound, tungsten salt, and chloride ions to a sulfuric acid-copper sulfate electrolyte and performing electrolytic deposition.

Abstract: The invention relates to an electrolytic copper alloy foil having large mechanical strength in an ordinary state and showing resistant to heat deterioration even when it is heated to 300° C. or more. That electrolytic copper alloy foil, which contains tungsten copper, preferably incorporates tungsten into copper foil as a copper alloy, has a tensile strength at ordinary temperature of 650 MPa, has a tensile strength after heat treatment at 300° C. for 1 hour of 450 MPa or more, and has a conductivity of 80% or more. Further preferably, the electrolytic copper foil has an elongation at ordinary temperature of 2.5% or more and an elongation after treatment at 300° C. for 1 hour of 3.5% or more. The electrolytic copper foil is produced by adding a thiourea compound, tungsten salt, and chloride ions to a sulfuric acid-copper sulfate electrolyte and performing electrolytic deposition.