ELECTROLYTIC COPPER FOIL AND METHOD FOR PRODUCING ELECTROLYTIC COPPER FOIL

The present invention provides an electrolytic copper foil that has a high normal tensile strength, a low decrease in tensile strength after a thermal history, and a low concentration of impurities in the copper foil and a method for producing the copper foil. Specifically, the electrolytic copper foil in which a sulfur concentration of the copper foil is not less than 10 ppm by mass but no more than 50 ppm by mass, wherein when lattices with a spacing of 10 nm in a STEM image observed with a scanning transmission electron microscope at a magnification of 1 million times are formed and intersections of each lattice are used as a measurement point for determining a sulfur concentration, there is a measurement point at which the sulfur concentration is higher as compared to the sulfur concentration of the copper foil.