COPPER FOIL FOR PRINTED WIRING BOARD

摘要

Provided is a copper foil which is a thin foil of no more than 18μm in thickness that is required for a copper foil for a printed wiring board such as a flexible copper clad laminate (FCCL) or a flexible printed circuit board (FPC), for which foil breakage or wrinkling does not occur when using roll-to-roll conveyance, which is sufficiently softened after heat treatment at a polyimide curing temperature, and which demonstrates high bendability and flexibility. The copper foil for a printed wiring board, the copper foil being copper or an alloy of copper and having a thickness of no more than 18μm, is characterized by the following: a temperature Tmax, at which a gradient (S) of tensile strength represented by formula (1) becomes largest, is 150°C-370°C in a range of no more than 400°C; in such a case, a gradient (Smax) is at least 0.8; and the tensile strength after heat treatment for one hour at Tmax is 80% or less of normal strength. Formula (1): S=(Ts(T-50)-Ts(T))/50 Here, Ts(T) is the tensile strength after heat treatment for one hour at T°C.