Rolled copper foil for flexible printed circuit and method of manufacturing the same

Abstract

A rolled copper foil for flexible printed circuits contains not more than 10 ppm by weight of oxygen and has a softening-temperature rise index T defined as T=0.60[Bi]+0.55[Pb]+0.60[Sb]+0.64 [Se]+1.36[S]+0.32[As]+0.09[Fe]+0.02[Ni]+0.76[Te]+0.48[Sn]+0.16[Ag]+1.24[P] (each symbol in the brackets representing the concentration in ppm by weight of the element) in the range of 4 to 34. The concentrations of the elements are in the ranges of[Bi]<5, [Pb]<10, [Sb]<5, [Se]<5, [S]<15, [As]<5, [Fe]<20, [Ni]<20, [Te]<5, [Sn]<20, [Ag]<50, and [P]<15 (each symbol in the brackets representing the concentration in ppm by weight of the element). The foil has a thickness in the range of 5 to 50 μm and a half-softening temperature of 120 to 150° C., is capable of continuously retaining a tensile strength of at least 300 N/mm2 at 30° C., and possesses excellent flex property and adequate softening property.

Dependencies are inferred from the claim text.