US Patent 9462688 Flexible metal laminate containing fluoropolymer

The present invention relates to a flexible metal laminate with low dielectric constant, which may be applied for a substrate for a flexible printed circuit. A flexible metal laminate according to one aspect of the invention includes a first metal layer; a first polyimide layer; a polyimide layer including fluoropolymer dispersed therein, formed on the first polyimide layer; and a second polyimide layer formed on the polyimide layer including fluoropolymer dispersed therein; wherein in the polyimider layer including dispersed fluoropolymer, the content of the fluoropolymer per unit volume is higher at 40 to 60% depth than at 5 to 10% depth of the total thickness from the surface of the polyimide layer.