Patent ID: 8318315

Claim:
A flexible metal-clad laminate of polyimide formed by coating each of two kinds of polyimide precursor solutions on a conductive metal clad and then performing a heat treatment process at least once, the flexible metal-clad laminate including: a first polyimide layer that is disposed on one surface of a metal clad and has thermal expansion coefficient of 20 ppm/K or less, wherein a glass transition temperature T g of the first polyimide layer is 300° C.≦T g ≦350° C., which is lower than a maximum curing temperature; and a second polyimide layer that is disposed on one surface of the first polyimide layer and has thermal expansion coefficient of 20 ppm/K or more, wherein a difference between the thermal expansion coefficients of the first and second polyimide layers is 5 ppm/K or less, and wherein the heat treatment temperature is 20 to 40° C. higher than the glass transition temperature T g of the first polyimide layer, once or more during the heat treatment process.