| 摘要 |
PROBLEM TO BE SOLVED: To simply enable thick constitution with little warp, by forming a metal foil bonded to one surface of a polyimide film via a thermoplastic polyimide layer, and forming a heat-resistant polyimide layer which is formed by applying heat-resistant polyimide to the other surface and curing polyimide. SOLUTION: In a flexible printed circuit board 1, a metal foil 12 is bonded to one surface of a polyimide film 10, via a thermoplastic polyimide layer 11, and heat-resistant polyimide precursor is spread on the other surface and cured to form a heat-resistant polyimide layer 13. The polyimide layers formed on both sides of the polyimide film 10 symmetrically warp with the same tensions, while sandwiching the polyimide film 10, so that the warps cancel each other. As a result, practically serious warp is not generated. The upper limit of the polyimide film thickness does not exist. If necessary, by using a thick polyimide film 10, the flexible printed circuit board can be thickened. |
