Patent ID: 8383230

Claim:
A flexible printed wiring board comprising: a first electric insulating layer having a first surface and a second surface opposite the first surface; a second electric insulating layer having a first surface and a second surface opposite its first surface; a first conductor layer located on the first surface of the first electric insulating layer; a second conductor layer located on the first surface of the second electric insulating layer; wherein: the second surface of each said electric insulating layer is undulated and has: (a) a 10-point average roughness of at least 1.5 μm and less than 2.0 μm and a contact angle of at least 60° and less than 120°,or (b) has a 10-point average roughness of at least 2.0 μm and less than 4.0 μm; and the second surfaces of the first and second electric insulating layers are adjacent, face each other, and do not stick together.