| 摘要 |
PURPOSE: To provide a flexible printed board which is free from curling, twisting, deflecting, etc., even if heat history is applied, and/or has sufficient adhesion, resistance against bending, size stability, etc., and is excellent in workability and industrially useful with a small curl after a conductor is etched, and a flexible printed board which can easily satisfy diverse needs of demanders. CONSTITUTION: A flexible printed board formed by applying a resin layer directly on a conductor and having at least the conductor and an insulator is of a multilayer structure wherein the insulator comprises a plurality of polyimide resin layers having different linear expansion coefficients from one another. In addition, a resin layer having a higher thermal expansion is in contact with the layer wherein conditions that a ratio (t2 /t1 ) of a thickness (t1 ) of the resin layer having the higher thermal expansion and a thickness (t2 ) of a resin layer having a lower thermal expansion is in a range of 0.01<t2 /t1 <20,000 (where t1 and t2 is a sum of thickness of respective resin layers) are satisfied. |
