| 摘要 |
PURPOSE: To prevent damage in high humidity, and improve dimensional stabil ity, by using, as an insulating board, an extensible film of polycyanoaryl ether whose water absorption and coefficient of humidity expansion are small. CONSTITUTION: Polycyanoaryl ether contains at least 50mol% of repeating units shown by the formula. The reduction viscosity [ηSD/C] of solution at 60 deg.C wherein solvent is P-chlorophenol and concentration is 0.2 gram/deciliter is 0.5-3 deciliter/gram. An extensible film is formed by longitudinally and laterally drawing a film obtained from the polycyanoaryl ether at a draw ratio of at least 1.2. A conductive layer is formed on the surface of the extensible film. The coefficient of linear expansion of the film is 1.0×10<-5> -4.0×10<-5> / deg.C. The maximum coefficient of humidity expansion is 1.5×10<-5> /%RH. By using the extensible film and the conductive layer, a printed circuit board having excellent characteristics can be obtained.
|
