| 摘要 |
PURPOSE: To obtain the resisting property for the breakage caused by thermal stress and heat circulation on a board material by a method wherein the board material is formed in multilayer by a woven cloth which is impregnated by thermoplastic polymerized resin varnish having specific characteristics, and one or more layers of internally conductive pattern is provided. CONSTITUTION: A board material is formed by a piece of multilayered cloth on which thermosetting polymerized resin varnish is impregnated, and an inner conductive pattern layer in one or more layers is provided. The varnish contains fillers. Also, a threshold value with time weight of eight hours for the human exposure, which is larger than 1 mg/m<3> , is set. Besides, Mohs hardness of the board material is set at 7 or smaller, the substrate material is not decomposed at the temperature of 300 deg.C or lower and the water contained therein is not discharged, and the material has non-moisture absorbing property. The quantity sufficient to give an average thermal expansion coefficient in Z-axis direction, which is equal to the value obtained by adding the maximum elongation percentage of copper at 270 deg.C which is suitable in formation of conductive pattern on the wall of hole of a printed wiring board, is compounded. |
