| 摘要 |
PROBLEM TO BE SOLVED: To form a plated layer without the necessity to perform an etching treatment and enhance the economy and the productivity and further avoid the deterioration of electric insulating properties by filling a fluororesin with a hydrophilic solid inorganic matter weighing within a specific range to the weight of the fluororesin. SOLUTION: Fluororesin layers 12a, 12b are formed on both faces of a glass cloth 11 by impregnating the glass cloth 11 with the fluororesin layers 12a, 12b and baking the layers 12, 12b. That is, not only the fluororesin layers 12a, 12b are formed on both faces of the glass cloth 11 but also the glass cloth 11 is impregnated with part of the fluororesin layers 12a, 12b. In this case, each of the fluororesin layers 12a, 12b is filled with fluororesin and silica as a hydrophilic solid inorganic matter. That is, the blended content of the silica is 5-100 pts.wt. to 100 pts.wt. entire fluororesin contained in the fluororesin layers 12a, 12b. Thus a prepreg sheet 13 comprising the glass cloth 11 and the fluororesin layers 12a, 12b is constituted. The prepreg sheet 13 is, for example, of a five-layer laminate 14, on both faces of which copper foilds 15a, 15b are applied. |
