| 摘要 |
PROBLEM TO BE SOLVED: To form blind through-holes good in electrically connecting conduction, which in physical strength, durable for long use and high in reliability. SOLUTION: These blind through-holes for electrically connecting an outer layer foil 13 disposed an epoxy film 12 to inner layer circuit 10 disposed in the film 12 is formed by laying a metal mask 20, having holes of a diameter smaller than that of holes 13a of the foil 13 on the upper surface of the foil 13, and making a laser beam 15 irradiate the epoxy film 12 through the holes of the mask 20. |
