| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for form through holes in a build-up substrate in which the collapse of hole wall in the through hole can be prevented by eliminating mechanical stress when the resin surface of an insulation layer is drilled or thermal influence during rotation of drill so as to prevent an influence on the resin. SOLUTION: A ring-like groove 6 whose outer diameter 6a of an opening is larger than that of a through hole 5 and whose inner diameter 6b is smaller than that of the through hole 5, is formed in a part to form the through hole 5 on a build-up substrate A by laser processing, and then the center of the ring-like groove 6 is drilled by a drill 7 to make the through hole 5. |
