| 摘要 |
A first plating foundation layer is formed by printing on a front face of a sheet-shaped insulating substrate. By inserting a punch into the sheet-shaped insulating substrate having the first plating foundation layer, a through hole is formed while leaving a piece having the plating foundation layer in the portion where the punch is inserted. A second plating foundation layer is formed by printing on a rear face of the sheet-shaped insulating substrate. A first and second wiring layers composed of a metal plating layer are formed by performing electroless plating, and at the same time, a metal plating layer connecting between the first and second wiring layers is formed in the through hole using the plating foundation layer on the piece. |
