| 摘要 |
PURPOSE:To electrolessly plate only the inner wall of a through hole and to maintain reliability of connection even without considering the positional accuracy of the hole at a conductor circuit by selectively allowing a catalyst only on the inner wall of a hole which constitutes a through hole by using a difference of adhering easinesses of the catalyst of the surface of a plating resist and the inner wall of the hole. CONSTITUTION:An inner layer circuit 2 is formed of glass cloth epoxy resin as an insulating layer 3, another insulating layer 3 is further superposed to form a circuit conductor layer 1 on the surface, and a plating resist 4 is formed. Then, a hole 5 is opened at a position necessary to be connected, and the entire surfaces of the inner wall and the surface of the hole 5 are adhered with catalyst 6 for electroless plating. Thereafter, it is dipped in solution containing 0.5g/l of ferric chloride and 100ml/l of hydrochloric acid at 25 deg.C for 10min to remove the catalyst adhered to the resist 4. Then, it is dipped in electroless copper plating solution to form a metal layer 7 of about 30mum of thickness on the inner wall of the hole 5. Eventually, the resist 4 is peeled as a multilayer printed circuit board. Plating metal is not precipitated on the surface circuit of the formed board, and the layer 7 of the inner wall of the hole becomes an excellent plating. |
