| 摘要 |
PROBLEM TO BE SOLVED: To form via holes without impairing conductivity by providing a light-absorbing layer on a surface of a conductor layer of an electrically insulating layer having the conductor layer arranged on its surface, laminating other electrically insulating layer via the conductor layer, forming an opening at the insulating layer, and forming the conductor layers on the other insulating layer and on an inner surface of the opening. SOLUTION: A core board layer 2 is a copper-clad laminate in which copper foils 2a are laminated on both side surfaces, an opening 10 for passing the layer 2 is formed, and a light-absorbing layer 11 is formed on a front layer of a second conductor circuit pattern 4b. Then, a resin-insulating layer 3 is laminated on an upper surface of the layer 2, and an opening 12 is formed at the layer 3 by a laser beam. Here, the beam is absorbed by the layer 11 provided on the pattern 4b to suppress reflection. The layer 3 is scarcely retained in the opening 12 to stably form an electroless plating film and a conductor layer 5b made of an electrolytic plating film laminate on an inner surface as a via hole 5 for electrically connecting the second and third conductor circuit patterns 4b, 4c. |
