Multi-layer printed wiring boards having blind vias

摘要

A multi-layer printed wiring board having via holes is characterized by having the outer copper wifing circuit lines on a layer of an alkaline refractory metal which is adjacent to a thermosetting resin layer. An alkaline refractory metal which is insoluble is alkaline etching solutions, is electrodeposited on the surface of copper foil, then a thermosetting resin is applied to the surface and semi-cured to obtain a coated copper foil. The coated copper foil is bonded to one or both faces of an inner layer board having wirings on one or both of its faces. Then, the copper foil on a surface of this laminate is removed by alkaline etching, while selectively leaving the alkaline refractor metal layer. A laser beam is used to form via holes in both the alkaline refractory metal layer and the thermosetting resin layer simultaneously. Via holes of the multi-layered printed wiring board can be easily formed using a laser, and adhesion between the outer wirings made from the plated copper and the insulating resin is improved.