Method for producing vias in the manufacture of printed circuit boards

A method for making a multilayer printed wiring board comprising:

• (a) laminating to an inner wiring pattern having a defined thickness greater than zero, an ultra-thin copper foil having two sides and a defined thickness greater than zero and supported on a carrier, one side of said foil being adjacent to said carrier and an opposite side of said foil having an organic insulating resin layer disposed thereon, said insulating layer being disposed between said inner wiring pattern and said copper foil, wherein a maximum thickness of said ultra-thin copper foil is a lesser of 7 μm or {fraction (1/4.5)} times the thickness of the inner wiring pattern;
• (b) removing said carrier to obtain the multilayer board having an outer copper foil layer and an insulating layer disposed on said inner wiring pattern;
• and then
• (c) forming a via hole through said outer copper foil layer and said organic insulating layer to said inner wiring pattern by simultaneously irradiating said copper foil and said organic insulating layer with a carbon dioxide laser.