A study of microvias produced by laser-assisted seeding mechanism in blind via hole plating of printed circuit board

Abstract

The laser-assisted seeding (LAS) mechanism has the potential to replace the conventional electroless copper plating in printed circuit board (PCB) manufacture because it combines the steps of drilling and electroless plating into one. The LAS mechanism should be able to plate microvias with high aspect ratio that may not be feasible by conventional electroless plating due to the small via geometry. The conventional electroless plating process generates considerable quantities of chemical waste. In particular, the plating of microvia with high aspect ratio close to 1 is difficult due to the limited accessibility of chemical solution to the via internal wall surface in conventional plating technology. LAS is a promising alternative. The objectives of this paper are to report the deposition mechanism of a thin copper film layer (laser-assisted seeding) on PCB microvias dielectric and to study the thermal reliability of the microvias produced by this mechanism. Results find that the microvias produced by LAS are thermally and electrically as reliable as conventional electroless plating technology.