Quality and reliability of high aspect-ratio blind microvias formed by laser-assisted seeding mechanism in PCB

The laser-assisted seeding (LAS) mechanism should be able to plate microvias with a high aspect ratio that may not be feasible by conventional electroless plating due to the small via geometry. In particular, the plating of microvias with a high aspect ratio close to one 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 printed circuit board (PCB) microvias dielectric and to study the quality and reliability of the microvias produced by this mechanism. Results find that the microvias produced by LAS have acceptable quality and are as reliable as that formed by conventional electroless plating technology. The hole wall of the microvia was covered with deposited copper, and the thickness of which was found related to some LAS parameters. A set of experimental best LAS processing conditions is also given.