Development of Laser Direct Ablation Process on Solder Resist in Printed Circuit Boards

摘要

In recent, the laser direct ablation process (LDA) for opening solder resist (SR) is getting thespotlight because this process favors small size opening and process shortening. However, it is concomitantwith a desmear process which causes SR whitening defect. The SR whitening, in general, is known to be causedby the diffused reflection of the SR surface reformed and coarsened by the chemical reaction between thepermanganate and SR polymer components. The process comprising the surface treatment on the SR prior toconducting LDA is proposed to resolve the problem. Therefore, the whitening defect-free products can beobtained even after the wet chemical desmear or plasma desmear. As an application, selective surface finishproducts, which are treated by gold surface finish and organic surface finish at different areas in the samesubstrate, can be fabricated using the LDA process.