Printed circuit board having permanent solder mask

摘要

A printed circuit board having a permanent solder mask includes a substrate made of a glassfiber reinforced epoxy resin material. The top and bottom surfaces of the substrate are disposed thereon a conductive pattern respectively. An epoxy resin solder mask is coated on each surface of the substrate in such a way that the conductive pattern is divided into a sheltered portion covered by the solder mask and an unsheltered portion exposed outside. The solder mask also has an even and smooth outer surface with a micro-roughness ranging between 0.5 mum~10 mum and an optimum thickness ranging between 2 mum~200 mum.