Next Generation Pb-free Immersion Finishes, Methodologies used to Determine Coating Thickness and the Impact of Thickness Variations and Rework on Soldering

摘要

The next generation of surface finish coatings to replace HASL are now being installed by various PWB manufacturers and have been implemented by many OEMs. Coating thickness requirements are part of the OEMs' specification given to the board manufacturer. Clearly from previous and existing final finish coating performances, thickness has shown to have a major impact on the performance of the surface finish during soldering. OEMs have traditionally specified wide thickness specifications, to meet production variations by PWB producers. This paper investigates the current methodologies / alternatives used to determine accurately and consistently the thickness of these new immersion silver & tin coatings, and how this variation may impact solderability performance under various pre-conditioned states.