Investigation of atmospheric pressure plasma treatment on PCB surface finishes

Abstract

Flux is a necessity in the lead-free soldering process. Inactivated flux residues can cause electrical shortages and functional issues by ion migration. Because of miniaturization and the complexity of recent electronic products a cleaner manufacturing process is required. Atmospheric pressure plasma treatment (PT) is a commonly applied surface cleaning method in the manufacturing industry and has been proved to be effective in improving the wettability in case of metal and polymer surfaces. Three different types of printed circuit board (PCB) surface finishes were investigated before and after plasma treatment. The aim of this study is to investigate the mechanisms of plasma cleaning and to possibly determine the root cause of the improvement of solderability on printed circuit boards resulting from atmospheric pressure plasma treatment. For this investigation of the PCB surface finishes, scanning electron microscopy (SEM) images were taken, and the composition of the surfaces were analyzed by energy dispersive X-ray spectrometry (EDAX) and laser-induced breakdown spectrometry (LIBS) as well.