Investigation of Atmospheric Pressure Plasma Treatment on PCB Surface Finishes

Flux is a necessity in the lead-free soldering process. Inactivated flux residues can cause electrical shortages and functional issues by electrochemical 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 PT. Improvement on wettability of the PCB pads is demonstrated. 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 PCBs resulting from atmospheric pressure PT. For this investigation of the PCB surface finishes, the scanning electron microscopy (SEM) images were taken, and the composition of the surfaces was analyzed by energy dispersive X-ray spectrometry (EDAX) and laser-induced breakdown spectrometry (LIBS) as well.