Investigation of the effect of nitrogen and air atmospheres on solder wettability of plasma-treated HASL finish PCBs

Purpose - The purpose of this paper is to evaluate the effect of nitrogen and air atmospheres on the solderability testing of plasma-treated hot air solder level (HASL) finish printed circuit boards (PCBs). Design/methodology/approach - In this paper, the soldering performance of plasma-treated HASL finish PCBs in nitrogen and air atmospheres have been evaluated using the wetting balance technique. The results were compared with the performance of conventionally flux-treated samples soldered in air and nitrogen atmospheres and non-flux treated samples soldered in air. Auger chemical analysis results were also compared with the solderability test results in order to obtain a complete profile of the plasma-treated and non-treated surfaces. Findings - The results of the auger chemical analysis show high organic (carbon) levels in the control samples and a significant drop in organic levels in the plasma-treated samples. The significant drop in the level of carbon leads to a decrease in contact angle and an increase in both surface energy and solder wettability. The results indicate that plasma cleaning of PCBs prior to soldering is a viable alternative to the conventional use of flux. Originality/value - The paper indicates that the soldering performance of plasma-treated PCBs in air and nitrogen atmosphere are comparable. The findings give the motivation for the use of plasma-assisted dry cleaning for fluxless soldering.