How Residues Form

摘要

The customer submitted several board assemblies that failed in the field and exhibited corrosion in close proximity to on-board components. The most common source of corrosion on electronics assemblies is residual flux. Fluxes can be highly reactive chemicals that, if left on the assemblies, can lead to corrosion, electrical degradation, and decreased reliability. In the presence of moisture and electrical bias, flux residue can enable dendritic growth as a result of electrochemical migration.rnTo establish the source of the corrosion, technical data sheets and materials safety data sheets (MSDS) can be used to help evaluate the chemistries of the approved fluxes. The cleaning process also is evaluated to ensure the efficacy of cleaning the fluxes. Further, by establishing a correlation between the composition of the residues and flux chemistries, one can eliminate or confirm the source of the corrosion. Analysis of the residues may be accomplished by employing scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS).