Contamination of Various Flux/Cleaning Combinations on SMT Assemblies: A Discussion of Different Analysis Methods

The contamination on SMT assemblies caused by a number of flux/cleaning variation has been investigated, with several analysis methods used to quantify the contamination. The results from analysis of test printed circuit boards (PCBs) using anion separation, conductivity, ionic contamination measurement, visual and SEM inspection, microsections and surface insulation resistance (SIR) methods were compared. The best cleaning result was observed with the combination of water soluble (WS) solder cream and water cleaning. The best measurement method for cleanliness of PCBs was considered to be SIR measurement. For WS fluxes, the iconic contamination test offers effective measurement of the amount of residues left on the PCBs.