Influence of No-Clean Flux on The Corrosivity of Copper After Reflow

The use of flux when soldering is essential to obtain a reliable solder joint. No-clean fluxes are most often used in lead-free soldering. This raises the question of the need to clean the flux residues due to their aggressiveness. The purpose of this work is to understand the importance of the flux chemistry and impact of weak organic acids (WOAs) on the corrosivity of copper surface after reflow. During this investigation the aggressiveness of six different no-clean fluxes for lead-free soldering on toward copper surface was observed. The results showed the flux aggressiveness depended on the flux composition. Fluxes Weller Lötwasser and Topnik RF800 showed less aggressive effect toward copper surface after heat treatment. The results of the study also showed that one of more aggressive fluxes, such as Topnik LP-1, corroded the copper surface to a depth of about 50 $\mu m$.