Ultrasonically enhanced chemical dissociation from solid surfaces with application to cleaning electronic circuit boards

The Galvani potential has been used to study the removal of solder flux from electronic circuit boards with and without ultrasound. First a theory of the Galvani potential as applied to decontamination studies is presented. Then theoretical decontamination curves are presented, based on simple chemical kinetics coupled to mass diffusion to and from the surface through a passive boundary layer. Finally, the theory is tested and illustrated by removal of solder flux from finger structures in various solvents including freon, Prelete, and isopropanol in water. Clear differences in how quickly the Galvani potential decreased with time were noted. The fastest results were obtained for 80% isopropanol in water, but it is likely that more metallic salts were left behind on the surface than in the slower methods. The saturation of the solvents is also discussed. Finally, methods of on-line testing solvents and circuit boards based on the Galvani potential are discussed.