Effect of Surface Contamination of Copper, Arising from Water Rinsing on Solderability

Rinsing treatments on copper after etching are investigated by using the adverse effect they have on solderability. The wetting time, as measured by the GEC Meniscograph, is a sensitive indicator of the effect of varying contact times with water (the most obvious way of removing etching residues). Several variables of the water were examined such as dissolved impurities (as indicated by a comparison of demineralised, boiled demineralised and tap‐water) rinsing time in tap water and water temperature. Wetting time is found to rise with all of these and demineralised water is superior to tap water, as might be expected. Very small amounts of acid added to the rinsing solution appear to retard almost completely the contamination effects of the water. All the findings underline how important surface cleanliness is to a successful soldering operation. By corollary it appears that solderability tests (especially the GEC Meniscograph) are very good indicators of extremely low levels of surface contamination.