New method of water cleaning for circuit substrates

Water-soluble flux which has characteristics equivalent to those of rosin flux has been developed by improving its activator and rheological modifier. Cleaning equipment has also been developed. The method was applied to cleaning on-board power-supply products, and the products passed a 1500-h temperature-humidity-bias test. It was demonstrated that combining the water-soluble flux and the cleaning equipment can provide the same reliability of reflow-soldered product as that of the product processed by the conventional cleaning method using rosin flux and solvent