This company recently developed a lead-free, halogen-free, water washable solder paste.
The new solder paste, LOCTITE GC 3W, is reportedly a market first for water washable materials. With temperature stability similar to that of LOCTITE GC 10, the paste offers performance stability at 26.5°C for six months and at 40°C for one month. GC 3W combines the properties of high-activity flux performance and temperature stability.