WATER SOLUBLE FLUX

PROBLEM TO BE SOLVED: To obtain water soluble flux compatible with a human body and a environment, not having corrosiveness and excellent in wettability and solder spread by containing a rosin soap in water. SOLUTION: A rosin soap is produced by dissolving alkali into water, heating and adding rosin while agitating. In the case water soluble flux is a liquid type, the rosin soap of 1-30 pts.wt. is dissolved in 100 pts.wt. water, in the case of a paste type, the rosin soap of 31-60 pts.wt. is dissolved, further a organic solvent is preferably not contained. Solder spread is improved by adding an organic acid, a halide and an organic halide. By adding a fungus preventive of 0.001-0.1 wt.% in a water soluble flux, long term storage is made possible. The fungus preventive preferably uses water soluble. An adding agent of surface active agent, thickner, defoaming agent, etc., may be added.