In this study, dicarboxylic compounds and amine hydro-halide compounds with water solubility of at least 50 mg/L and a melting point of at least 100°C were selected for the production of water-soluble soldering fluxes. Figures 11 and 12 show the spreading ratios (%) of dicarboxylic compounds and amine hydro-halides; amine hydro-halides had a higher spreading ratio than did dicarboxylic acid. This finding is due to the active functional group of the amine hydro-halides (HCl and HBr) being more active than the carboxylic acid (-COOH) group of the acid activator. For the amine hydro-halides activator, ethyl ammonium chloride (ET.HCl) and diethyl ammonium bromide (DE.HBr) showed the highest spreading ratio (%) because this chemical has the lowest melting point and highest amount of hydrogen chloride and hydrogen bromide was obtained in the soldering process; hence, ET.HCl and DE.HBr were selected as the halide activator in this study. Oxalic acid, malonic acid, and pimeric acid had low spreading ratios due to their melting points and boiling points. Because the flux’s activity was initiated when the acid melted (Timothy et al., 2004), dicarboxylic acids with lower melting points allowed more time for the action of the flux to take place. For this reason, GA and SA were selected for production of WSRFs in this research.