Water-soluble fluxes for Sn-4Zn-0.89Cu-3.5Bi-0.3Re alloy lead-free solder

Spreading areas were measured to characterize the influence of various water-soluble fluxes on Sn
₄
Zn
_0.89
Cu
_3.5
Bi
_0.3
Re alloy solder wettability. The fluxes were composed of glutamic acid, dense hydrochloric acid, water, zinc chloride, ammonium chloride, turpentine, glycerin, ethanol, cupric chloride, acetone, citric acid, methanoic acid, carbmide and water. The microstructure and elemental distribution at the interface between the solder alloy and the Cu substrate were analyzed by EPMA. Results show that the wettability of Sn
₄
Zn
_0.89
Cu
_3.5
Bi
_0.3
Re solder alloy to copper can be greatly influenced by flux composition. A flux consisting of glutamic acid, dense hydrochloric acid and water has the best overall properties.