Development of flux for Sn-Zn lead-free solder

The speadabitity of Sn-9Zn solder on Cu substrate with four different types of flux was studied by spreading experiment method.The experimental results indicated that Sn-9Zn solder, matching the flux-A4 with stannous sulfonate(20%) as the main activator without halogen which exhibited excellent wettability.The largest spreading area was 65.7 mm², increased respeetively by 16.1%, 116.1%, 85.1% compared with the NH₄Cl-ZnCl₂, resin and water-solubility fluxes.Besides, the newly developed flux with combination of 20% stannous sulfonate and diethanolamine, succinic acid could remarkably improve the wettabiltiy of Sn-9Zn solder that the largest spreading areas were 76.5 mm², 72.5 mm² when the contents of diethanolamine, succinic acid were at 8%, 10%.