Wettability of lead-free solders of Sn-Zn-xAl

At different temperatures, the wettability of leadfree solders of Sn-9Zn-xAl was tested by means of wetting balance method in air and N₂ atmospheres.Effects of addition of Al, atmosphere and temperature on the wettability of lead-free solders of Sn-Zn-xAl were studied.The results indicate that with the addition of Al, the wettability of Sn-9Zn lead-free solders is improved obviously.With the ZnCl₂-NH₄Cl flux, the optimal addition of Al is about 0.02wt.%, and with the non-cleaning flux, the optimal addition of Al is about 0.005wt.%.In N₂ atmosphere, the wettability of solder on Cu substrate was extremely improved because the surface tension of the Cu substrate increases and the oxidation of the solders decreases, the surface tension of the solders decreases.With the increase of the temperature, from 215℃ to 245℃, the wettability of the solders is improved due to the decrease of the surface tension of the solders.