Effects of temperature and coatings on wettability of Sn-Cu-Ni lead-free solder

Wetting times and wetting forces of Sn-Cu-Ni lead-free solder for different temperatures and three kinds of substrates, including Cu, Au/Ni/Cu, and SnBi/Cu, were measured by means of wetting balance method.The effects of soldering temperature on wettability of Sn-Cu-Ni lead-free solder on different substrates were also studied. The results indicate that with the increase of tempera-ture, the surface tension of the lead-free solder decreases, and the wetting times are reduced observably, and the wetting forces are in-creased evidently.The wettability of solder on Au/Ni/Cu or SnBi/Cu substrate is better than that on Cu substrate owing to the decrease of the interfacial tension between solder and substrate by way of plat-ing Ni/Au or SnBi coating.