Abstract: The wettability of Sn-Cu-Ni-Ce solder on Cu substrate was investigated by wetting balance testing method under the conditions of different temperatures and atmospheres, and the effects of atmosphere, temperature and small amount of rare-earth element Ce added to the solder on the wettability of Sn-Cu-Ni solder were also studied respectively.The results indicate that wetting time of the lead-free solder is reduced by 20%-50%, and the wetting force is also increased in N₂ atmosphere because of the surface tension increase of the Cu substrate and the surface tension decrease of the Sn- Cu-Ni-Ce solder.With temperature increasing, the surface tension of the Sn-Cu-Ni-Ce solder decreases, so wetting time is observably reduced.rare-earth element Ce could lead to decrease evidently the surface tension of the Sn-Cu-Ni solder as well as the interfacial tension between solder and Cu substrate, so the wettability of Sn-Cu-Ni- Ce solder is better than that of Sn-Cu-Ni solder.