Abstract: Wetting properties of Sn-3.5Ag-0.5Cu solder with no-clean flux on Sn,Sn-Cu,Sn-Bi coatings were tested and studied on the basis of wetting balance principle under the conditions of five temperature,three kinds of coatings and two atmospheres.The results indicate that the wettability of Sn-Bi coating in air at lower temperature is prefect,but they are almost same at higher temperature for the wettability of three coatings.The wettability can be obviously improved and the wetting time is reduced by 22%~40% in N₂ atmosphere and the wettability of Sn-(3.5Ag)-0.5Cu solder on three kinds of coatings is nearly same at the same temperature.