Abstract: By means of wetting balance method,the wetting time,wetting force and the effects of soldering temperature on wettability of Sn-Ag-Cu lead-free solder were tested under the conditions of two temperatures and three substrates.The results indicate that the higher temperature remarkably improves wettability of lead-free solder on substrate.The wetting time of Sn-Ag-Cu lead-free solder on Cu substrate is close to that of Sn-Pb solder,and the wetting force is greater than that of Sn-Pb solder at 260℃.The wetting time of SnAg-Cu lead-free solder on Ni/Au and SnBi coatings are obviously shorter than that on Cu substrate,and the wetting time of Sn-Ag-Cu solder on three substrates are decreased by 34%~67% compared with that of Sn-Ag-Cu at 235℃.