Abstract: It is known that rare-earth elements exhibit high chemical activity and adding trace amount of rare-earth(RE) in the solder can significantly improve the properties of solder alloy.However, RE-phases with large size precipitated in the Sn-3.8Ag-0.7Cu-1.0 RE solder alloy are oxidized when exposed in air, tin whiskers growing rapidly on the surface of the oxidized RE-phases.Tin whisker growth on the surface of the oxidized YSn₃ phase is investigated at room temperature and 150℃ storage in air respectively.The results indicate that tin whiskers grow slowly and distribute unevenly on the surface of the oxidized YSn₃ phases during room temperature storage in air, but tin whiskers grow rapidly and the YSn₃ phase is extruded around even solder matrix during 150℃ storage in air.