Special tin whisker growth on surface of oxidized RE-phases

CeSn₃ and ErSn₃ phases with large size were precipitated in the Sn-3.8Ag-0.7Cu-1.0Ce/Er solder alloys.The aging treatment at room temperature and 150℃ was carried out for the prepared sample of Sn-3.8Ag-0.7Cu-1.0Ce/Er solder alloy,respectively.After various storage periods,the tin whiskers appeared on the specimen surfaces were analyzed by scanning electron microscopy(SEM).The results indicated that a great number of needle-like and thread-like tin whiskers were formed on the surface of the oxidized RE phases.It was noteworthy to mention that these tin whiskers kept the constant cross section during growth process.However,besides these regular tin whiskers,some new ones with special morphology,such as lapped whiskers,branch and combination of whiskers,were also found.