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°C　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.