Solder　ball　is　the　main　joining　element　of　ball　grid　array　packaging.　The　excellent　surface　of　brightness　and　the　reliability　of　contact　points　are　required　for　the　high　degree　of　automation　production.　Lead-free　solder　balls　are　manufactured　by　a　uniform　droplet　spray　(UDS)　method　in　this　study.　The　solidification　behavior　of　alloy　droplet　is　explained　from　the　microstructure　of　solder　ball.　By　comparing　the　smooth　and　ragged　portions,　the　microstructure　characteristic　of　ragged　portion　is　drawn.　Finally,　the　effects　of　rare　earth　element　on　the　microstructure　and　surface　condition　of　Sn-3.8Ag-0.7Cu　solder　ball　are　studied.