Solder　joints　in　practical　service　conditions　are　usually　subjected　to　simultaneous　current　stressing　and　thermal　cycling.　At　present,　most　studies　focus　on　either　thermal　cycling　or　current　stressing.　Therefore,　the　existence　of　coupling　between　these　two　factors　remains　in　doubt.　In　this　study,　experiments　are　conducted　to　reveal　the　effect(s)　of　current　density　magnitude　on　the　thermomechanical　fatigue　(TMF)　behavior　of　solder　joints.　At　the　early　stage　of　coupling　stressing,　damage　accumulation　contributed　to　TMF　at　both　high　and　low　current　densities.　Fatigue　micro-cracks　readily　nucleated　and　propagated　along　the　boundary　of　Sn-rich　and　Bi-rich　phases.　Fatigue　crack　formation　could　be　retarded　through　mass　transport　and　Joule　heating　effects　at　an　early　stage.　At　later　stages,　the　high　current　density　led　to　electromigration　(EM),　which　played　an　important　role　in　the　failure　process　by　changing　interfacial　mechanics　due　to　the　mass　transport.　EM　led　to　the　final　failure　of　solder　joint,　where　fracture　was　located　at　the　interface　between　the　intermetallic　compound　and　solder.