The　microstructure　evolution　of　the　interface　of　Sn-3.8Ag-0.7Cu/Cu　solder　joint　after　aging　for　different　time　at　150°C　was　investigated.　The　tensile　strength　test　was　carried　out　on　the　samples　after　aging　for　different　time　and　dynamic　tensile　in　situ　observation　and　tensile　fracture　surface　of　the　samples　were　studied　by　SEM　(scanning　electron　microscopy).　The　results　show　that　scallop-like　Cu6Sn5　IMC　(intermetallic　compound)　layer　formed　at　the　interface　of　Sn-3.8Ag-0.7Cu/Cu　joint　as　soldered.　With　the　increase　of　aging　time,　the　depth　of　interfacial　IMC　increased　and　Cu6Sn5　column　became　lengthened　and　coarsened　and　finally　left　interfacial　IMC　layer　into　solder.　The　Ag3Sn　phase　formed　at　the　interface　of　solder　and　Cu6Sn5　after　aging　for　480　h.　The　results　of　tensile　experiment　show　that　the　tensile　strength　of　the　joint　slightly　increases　at　the　initial　stages　of　aging　and　decreases　gradually　after　aging　for　48　h.　The　results　of　dynamic　tensile　show　that　fracture　took　place　inside　the　solder　matrix　at　the　initial　stages　of　aging.　With　the　increase　of　aging　time,　the　position　of　fracture　gradually　moves　to　interface　and　after　aging　for　480　h,　the　fracture　completely　took　place　at　the　interfacial　IMC　layer.