Conventional　solder　joints　were　prone　to　remelting　during　multiple　reflow　packages,　causing　the　chip　and　substrate　to　collapse　and　trigger　a　short　circuit　in　the　device.　Sn-based　Cu-cored　solder　joints　avoid　remelting　and　have　better　thermal　fatigue　resistance　than　conventional　solder　joints.　The　morphology　evolution　and　thermal　fatigue　behavior　of　pure　Sn　Cu-cored　and　SAC305　Cu-cored　BGA　solder　joints　during　thermal　fatigue　were　investigated.　The　presence　of　Ag3Sn　eutectic　network　in　the　SAC305　Cu-cored　BGA　solder　joints　provided　higher　mechanical　properties.　The　morphology　evolution　during　thermal　fatigue　is　more　moderate　than　that　of　pure　Sn　Cu-cored　BGA　solder　joints.　Pure　Sn　Cu-cored　BGA　solder　joints　are　not　strengthened　by　alloying　elements　and　heterogeneous　particles,　and　recrystallization　already　occurs　in　the　early　stages　of　thermal　fatigue.　However,　at　the　same　thermal　fatigue　cycle,　early　recovery　phenomenon　occur　in　the　SAC305　Cu-cored　BGA　solder　joints.　In　addition,　comparative　analysis　of　SAC305　Cu-cored　and　conventional　SAC305　BGA　solder　joints　during　thermal　fatigue　is　defined　by　finite　element　analysis.　The　results　show　that　the　Cu　core　ensures　that　both　sides　of　the　substrate　are　coplanar,　further　avoiding　the　effects　of　shear　stress　and　reducing　thermal　fatigue　damage.