Sn-37Pb　and　Sn-3.0Ag-0.5Cu　solder　pastes　printed　onto　a　board　were　attached　to　ball　grid　array　(BGA)　samples　using　Sn-3.0Ag-0.5Cu　solder　balls.　Before　thermal　shock,　the　initial　grain　orientations　on　the　cross-section　were　obtained　by　scanning　electron　microscopy　equipped　with　an　electron　backscattered　diffraction　system.　Three　mixed　solder　joints　(two　from　the　corner　and　another　from　the　middle　of　the　BGA　component)　and　three　lead-free　solder　joints　(at　the　same　positions)　were　selected　to　investigate　the　recrystallization　behavior　under　thermal　shock　(TS)　cycling　conditions.　All　of　the　mixed　and　lead-free　solder　joints　were　initially　single　crystal.　The　results　showed　that　recrystallization　occurred　in　both　the　mixed　and　lead-free　solder　joints　after　200　TS.　For　the　mixed　solder　joints,　more　recrystallization　was　observed　and　the　location　of　samples　had　a　significant　influence　on　their　recrystallization　behavior,　while　location　was　not　as　important　for　the　lead-free　samples　after　200　TS　in　this　study.　Both　the　mixed　and　lead-free　solder　joints　at　the　corner　of　BGA　components　showed　the　poorest　reliability.　According　to　misorientation　distribution　maps　and　subgrain　rotation　behaviors,　the　reliability　of　mixed　solder　joints　was　much　poorer　than　that　of　lead-free　solder　joints.