Ball　grid　array　(BGA)　samples　were　soldered　on　a　printed　circuit　board　with　Sn37Pb　solder　paste　to　investigate　the　recrystallization　induced　by　subgrain　rotation　during　thermal　shock.　The　composition　of　the　solder　balls　was　Sn3.0Ag0.5Cu-Sn37Pb,　which　comprised　mixed　solder　joints.　The　BGA　component　was　cross-sectioned　before　thermal　shock.　The　microstructure　and　grain　orientations　were　obtained　by　a　scanning　electron　microscope　equipped　with　an　electron　back-scattered　diffraction　system.　Two　mixed　solder　joints　at　corners　of　the　BGA　component　were　selected　as　the　subjects.　The　results　showed　that　recrystallization　occurred　at　the　corner　of　the　solder　joints　after　200　thermal　shock　cycles.　The　recrystallized　subgrains　had　various　new　grain　orientations.　The　newly　generated　grain　orientations　were　closely　related　to　the　initial　grain　orientations,　which　indicated　that　different　subgrain　rotation　behaviors　could　occur　in　one　mixed　solder　joint　with　the　same　initial　grain　orientation.　When　the　misorientation　angles　were　very　small,　the　rotation　axes　were　about　Sn　[100],　[010]　and　[001],　as　shown　by　analyzing　the　misorientation　angles　and　subgrain　rotation　axes,　while　the　subgrain　rotation　behavior　with　large　misorientation　angles　in　the　solder　joints　was　much　more　complicated.　As　Pb　was　contained　in　the　solder　joints　and　the　stress　was　concentrated　on　the　corner　of　the　mixed　solder　joints,　concaves　and　cracks　were　formed.　When　the　adjacent　recrystallized　subgrains　were　separated,　and　the　process　of　the　continuous　recrystallization　was　limited.