A　ball　grid　array　specimen　with　cross　sectioned　edge　row　was　thermally　shocked　to　investigate　subgrain　rotation　of　recrystallized　region　in　lead-free　solder　joints.　Scanning　electron　microscopy　(SEM)　and　electron　backscattered　diffraction　were　used　to　obtain　the　microstructure　and　orientations　of　Sn　grains　or　subgrains　in　as-reflowed　and　thermally　shocked　conditions.　Orientation　imaging　microscopy　showed　that　several　subgrains　were　formed　at　the　tilted　twin　grain　boundaries　after　200　thermal　shocks　due　to　high　mismatched　coefficient　of　thermal　expansion　of　twin　grains.　And　four　subgrains　in　the　solder　joint　were　selected　and　divided　into　two　parts　to　research　the　grain　rotation　behavior　in　lead-free　solder　joint.　The　analysis　of　subgrain　rotation　indicated　that　there　were　three　ways　of　subgrain　rotation　during　localized　recrystallization　after　200　thermal　shocks,　which　were　about　the　Sn　[100],　[101]　and　[110]　axes.　There　were　three　slip　systems　(010)[],　(101)[010]　and　(110)[]　which　closely　related　with　the　subgrain　rotation　about　Sn　[100],　[101]　and　[110]　axes,　so　the　three　ways　of　subgrain　rotation　were　possible.　Furthermore,　SEM　showed　that　a　concave　region　was　generated　at　the　top　of　the　joint　after　200　thermal　shocks　due　to　the　different　misorientation　angles　between　nonrecrystallized　region　and　subgrains.