Grain　orientations　are　a　significant　factor　under　high-density　current　stressing,　but　there　are　few　literature　reports　about　the　influence　of　grain　orientation　on　electromigration　in　composite　solder　joints.　Most　research　relating　to　the　electromigration　behavior　of　composite　solders　have　been　carried　out　by　adding　different　kinds　of　reinforced　particles　in　order　to　relieve　the　electromigration　phenomena,　while　the　impacts　of　grain　orientation　on　the　electromigration　have　been　neglected.　In　this　paper,　Sn-3.5Ag　composite　solder　joints　reinforced　by　2　vol.%　Cu　were　fabricated　to　investigate　the　effects　of　Sn　grain　orientation　on　electromigration.　The　one-dimensional　single-grained　solder　joints　were　stressed　under　a　constant　current　density　of　10(4)A/cm(2)　for　different　times　at　room　temperature.　The　samples,　of　which　the　c-axis　of　the　Sn　grains　was　nearly　parallel　to　the　electron　flow　direction,　exhibited　serious　electromigration-induced　phenomena　after　current　stressing　for　528　h.　However,　electromigration　was　not　observed　in　the　samples　where　the　Sn　grains　had　their　c-axis　perpendicular　to　the　electron　flow　direction.　Therefore,　the　grain　orientations　have　a　great　influence　on　the　electromigration　behavior　in　composite　solders　and　Cu　atoms　moved　faster　along　the　c-axis　of　the　Sn　grains　than　along　the　a-　and　b-axes　during　current　stressing.