Whiskers　were　observed　on　both　the　anodic　and　cathodic　Cu　substrate　with　current　density　of　3x10(3)　A/cm(2)　at　100　degrees　C　in　Cu/eutectic　SnBi/Cu　solder　joint.　EDX　compositional　analyses　indicate　that　these　whiskers　were　composed　of　Sn　and　Bi.　After　polishing,　plenty　of　Cu6Sn5　intermetallic　compounds　were　found　on　the　Cu　substrate　surface.　Experimental　results　show　that　with　stressing　time　increasing,　SnBi　solder　started　to　diffuse　and　migrate　towards　the　Cu　substrate　by　electromigration　force,　which　formed　a　thin　film　layer　on　the　Cu　substrate.　With　the　dual　effect　of　Joule　heating　and　circumstance　temperature,　Sn　reacted　with　Cu　to　form　Cu6Sn5　intermetallic　compounds　resulting　in　compressive　stress　formation　in　the　thin　film　layer.　To　relieve　the　compressive　stress,　Sn-Bi　whiskers　were　extruded　out.