Cracking　along　the　intermetallic　compound　(IMC)　interface　in　solder　joints　is　the　most　important　failure　mechanism　in　electronics　packages.　In　order　to　understand　the　failure　mechanism　well,　a　2D　solder/IMC　interface　model　is　used　to　examine　the　stress　around　the　interface.　Three　solder　materials,　Sn37Pb,　Sn3.5Ag　and　Sn3.0Ag0.5Cu,　and　various　IMC　thicknesses,　which　represent　different　growth　stages　of　the　IMC,　are　considered　to　investigate　their　effects　on　the　interfacial　stress.　The　stress　intensity　factor,　H,　which　is　used　as　bi-material　interface　failure　criterion,　are　calculated　for　various　IMC　thicknesses.