Quad　Flat　non-lead　(QFN)　packages　known　with　many　outstanding　properties.　However　the　thermal　stresses　and　plastic　strain　accumulation　in　solder　joints　during　temperature　and　power　cycling　can　be　induced　due　to　the　significant　mismatch　in　the　coefficients　of　thermal　expansion　(CTE)　of　dissimilar　materials.　The　damage　caused　by　these　stresses　and　plastic　strain　accumulation,　which　are　induced　during　accelerated　temperature　cycling　due　to　the　CTE　mismatch　between　the　various　materials　that　encompass　the　QFN　package,　ultimately　cause　the　failures　of　solder　joints.　In　this　paper　the　ANSYS　software　is　adopted　to　build　a　quarter　of　model　about　QFN,　which　is　subjected　to　the　thermal　recycling　of　-40∼125°C.　The　thermal　fatigue　life　of　QFN　is　calculated　based　on　the　maximum　strain　range　and　the　Coffin-Manson　equation.　Anand＇s　viscoplastic　material　model　is　used　to　describe　the　constitutive　equation　of　the　solder　joints　in　this　study.　A　L27(38)　orthogonal　array　is　built　based　on　Taguchi　Method　to　figure　out　the　optimized　conditions.　Besides,　in　order　to　avoid　accidental　error,　ANOVA　is　carried　out　to　estimate　the　error　and　find　the　most　important　factors.　The　results　indicate　that　only　five　material　and　structural　factors　are　the　most　important　ones,　and　the　other　factors　are　selected　by　price　or　convenience.　Finally,　the　fatigue　life　after　optimal　design　by　Taguchi　method　has　3.43　folds　on　the　fatigue　life　over　the　original　design.　©　2012　IEEE.