Drop/impact　causes　high　strain　rate　deformation　in　solder　joints　of　microelectronics　package.　It　is　important　to　understand　mechanical　behavior　of　solder　joints　under　high　strain　rate　for　reliability　design　of　products.　In　this　paper　mechanical　behaviors　of　two　lead-free　solder　alloys,　Sn3.5Ag　and　Sn3.0Ag0.5Cu,　were　investigated　by　quasi-static　tests　and　the　split　Hopkinson　tension/pressure　bar　testing　technique　under　high　strain　rate　(600-2200s　-1).　The　experimental　results　show　that　the　two　materials　are　sensitive　to　strain　rate　and　their　dynamic　flow　stresses　are　much　greater　than　their　static　flow　stresses.　The　higher　the　strain　rate,　the　greater　their　tensile　strength　but　less　their　fracture　strains.　Based　on　the　experimental　data,　constitutive　models　in　the　Johnson-Cook　form　for　the　two　lead-free　alloys　were　derived.　The　models　were　then　used　to　simulate　the　testing　process　by　incorporating　it　into　ABAQUS.　The　good　agreement　between　the　numerical　simulations　and　the　experiments　indicates　that　the　presented　Johnson-Cook　models　are　suitable　and　reliable　to　describe　dynamic　behavior　of　the　two　solder　alloys　under　high　strain　rates.　Finally,　the　proposed　constitutive　models　were　used　to　compute　peeling　stress　and　plastic　strain　of　solder　joints　under　drop/impact　loadings,　and　the　results　were　compared　with　that　by　linear　elastic　model　and　tri-linear　elastic-plastic　model　to　show　the　necessity　of　using　a　strain　rate　dependent　material　model　in　simulation　of　drop/impact　of　solder　joints.　©　2008　IEEE.