Thermomechanical　fatigue　damage　is　a　progressive　process　of　material　degradation.　The　objective　of　this　study　was　to　investigate　the　damage　behavior　of　SnAgCu/Cu　solder　joints　under　thermomechanical　cycling.　A　damage　model　was　proposed　based　on　continuum　damage　mechanics　(CDM).　Based　upon　an　analysis　of　displacements　for　flip-chip　solder　joints　subjected　to　thermal　cycling,　a　special　bimetallic　loading　frame　with　single-solder　joint　samples　was　designed　to　simulate　the　service　conditions　of　actual　joints　in　electronic　packages.　The　assembly,　which　allowed　for　strain　measurements　of　an　individual　solder　joint　during　temperature　cycling,　was　used　to　investigate　the　impact　of　stress-strain　cycling　on　the　damage　behavior　of　SnAgCu/Cu　solder　joints.　The　characteristic　parameters　of　the　damage　model　were　determined　through　thermomechanical　cycling　and　strain　measurement　tests.　The　damage　variable　D　=　1　-　R-0/R　was　selected,　and　values　for　it　were　obtained　using　a　four-probe　method　for　the　single-solder　joint　samples　every　dozen　cycles　during　thermomechanical　cycling　tests　to　verify　the　model.　The　results　showed　that　the　predicted　damage　was　in　good　agreement　with　the　experimental　results.　The　damage　evolution　law　proposed　here　is　a　function　of　inelastic　strain,　and　the　results　showed　that　the　damage　rate　of　SnAgCu/Cu　solder　joints　increased　as　the　range　of　the　applied　strain　increased.　In　addition,　the　microstructure　evolution　of　the　solder　joints　was　analyzed　using　scanning　electron　microscopy,　which　provided　the　microscopic　explanation　for　the　damage　evolution　law　of　SnAgCu/Cu　solder　joints.　(c)　2013　Elsevier　B.V.　All　rights　reserved.