The　morphological　features　and　growth　kinetics　of　interfacial　IMCs　have　shown　significant　effect　on　the　mechanical　properties,　and　hence,　on　the　reliability　of　lead　free　solder　joints.　The　growth　behavior　of　the　interfacial　IMCs　of　SnAgCu/Cu　solder　joint,　in　reflow　and　thermal　cycling,　was　investigated　with　the　focus　on　the　influence　of　reflow　dwell　time　and　the　cyclic　parameters　on　the　growth　kinetics.　The　three-dimensional　IMCs　feature　was　explored　by　etch　the　solder　matrix　out　of　the　SnAgCu/Cu　interface.　The　phases　of　IMCs　were　identified　by　energy　dispersive　X-ray　(EDX).　The　thickness　of　the　IMCs　was　measured　by　element　mapping　and　phase　constitution　analysis.　The　thermal　cycling　of　SnAgCu/Cu　soldered　joints　was　performed　within　the　temperature　region　of　-25C　to　125C　and　-40C　to　125C　respectively.　The　corresponding　IMCs　growth　rates　were　formulated　according　to　the　data　from　various　thermal　cycles.　The　growth　kinetic　of　the　IMCs　was　analyzed　in　the　framework　of　diffusion　principles.　The　shear　strength　of　the　joint　was　evaluated　and　the　fracture　mechanism　was　analyzed　in　accordingly.　It　was　found　that　Cu6Sn5　was　formed　and　followed　by　rapid　coarsening　at　the　solder　and　Cu　interface　during　reflowing.　During　thermal　cycling,　however,　IMCs　grain　coarsening　and　breaking　were　noted.　The　thickness　of　IMCs　was　found　increases　with　the　thermal　cycles;　however,　the　growth　rate　is　less　than　that　of　thermal　aging.　The　dwell　time　in　high　temperature　portion　of　a　thermal　cycle　was　found　has　significant　influence　on　the　growth　rate　of　the　IMCs.　The　growth　of　the　IMCs,　both　for　reflowing　and　thermal　cycling,　was　found　follows　diffusion　model.　The　shear　strength　of　the　joints　was　found　decreases　both　with　the　increase　of　the　thermal　cycles　as　well　as　with　the　decrease　of　the　cooling　dwell　temperature　in　the　thermal　cycles.　©2009　IEEE.