For　understanding　full　IMCs　solder　joints　comprehensively,　the　widely　used　Cu-Sn　system　was　adopted　as　the　research　object.　A　study　on　optimization　of　process　parameters,　microstructure　evolution　and　fracture　behavior　for　full　Cu3Sn　solder　joints　in　electronic　packaging　was　conducted　systematically.　For　forming　full　Cu3Sn　solder　joints,　260°C,　1N,　5h　was　determined　as　the　optimal　parameter　combination.　At　260°C　and　1N,　planar　Cu6Sn5　was　first　precipitated　at　Cu-Sn　interface,　which　was　followed　by　the　formation　of　planar　Cu3Sn.　Until　the　total　consumption　of　residual　Sn,　the　Cu6Sn5　continued　to　grow　with　a　transition　from　the　planar　shape　to　scallop-like　shape,　while　the　Cu3Sn　continued　to　grow　with　a　round-trip　change　from　the　planar　shape　to　wave-like　shape.　After　the　formation　of　full　IMCs　solder　joints　including　Cu3Sn　and　Cu6Sn5,　the　Cu3Sn　continued　to　grow　at　the　expense　of　Cu6Sn5　until　full　Cu3Sn　solder　joints　were　obtained　by　300min.　When　the　loading　rate　was　0.001mm/s,　0.01mm/s　and　0.1mm/s　respectively,　the　shear　strength　of　full　Cu3Sn　solder　joints　was　46.1MPa,　50MPa　and　60.5MPa　correspondingly.　Through　analysis　of　fracture　surface,　we　found　that　different　microscopic　fracture　mechanisms　led　to　different　strength　of　full　Cu3Sn　solder　joints　when　the　loading　rate　was　varied.　©　2016　IEEE.