The　types,　morphology　and　distribution　of　intermetallic　compounds　(IMCs),　and　the　evolution　of　the　types　and　composition　and　morphology　of　IMC　in　the　joints　during　the　subsequent　aging　process　were　presented.　The　analysis　results　show　that　the　types　of　IMCs　mainly　depend　on　solder　composition　and　the　solubility　and　diffusion　rate　of　metal　substrate　in　solder　alloy;　the　morphology　of　IMC　is　closely　related　with　the　soldering　peak　temperature,　cooling　rate　and　the　thermal　gradient　of　the　interface　of　joints;　the　distribution　of　IMC　is　related　with　solder　composition　and　the　diffusivity　of　metal　elements　in　the　joints.　The　analysis　results　also　show　that　the　fracture　mechanism　of　the　joints　is　mainly　controlled　by　the　solder　composition,　the　peak　temperature　and　duration　of　aging　as　well　as　the　applied　loads.　The　eutectic　structures　of　the　solder　are　coarsened　during　the　aging　process　and　the　strength　of　the　solder　decreases,　thus　the　fracture　occurs　inside　the　solder.　If　the　thickness　of　IMC　increases　to　critical　size,　the　stress　concentration　will　be　serious.　Some　time　multilayer　IMCs　will　be　formed　and　cavity　will　be　formed　and　grow,　and　the　fracture　will　occur　in　the　interfacial　layer　of　IMCs.　If　the　strengths　of　the　solder　and　IMC　are　close　during　aging,　the　fracture　will　occur　both　inside　the　joints　and　in　the　interfacial　layer　of　IMCs.