In　order　to　solve　the　coarsening　problem　of　reinforcing　particles　in　fabrication　of　traditional　composite　solders　and　enhance　the　properties　of　lead-free　composite　solders,　the　eutectic　Sn-3.5Ag　and　Sn-3.0Ag-0.5Cu　were　selected　as　solder　matrix,　and　three　different　nano-sized　polyhedral　oligomeric　silsesquioxane　(POSS)　particulates　were　used　as　reinforcing　particles　to　form　composite　solders.　The　spreadability　properties,　mechanical　performance,　and　creep　rupture　lives　of　solder　matrix　and　their　new　composite　solders　with　different　mass　fractions　were　studied.　The　experimental　results　indicate　that　the　new　composite　solders　and　their　joints　show　better　wettability,　mechanical　properties,　as　well　as　longer　creep　rupture　lives　than　those　of　the　solder　matrix.　Besides,　Sn-Ag-Cu　composite　solder　joints　exhibit　better　properties　compared　with　SnAg　composite　solder　joints.