In　the　current　research,　trace　rare　earth　(RE)　element　Y　was　incorporated　into　a　promising　lead-free　solder,　Sn3.8Ag0.7Cu,　in　an　effort　to　improve　the　comprehensive　properties　of　Sn3.8Ag0.7Cu　solder.　The　range　of　Y　content　in　Sn3.8Ag0.7Cu　solder　alloys　varied　from　0　wt.%　to　1.0　wt.%.　As　an　illustration　of　the　advantage　of　Y　doping,　the　melting　temperature,　wettability,　mechanical　properties,　and　microstructures　of　Sn3.8Ag0.7CuY　solder　were　studied.　Trace　Y　additions　had　little　influence　on　the　melting　behavior,　but　the　solder　showed　better　wettability　and　mechanical　properties,　as　well　as　finer　microstructures,　than　found　in　Y-free　Sn3.8Ag0.7Cu　solder.　The　Sn3.8Ag0.7Cu0.15Y　solder　alloy　exhibited　the　best　comprehensive　properties　compared　to　other　solders　with　different　Y　content.　Furthermore,　interfacial　and　microstructural　studies　were　conducted　on　Sn3.8Ag0.7Cu0.15Y　solder　alloys,　and　notable　changes　in　microstructure　were　found　compared　to　the　Y-free　alloy.　The　thickness　of　an　intermetallic　compound　layer　(IML)　was　decreased　during　soldering,　and　the　growth　of　the　IML　was　suppressed　during　aging.　At　the　same　time,　the　growth　of　intermetallic　compounds　(IMCs)　inside　the　solder　was　reduced.　In　particular,　some　bigger　IMC　plates　were　replaced　by　fine,　granular　IMCs.