The　effects　of　minimal　rare　earth　(RE)　element　additions　on　the　microstructure　of　Sn-Ag-Cu　solder　joint,　especially　the　intermetallic　compounds　(IMCs),　were　investigated.　The　range　of　RE　content　in　Sn-Ag-Cu　alloys　varied　from　0　wt.%　to　0.25　wt.%.　Experimental　results　showed　that　IMCs　could　be　dramatically　repressed　with　the　appropriate　addition　of　RE,　resulting　in　a　fine　microstructure.　However,　there　existed　an　effective　range　for　the　RE　addition.　The　best　RE　content　was　found　to　be　0.1　wt.%　in　the　current　study.　In　addition　to　the　typical　morphology　of　Ag3Sn　and　Cu6Sn5　IMCs,　other　types　of　IMCs　that　have　irregular　morphology　and　uncertain　constituents　were　also　observed.　The　IMCs　with　large　plate　shape　mainly　contained　Ag　and　Sn,　but　the　content　of　Ag　was　much　lower　than　that　of　Ag3Sn.　The　cross　sections　Of　Cu6Sn5　IMCs　whiskers　showed　various　morphologies.　Furthermore,　some　eutectic-like　structures,　including　lamellar-,　rod-,　and　needle-like　phases,　were　observed.　The　morphology　of　eutectic-like　structure　was　related　to　the　RE　content　in　solder　alloys.　When　the　content　of　RE　is　0.1　wt.%,　the　needle-like　phase　was　dominant,　while　the　lamellar　structure　prevailed　when　the　RE　content　was　0.05　wt.%　or　0.25　wt.%.　It　is　suggested　that　the　morphology　change　of　the　eutectic-like　structure　directly　affects　the　creep　properties　of　the　solder　joint.