The service temperature of power electronic components is much higher than normal temperature，and the mismatch between heat generation and heat dissipation of devices is becoming increasingly prominent. Thegood thermal conductivity of foamed Cu is used to fill the welding material with PbSnAg alloy. It is expected toimprove the thermal conductivity of existing PbSnAg joints. The study focused on thermal resistance ，microstructureand shear strength of the copper foam enhanced Cu /Pb-Sn-Ag /Cu joint. The microstructure of PbSnAg alloy isconsists of matrix high lead and the mixed structure of high lead and IMCs ( intermetallic compounds ) .Experimental result shows that the grain of PbSnAg coarsened after the addition of Cu foam. The component of theIMCs at the copper foam and the Cu substrate are Cu3Sn. A layer with high Pb content was found between Cu andCu3Sn. The shear strength of the solder joint decreases slightly due to the addition of the copper foam，and theCu3Sn IMCs can be found on the shear fracture.