This study investigates the microstructure, intermetallic compound (IMC) morphology and shear strength of Sn4.38Ag solder joints with different percentages of Sb content. The paper also evaluates, and compares, the thermal resistance of solder joints with different Sb content by means of high temperature storage testing. In order to achieve solder joints of the size found in the BGA package, this study used pure copper wires of 1 mm diameter as substrates for hot-dipping soldering. Solders with different compositions were selected for investigation, namely Sn4.38Ag, Sn3.9Ag0.9Sb, Sn4.4Ag1.44Sb and Sn4.11Ag1.86Sb, while a Sn40Pb solder was chosen for comparison purposes. High temperature storage testing was performed after soldering, with storage temperatures of 150°C and 200°C, respectively, and storage times of 0, 25, 100, 228 and 625 hours, respectively. Experimental results show that most of the Sb which is added to the solder is soluted in the β-Sn matrix, with the remainder reacting with the Sn and Ag atoms to form an ε-Ag3(Sn,Sb) compound.