Influences of Microstructure and Specimen Size on Creep Properties of Solders

Abstract

The influences of microstructure and specimen size on creep properties of Sn-37Pb and Sn-3.5 Ag solders were investigated by nano-indentation tests and tensile creep tests for fine wire solders. The nano-indentation tests enabled us to measure the indentation creep properties of the specific microstructures individually. Tensile creep experiments were performed on our original creep testing machine for fine wire solders with the diameters of 0.2, 0.5 and 1.0 mm. For the Sn-37Pb solder, the creep deformation properties were uniform for both α and β phases and grain boundary sliding was the dominating creep mechanism. For the Sn-3.5Ag solder, creep deformations of α phase were observed under much smaller stress levels than those for ε phase, and thus the creep deformations occurred only in α phase, which resulted in the nucleation of microvoids around the ε phase. The tensile creep tests for wire solders revealed that the significance of specimen size on the creep properties is strongly influenced by the microstructure of the solders.