Abstract
A convenient method for predicting mechanical properties of solder materials was proposed. Indentation method was used to obtain mechanical properties including elastic, plastic and creep deformations. Elastic-plastic FEM correlated Young's modulus and yield stress with unloading portion of load-displacement curve and Vickers hardness, respectively. Tensile creep properties were lead by measured indentation creep properties, where the creep properties were evaluated in terms of the Norton's law. The agreement of the prediction was confirmed for Sn-37Pb (mass %) eutectic solder in the range between room temperature and 125℃. The above prediction methods were established based on elastic-plastic-creep analysis of FEM for an indenter with rotational symmetry, whereas the Vickers indenter is a three-dimensional configuration of quadrangular pyramid. The agreement of the prediction methods was confirmed by three-dimensional analysis of FEM. Using the proposed method, mechanical properties of lead-free solders such as Sn-3.5Ag and Sn-3Ag-0.5Cu-0〜3Bi alloy systems were determined for the temperature between -20℃ and 160℃. The predicted results revealed that mechanical properties of Sn-3.5Ag and Sn-3Ag-0.5Cu alloys were similar, and that Young's modulus, yield stress and creep properties of Sn-3Ag-0.5Cu-0〜3Bi lead-free solders were strongly influenced by Bi content.
