Reliability is one of the major research topics of modern electronic packaging technology. The characterization of Au-Sn dia-attach solder material properties, including viscoplastic properties is requested for fast and accurate reliability assessment by industry. In this thesis, a detailed experimental based methodology to characterize Au-Sn solder's viscoplastic properties, including raw material introduction, test specimen preparation, shear creep experiments and test data analyze is provided. Furthermore, a study of microstructure effect on Au-Sn solder viscoplastic performance by experiments and following reliability analysis is presented.