Evaluation of Mechanical Properties and Nano-Structure Analysis of Au-20Sn and Au-12Ge Solders
Tatsuya NISHIYAMA, Takeshi OGAWA and Hiroo SAKAMOTO
Abstract:Au alloys have great potentialities as solder joints of electronic packaging. However, studies on mechanical properties of Au solders, especially on creep properties, are very limited. Mechanical properties of Au-20Sn and Au-12Ge were measured by indentation tests ranging between nano and macro scales. First, macro indentation creep tests were carried out at various temperatures, I.e. 295K, 323K, 373K, 398K and 423K. It was found that the indentation creep deformation was observed at room temperature for Au-20Sn, while above 373K for Au-12Ge. Second, the indentation creep properties were measured for ƒÄ and ƒÂ phases of Au-20Sn using a nano-indentation testing machine in order to investigate the influences of microstructure on the creep properties. Finally, we evaluated anisotropy of textured microstructure of Au-12Ge, where the dent shapes were distorted. This behavior was attributed to the three dimensional configurations, namely pile-up and sink-in. Based on the results of nano-indentation tests, numerical model for the microstructure of Au-12Ge was established and the mechanisms of the pile-up and sink-in were discussed. Key Words:Au solder, Indentation test, Indentation creep, Microstructure, Anisotropy, Plastic properties, Finite element method