Experimental studies of the temperature dependence of mechanical solder material properties using nanoindentation

Microelectronic components are subjected to a continuous miniaturization process. These efforts of a modern electronic industry require quantitative knowledge of the solder material properties in order to guarantee the reliability of the joining process. Of particular interest are the values of Young´s modulus and hardness. Corresponding to the small-size of microelectronic devices is required to use adequately sized specimens and miniature tests. In these studies nanoindentation is applied to determine the material properties of Sn91Zn9 and Sn42Bi58 solder alloys, and also of copper (for a first orientation) and fused silica, which is used for the indenter calibration. Moreover, the potential change of material properties at elevated temperatures is investigated for the materials mentioned. A hot stage add-on allows nanoindentation measurements up to +500°C in order to characterize the various materials in great detail. The melting points of the solder alloys are 199°C and 138°C for Sn91Zn9 and Sn42Bi58, respectively. The prohibition of the lead containing eutectic SnPb solder alloy requires research work in lead-free materials. This paper describes the setup and the analysis of temperature-dependent material tests and presents first results for Young´s modulus, hardness, and yield stress, which are compared to literature, at least as far as possible. Furthermore this paper has the goal to verify the measurement setup and the subsequent data evaluation.