Experimental characterization of the mechanical behavior of two solder alloys for high temperature power electronics applications

Keywords: Power electronics High temperature Shear Creep Nano-indentation Hardening a b s t r a c t An experimental investigation of two potential candidate materials for the diamond die attachment is presented in this framework. These efforts are motivated by the need of developing a power electronic packaging for the diamond chip. The performance of the designed packaging relies particularly on the specific choice of the solder alloys for the die/substrate junction. To implement a high temperature junction, AuGe and AlSi eutectic alloys were chosen as die attachment and characterized experimentally. The choice of the AlSi alloy is motivated by its high melting temperature T m (577 °C), its practical elaboration process and the restrictions of hazardous substances (RoHS) inter alia. The AuGe eutectic solder alloy has a melting temperature (356 °C) and it is investigated here for comparison purposes with AlSi. The paper presents experimental results such as SEM observations of failure facies which are obtained from mechanical shear as well as cyclic nano-indentation results for the mechanical harden-ing/softening evaluation under cyclic loading paths. Nowadays, high-temperature power electronics packaging designed for the power electronics systems are paramount components of the electrical inverters in the hybrid electrical vehicles as well as the aeronautical and military engines. Mainly, a power electronic packaging is subjected to a high thermomechanical and power cycling as well as external environmental conditions such as moisture and corrosion. At the end of the packaging lifetime , the failure happens very often due to the voids growth and microcracks propagation in the solder alloy. The last constitutes the major cause of the lifetime reduction. To take up the wide temperature ranges and the high current densities, a new high temperature packaging generation is currently investigated. In power electronic applications, diamond based semiconductors appear to be the solution in order to widely increase the capabilities of the power electronic converters [1]. Diamond is known to have exceptional thermal, electrical and mechanical properties. In order to make use of the exceptional characteristics of the diamond and increase the packaging reliability at high temperatures, a good choice of the die attachment is primordial to improve the thermomechanical behavior of the electronic device. Many technologies have been proposed in the literature [4,5]. The first technology is concerning solders with a high melting temperature. Inspite of the availability of high temperature solders in power electronics, researches involving this kind of materials are scarce. …