Reliability assessment of indium solder for low temperature electronic packaging

Indium is the choice of material for cryogenic joining applications. It is superior under repeated wide temperature excursions including extreme cold temperatures (below −55 °C) because of its excellent electrical conductivity and ductility at cryogenic temperatures. In particular, it is being considered for die/substrate attaches in low temperature SiGe BiCMOS modules for Martian and Lunar exploration. An efficient and systematic assessment was conducted to evaluate the reliability of indium solder under thermal fatigue and extended cold temperature mechanical fatigue conditions encountered in space exploration missions. In addition, fatigue failure sites, modes and mechanisms in indium solder at low temperature were investigated. A fatigue model was also calibrated for indium solder joint at cryogenic temperatures.