Morphological and Compositional Evolution of InPb/Au Solder Joints under Thermal Ageing in Atmospheric and Vacuum Environments

Solder joints are critical elements in electronic devices used in Space and Aerospace applications, where in-situ repair is generally unfeasible and extreme environments accelerate failure mechanisms—such as formation and propagation of brittle intermetallic compounds (IMCs). These failures are among the primary causes of electronic malfunction in spacecraft and satellites. Therefore, predicting the long-term behavior of these elements is essential to improve reliability assessments. This study investigates the stability of indium-lead on gold (InPb/Au) solder joints under thermal ageing at various pressures (atmospheric and high vacuum) and temperatures (25°C, 85°C, and 125°C). Non-destructive characterization techniques (ODM, SEM, EDS, XRM) were employed to enable dynamic analysis over time without damaging or sacrificing the samples through microsectioning. Large volume shrinkage and IMC growth were observed monitored under each condition, and their Activation Energy (Ea) and Acceleration Factor (AF) were estimated, highlighting the impact of environmental conditions on solder joint degradation.