Fatigue Behaviour of Lead-Free Solder Joints Under Combined Thermal and Vibration Loads

The increasing demand for highly reliable electronic devices, even though they are exposed to harsh use conditions, is one of the main drivers for the development of electronic systems. System development process relies on the selection of materials, technologies and a proper design to meet the mission profile's demands. Among many others, the lead-free solder alloy SnAg1.0Cu0.5 (SAC105) is widely used for many electronic assemblies deployed for various applications. The fatigue behaviour of SAC105 under thermal loads (namely temperature cycling and shock testing) and drop testing has been covered extensively in the literature. Work on damage accumulation under vibration conditions has been accomplished but primarily at room temperature. Therefore, this work aims to expand knowledge of the fatigue behaviour of SAC105 under combined thermal and vibration loading. In this work, vibration durability experiments were conducted at temperatures from -40°C to +125°C and vibration peak-to-peak amplitudes from 0.6 mm to 1.6 mm. Currently, specimens have been subjected to tests with durations of 75x10E6 or 150x10E6 vibration cycles. Cross sections were analysed to relate damage locations and severity to stress conditions (temperature and vibration amplitude). As expected, damage levels were observed to increase with increasing temperatures and vibration amplitudes.