Shock and Vibration Simulation for PBGA Board Assemblies with SAC Solder Interconnects using Non-Linear High Strain Rate Properties

Advanced electronics are required by current vehicle trends for better control, safety, efficiency, and entertainment. Many electronic systems like engine control units, power control units, and sensors are under-hood. Electronics will experience high and low operating temperatures during operations, handling, and storage in harsh environments such as aviation and defense. In drop, shock, and vibration loads, the temperature can fluctuate in wide extremes from -65 to +200°C. Vibration at high temperatures accelerates the rate of damage accumulation on the solder interconnects. Finite element modeling has been widely employed for solder interconnection design for harmonic vibration and drop & shock simulation in electronic packaging. The Anand constitutive model is one of the most popular models for capturing non-linear solder behavior in thermo-mechanical loads. Previously, Anand constitutive models were used to characterize the material behavior for SAC solder alloys and SnPb solder alloys. Literature is scarce on the mechanical behavior of lead-free alloys in the severe environment of high-temperature vibration and drop and shock. The current work fills this gap in the literature by examining the evolution of Anand parameters for doped SAC-Q solder alloys during varied thermal aging up to one year. The measured Anand parameters were applied in a FE framework to model drop and harmonic vibration events for a ball-grid array package on printed circuit board assembly. The drop event were simulated at 1500 g and 0.5 ms for various operating temperature ranges (-65 to +200 C) and thermal aging (up to 1 year). High-speed cameras and digital image correlation were used to extract full-field strain. Stresses in solder interconnects have been extracted from FEA-based simulation. Hysteresis loop and plastic work density are extracted form harmonic vibration and drop and shock simulation. The plastic work per shock event is used to measure the progression of damage in solder interconnects. Evolution in hysteresis loop and plastic work has been studied due to thermal aging and operating temperatures for drop events.