Influence of Low Temperature Swings on Solder Joint Reliability

Abstract

The evolution in modern-day electronics extends beyond miniaturization and significantly increases the number of power cycles operating with low temperature swings (few tens of degrees). This shift has raised the reliability requirements and expectations for electronics systems to last longer. The transition of vehicles and autonomous systems to zonal architectures, driven by electrification, has increased power-on hours of electronic components, leading to higher system complexity and more challenging reliability testing. Currently, standardized stress- based tests and predictive models have constraints, as they are designed for large temperature swings and are inaccurate for evaluating low T conditions. Additionally, the damage caused by Δ millions of low thermal swings is less explored in simulation and qualification, making it important to analyze the influence of low ΔT on solder joints to understand field reliability risks.An Arduino-based testing setup was developed to apply active thermal cycles to WLCSP40 using relay-controlled switching with 6-second cycles. Samples were tested from 50k to 800k cycles to analyze the long-term damage accumulation under such conditions. In addition to experiments, a thermomechanical simulation in COMSOL incorporated ΔT values obtained from thermal camera characterization to establish realistic boundary conditions. It helps to correlate experimental results and identify critical locations within the solder joints where damage is most likely to occur.Cumulative plastic strain analysis and cross-sectional imaging revealed cracks in the solder bulk at 40 °C, demonstrating microstructural fatigue under low ΔT cycling. Furthermore, based on strain per cycle values, the results exhibit how the active and passive thermal cycles differ.