High Temperature-Vibration Reliability of SnAgCu Leadfree Assemblies in Automotive Environments

Electronics in downhole-drilling, automotive, and defense applications can experience high-temperatures in conjunction with high-strain rate loads during the entire operational life. The specific temperature and the accrued damage in the electronic assemblies depends on location use-profile and thermal architecture. Temperatures in extreme environment applications can range from -65 to +200°C with vibration G-level up to 10g in automotive underhood applications. An electronic component can experience 1-100 per sec of strain during lifetime. The combined effect of higher temperatures and vibrations in electronic components can cause a faster failure. Most earlier solder joint research focuses on either vibrational stresses or thermal cycling. In this paper, various SAC alloy failure modes has been studied at higher temperatures of 25, 55 and 155°C and vibrating conditions of 5 g and 10 g. The harmonic vibration at the first natural frequency at three test temperatures and two vibration g-levels was performed in pristine and aged test boards with CABGA daisy-chained packages. Assembly response and resistance data were measured using high-speed data acquisition in conjunction with high-speed imaging. Tensile tests were used to calculate the material properties of the printed circuit board at high temperatures. High-speed camera was used to capture the vibration event during testing using digital image correlation to capture strain-data from the center of test board. Stresses in solder interconnects have been extracted from FEA-based simulation. Effect of packages location, g-levels, operating temperatures and different SAC alloys compositions on hysteresis loop and plastic work density have been studied. Failure mode analysis has been done for test board. Anand Viscoplasticity material data from the prior studies by the authors have been used to capture the high-strain rate temperature dependent aging behavior of the solder joints. A comparison between simulation and experimental results has been done to validate the model.