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Abstract

Electronic products are exposed to a combination of loading types in their application environments. In particular, the combination of vibration and temperature can cause electronic devices to fail. This combination occurs in many applications, e.g. in oil/gas exploration as well as in transportation platforms such as locomotive, aerospace, shipboard, and automotive systems. Failure under combined vibration and temperature cycles can be due to fatigue of material systems used to interconnect electronic devices on a printed wiring board. In particular, solder interconnects, copper traces, and device terminals can fracture, creating increased resistance or inductance (or even open circuits) in electronic assemblies. To assure the reliability of electronic products under such combined environments, acceleration models between test conditions and end-use conditions are needed.

This webinar will review efforts to understand failure in electronic assemblies under vibration at different temperatures, as well as reliability physics approaches for predicting interconnect life expectations. The test vehicles for this study used chip resistors interconnected to a printed wiring board with SnAg1.0Cu0.5 solder and were pre-aged in two different ways: (i) 10 years at room temperature and (ii) artificial aging for 100 hours at elevated temperature. As a first step, the effect of temperature on vibration failure is studied at three different temperatures: -40C, 25C, and 125C. These conditions were selected as a precursor to future testing that will include -40 to 125C temperature cycling. Detailed non-linear finite element analysis is used to characterize the stress-strain history at potential failure sites. Non-destructive and destructive physical analysis is used to identify the failure site and mechanism. Finally, model constants are derived for fatigue under harmonic vibration, using a generalized Basquin-Coffin-Manson fatigue life model at 25C, and power-law model at extreme temperatures (-40 C, and 125C).

About the Presenter: David Leslie is currently a PhD candidate in Mechanical Engineering and a graduate research assistant at the Center of Advanced Life Cycle Engineering (CALCE), at the University of Maryland, College Park. He is advised by Professor Abhijit Dasgupta, and his dissertation research is in the field of nanoindentation of viscoplastic heterogeneous solids with specific application to pressure-less sintered silver interconnect materials used in high-temperature electronic systems. He has authored numerous papers in international and national conferences and made numerous research presentations to CALCE sponsors. Before arriving at UMD, he graduated from Davidson College with a B.S. in Physics.