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Abstract

Harmonic vibration durability tests were conducted on several low-temperature solder (LTS) interconnects using printed board assemblies (PBA) populated with 24 surface-mounted daisy-chained components, including four replicates each of CABGA192, CTBGA228, CVBGA360, and QFN68, and eight surface-mounted resistors (SMR1206) which were not tested to failure. Each test vehicle was assembled using one of four distinct solder alloys: SAC305, LTS1, LTS2, or LTS3, with SAC305 serving as the benchmark. All test specimens were evaluated under clamped-free-clamped-free (CFCF) boundary conditions with durability trials conducted at the first resonant frequency to trigger a Mode 1 bending response. Component failure was defined as a 20% increase in resistance over five consecutive scans. A calibrated finite element global model was used to estimate board-level strain amplitudes, which were combined with cycles-to-failure data to construct durability plots for each solder alloy and component type. Durability test results indicate that SAC305 consistently performs the worst, while LTS1 and LTS3 generally provide the highest vibration durability. A multiscale global/local sub-modeling approach was developed to estimate volume-averaged Von Mises strains within the critical solder joints of the CABGA192 and QFN68 components, enabling the extraction of Basquin-Coffin-Mason fatigue model constants and fatigue life estimations for each tested interconnect. The interconnects of the CABGA192 and QFN68 components were found to exist in different stress states due to distinct aspect ratios, this was confirmed through analysis of the stress triaxiality ratio and contributes to differences in their fatigue damage accumulation rates. Nonlinear dynamic behavior was observed in the acceleration and strain response of the PBA in the form of superharmonics, which introduced piece-to-piece variability in cycle counting, PBA strain amplitudes, and PBA acceleration response amplitudes.

Jonathan Martin is a researcher with the Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland. He specializes in the reliability of electronic interconnects under vibration. His current work focuses on the vibration durability of low-temperature solders for next-generation electronic assemblies, with expertise in vibration testing, fatigue modeling, and finite element analysis. Jonathan has contributed to publications on solder reliability, including co-authorship of "Effect of Isothermal Aging on Anisotropic Creep Properties of SAC305 Single Crystals." As well as co-authorship of "Fatigue Degradation Sensing with Surface-Mounted Conjugate-Stress (CS) Sensor".

Copyright(c) CALCE/University of Maryland