Fatigue life assessment and prediction of ball grid array package under environmental conditions

In this dissertation both finite element modeling and experimental techniques are employed to assess and predict the fatigue life of electronic components under environmental loadings. Since the random vibration, drop impact and thermal cycling loading are major driving forces for the electronic packages failures, the fatigue life estimation procedure, that would help analyst to make relatively accurate fatigue life prediction, has presented and each step of the procedure has been explained and validated through experiments.;The first part of dissertation develops an assessment methodology based on vibration tests and FEA to predict the fatigue life of electronic components under random vibration. The FE based fatigue life prediction approach consists of two steps: The first step aims at characterizing fatigue properties of solder joint by generating the S-N curve. Spectrum analysis of random vibration, as the second step, was performed numerically to obtain the response PSD of critical solder joint. The calculated fatigue life based on the cycle counting results, S-N curve, and the modified Miner's rule agreed with actual testing results.;As handheld devices are prone to drop impact, which results in solder joint failures, both the dynamic responses of PCB and the impact life of solder joints with different shield-can designs were investigated, which are seldom explored. An accurately validated FE model has been developed. The stress analysis was performed to understand the failure mechanism and correlate with impact life of solder joint.;The ever increasing power density requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive loading was applied to reduce the thermal resistance between package and heat sink. Both numerical modeling and experimental approaches were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling. The time to crack initiation and permanent failure were identified based on in-situ resistance measurement results. The failure analysis was performed to identify the failure modes. A thermal fatigue life prediction model for preloaded solder joint was also developed to understand the thermal fatigue crack behaviors of solder joint and successfully validated with the experimental results.