Assessment of Accrued Damage and Remaining Useful Life in Leadfree Electronics Subjected to Multiple Thermal Environments of Thermal Aging and Thermal Cycling

A method has been developed for prognostication of accrued prior damage in electronics subjected to overlapping sequential environments of thermal aging and thermal cycling. The presented approach uses the LM Algorithm in conjunction with microstructural evolution of damage based leading indi- cator for estimating prior stress history. Specific damage proxies examined include the phase-growth indicator and the IMC thickness. The viability of the approach has been demonstrated for leadfree test assemblies subjected to thermal aging at 125 °C and redeployed in cyclic thermo-mechanical environment −55–125 °C. Damage equivalency relationships between thermal aging during storage life and the resulting reduction in thermo-mechanical reliability in cyclic thermal environments during field deployment has been derived and validated based on two damage proxies. Convergence of the damage mapping to a common solution from data based on the two separate leading indicators has been demonstrated. Assemblies subjected to sequential stresses have been prog- nosticated for accrued damage from sequential overlapping stresses of thermal aging and thermal cycling. Correlation between the prognosticated damage and the actual accrued damage demonstrates that the proposed approach can be used to assess damage accrued under overlapping thermo- mechanical stresses of thermal aging and thermal cycling. In addition, prognostics metrics have been used to quantitatively evaluate the performance of the prognostic algorithms using both the leading indicators. Results demonstrate that both damage proxies work well in estimating accrued damage and estimating residual life.