Asymmetric accelerated thermal cycles: an alternative approach to accelerated reliability assessment of microelectronic packages

This work uses MicroBGA assemblies on an organic substrate to compare different symmetric and asymmetric accelerated thermal cycles (ATCs) using numerical simulations and experimental measurements. This work has developed several finite-element models: a 2D plane strain model, a generalized plane deformation (GPD) model, and a 3D quarter symmetry model, with different solder constitutive models: bi-linear kinematic hardening, multilinear kinematic hardening with power-law creep, and Anand´s viscoplastic model. The symmetric cycles examined in this work are: (a) 125°C to -40°C with ten-minute dwell each at 125°C and -40°C, and (b) 150°C to -65°C with ten-minute dwell each at 150°C and -65°C. The asymmetric cycles examined are: (c) 150°C to -65°C with a ten-minute dwell at 150°C and a five-minute dwell at -65°C and (d) 150°C to -65°C with a ten-minute dwell at 150°C and a three-minute dwell at -65°C. Transient thermal analysis has been done to ensure that the components reach a steady-state temperature, when the dwell time is reduced. The numerical simulations show that there is little difference in the predicted number of cycles to failure, between symmetric and asymmetric cycles, and the experimental data agrees with the predictions by the numerical models.