Thermal–Mechanical Coupling Analysis for Coupled Power- and Thermal-Cycling Reliability of Board-Level Electronic Packages

In this paper, we apply the sequential thermal-mechanical coupling analysis that solves, in turn, the transient temperature field and subsequent thermomechanical deformations to investigate thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball-grid-array chip-scale packages under coupled power- and thermal-cycling test conditions. Pure thermal-cycling and pure power-cycling test conditions are also examined and compared. From the comparison of different test conditions, we note that the presence of power cycling leads to significant deviations of junction and mold-top temperatures from the thermal-cycling profile. Nevertheless, for components away from the die, the deviations are less significant. As the power specified to the test vehicle is low, temperature histories on the components induced by coupled power and thermal cycling can be approximated by superposition of the temperature histories induced by pure power cycling and the ones by pure thermal cycling. For the test conditions proposed in this paper, pure power cycling leads to the longest fatigue life among all. For coupled power and thermal cycling, the involvement of power cycling reduces the fatigue life of the test vehicle by about 50% as compared to pure thermal cycling.