A unified thermomechanical model for stress prediction in heterogeneous electronic laminates: Closed-form solutions and experimental validation

The relentless drive toward miniaturization and higher power densities in modern electronics has amplified reliability demands on plastic-encapsulated packages. A persistent challenge lies in critical failures triggered by interfacial stresses arising from thermomechanical mismatches in heterostructured laminates. Despite extensive research, existing models lack closed-form solutions capable of simultaneously resolving in-plane normal, interfacial shear, and peeling stresses. This limitation obscures the understanding of coupled stress-driven failure modes and hinders accurate failure prediction. Here, we present an integrated approach to bridge this gap: a closed-form theoretical model that explicitly solves these three coupled stresses, synergistically validated through in situ experimental testing and numerical simulation. The model demonstrates exceptional predictive accuracy, with deviations from independent experiments and simulations remaining below 6%. By enabling rapid parametric assessment, these closed-form solutions provide explicit design guidelines that directly link predictive mechanics to packaging reliability. Crucially, this analytical capability circumvents the computational bottlenecks of pure numerical simulations, offering a powerful tool for the rational design and optimization of heterogeneous laminates.