Simulation and Experimental Validation of the Cure Process of an Epoxy-Based Encapsulant

BackgroundReliable numerical predictive tools are instrumental in the high-end and robust design of encapsulated electronic assemblies. Process optimization and residual stress calculations require a rigorous cure simulation, which considers the transient chemical, thermal and mechanical constitutive behavior of the curing resin. Though this subject has been widely studied for epoxy-based composite materials, fewer studies have been presented on a non-reinforced bulk of low glass-transition temperature (Tg) resin.ObjectiveThis research aims to numerically and experimentally study the cure behavior and the development of residual stresses and strains in such epoxy based encapsulants.MethodsThe computational study is performed using a commercially available finite element cure process analysis software, and the experimental study is performed by a specially designed test specimen, employing various strain sensing techniques.ResultsThe results show good compatibility between experimental and numerical predictions of the thermal behavior and cure-induced residual stresses, which validates the use of the simulative tool for process design. Process induced stress relaxation in the resin is numerically and experimentally demonstrated, which enables a mapping of the process stages at which full viscoelastic modeling is required. The substantial effect of chain mobility on cure shrinkage and residual stress development in this type of materials is numerically demonstrated.ConclusionThe extensive numerical and experimental investigation of the cure process performed in this study provided insights to both process modeling and design.