Thermal Aging on Molding Compounds: Material Characterization and Modeling

Epoxy molding compounds are commonly employed materials for encapsulation and protection of semiconductor packages. Crosslinked molding compound undergoes thermal aging upon operational working conditions and given the proper conditions could lead to thermal oxidation. Such oxidation could significantly impact the thermomechanical properties of the resin and therefore the reliability of the product.To assess the impact of this process, a new resin for high temperatures application underwent high-temperature storage at 3 different conditions: 150°C, 175°C, and 200°C up to 1000 hours. At periodic intervals of 250 hours, the samples are characterized in terms of thermomechanical properties such as elastic modulus, coefficient of thermal expansion, shrinkage, and the evolution of the oxide layer over time. The detailed experimental investigation highlights the strong impact of thermal oxidation on resin properties changes. This effect is also included into a numerical model which evaluates the stresses at a critical material interface when a structure is subjected to thermal aging.