Modelling of Thermal Aging of Moulding Compound by using an Equivalent Layer Assumption

Abstract

Currently, the use of electronic components for automotive and aerospace applications is developing quickly. More and more components will be exposed to harsh environments, such as high temperature and high moisture. In general, this high temperature is always above the glass transition temperature (Tg) of the encapsulation material, being Epoxy Molding Compound (EMC). EMC exposed to high temperature could induce reliability problems of components due to changes of its material properties accompanied with volume shrinkage. Therefore, the characterization and modelling of the aging process in EMCs during high-temperature conditions has become an important issue. In our previous work [1], the characterization methods to obtain the material properties as function of aging time were discussed and introduced. The present work focuses on a new and efficient method to model the impact of the aging process of EMCs on the warpage and the stress state of a package using FEM simulation. Here, an “equivalent layer” model, which includes a fully oxidized layer and an unaged core, is applied to simplify the modelling of the thermal aging effects. The current thickness of the “equivalent oxidized layer” is obtained by combining the experimental results and numerical analyses of properly chosen samples. At the end of the paper the aging shrinkage is estimated by using the equivalent thickness concept