Effect of high temperature aging on reliability of automotive electronics

In this paper, an investigation on the effect of high temperature aging on the thermomechanical properties, microstructure of the molding compounds and the reliability issues of the packages is presented. Experimental characterizations of aging effect on the packaging materials and the package were carried out. DMA, TMA and TGA were used to measure the moduli, coefficients of thermal expansion (CTE), and the shrinkage induced by the aging process. Construction analysis was performed to examine the aging effect on the microstructure of the aged samples. It is found that aging has significant influence on the rubbery modulus, the glass transition temperature (Tg) and the strength. Aging-induced shrinkage was also found. Oxidation is believed to be one of the main mechanisms for the degradation of the material properties. Finite element modeling is applied to investigate effect of aging on the reliability of the packages. An aging-dependent elastic model has been established to describe the material property evolution caused by aging. 2D finite element models were established to simulate the impact of the aging effect on the stress/strain of the package. Aging-induced shrinkage was also considered in the model, which was applied to the surface layer. The modeling results indicate that the aging of the compounds has a significant impact on the stress/strain status in the package. And the aging-induced shrinkage cannot be simply neglected. Further research work on the experimental aspects and improvement of the aging-related material models are needed.