No abstract

Post mold thermal processing of epoxy encapsulated semiconductor devices is accomplished in order to optimize the properties of the encapsulating material. Traditionally, such processes were believed to alter solely the state of cure in such systems. We have examined the effects of aging at temperatures close to, but below the molding temperature via dynamic mechanical spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry as a function of molding temperature. The large property changes observed during aging for samples molded at the lowest temperatures studied were attributed to physical aging phenomena in the presence of low levels of chemical reaction. A s the molding temperature was increased chemical aging phenomena began to precede the volume recovery associated with physical aging, and the overall property shift was altered. It is the intent of this paper to examine in detail the microstructural basis for such observations, as well as the time dependence of the overall property shifts. z J