Plastic encapsulated microcircuits (PEMs) are increasingly used in many rugged applications, but for their inherent reliability issues such as narrow temperature range, moisture sensitive, delamination and without screening. In this paper, the corresponding countermeasures are discussed, and five types of PEMs assessment practices including a series of measures of destructive physical analysis (DPA), up-screening, extended temperature cycling and stability, highly accelerated stress test (HAST) and high temperature operational lifetest (HOTL) test are illustrated, which will be helpful to reduce the risk of upgrade application.