Abstract: Industry-level surface mounted and plastic encapsulated devices are restrictedly used in the area of high reliability applications. In order to improve the unit reliability, the screening procedures of surface mounted and plastic encapsulated devices are needed, among which the burn-in test is a key part. The burn-in test method for line package devices is now a mature technique, but there are still some problems to be studied for surface mounted and plastic encapsulated devices. In this paper, the differences of junction temperature control methods between the surface mounted plastic encapsulated devices and the line package devices are analyzed. A burn-in test method for the surface mounted and plastic encapsulated devices is then proposed. The junction temperature control is based on the case temperature control and the equivalent thermal resistance value estimation and the burn-in tests were carried out for SC-75 and UCSP packages. These post-screening packages have been applied in practice.