Reliability of commercial plastic encapsulated microelectronics at temperatures from 125°C to 300°C

Over 97% of all integrated circuits produced today are available only in plastic encapsulated, surface mountable, commercial grade or industrial grade versions. This is especially true for the most advanced technologies, such as high-speed microprocessors. The cost, availability, and functionality advantages of these devices are causing many electronics manufacturers to consider using them in elevated temperature applications such as avionics and automotive electronic systems to ensure early affordable access to leading edge technology. However, manufacturers only guarantee the operation of commercial devices in the 0 to 70°C temperature range, and the industrial devices in the -40 to 85°C temperature range. This paper describes the first study which addresses the reliability of plastic encapsulated microcircuits (PEMs) in the range from 125 to 300°C, well outside the manufacturer´s suggested temperature limits. In this study, Motorola MC68332 microcontroller, which is widely used in avionic systems, remained fully functional to 180°C. However, this study also revealed that industrial grade, plastic encapsulated MC68332 devices had less than half the lifespan at 180°C of similar MC68332 devices packaged in hermetic ceramic packages. In addition to the MC68332, the other nine types of plastic components studied had a shorter lifespan at 180°C than their ceramic packaged counterparts. Outgassing of flame retardants with the associated catalysis of the growth of intermetallics was determined to be the principal cause of failure in the plastic components. Further studies conducted on 84-lead PQFP leadframes encapsulated in two different molding compounds revealed that the plastic encapsulant itself begins to lose its ability to insulate leads at temperatures greater than 250°C and can actually combust at temperatures greater than 300°C. Both insulation resistance degradation and cracking were found to be more prevalent in novalac than biphenyl