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

This paper describes the first study which addresses the reliability of plastic encapsulated microcircuits (PEMs) in the range from 125°C to 300°C, well outside the manufacturer´s suggested temperature limits. A Motorola MC68332 microcontroller, widely used in avionic systems, remained fully functional to 180°C. However, 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, other 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. Further studies on 84-lead PQFP lead frames 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