Plastic packaging is highly reliable

摘要

Plastic encapsulation is now a highly reliable method of packaging active semiconductor devices and microelectronics in general. In this new work, tropical climates have been analysed and shown to be significantly more severe than those safeguarded by current hermeticity and accelerated test standards in Mil-Std-883, Test Methods & Procedures for Microcircuits. Field failure returns have revealed that Mil-Std-883 approved hermetic CerDIP (ceramic dual-in-line) packaged ICs,installed in digital switching systems, failed catastrophically with a failure rate of 1755 FITs. The cause of failure was severe ingress of moisture, resulting in dewpoints up to 30 deg C. Alternative indigenous developments of modular digital switches for widespread rurual use in India have incorporated plastic encapsulated components selected according to the criteria developed from earlier extensive and successful reliability work by British Telecommunications (BT). Such criteria include the use of HAST (highly accelerated stress test, invented at BT Labs). The pioneering work at BT Labs demonstrated that commercial plastic packaged devices from certain sources were more reliable than their hermetic counterparts, and that both plastic and hermetic package devices should be subjected to similar environmental tests, including HAST, in order to separate the robust from the vulnerable packages.