Reliability Evaluation of Trimetal Integrated Circuits in Plastic Packages

The development of hermetically passivated, corrosion-resistant titanium, platinum, gold metallized integrated circuits has provided a technological base for plastic packages with unmatched reliability capability under a wide range of severe environmental conditions. Metallization and dielectric overcoating processes for trimetal IC´s are reviewed, and the meatallurgical structures of both wire-bonded and automated beam-tape DIP assemblies are detailed. These processes are identical for both CMOS and bipolar devices. The ability of such devices to withstand long exposures to humid atmospheres is demonstrated under biased accelerated-testing conditions. Metallurgical failure mechanisms uniquely associated with the high-temperature accelerated life testing required for the establishment of the high-reliability criteria are identified and analyzed. Data are presented comparing temperature-humidity-bias test performance of aluminum and trimetal circuits coated with dielectric protective layers consisting of either chemically vapor-deposited phosphorus silicate glass or plasma-reactor deposited silicon nitride.