Evaluation of Non-Hermetic Coatings for Mcm Applications through Hast, 85/85 and Pct

The goal of the Reliability without Hermeticity (RwoH) Project is to find non-hermetic coatings for use on MCMs. As a means of down-selecting coating materials, Sandia ATC01 test chips in 40 pin DIPs were coated with non-hermetic, polymer materials, including silicone gel, filled epoxy, and polyimide. After preconditioning through temperature cycling and atmosphere, the parts were subjected to one of three different temperature, humidity, and bias conditions: HAST (140/spl deg/C, 85% RH, +40V), 85/85 (85/spl deg/C, 85% RH, +40V), or PCT (121/spl deg/C, 99.6% RH). No universal relationship between lifetime in HAST and 85/85 testing was observed-the effects appear to be material dependent. Electrical test data suggest that failures on coated parts (with standard SiN chip passivation) do not occur on die circuitry (triple tracks) and instead occur on bond-wires and bond-pads.