Michael Osterman
CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20740, USA
Abstract:
Nickel-palladium-gold-finished terminals are susceptible to creep corrosion. Excessive creep corrosion
can result in device failure due to insulation resistance loss between adjacent terminals. The mixed
flowing gas test has been demonstrated to produce creep corrosion on parts with nickel-palladium-goldfinished
terminals. Conformal coats are often used to protect printed wiring assemblies from failure due
to moisture and corrosion. However, coating may not be sufficient to protect lead terminations from
failure. In this study, acrylic, silicone, urethane, parylene, and atomic layer deposit (ALD) coatings
were examined for their effectiveness at preventing corrosion of nickel-palladium-gold-finished
terminals. The coverage of each coating was examined, and assemblies were subjected to eight hours of
mixed flowing gas as well as temperature cycling. Non-uniform coating thickness was observed with
areas of terminals little to no coating material was found for the acrylic, silicone, and urethane coatings.
Parylene, which had the most uniform coating, was found to provide the best resistance to corrosion,
while corrosion products were observed on the terminals of inspected parts protected by the other
coatings.