CORROSION BEHAVIOR OF TIN AND SN-COATINGS DEPOSITED ONTO BRASS SUBSTRATES FOR ELECTRICAL CONTACT INTERFACES

TiN films, prepared by reactive radio frequency magnetron sputtering and electroplated Sn films, are deposited onto brass substrate. They are investigated for their suitability as coatings for connectors. The contact resistances R(c) in static and insert mode are measured versus load F(c) for plane shapes in the range 0.1-10 N. Results show that TiN has a higher constriction resistance compared to uncoated brass, Sn- and Au-coated brass. Accelerated aging in a contaminated atmosphere shows that TiN surface-coated brass is partially covered by Cu2S sulphide, while Sn-coated brass is oxidized to SnO. Also accelerated aging in a humid and ''high'' temperature atmosphere shows an increase in contact resistance for both coatings. In both corrosion tests, current-voltage (I-V) plot characteristics for corroded TiN layers showed an ohmic resistance behaviour, while for uncoated brass and Sn-coated brass non-linear and breakdown effects were apparent. Finally, the tribological testing based on fretting corrosion showed that TiN coatings delayed contact resistance enhancement.