The feasibility of using Plasma-Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films as diffusion barriers over metal bondpads, bonds, and bondwires in microelectronic packagings was investigated. Films between 550 to 5000 Å were almost impervious to salt solution over 36 h. Film over a micron cracked spontaneously from internal stresses. Film thickness measurement under a 1 mil bondwire over a flat silicon substrate by a stylus profilometer showed that the film began to get significantly thinner starting over four wire diameters away from the center of the bond. Salt immersion test indicated that the failure mechanism was corrosion of bondpad metallization starting under the stitch bond due to incomplete coverage of the silicon nitride film. Thermal shock cracked the films and caused severe corrosion on the metal bonding areas as evidenced by hydrogen evolution during salt immersion testing. The results showed that PECVD silicon nitride thin film can be potential protective films over metal areas in microelectronic assemblies, by optimizing the deposition conditions for more conformal coating in the occluded cavity under the stitch bond and increased resistance to thermal stress-induced cracking.