Electrodeposition and Characterization of Nanocrystalline Ni-NbOx Composite Coatings from Glycol-based Electrolytes for High Temperature Electronics Packaging.

The present investigation demonstrates a novel electrochemical route for the production of bright, compact, dense and high purity Ni-NbO_x nano-composite coatings on Cu, from glycol-based electrolytes consisting of NbCl₅, NiCl₂ ⋅ 6H₂O and propylene glycol. The effects of both cathodic current density and metal electrodeposition bath concentrations on the surface morphology and composition of the coating were examined. The highest relative metal percentage of co-deposited Nb was 14.3 at% obtained at a current density of 400 mA/cm². Scanning transmission electron microscopy (STEM) revealed a nanocrystalline FCC Ni structure without any significant lattice distortion, as well as an as-yet-unidentified compound. STEM X-ray mapping suggests Nb and O were uniformly distributed in the Ni matrix, without any significant phase segregation, which is consistent with XPS compositional depth profiling. Also, according to the XPS spectra, a 0.7 eV shift to lower binding energy for the Nb (V) species may suggest the partial chemical reduction of Nb₂O₅ due to possible Ni-Nb bonding. It is thus proposed that a Ni-NbO_x deposit was formed by two parallel electrochemical reduction routes: 1) deposition of Ni metal; 2) deposition of a Ni-Nb-O compound as nano-clusters. [ABSTRACT FROM AUTHOR]