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

Abstract

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 NbCl 5 , NiCl 2 • 6H 2 O 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/cm 2 . 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 Nb 2 O 5 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.

Diffusion Barrier Characteristics of Ni-NbOxComposite Electrodeposits for Liquid In-Sn Solder Interconnects

“…However, the Nb atoms did not appear to migrate significantly with the reaction front, which eventually resulted in Zone III with Nb contents intermediate between that of Zone II and Zone IV. We have demonstrated in the previous paper 6 that, the composition of the Ni-NbO x layer across the deposit thickness was almost constant, with only slight compositional fluctuations. Therefore, the present multi-layer interfacial structure is likely to be an intermediate stage during the redistribution of the Nb species, as the diffusion rate of the O-bonded and presumably Inassociated Nb may be slower than that of Sn.…”

“…The procedure of making the electrolyte was reported by the authors previously in Ref. 6. Table I summarizes the formulation of the Ni-Nb electrodeposition baths.…”

“…It has been noted that by co-depositing Ni-P with W, certain improvement in the diffusion barrier capability of the former has been promoted. 5 It is of interest, therefore, to examine the possible role of Nb as a diffusion barrier enhancer for Ni layers.In our previous paper, 6 we have explored a novel electrodeposition route for the preparation of Ni-NbO x composite diffusion barrier * Electrochemical Society Student Member.z E-mail: J.Wang@lboro.ac.uk layers from non-aqueous, glycol-based electrolytes. Due to the high affinity of Nb to O, Nb could not be electrochemically reduced to its metal state.…”

“…In our previous paper, 6 we have explored a novel electrodeposition route for the preparation of Ni-NbO x composite diffusion barrier * Electrochemical Society Student Member.…”

“…In our previous paper, 6 we have explored a novel electrodeposition route for the preparation of Ni-NbO x composite diffusion barrier layers from non-aqueous, glycol-based electrolytes. Due to the high affinity of Nb to O, Nb could not be electrochemically reduced to its metal state.…”