Effects of Dimethylamine Borane in Electroless Ni-B Plating

By electroless plating in a pH 7 bath at 50 degrees C, Ni B alloy films with nano-crystallite size (3 similar to 6 nm) were formed on screen printed Ag paste. According to the addition of DMAB (dimethylamine borane), the boron concentration in the Ni B alloy films increased systematically from <1 at.% to similar to 10 at.%, and the crystallite size of the Ni B alloy films decreased gradually. The crystal/electronic structures of the Ni B alloys were studied using XAS (X-ray absorption spectroscopy), XRD, etc., with changes of boron contents. In the crystalline structure, the ordering of fcc type was broken upon alloying and then the samples with additions of 0.5 M and 1 M DMAB had amorphous-like structures with decreases of crystallite size. In the electronic structure, the unoccupied d states of the Ni sites were filled as the B concentration increased upon alloying. From the electronegativity rule and the broken orderging upon alloying, we can suggest that an overall charge transfer occurs from the Ni sites toward the alloying B sites with intra-atomic charge redistribution, leading to an increased occupancy of the Ni 3d states in the alloys.