Effect of molybdenum codeposition on the thermal properties of electroless Ni-B alloy plating films.

Electroless Ni–Mo–B alloy films from a bath using dimethylamine–borane(1/1) (DMAB) as a reducing agent were investigated. Only a small amount of Mo-complex addition to the bath decreased the boron content and increased the molybdenum content drastically. The maximum molybdenum content and maximum resistivity under as-plated conditions were obtained as 22.1 wt% and 322 μΩ cm respectively. Such a high resistivity is characteristic of Ni–Mo–B alloy films. Both crystallized and amorphous states of Ni–Mo–B alloy films, whose Mo contents were above 20 wt% with a small amount of boron, were prepared by controlling the Mo-complex concentration in the bath. The heat change properties of Ni–Mo–B alloy films were quite different from those of the electroless Ni alloy films reported previously. The resistivity of Ni–Mo–B alloy films after heat treatment at 500 or 600 °C became higher than that of those created under as-plated conditions. The structure transformation of Ni–Mo–B alloy films after heat treatment was quite different from that of ordinary electroless Ni alloy films. The Ni–Mo–B alloy film after heat treatment was confirmed by TEM observation to show a mosaic-like structure. Therefore, it was thought that such a high resistivity and such thermal properties of Ni–Mo–B alloy films are caused by such a mosaic-like structure.