An electroless plating bath for amorphous Ni-W-P alloy films was developed and their heat change properties were investigated from the viewpoint of W codeposition effect. The alloy films kept amorphous state with increasing W content even though the P content decreased. Moreover, the films became more amorphous, and their thermal stability increased with an increase of W content in the deposit. The tungsten content was varied from 0 to 20.8 weight percent (w/o) with a decrease in P content from 14.0 to 6.2 w/o by increasing the Na2WO4concentration in the bath. Two characteristic heat change behaviors were observed in the Ni-W-P alloy films. One was the formation of metastable phase in spite of low P content. The other was direct formation of Ni-W alloy phase. The tungsten codeposition increased the thermal stability of amorphous Ni-W-P alloy films plated from the baths with higher Na2WO4 concentration by suppressing the Ni crystallization prior to the Ni3P compound formation. The thermal changes of resistivity strongly depended on the crystallization of the Ni3P compound and Ni alloy phase. Both crystallization reactions were controlled by the P and W contents in the deposits.
ASJC Scopus subject areas