The Crystallization of an Electroless Ni-P Deposit

The crystallization behavior of the electroless Ni-P deposit was investigated in detail with the aid of SEM, TEM, XRD, and electron diffraction techniques. The as-deposited film was shown to exhibit amorphous structure with XRD (x-ray diffraction) and electron diffraction. The XRD and ED AX results show that heat-treatment at temperatures above 300°C gives rise to Ni and Ni₃P phases. The fee Ni and tetragonal Ni₃P grains of the film heated at 800°C are identified with electron diffraction. The occurrence of the maximum hardness achieved upon heating of the electroless Ni-P plating is explained in terms of crystallization, grain coarsening, and defect change. The grain coarsening is also responsible for the random distribution of the phosphorus content across the deposit at temperatures above 600°C.