CHARACTERIZATION OF THIN NICKEL ELECTROCOATINGS BY THE LOW-INCIDENT-BEAM-ANGLE DIFFRACTION METHOD

The low-incident-beam-angle diffraction technique (LIBAD) has been developed as a powerful X-ray diffraction tool for the characterization of thin crystalline coatings. The technique can be implemented to determine the residual stress state in thin coatings, their crystallographic texture, by means of the orientation distribution function, and thickness, as well as the stress profile in a coating as a function of depth. As an example, electrodeposited nickel coatings on a copper substrate have been characterized with this technique for thicknesses varying from 0.6 to 3.8 mum. Crystallographic texture and mean residual stress appear to be correlated with the coating thickness. So, for example, the residual stress of the coatings evolves from a low to a high tensile stress with increasing coating thickness. The stress in the uppermost region of the substrate is influenced by the stress state in the coating. The stress profile in the coating was found to be linearly dependent on the information depth.