Yoonhwan Woo, Sang-Hyun Kim*
The Journal of Mechanical Science and Technology, vol. 25, no. 4, pp.1017-1022, 2011

Abstract : In this paper, we report the detailed investigation into the effects of plating temperature and applied current density upon the mechanical properties of plated nickel film such as Young’s modulus and residual stresses. This method uses the resonance method of atomic force microscope, which does not require specially microfabricated cantilevers and additional experimental set-up. Thin layers of nickel are electroplated onto the tip surface of AFM cantilevers and plating thicknesses were measured at the end of each plating step. The selfdeformation of the released AFM cantilever is also measured as a function of the plated nickel thickness, which is converted into the quantitative residual stress by appropriate mechanics. The measured Young’s modulus is as high as that of bulk nickel at low plating temperature and at low applied current density, but drastically drops at high temperature or current density. The dependence of Young’s modulus on the plating thickness is negligible in thin film less than few microns. The residual stress is also a strong function of the process conditions, and decreased with the elevation of the current density and plating temperature. And the intrinsic and extrinsic stresses of plated nickel are separated from the measured residual stress, and correlated with plating conditions. Dependence of the plated thickness on Young’s modulus and residual stress is also considered.

Keyword : Atomic Force Microscope; Plating conditions; Residual stress; Resonant frequency; Young’s modulus