On the loading curve in microindentation of viscoplastic solder alloy

Berkovich microindentation test has been done on a viscoplastic solder alloy whose mechanical response is significantly rate-dependent. Test results showed that the indentation load vs. penetration depth (P–h) curve is a function of the loading rate, which cannot be expressed by traditional Kickʹs law. Based upon the dimensional analysis after Cheng and Cheng (Surf. Coat. Technol. 133–134 (2000) 417), by means of an overstress viscoplastic constitutive model, a new expression of the P–h relation in microindentation of viscoplastic materials is presented.