Plasticity in LIGA Nickel MEMS Structures: Size Effects and Dislocation Substructures


J. Lou*, P. Shrotriya*, S. Allameh*, N. Yao*, T. Buchheit**, and W.O. Soboyejo*

*Princeton Materials Institute and Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544

**Reliability and Modeling Department, Sandia National Laboratories, Sandia National Laboratories, New Mexico, Albuquerque, NM 87185

This paper presents the results of a combined experimental and theoretical study of plasticity in LIGA Ni MEMS structures. Experimental techniques and theoretical approaches are presented for the measurement of plasticity length scale approaches associated with stretch and rotational strain gradients. These include nano-indentaiton/micro-bend techniques, and dislocation mechanics models. Dislocation substructures associated with known strain gradients and stress levels are also compared with those in undeformed specimens and tensile specimens in which there are no applied strain gradients. The implications of the results are then discussed for the development of dislocation.