Microsample tensile testing of LIGA nickel for MEMS applications

Electro-deposited LIGA Ni components are being considered for use in a number of microelectromechanical systems (MEMS) and applications. The metrology of these components and their non-equilibrium microstructures play an important role in determining the mechanical response of these structures. Microsample testing has proven to be a reliable way of measuring the elastic and plastic tensile properties of these 100–200 μm thick films. Measured values of the in-plane Youngʹs modulus (180±24 GPa) are significantly lower than the modulus for bulk coarse grained Ni (207 GPa), but can be explained and modeled in terms of the crystallographic texture in the as-deposited films. Variations in strength associated with post-processing heat treatments are highlighted and explained in terms of microstructural coarsening. The effect that coarsening and the related drop in strength have on the performance of LIGA Ni spring-like structures is discussed, and the need for further high temperature testing is highlighted.