LIGA (a German acronym for lithography, electroplating and molding) is a micromachining technology used to produce MEMS devices from metals, ceramics or plastics. Electroplated LIGA Ni structures offer higher aspect ratios and greater functionality than traditional vapor deposited thin films. LIGA Ni structures have been found to have an attractive balance of room temperature properties, but these properties have been found to be extremely sensitive to processing parameters. This variation in properties is closely tied to the fact that the underlying microstructures are deposited far from their equilibrium condition. Our current understanding of the effect of electroplating parameters on these non-equilibrium microstructures is currently rather limited, and this point is exacerbated by the fact that thermal exposure can lead to significant changes in both microstructure and properties. These points will be illustrated in a structure-properties case study of LIGA Ni structures that were considered as candidate materials for a MEMS safing/fuseing and arming device. Microsample tensile, creep and fatigue test were conducted to measure a full range of mechanical properties, and microstructural observations were used to explain the observed mechanical behavior. Variations in Young's modulus of 15% have been measured and related to variations in crystallographic texture caused by changes in the current density used to deposit the LIGA Ni structures. Dramatic variations in room temperature tensile strength have also been related to significant reductions in grain size as a result of process variations, and the elevated temperature strength of this material has been found to be compromised by microstructural coarsening at relatively modest temperatures. Prospects for alternative elevated temperature LIGA materials will be discussed.