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Micro-powder injection moulding ( μPIM) is a promising mass manufacturing technique for the microsystem technology. Because typical applications - like sensors or actuators - need to withstand serious mechanical loadings, the investigations of the mechanical properties are of vital importance. Therefore, we implemented a small-scale testing setup that enables tensile and tension-tension-fatigue testing of freestanding micro-samples. This allowed for investigating tensile and fatigue properties of conventionally produced and μPIM 17-4PH stainless-steel thin membranes. The conventionally produced samples were machined from bulk material and showed properties and lifetimes comparable with the best bulk samples. The μPIM samples showed a weaker but more ductile behaviour, due to a ferritic phase and SiO2 inclusions. But their ultimate tensile strength of up to SU = 1021 ± 48 MPa and their relative fatigue strength of ≈46% SU ( R = −1) are still comparable with average bulk values. This indicates the high potential of μPIM materials. [ABSTRACT FROM AUTHOR]

Abstract: The requirements of mechanical devices (micro electro mechanical systems, MEMS, and surface acoustic wave filter, SAW) increase due to shrinking size, rising frequencies and driving power. This paper focuses on novel fatigue mechanisms stemming from the combination of small dimensions (100nm) and ultrahigh frequencies (GHz). Quantitative post-test analysis of in situ experiments showed a correlation between extrusion density and device performance. Qualitative microstructural analysis showed a good correlation between the location of defect formation and stress concentrations as calculated by finite element analysis. In situ measurements of the characteristic damage formation revealed a combined extrusion/void formation mechanism that operates on a short time scale. The underlying mechanism was assumed to be a combination of a dislocation and stress induced diffusion process, leading to the observed void and extrusion formation. [Copyright &y& Elsevier]

Abstract: This paper describes an experimental technique to identify robust nanoscale coatings for improving the long-term reliability of metallic microelectromechanical systems. More specifically, the influence of nanoscale alumina coatings on the fatigue crack initiation process in 20μm thick electrodeposited Ni films was investigated in a mild (30°C, 50% RH) and harsh (80°C, 90% RH) environment. Atomic-layer-deposited alumina layers, with thicknesses of 5 and 25nm, were coated on Ni fatigue micro-resonators, and the fatigue degradation behavior in the very high cycle fatigue regime was compared to that of uncoated structures. Evidence based on post-test scanning electron microscopy and resonant frequency evolution plots shows that the coatings do not prevent the formation of fatigue extrusions and micro-cracks. However, their formation is likely delayed for the 25nm thick alumina-coated Ni films. [Copyright &y& Elsevier]