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11 October 2015 Polishability of thin electrolytic and electroless NiP layers
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Proceedings Volume 9633, Optifab 2015; 963311 (2015)
Event: SPIE Optifab, 2015, Rochester, New York, United States
Ultra-precise metal optics are key components of sophisticated scientific instrumentation in astronomy and space applications, covering a wide spectral range. Especially for applications in the visible or ultra-violet spectral ranges, a low roughness of the optics is required. Therefore, a polishable surface is necessary. State of the art is an amorphous nickel-phosphorus (NiP) layer, which enables several polishing techniques achieving a roughness of <1 nm RMS. Typically, these layers are approximately 30 μm to 60 μm thick. Deposited on Al6061, the bimetallic effect leads to a restricted operational temperature, caused by different coefficients of thermal expansion of Al6061 and NiP. Thinner NiP layers reduce the bimetallic effect. Hence, the possible operating temperature range. A deterministic shape correction via Magnetorheological Finishing of the substrate Al6061 leads to low shape deviations prior to the NiP deposition. This allows for depositing thin NiP-layers, which are polishable via a chemical mechanical polishing technique aiming at ultra-precise metal optics. The present article shows deposition processes and polishability of electroless and electrolytic NiP layers with thicknesses between 1 μm and 10 μm.
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Jan Kinast, Matthias Beier, Andreas Gebhardt, Stefan Risse, and Andreas Tünnermann "Polishability of thin electrolytic and electroless NiP layers", Proc. SPIE 9633, Optifab 2015, 963311 (11 October 2015);

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