Mechanical properties of nickel fabricated by electroplating with supercritical CO2 emulsion evaluated by micro-compression test using non-tapered micro-sized pillar

This paper reports mechanical properties of nickel films fabricated by high pressure electroplating (HPE) and electroplating with supercritical CO2 emulsion (ESCE). Structures and mechanical properties of the plated films were examined by TEM, electron backscattered diffraction analysis and micro-compression test using a non-tapered micro-sized pillar. The films were electroplated in an electrolyte composed of Watts bath, supercritical CO2 and surfactant. Agitation in ESCE leads to the formation of many CO2-in-water type micelles. The micelles would cause an effect called periodic plating characteristic, and this effect refined the microstructure of the plated nickel from 3 μm of columnar grained structure to 8 nm diameter of equiaxial grained structure. Mechanical properties were also improved to 3.5 GPa of compressive strength, which was five times higher than the HPE nickel. The high strength in ESCE is believed to be largely a result of grain refinement and carbon impurity.

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► Nickel was plated using electroplating technique with supercritical CO2 emulsion.
► Non-tapered micro-sized pillar with square cross section was fabricated.
► Compression tests were conducted with test machine designed for micro-sized specimens.
► TEM shows equiaxial grains with mean grain size of 8 nm in nickel film.
► Maximum stress was reached to 3.5 GPa without any crack up to 9% of strain.