Micromachining of predesigned perpendicular copper micropillar array by scanning electrochemical microscopy

Because the electrochemical reactions can occur gently at normal temperature and pressure, electrochemical micromachining (ECMM) is an important nontraditional precision machining technique free of tool wear, heating effect, residual stress, surface and subsurface damage, comparing with the ultra-precision milling, electrical discharging machining, laser beam machining, etc. Although scanning electrochemical microscopy (SECM) has been proven powerful in ECMM, it is difficult to fabricate the predesigned perpendicular microstructures because of the inhomogenous potential distribution, the complex electrode reaction kinetics and the interfacial mass transfer processes. Here we succeeded in fabricating the copper micropillar arrays by combining the SECM direct-writing mode and the ultrashort voltage pulse (USVP) modulations. The machining accuracy and efficiency are affected by multiple technical parameters, including the amplitude, the period and the duty cycle of the USVP modulations, the components and concentration of the electrolyte solution, the tip-substrate distance, the motion mode of the tool electrode, etc. By employing multiple parameters central composite experimental designs, we succeed in optimizing the technical parameters and avoiding the complexities of electrode processes. The results demonstrate the powerful capability of SECM in the controllable micromachining of the perpendicular metallic microstructures.