Preparation of Flat and Smooth Copper Surface by Jet Electrochemical Machining and Electrochemical Polishing

Abstract

Ultra-flat and ultra-smooth copper (Cu) surfaces are widely used as optical mirrors, heat sinks, and substrates for functional material growth. Traditional polishing methods that rely on abrasive particles are easy to induce mechanical defects such as abrasives embedding and scratches on surfaces. A new stress-free machining process is proposed in this research to fabricate an ultra-flat and ultra-smooth Cu surface by combining jet electrochemical machining (Jet-ECM) and electrochemical polishing (ECP). With the accurate manipulating of material removal rate (MRR) and planning of nozzle trajectory, an ultra-flat surface can be obtained efficiently in the Jet-ECM process. The surface roughness of the workpiece can be further improved by ECP with the same electrolyte used in the Jet-ECM process. The results show that the surface peak-to-valley (PV) value which indicated the surface form error of the Cu surface was reduced from 4.4 μm to 1.7 μm and the surface roughness Sa was reduced from 70.3 nm to 13.5 nm. The combination of Jet-ECM and ECP which share the same electrolyte and apparatus can improve the surface flatness and roughness significantly. This study improves the machining accuracy of stress-free machining methods and has great implications for the further understanding of the electrochemical removal mechanism.