Investigation of ultra-smooth and uniform planarization of thin copper foils using magnetorheological polishing

With the increasing demand for miniaturized and high-frequency electronic devices, improvingthe surface quality of copper foils has become critical. However, achieving ultra-smooth anduniform planarization of thin copper foils remains challenging due to their low rigidity andclamping-induced deformation. Herein, a flexible magnetorheological polishing (MRP) methodwas developed for thin copper foils (<0.1 mm). Compared with chemical mechanical polishingMRP effectively compensates for local surface deformation, enabling uniform material removaland reducing fixture accuracy requirements. After optimizing slurry components, an ultra-smooth surface with Ra of 1.95 nm and Rz of 84.92 nm was achieved without obviousscratches or defects.