High-Speed Micromilling of Copper Microbeams: Dimensional Control and Fabrication Limits for MEMS Applications

Abstract

Copper microbeams are critical structural elements in microelectromechanical systems (MEMS), micro-sensors, and flexible electronic assemblies. However, their fabrication at microscales remains challenging due to copper’s high ductility and the dominance of size-effect phenomena. This study investigates the feasibility of high-speed micromilling for producing copper microbeams with widths ranging from $30~\upmu $ m down to $10~\upmu $ m. Experiments were conducted by varying feed per tooth and spindle speed to evaluate dimensional accuracy and burr formation mechanisms. Results show that $20~\upmu $ m microbeams fabricated at 20,000 rpm achieved dimensional deviations within 0.65–2.8%, demonstrating stable shearing-dominated cutting. In contrast, fabrication of $10~\upmu $ m beams was strongly influenced by the transition from shearing to ploughing, leading to pronounced burr formation and dimensional instability. Burr height decreased with an increase in feed rate from 1 to $2~\upmu $ m/tooth, but increased at $3~\upmu $ m/tooth, showing a narrow process window for burr-minimized fabrication. These findings establish the fabrication limits and process window for precision micromilling of copper microstructures and provide mechanistic insight into microscale material removal behavior relevant to MEMS device manufacturing. [2026-0034]