A Shunt-Assisted Silicon Electrode for Micro Electrochemical Machining

Stray current causes undesired material dissolution in micro electrochemical machining (Micro ECM). The reduction of stray corrosion, caused by stray current, continues to be a major challenge for accuracy improvement. To limit the distribution of stray current, a shunt-assisted silicon electrode, with an auxiliary anode sharing stray current, is proposed in this study. The auxiliary anode is arranged outside the insulating layer of the sidewall-insulated electrode. It is proved in simulation that the auxiliary anode can help reduce the average material removal rate on the machined surface by 55% and improve processing accuracy. A fabrication process of shunt-assisted silicon electrode by bulk silicon process and thin film deposition process is presented. Micro grooves and holes are machined in ECM experiments. The angle between each side-wall and the vertical plane is less than 10°. The gap between the sidewall of the machined structures and electrode-outer-contour is about 30 µm ± 6 µm for the grooves and 45 µm ± 10 µm for the holes. These Long term experiments and consistent processing results show the shunt-assisted electrode is reliable in ECM process. But due to the stray corrosion induced by DC power supply and conservative feed method, the effect of the shunt-assisted silicon electrode in inhibiting stray corrosion is not significant. In the future, a micro ECM system with novel power supply and active control methodologies is expected to better utilize the effect of the shunt-assisted silicon electrode.