Design and fabrication of a sensors-integrated silicon electrode for gap status monitoring in micro electrochemical machining

The monitoring of micro machining gap and the control of machining status within the gap have become bottlenecks in the research and development of micro electrochemical machining (ECM). General electrical signals are difficult to reflect the status of micro machining gap. Electrolytic products in micro machining gap are prone to precipitation and retention, leading to unstable material removal process. Micro ECM urgently requires gap status monitoring and feedback control. To realize gap status monitoring, a sensors-integrated silicon electrode, with a micro temperature sensor and a micro conductivity sensor on the silicon electrode near-front sidewall, is proposed innovatively in this study. Based on bulk silicon process and electroplating process, sensors-integrated silicon electrodes are designed and fabricated. Based on the signal processing system built for the temperature and conductivity sensor, the temperature and conductivity detection functions are verified and the sensors are calibrated. Micro ECM experiments with sensors-integrated silicon electrodes are carried out and micro holes with 200 μm depth are machined. For the conductivity sensor on the sensors-integrated silicon electrode, due to the affection of electrolytic environment, the function surface is contaminated and damaged, and the structural design needs to be further improved. For the temperature sensor, it is not affected by the electrolytic environment due to insulation-film’s protection, and reliable temperature monitoring is achieved in micro ECM. The detection results indicate that the temperature inside the machining gap has increased by 20 °C due to the electrochemical thermal effect and resistance thermal effect in micro ECM, and the temperature shows an increasing trend while machining depth increasing. The feasibility of process monitoring with sensors-integrated silicon electrode in micro ECM is preliminarily verified.