Micro hole machining of borosilicate glass through electrochemical discharge machining (ECDM)

The borosilicate glass serves as the substrates of the micro sensors owing to their excellent anodic bonding properties. To build up the electrical through channel and connect the internal system with the environment, micro holes should be drilled on the substrates. This investigation describes a novel process that combines micro electrical discharge machining (micro EDM) and electrochemical discharge machining (ECDM) to drill micro holes on the borosilicate glass plate. Experimental investigation of the novel process includes fabrication of micro tools via micro EDM and machining characteristics of the borosilicate glass by ECDM. This study also analyzes the basic material removal mechanism in the ECDM process. Four stages are identified in the ECDM process via rapid photography. Etching reaction is important in the machining mechanism of ECDM through SEM and EDX analysis. Unlike conventional EDM, the key reason for improving material removal rate and surface roughness is the etching reaction in the ECDM process. Also discussed herein are the effects of machining parameters, such as applied voltage, electrolytes, concentration of electrolytes, and temperature of electrolytes in ECDM. Furthermore, machining time, hole expansion and the surface roughness of inner holes are measured to assess hole quality. This novel process can improve material removal rate and surface roughness to 1.5mm/min and 0/08 mum, Ra Experimental results demonstrate that this process is excellent for fabricating micro holes on the borosilicate glass for MEMS.