Batch mode micro-electro-discharge machining

Abstract

This paper describes a micro-electro-discharge machining (micro-EDM) technique that uses electrode arrays to achieve high parallelism and throughput in the machining. It explores constraints in the fabrication and usage of high aspect ratio LIGA-fabricated electrode arrays, as well as the limits imposed by the pulse discharge circuits on machining rates. An array of 400 Cu electrodes with 20 m diameter was used to machine perforations in 50-m-thick stainless steel. To increase the spatial and temporal multiplicity of discharge pulses, arrays of electrodes with lithographically fabricated interconnect and block-wise independent pulse control resistance-capacitance (RC) circuits are used, resulting in 100 improvement in throughput compared to single electrodes. However, it was found to compromise surface smoothness. A modified pulse generation scheme that exploits the parasitic capacitance of the interconnect offers similarly high machining rates and is more amenable to integration. Stainless steel workpieces of 100 m thickness were machined by 100 m 100 m square cross-section electrodes using in 85 s using an 80-V power supply. Surface smoothness was unaffected by electrode multiplicity. Using electrode arrays with four circuits, batch production of 36 WC-Co gears with 300 m outside diameter and 70 m thickness in 15 min is demonstrated. [692] Index Terms-Electro-discharge machining (EDM), high aspect ratio, LIGA, metal microstructures.

A micromachined Kelvin probe with integrated actuator for microfluidic and solid-state applications

“…This technique is attractive because it can be used to fabricate parts from any electrically conductive material. Batch mode , performed with electroplated arrays of electrodes, offers very high throughput [28]. However, normal by itself does not allow electrical isolation since all the mechanically connected features are all electrically connected.…”

Macro Scale Arrayed Structure Fabrication using Reverse EDM

“…R-EDM technique found to be a prominent alternative to fabricate multiple microelectrodes of various shapes [4]. Also existing processes likeLithographie galvanoformung abformung (LIGA) and wire EDM (WEDM) have some inherent difficulties to produce high aspect ratio microelectrodes with predetermined accuracy level and are quite expensive [5]- [7]. An attempt has been made by Kim et al to fabricate the three microelectrodes of diameter 35 µm and 1.5 mm length on tungsten carbide rod by R-EDM.…”

Micro-Electro-Discharge Machining Technologies for MEMS

“…This means that the removal rate at individual electrodes will decrease, thus the throughput does not scale up as the number of electrodes increases. Further gains in throughput can be achieved by partitioning the electrode array into segments, each of which is controlled by a separate pulse generation circuit (Takahata & Gianchandani, 2002). The use of monolithically partitioned electrode arrays coupled with multiple R-C circuits through thin film interconnect patterned on their substrate demonstrated parallel discharging at the arrays, maximizing pulse frequencies at individual electrodes for accelerated processing.…”

“…In this application, the final step of molding is omitted, i.e., the electroplated structures are the end product, serving as the μEDM electrodes. This approach was advanced in the US, where LIGA fabricated electrode arrays were successfully utilized to demonstrate parallel machining of microstructures (Takahata et al, 2000;Takahata & Gianchandani, 2002). A LIGA process used for electrode fabrication is shown in Fig.…”