LOP PUBLISHING JOURNAL OF MICROMECHANICS AND MICROENGINEERING J. Micromech. Microeng. 18(2008)105009(7pp) doi:10.1088/0960-1317/8/10/105009 MEDM: MEMS-enabled micro-electro-diScharge machining Chakravarty Reddy alla Chaitanya and Kenichi Takahata Department of Electrical and Computer Engineering, The University of British Columbia, 2332 Main Mall uver BC V6T 1Z4 Canada E-mail: allac@ece. ubc. ca and takahata @ece. ubc.ca Received 17 July 2008, in final form 7 August 2008 Published 5 September 2008 Online at stacks. iop. org/JMM/18/105009 Abstract This paper reports a photolithography compatible micro-electro-discharge machining technique that is performed with microelectrode actuators driven by hydrodynamic force. The movable planar electrodes suspended by the anchors are microfabricated directly on the orkpiece. The electrode structures with fixed-fixed and cantilever configurations are defined by patterning 18 um thick copper foil laminated on the workpiece through an intermediate photoresist layer and released by sacrificial etching of the resist layer. All the patterning and sacrificial etching steps are performed using dry-film photoresists towards achieving high calability of the machining technique to large-area applications. The parasitic capacitance of the electrode structure is used to form a resistance-capacitance circuit for the generation of pulsed spark discharge between the electrode and the workpiece. The suspended electrodes are actuated towards the workpiece using the downflow of dielectric machining fluid, initiating and sustaining the machining process. Micromachining of stainless steel is experimentally demonstrated with a machining voltage of 90 V and continuous flow of the fluid at a velocity of 3. 4-3.9 s, providing a removal depth of 20 um with an average surface roughness of 520 nm. The experimental results of the electrode actuation are shown to agree well with the theoretical estimations (Some figures in this article are in colour only in the electronic version) 1. Introduction LIGA, however, incurs high costs in electrode fabrication There have been some efforts that attempt to address the cost Micro-electro-discharge machining (REDM) is a non-contact effectiveness issue in electrode fabrication, at the expense of micromachining technique that can be used to cut any compatibility with photolithography-based methods [6, 7]. In type of electrically conductive material. The technique is addition, the batch-mode method still requires an NC stage for capable of producing real three-dimensional microstructures advancing the arrays into the material while achieving the smallest size of 5 um with submicron It has recently been shown that uEDM can be lerance [1]. These attractive features have been leveraged implemented using electrodes that are microfabricated for producing micro mechanical components as well as directly on the surfaces of the workpiece using standard for prototyping various micro-electro-mechanical systems photolithography and etching processes [8]. This method MEMS) and devices [2, 3. However, the throughput is exploits the machining voltage to electrostatically actuate inherently low because the traditional technique is essentially movable microelectrodes, eliminating the need for NC a serial process that uses a single electrode tip together machines from the machining process. This approach is with numerical control (NC) of the tip and the workpiece, suitable for selected electrode structures and applications producing structures individually. Batch-mode HEDM for relatively shallow machining due to the limitation of that uses microelectrode arrays fabricated by a deep x-ray the electrostatic actuation range. This paper reports a new lithography (LIGA)process [4] was demonstrated to achieve MEMS-based micro-EDM(MEDM) method where planar high parallelism/throughput of the process [5]. The use of electrodes microfabricated on a workpiece are actuated with 0960-131708/10500907530.00 @2008 IOP Publishing Ltd Printed in the UKIOP PUBLISHING JOURNAL OF MICROMECHANICS AND MICROENGINEERING J. Micromech. Microeng. 18 (2008) 105009 (7pp) doi:10.1088/0960-1317/18/10/105009 M3 EDM: MEMS-enabled micro-electro-discharge machining Chakravarty Reddy Alla Chaitanya and Kenichi Takahata Department of Electrical and Computer Engineering, The University of British Columbia, 2332 Main Mall, Vancouver, BC V6T 1Z4, Canada E-mail: allac@ece.ubc.ca and takahata@ece.ubc.ca Received 17 July 2008, in final form 7 August 2008 Published 5 September 2008 Online at stacks.iop.org/JMM/18/105009 Abstract This paper reports a photolithography compatible micro-electro-discharge machining technique that is performed with microelectrode actuators driven by hydrodynamic force. The movable planar electrodes suspended by the anchors are microfabricated directly on the workpiece. The electrode structures with fixed–fixed and cantilever configurations are defined by patterning 18 μm thick copper foil laminated on the workpiece through an intermediate photoresist layer and released by sacrificial etching of the resist layer. All the patterning and sacrificial etching steps are performed using dry-film photoresists towards achieving high scalability of the machining technique to large-area applications. The parasitic capacitance of the electrode structure is used to form a resistance–capacitance circuit for the generation of pulsed spark discharge between the electrode and the workpiece. The suspended electrodes are actuated towards the workpiece using the downflow of dielectric machining fluid, initiating and sustaining the machining process. Micromachining of stainless steel is experimentally demonstrated with a machining voltage of 90 V and continuous flow of the fluid at a velocity of 3.4–3.9 m s−1 , providing a removal depth of 20 μm with an average surface roughness of 520 nm. The experimental results of the electrode actuation are shown to agree well with the theoretical estimations. (Some figures in this article are in colour only in the electronic version) 1. Introduction Micro-electro-discharge machining (μEDM) is a non-contact micromachining technique that can be used to cut any type of electrically conductive material. The technique is capable of producing real three-dimensional microstructures while achieving the smallest size of 5 μm with submicron tolerance [1]. These attractive features have been leveraged for producing micro mechanical components as well as for prototyping various micro-electro-mechanical systems (MEMS) and devices [2, 3]. However, the throughput is inherently low because the traditional technique is essentially a serial process that uses a single electrode tip together with numerical control (NC) of the tip and the workpiece, producing structures individually. Batch-mode μEDM that uses microelectrode arrays fabricated by a deep x-ray lithography (LIGA) process [4] was demonstrated to achieve high parallelism/throughput of the process [5]. The use of LIGA, however, incurs high costs in electrode fabrication. There have been some efforts that attempt to address the cost￾effectiveness issue in electrode fabrication, at the expense of compatibility with photolithography-based methods [6, 7]. In addition, the batch-mode method still requires an NC stage for advancing the arrays into the material. It has recently been shown that μEDM can be implemented using electrodes that are microfabricated directly on the surfaces of the workpiece using standard photolithography and etching processes [8]. This method exploits the machining voltage to electrostatically actuate movable microelectrodes, eliminating the need for NC machines from the machining process. This approach is suitable for selected electrode structures and applications for relatively shallow machining due to the limitation of the electrostatic actuation range. This paper reports a new MEMS-based micro-EDM (M3 EDM) method where planar electrodes microfabricated on a workpiece are actuated with 0960-1317/08/105009+07$30.00 1 © 2008 IOP Publishing Ltd Printed in the UK