Micro-EDM for silicon microstructure fabrication

Abstract

Currently, most silicon microstructures used in microsystems are produced by photolithographic methods. The reason for this is the well-developed etching technology, used in microelectronics, that has been transferred to the microsystem domain. But since the making of an arbitrary shape or angle on silicon mainly depends on the crystal orientation, some severe limits exist in the production of three-dimensional structures.Electro-Discharge Machining (EDM) is basically a thermal process. During the 11DM process material is removed by electric sparking. It is therefore completely different from etching. In this work, micro-EDM is introduced as a potential approach for solving the above mentioned drawbacks. First, this work presents several testing experiments with different process parameters to investigate the influence of the micro-EDM process on the silicon structure. Main emphasis is put on the surface roughness and on avoiding microcracks generated by the sparking process. It is found that microstructures with a sufficiently low surface roughness and with small microcracks can be produced. The remainder of the work concentrates on making small beam structures, which is a common structure in many microsensor designs. It is found that for a wafer thickness of 650 pm, the thinnest beam that can be produced is about 30 .tm wide. This means that micro-EDM can offer an aspect ratio of 20 in combination with a good dimensional control.

Modelling, characterization and testing of an ortho-planar micro-valve

“…This machine can operate with a 150 μm diameter electrode. There is also the possibility to locally reduce the diameter of the electrode using a wire system integrated into the machine [7,8]. In that way the diameter can be reduced down to 50 μm.…”

Effect of Crystallographic Anisotropy on Micro EDM Process

“…The polarity of workpiece electrode was kept positive in the experiments. It was found that when sparking energy level was more than 10 mJ, more and quite larger micro cracks would be induced in the machined surface of silicon [28]. Therefore, capacitance and open circuit voltage were determined as 220 pF and 60 V, respectively, considering the drilling experiments could be conducted under relatively low discharge energy.…”

A ferrofluid seal technology for fluidic microactuators

“…Here, a modified version of the heat-shrink based interconnections developed by Pan et al [9] has been incorporated in the cylinder wall. The interconnections developed here operate as follows (see figure 8): A tube with a flange is fabricated in the cylinder wall by µEDM with WireElectro-Discharge-Grinding (WEDG) [10] formed electrodes. Next a micro heat shrink tube [11] is placed over the flange, which is then heated until the heat-shrink tube is enveloping it.…”