High Resolution Lithography-Compatible Micro-Electro-Discharge Machining ofBulk Metal Foils for Micro-Electro-Mechanical Systems.

Micro-electro-Discharge Machining;Microfabrication;Stent;Batch Metal Machining;Electrical Discharge Machining;Wireless Machining Quality Monitoring;Biomedical Engineering;Electrical Engineering;Engineering (General);Materials Science and Engineering;Mechanical Engineering;Engineering;Science;Electrical Engineering

Richardson, Mark ThomasWise, Kensall D. ;

University of Michigan

关键词: Micro-electro-Discharge Machining;    Microfabrication;    Stent;    Batch Metal Machining;    Electrical Discharge Machining;    Wireless Machining Quality Monitoring;    Biomedical Engineering;    Electrical Engineering;    Engineering (General);    Materials Science and Engineering;    Mechanical Engineering;    Engineering;    Science;    Electrical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62427/mtrichar_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The application of batch mode micro-electro-discharge machining (µEDM) to the fabrication of micro-electro-mechanical systems has opened the door to lithographically compatible precision machining of all bulk metals.High volume applications in biomedical, communications, and consumer electronics devices are enabled by this technology.This dissertation explores the capabilities, limitations, and further improvement of high density batch mode µEDM.There are four parts to this effort described below.A machining resolution study of high density features in stainless steel identifies the design space.Lithographically fabricated copper tools with single cross, parallel line, and circle/square array features of 5-100µm width and 5-75µm spacing were used.The observed discharge gap varies with shape, spacing, and feature location from 3.8-8µm.As tool feature density is increased, debris accumulation effects begin to dominate, eventually degrading both tool and workpiece.Two new techniques for mitigating this debris build-up are separately investigated.The first is a silicon passivation coating which suppresses spurious discharges triggered from the sidewalls of the machining tool.By this method, for high density batch machining, mean tool wear rate decreases from a typical rate of about 34% to 1.7% and machining non-uniformity reduces from 4.9µm to 1.1µm across the workpiece.The second involves a two-step machining process that enhances the hydraulic removal of machining debris and therefore throughput.Wireless RF signals are inherently emitted by the micro-discharge process.This thesis describes the first reported wireless detection of debris accumulation during µEDM, enabling direct monitoring of machining quality in real time with 5dBm signal drop.The first wireless detection of the interface between two stacked metals during µEDM is also reported giving a 10dBm signal change.The technique enables direct monitoring of the discharge without the influence of terminal parasitics.Finally, the first study of the residual stress due to the recast layer left behind by µEDM is presented.The recast layer stress-thickness product ranged from 0.5-6 GPa-µm for discharge energies from 0.03-20µJ.The recast layer thickness ranges from 0.2-3.3µm.Low energy discharges allow precision microstructures to be fabricated from bulk metals.Application of µEDM technology to RF switches and stents is in the appendices.