Formative Time Lag toBreakdown inMicro Gap

Thispaperstudies thedischarge development in amicrogapbetween metalmaterials inairexperimentally andanalytically. As a highvoltage sideelectrode is stressed bydifferent voltages atafixed gaplength withUV irradiation, theelectrical breakdown voltage ismeasured asafunction ofthetimelag. Themeasured timelaguntil thesparkbreakdown ranges from10-1 to104 sbetween 190 Torrand760Torr. Usingthemeasuredtimelagtothebreakdown, the formative timelagtobreakdownisobtained andthe formative timelagtobreakdown iscalculated byyi, ypand Ym.Thecalculation results oftheformative timelagagree withtheexperiment results. Theobtained values ofyi, yp andYmareapplied totheestimate theformative timelagto breakdownatvarious pressures, from190Torrto760 Torr, between metalelectrodes inauniform electric field. I.INTRODUCTION Electrostatic actuation isefficient method offorming MicroElectro Mechanical Systems (MEMS)devices because ofitssimplicity andlowpowerconsumption. These actuators require alarge force, alarge amountof stored energy, anda longstroke. Theforceis proportional tothesquare ofelectric field strength, makingiteffective fordecreasing gaplength in actuators under agiven applied voltage. Theforce is limited bythemaximumelectrostatic field strength, whichisrestricted bytheelectrical breakdown voltage. Sometimes thiselectrical field breakdown seriously damages theactuators (1). Inaddition, thedischarge phenomena intheelectrical discharge machining process greatly influence the removal rate ofmaterial andtheaccuracy ofmachining geometry (2). Although several researchers havestudied the discharge phenomena attheinterface, little information isavailable ontheelectrical discharge phenomena ina micro gapfilled withgaseous material. We studied the breakdown phenomena inamicrogapatatmospheric pressure. Theformative timelagdiscussed inthis paper ranges from1to10hts. Thesecondary electron emission coefficient yi,ypandym isestimated basedonthe assumption that thedischarge phenomena inamicro gapcanbeexplained through Townsend's theory. The order ofyiis10-3(3). Thispaper reports thedischarge phenomena thatoccurina microgap atlow atmospheric pressure. An experimental set-upis assembled forobserving themicro-meter order phenomena. The development of theelectrical breakdown between metal electrodes isstudied through this experiment. Thetimelagtospark breakdowns is measured; thenthestatistical timelagandtheformative timelagareestimated fromthemeasurements.