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首页 Designs of MEMS

Designs of MEMS.ppt

Designs of MEMS

xiao_20141220
2010-08-27 0人阅读 举报 0 0 暂无简介

简介:本文档为《Designs of MEMSppt》,可适用于工程科技领域

LectureDesignsofMEMSNEMSLectureDesignsofMEMSNEMS清華大學材料科學與工程系廖建能教授MEMSNEMSDesignMEMSNEMSDesignIdeasFunctionality,applications,problemslimitations,…MicroNanoscaleoperationprinciplesPhysical,chemicalandbiologicalmodels,materialproperties,scalingeffect,…AnalysisandmodelingofdevicesandsystemsPackagingandintegrationEnergyTransformationEnergyTransformationThermalMechanicalElectricalThermoelectric,Jouleheating,thermalresistive,…Piezoelectric,piezoresistive,…Thermalexpansion,Tdependentphasetransformation,…ThermalActuatorsThermalActuatorsThermalenergytransformedintomechanicalmovementOnceapplyingacurrent,thenarrowbeamwillbeheatedupmoreandexpandmoreduetohigherresistanceandcurrentdensityOncestoppingcurrentinput,thestructurewillcomebacktooriginalpositionThermalActuatorsThermalActuatorsThermallydrivencantileverbeamThermalexpansionmismatchinducedactuationThermalresistiveheating(polywire)tochangethetemperatureofthebeamElectrical→Thermal→MechanicalShapeMemoryAlloysShapeMemoryAlloysMedicalMicrosurgicalinstruments,stents,artificialmuscleAerospaceConnectors,lockringsAutomotiveNiTithermostatIndustrialValves,pipeconnectorsConsumerEyeglassframesSafetyFiresafetyvalvesSMAvalveopenandreleasehotwateratthepropertemperatureNiTisurgicaltools:PrecisebendingofthetooltothepropershapeinmicrosurgeryPiezoelectricActuatorPiezoelectricActuatorPiezoelectricstackactuatorPiezoelectricbimorphactuatorInchwormsteppingmotorsInchwormsteppingmotorsMovementalongarodbypiezoelements“Unlimited”movementGoodresolutionMaximumspeedmmsDrawbacksExpensiveSmalllateralloadPiezoresistiveAFMPiezoresistiveAFMElectromagneticActuatorElectromagneticActuatorThermoelectricCoolersThermoelectricCoolersLasercoolingmodulesFiberopticscoolingmodulesMultistagemoduleTelcomcoolingmoduleThermoelectricSensorThermoelectricSensorIRdetectorsThermalsensorsThermoelectricaccelerometerThermoelectricaccelerometerPolySiheatingwiresuspendedacrossacavityHeattransferbynaturalconvectionAlpolySithermopilesmeasurechangesofthermalprofilecausedbyaccelerationPiezoresistivePressureSensorsPiezoresistivePressureSensorsMeasuresmaterialstressesResistorsnormallyarrangedinaWheatstonebridgetocancelTCReffectSensitivityofpiezoresistorsdecreasesastemperatureincreasesNonlinearityofresponsetoappliedpressuredependsuponthelocationofresistorsinthestrainfieldandthedeflectionofmembraneCapacitivePressureSensorCapacitivePressureSensorMeasuresaveragedeflectionThechangeofcapacitanceisnotlinearwithrespecttodeformationorpressure(buttherelationshipisreproducible)Disadvantage:smallcapacitance(generallypF)=>measurementcircuithastobeintegratedonthechiporspeciallydesignedtothestraycapacitanceActuatorSensordesignconsiderationsActuatorSensordesignconsiderationsOperationalprincipleProcessfeasibilityResponsibility(outputsignalinputphysicalquantity)Sensitivity(signaltonoiseratio)OutputforceenergypowerFrequencyresponseDynamicrangeLimitations:Qfactor,FailuremodeTemperature(orotherfactors)dependencyReliabilityIntegrationandpackagingOperationprinciplesandmaterialspropertiesOperationprinciplesandmaterialspropertiesExamples:ElectrostaticcapacitorSolenoidinductorShapeMemoryAlloyThermoelectriceffectPiezoelectriceffectThermalexpansionandthermoresistiveElectrostaticForcesElectrostaticForcesCapacitance:C=QV=eoerAde=xFmer:dielectricconstantStoredenergyStoredenergydensityElectrostaticForceElectrostaticForcePerpendicularmotionLateralmotionindependentonyPrincipleofElectrostaticActuatorPrincipleofElectrostaticActuatorDielectricslabConductorslabElectrostaticActuationElectrostaticActuationSolenoidinductorSolenoidinductorAmpere’slawInductanceofsolenoidStoredenergydensity:Storedenergy:MagneticForceMagneticForceTranslationalmotionn=NLm:permeabilityc:susceptibilityMagneticrestoringforceTheoryofShapeMemoryAlloys(SMA)TheoryofShapeMemoryAlloys(SMA)ReversiblethermalmechanicaltransformationoftheatomicstructureofthemetalatcertaintemperaturesAusteniteform=hightemperatureshapeAlloyabovetransformationtemperatureAlloyreturnstoadesiredshape(afterdeformationatmartensiteform)andgeneratesforcestressandadisplacementMartensiteform=lowtemperatureformAlloybelowtransformationtemperatureRemainsinausteniteformpositionifthereisnoexternalstressAlloycanbedeformedwithanexternalstressSMAOperationPrincipleSMAOperationPrincipleSMAoperationprincipleSMAoperationprincipleTemperaturerises,Mart→AustformlengthdecreasesTemperaturefalls,Aust→Martformlengthincreases(ifexternalforcepresent)TransformationhysteresisexistsShapeMemoryAlloy(SMA)ShapeMemoryAlloy(SMA)HeatingofSMAbyelectriccurrentfedthroughtheelementCoolingwithambientmaterialair,water,etc),alsoadditionalcoolingpossibleMaximumdeformation,usuallyapproxSeveralalloyswithdifferentpropertiesNiTialloymostcommonAlsoAu,Cd,CualloysAlloycompositionaffectstransformationtemperatures,hysteresis,maximumforce,…SMAActuatorSMAActuatorAdvantagesHighforceweightandforcevolume–ratiosLargedeformationHeatingbycurrentfedthroughthealloy=>simpleCoolingbyambientmaterial=>simpleRawmaterialinexpensiveDisadvantagesOneway–operation=>biasforcerequiredHeatingcoolingcyclesreducebandwidthAmountofcyclesreducesmaximaldeformation(>cycles=>maximaldeformation)CyclingchangesthepropertiesofthealloyHysteresis(…°C),nonlinearityEnergydensityfordifferentenergyformsEnergydensityfordifferentenergyformsThermoelectriceffect:SeebeckThermoelectriceffect:SeebeckSAB=SASB=(DVDT)Je=KnownasThermocoupleThermoelectriceffect:PeltierThermoelectriceffect:PeltierAthermodynamicallyreversibleprocessAmeasureofentropychangewhencarrieracrossthejunctionPeltiercoefficientisdefinedpAB=JQJEThermoelectricOperationprincipleThermoelectricOperationprincipleTCThermoelectricGenerationThermoelectricGenerationI=S(THTC)(RLr)ZToptThermoelectricRefrigerationThermoelectricRefrigerationZToptRequirementsofgoodTEmaterialsRequirementsofgoodTEmaterialsHighfigureofmeritZ(=S)Bothandincreasewith(ZT)HighSeebeckcoefficientSHighElectricalconductivityσLowThermalconductivityλPiezoelectriceffectPiezoelectriceffectAforcedeformsancrystalandformsanelectricdipolebydisplacingthedistancebetweenpositiveandnegativechargecenterConversely,theapplicationofanelectricfieldtoapiezoelectriccrystalleadstoaphysicaldeformationPiezoelectriceffectPiezoelectriceffectDirecteffectDi=dikske(d)ikEiInverseeffectek=dikEi(Sik)Eski=,,indicesofcomponentsofpolarizationk=……ofmechanicalstressandstrainDiiselectricdisplacementvectorx,CmEiistheelectricfieldvectorx,Vmsiisstress(forceunitarea)tensorx,Nmekisstrain(relativedisplacement)tensorxdikisamatrixofpiezoelectricconstantsx,mVe(d)ikisthepermittivitymeasuredatconstantstressx,AsVmSEistheelasticcompliancematrixwhensubjectedtoaconstantelectricfieldx,mNPiezoelectriceffectPiezoelectriceffectPiezoelectriceffectPiezoelectriceffectPiezoelectricMaterialsPiezoelectricMaterialsThermalExpansionEffectThermalExpansionEffectThermalexpansionmismatchcausesstressesinbondedlayersandthinfilmsThermoresistiveEffectThermoresistiveEffectApplications:heatingwireortemperaturesensorsScalingeffectScalingeffectThechangeofdominantphysicalquantitiesbetweendifferentscalesiscalledscalingeffect–gravitational,inertialforcesbecomelesseffective–vanderWaalsforces,electrostaticforces,surfacetensionforcesbecomemoreimportantScalingofDObjectsScalingofDObjectsSurfaceareaA~LVolumeV~LMass(weight)m=rV~LMomentofinertiaI=mR~LTorquet=(ma)R~LScalingeffectScalingeffectResonancefrequencyf~LElectrostaticforce:Fisindependentofscale,F~VLPerpendicularmotionLateralmotionElectrostaticforceElectrostaticforces=QAScalingeffectonthermalconductionScalingeffectonthermalconductionPhonontransportimpactedbymaterialsizeElectricalMechanicalSystemsElectricalMechanicalSystemsdisplacementxchargeqforceFvoltageVvelocitydxdtcurrentI(=dqdt)massminductanceLspringKcapacitanceCdampingbresistanceRModelofelectrostaticactuatorModelofelectrostaticactuatorportcapacitorElectrostaticactuatorchargecontrolElectrostaticactuatorchargecontrolWhenQ=Q,g→ElectrostaticactuatorvoltagecontrolElectrostaticactuatorvoltagecontrolcoenergyW*(V,g)W*(V,g)=QVW(Q,g)dW*(V,g)=QdVFdgPullinofelectrostaticactuatorPullinofelectrostaticactuatorVin↑g↓g↓↓positivefeedbackWhenV>VPI,systemloseequilibriumF>inthedirectionofincreasinggwhendg>,thesystembecomesunstableifdFnet>thesystembecomesstableifdFnet<forastableequilibriumPullinconditionsPullinconditionsTwoequilibriumpointsmergewhenz=andv=Equilibriumconditionv=ModelofelectrostaticactuatorModelofelectrostaticactuatorElectricaldomain,Mechanicaldomain,displacementgchargeqforceFvoltageVvelocitydgdtcurrentI(=dqdt)massminductanceLspringKcapacitanceCdampingbresistanceRModelofelectrostaticactuatorModelofelectrostaticactuatorBlockedelectricalimpedanceOpencircuitmechanicalimpedanceOpencircuitelectromechanicaltransductionimpedanceBlockedmechanicalelectrotransductionimpedanceDynamicsofelectromechanicalsystemsDynamicsofelectromechanicalsystemsAnalogyofElectricalMechanicalResonatorsAnalogyofElectricalMechanicalResonatorsmassminductanceLspringKcapacitanceCdampingbresistanceRMechanicalresonatorunderdampingMechanicalresonatorunderdampingFrequencyandphaseshiftEnergydissipationQualityFactor(Qvalue)QualityFactor(Qvalue)Definition:ratioofstoredenergyandlostenergyinonecycleMechanicalsystem:Electricalsystem:AnalogyofelectricalmechanicalresonatorsAnalogyofelectricalmechanicalresonatorsMechanicalResonatorElectricalResonatorNanocantileverMassSensorNanocantileverMassSensorAbadaletal,Nanotechnology()–CantileverbeamdrivenbyneighboringelectroplateResonancefrequencyofthecantileverbeamchangewithbeammassNanocantileverMassSensorNanocantileverMassSensorSpringconstantkResonancefreqMasssensitivity:xgHzformmbeamlengthMicroelectronicsvsMEMSpackagingMicroelectronicsvsMEMSpackagingMicroelectronicpackaging:weaklydependentonchipfunctionalitytestedatwaferlevelachievablepackagingstandardMEMSpackaging:stronglydependentondevicefunctionalitytestedatdielevelorpostpackagingdifficulttoachievepackagingstandardIntegratedvsmultidevicehybridsIntegratedvsmultidevicehybridsSystempartitioningMonolithicdeviceorASICMEMShybridDecisionmakingprocessflexibilitysystemsizeinterconnectreliabilitydieyielddeviceperformancecostSysteminterfacespecificationsSysteminterfacespecificationsSignalreceivingandresponsesignalforms:thermal,electrical,mechanical,…environmentalissues:temperature,pressure,stress,parasiticeffect,biocompatibility,…Designspecificationsperformanceoveroperatingtemperaturerange,environmentconditionsnumberandlocationofelectricalconnectionsdevicereliabilityMotorolapressuresensorMotorolapressuresensorBulkmicromachinedSidiaphragmssensedwithpiezoresistanceAnabsolutepressuresensorrequiresabackplatetosealthespacebeneaththediaphragmundervacuum

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