工艺技术_esd protection design seminar

ESDProtectionDesignSeminarJimSutherlandSeniorApplicationsEngineer Outline WhatisESD Whatdamagecanitcause Whyistheproblemgrowing Whataretheissuesforthedesigner Howcanwemeasureit HowcanweprotectequipmentfromESD WhatIsESD ESD ElectroStaticDischargeGenerationTriboelectric frictioncausesaccumulationofcharge Induction fieldinducescharge DischargeDielectric air breakdownElectricfieldincreaseswhenchargedbodiesapproacheachotherCurrentflowintocircuitry ESDDamageofICs PermanentOxidebreakdown shorts opens latch upTemporaryLatch up groundbounceLatentDegradationfromanESDevent ESDproblemisgrowing Circuits SystemsOld RobustICs LowspeedsignalsNew SensitiveICs HighspeedsignalsEnvironmentOld Manufacturing CorporateNew Home Outdoors Person ESDIssuesfortheDesigner MustmeetESDspecificationsSelectESDtolerantcomponentsMinimizesignaldegradation fromR L C Boardspace weight properdesignComponentcostAssemblycostLifetimecost stability Testthesystem InternationalESDStandards HumanBodyModel HBM fordevicesEIA JESD22 A114 AANSI EOS ESD S5 1 1993MIL STD 883 method3015 IEC1000 4 2 1995 forsystemsMachineModel MM lesscommonEIA JESD22 A115 AANSI EOS ESD S5 1 1993ChargeDeviceModel CDM lesscommonJESD22 c101 HumanBodyModel HBM Dischargefrom100pFcapacitorthrough1 5kOhmresistor6ESDpulses3positive 3negative 1secseparationPin to pintestingN N 1 2combinationsUsedforcomponentcharacterizationWidelyused HBMCurrentWaveform RiseTime 2nS Tr 10nS IEC1000 4 2 1995Standard Dischargefrom150pFcapacitorthrough330ohmresistor6ESDpulses3positive 3negativeUsedforsystemcharacterization Contact v Air dischargeDifferentlevelsDifferentapplications IEC1000 4 2CurrentWaveform Veryfastrisetime Tr 1nS 60ns IEC1000 4 2TestLevels Contactdischargeisthepreferredtestmethod airdischargesarenotrepeatableAirdischargesusedwherecontactdischargecannotbeappliedNoimpliedequivalenceintestseveritybetweenthetwotestmethods IEC1000 4 2BenchTestSpecification ESDProtectionTechniques ClampdiodesinICNotsufficientprotectionShieldingLoweffectivenessBypasscapacitororseriesresistor inductorCandegradesignal manycomponents largeboardareaSparkgapLowcost lowstability largeboardareaDiscreteZenerdiodesHighcapacitance manycomponents largeboardareaDiscretePNdiodesLowcapacitance manycomponents largeboardareaIntegratedPNdiodes IntegratedDiodeNetworks SuperiordownstreamESDprotectionHighspeedresponseESDcurrentsteeredtoGNDorVCCMinimumSignalDegradation LowC Minimalboardspace weightLowassembly manufacturingcostsMinimalDesign InTimeLong termreliability ChoosinganESDDiodeNetwork Howmanylinesareneeded Howmuchcapacitance e g 5pF WhatistheHBMrating e g 15kV Whatisthedownstreamclampvoltage e g 13V 15kVHBMpulse Whatisthecontactdischargerating e g 8kV Whatistheairdischargerating e g 15kV Whatpackage e g 24 pinQSOP ESDDiodeNetworkPlacement TheNeedtoKeepESDDiodes DownstreamofLineInductances AlsoputprotectiondiodesatmostlikelyESDentrypoint theconnector DesigningforMinimalPowerRailInductance AddBypassCapacitor PlaceCeramicbypasscapacitor 0 1 0 2uF ascloseaspossibletoESDdiodenetworkpowerrailtoshuntESDcurrenttobothpowerrailsMaybeaddZenerinparallelwithcapacitortominimizeparasiticinductanceofbypasscapacitor Protected Device Gnd Vcc C UsingaSeriesResistortoMinimizeDownstreamCurrent Canbeconsideredforlatch upsensitiveapplicationsGuaranteedclampingvoltagelimitscurrentdownstream I V R OnlyforinputswithhighZOnlyforoutputdriverswithlowZwatchoutforfilteringofsignal Power downIssues DiodeprotectedsystemsthatarepowereddowncandraincurrentfromanactivehighinputthroughthediodetoVCCThiscandrainbatteriesand ordamagedevicesonthesamelineToavoidthis isolateVCCfromthebypasscapacitorwithablockingdiodeOnediodesolution ComponentandSystemSpecifications ThereisnosimpleformulatotranslatesystemspecificationsintocomponentspecificationsIEC1000 4 2SpecificationismoreseverethanHBMLinecapacitanceandinductanceshapetheESDpulse reducingitspeakvaluePoordeviceplacementcandegradeperformanceIftherearemultipledevicesonaline decidewhichtoprotectTherelationshipbetweendownstreamclampvoltageanddownstreamprotectionisnotexact ValidatingtheDesign Definethepracticallimitsoffunctionalfailure e g Dataintegrity recoverytime TestonlyatthoseplacessubjecttotouchduringnormaloperationUseContactESDischargestocouplingplanes conductivesurfaces I Opins flexpads andpowerpinsUseAirESDischargestoinsulatingsurfaces openingsatedgesofkeys flexcables ventareas seams slots