【SMT】ESD介紹(英文)課件

1、ESDdocin/sundae_mengESD Presentation OutlinePart 1: Introduction/Background Part 2: Electrostatic Problems Part 3: ResistancePart 4: IonizationPart 5: Charge Measurementdocin/sundae_mengCharging MechanismsTriboelectric ChargingInduction Chargingdocin/sundae_mengTriboelectrification+-+-MATERIAL CONTA

2、CTdocin/sundae_mengTriboelectrification+-+-MATERIAL SEPARATION-docin/sundae_mengTriboelectric ChargingThe amount of charge transferred depends onTypes of materials involved Area of contactNumber of contacts Rate of separationSurrounding environmentdocin/sundae_mengTriboelectric ChargingGlass Human H

3、air NylonWool Aluminum Paper Cotton Steel RubberNickel, Copper Brass, SilverPolyester Polyurethane Polyethylene Polypropylene PVCSilicon Teflon_+Triboelectric Seriesdocin/sundae_mengTypical Charge LevelsTypical charge (voltage) measured for different activitiesWalking on an untreated vinyl floor12 k

4、V for 10% RH3 kV for 55% RHWorker standing up6 kV for 10% RH400 V for 55% RHdocin/sundae_mengTypical Charge LevelsTypical charge (voltage) measured on common objectsWafers5 kVWafer Carriers35 kV Quartz Ware15 kVPlastic Film40 kVSmocks10 kVdocin/sundae_mengInduction Charging-+-+docin/sundae_mengCharg

5、e by Induction_ _ _ _+_+docin/sundae_mengProblemsElectrostatic AttractionContamination “Static Cling”ESDDevice Damage Equipment Latch Up(ESC)docin/sundae_mengProblemsElectrostatic AttractionContamination“Static Cling”docin/sundae_mengProblemsElectrostatic AttractionContamination“Static Cling”docin/s

6、undae_mengProblemsESDDevice DamageEquipment Latch Updocin/sundae_mengProblemsESDDevice DamageEquipment Latch UpOften misdiagnosed as software bugs.Induced EM DisturbanceAn Extra Pulsedocin/sundae_mengDischarge ModelsTribocharging or induction charging + metal contact = ESDHuman Body Model (HBM) Mach

7、ine Model (MM)Charged Device Model (CDM)are used to simulate ESD events from various sourcesdocin/sundae_meng1500 ohmsHuman Body Model100k ohmsHVPower Supply100 pFDUTdocin/sundae_mengMachine ModelZero ohms andlow L100k ohmsHVPower Supply200 pFDUTdocin/sundae_mengCharged Device ModelHVPower SupplyCha

8、rge Platedocin/sundae_mengCharged Device ModelHVPower SupplyCharge Platedocin/sundae_mengGrounding (first line of defense)Grounding prevents charging.Ground everything- floors, mats, personnel, chairs, garments, machine parts.docin/sundae_mengSoft GroundsUse soft grounds to control discharges.Using

9、dissipative materials limits discharge current to a level that does not causedamage.docin/sundae_mengResistance MapInsulative1031041051061071081091013 1014 10151010 1011 1012Surface Resistance (Ohms)101102DissipativeConductiveShieldingdocin/sundae_mengThe Need forStandardsMany common items are rende

10、red dissipative to control discharges.ESD control programs require qualification of these items. Thus a need for standardized test methods.Flooring Work Surfaces ChairsGloves Garments Packagingdocin/sundae_mengESD Association StandardsGarments WorksurfacesFlooring ChairsPlanar Materials10V100V103104

11、105106107108109101310101011 1012Surface Resistance (ohms)docin/sundae_mengTEST VOLTAGEINPUTSHIELD/GROUNDVIPoint-To-Point MeasurementsFacility GroundRegulated Test Voltagedocin/sundae_mengINPUTITEST VOLTAGEVSHIELD/GROUNDRTG MeasurementsFacility Grounddocin/sundae_mengMeasuring Small Objects5 lb probe

12、s are tool large to measure many objects of interest.ThermoformedTrays ClamshellsTape and Reel CarriersPick and Place Suction Cupsdocin/sundae_mengIonizationInsulators cannot be grounded.Methods of Ion Generation Ionization by Radiation Electrical (Corona) Ionizationdocin/sundae_mengIonization by Ra

13、diationRadioactive Decay Alpha particlesElectromagnetic Radiation Soft X-RayUltravioletInherently balanceddocin/sundae_mengCorona Ionization+_HIGH VOLTAGE (+)docin/sundae_mengCorona IonizationHIGH VOLTAGE (+)+docin/sundae_mengCorona IonizationTypes of Electrical IonizersAC DCPulse DCdocin/sundae_men

14、gAC and Pulse DC Ionization+_HIGH VOLTAGE (AC)docin/sundae_mengAC IonizationStep up line voltageLow costHigh airflow required to prevent recombination No control of balancedocin/sundae_mengPulsed DC IonizationFast transport of ions without air flowMinimum recombination Good for room ionizationdocin/

15、sundae_mengDC IonizationAir ions will recombine and drift in the electric field.+_HIGH VOLTAGE (+)HIGH VOLTAGE (-)docin/sundae_mengEfficiency and Balance_+HIGH VOLTAGE (+)HIGH VOLTAGE (-)docin/sundae_mengTesting IonizersSuitability for ApplicationIncoming Test Periodic Verificationdocin/sundae_mengH

16、ow We Test IonizersTest efficiency of ion generation.How quickly will the ionizer discharge a charged surface.Test the balance of positive and negative air ions.An imbalance will charge an uncharged surface.docin/sundae_mengHow We Test IonizersThe instrument used to test ionizers is the Charged- Pla

17、te Monitor.docin/sundae_mengDischarge (Decay) TestsEvaluate the quantity of ions produced by the ionizer.Charge a surface and measure the time to neutralize the charge.Perform for positive and negative charges.docin/sundae_mengFloat (Balance) TestEvaluate the balance of positive and negative ions pr

18、oduced by the ionizer.docin/sundae_mengCharged-Plate Monitors (CPMs)Conventional Constructiondocin/sundae_mengProperties of Charged, Isolated Conductors_GROUNDQ = CVCharges are mobile. They are free to redistribute themselves on the surface of the objectCharge (Q) is fixed.Capacitance and voltage de

19、pend on the location of the charged (conductive) object.Cdocin/sundae_mengProperties of Charged Insulators_GROUNDQ X= CVCharges are not mobile. They cannot redistribute themselves on the surface of the object.Charges on an insulator cannot be removed by connecting the surface of the insulator to gro

20、und.Charged insulators are more troublesome to characterize.Strictly speaking, the behavior of charged insulators cannot be characterized by Q = CV.XCdocin/sundae_mengDirect Measurement of ChargeGROUNDDischarge isolated conductive objects into a coulombmeter.Destructive test.Cant test insulators thi

21、s way.C_+_Q = CVdocin/sundae_mengDirect Measurement of ChargeOther objects (charged insulators) must be placed in a Faraday enclosure that is connected to a coulombmeter.+_docin/sundae_mengDirect Measurement of ChargeIt is challenging to place object into a Faraday enclosure without adding or subtra

22、cting charge.Measuring charge using these direct methods may be impractical. (Objects may be too large to place into a Faraday enclosure or not removable.)+_docin/sundae_mengMeasuring Voltages on Isolated Conductors0000GROUNDFamiliar test equipment, such as digital voltmeters and oscilloscopes, cann

23、ot be used to characterize electrostatic charges.Contacting charged conductive objects quickly discharges the object.Contacting insulators discharges the contact point and doesnt measure the un-contacted surface._docin/sundae_mengContacting ElectrometersVery high input impedance.GROUNDMinor loading

24、of the charged conductor.Okay for measuring isolated conductors. Doesnt work for insulatorsC_+_docin/sundae_mengGROUNDVoltage followerMinimal loading of the charged conductorStill cant measure an insulatorC+_Contacting Electrometersdocin/sundae_mengProperties of Charged ObjectsWe often evaluate a ch

25、arged object indirectly by evaluating its electric field.Instruments that sense electric fields includeElectrostatic FieldmetersElectrostatic Voltmeters Non-contacting test method.+docin/sundae_mengFieldmetersFieldmeters were originally used to measure large objects.Measuring in a uniform electric f

26、ield is desired.Point-to-point or point-to-plane measurements yield different measurement results.docin/sundae_mengFieldmetersElectrostatic fieldmeters measure the field strength associated with a charge.The unit of measure is the volt/meter (or some other convenient distance).Indicates the presence

27、 and approximate level of charge.Usually hand-heldBest suited for making general auditsCost-effective for measuring voltages above 3kV.docin/sundae_mengFieldmetersFieldmeters do not resolve low voltages.Fieldmeter measurements vary significantly with distance from the charged object.Fieldmeters do n

28、ot resolve small surface areas. Two common types of fieldmeters areInduction FieldmetersChopper-Stabilized Fieldmetersdocin/sundae_mengSimplest type of fieldmeterNo system to improve drift and instabilityWont operate reliably in the presence of ionizationFieldmeters are grounded instruments and modi

29、fy the data.Induction Fieldmetersdocin/sundae_mengChopper-Stabilized FieldmetersDo operate in the presence of ionizationFeedback systems to improve drift and instability performanceStill require a fixed spacingdocin/sundae_mengElectrostatic VoltmetersElectrostatic voltmeters use voltage feedback to

30、null the electric field between the surface under test and the voltmeter probe.Also known as voltage follower or electrometerHigh degree of accuracy that is independent of the distance from the charge.Electrostatic voltmeters generally provide a better approximation of the charge level as compared t

31、o fieldmeters, and are better suited for making accurate and repeatable measurements.docin/sundae_mengElectrostatic VoltmetersThe sensor can be placed very close to the charged surface without arc-over.The sensor can resolve small surface areas. Very free of drift and environmental instability. Well

32、 suited for fixed installation in equipment. Not a grounded probePresence of high voltage on the reference surfaceWorks in ionization because they are chopper-stabilizeddocin/sundae_mengAC-Feedback VoltmeterAC-feedback electrostatic voltmeters are part fieldmeter and part electrostatic voltmeter- a

33、hybrid instrument with some characteristics of fieldmeters and some characteristics of electrostatic voltmeters.AC-feedback electrostatic voltmeters sense electric field and sense capacitance (distance) changes between the surface under test and the probe to indicate surface voltage even if the dist

34、ance changes.Spacing independent accuracy of electrostatic voltmeters.Resolve small surface areas.docin/sundae_mengAC Feedback Electrostatic Voltmeterdocin/sundae_mengAC Feedback Electrostatic VoltmeterAlso known as a spacing compensated fieldmeter, spot meterHow it is like a voltmeterHow it is like

35、 a fieldmeter Reports surface voltageLow costSpacing independent accuracyA grounded instrumentResolves small objectsArc over if used too close Good stability and drift performancedocin/sundae_mengComparisonsVoltmetersNot cost effective above 3kVExcellent spatial resolutionIntended for close spacing,

36、 measuring small objectsNot grounded Spacing independentaccuracyLow driftAC-FeedbackCost effective above 3 kVGood spatial resolutionGood at close spacings, measuring small objectsGroundedSpacing independent accuracyLow driftFieldmetersCost effective above 3 kVLow spatial resolutionIntended for wide

37、spacing, measure large objectsGroundeddocin/sundae_mengUsing Voltmeters and Fieldmetersd4d - 5dAs electrostatic voltmeters can be operated close to a charged surface without fear of arc-over, they can resolve smaller surface areas.Extraneous fields can negate the whole notion of spatial resolution.d

38、ocin/sundae_mengUsing Voltmeters and Fieldmeters_ _ _ _ _ _+ + + + + +Insulators do not have uniform charge distribution.As charge density is non- uniform, surface potentials are non-uniform.What is measured is nebulous. Provides a figure of merit.docin/sundae_mengAuditingHand-held meters are partic

39、ularly useful for auditing.Grounding is important, especially for battery-operated instruments. Charge up objects of interest and see if they retain charge.docin/sundae_mengDiagnostics and Continous MonitoringHand-held instruments are cumbersome for monitoring inside of process equipment, but many do have electrical outputs.Both fieldmeters and electrostatic voltmeters can have remote probes. Probes ca