ESD Control.docx
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ESDControl
Confidential
PeopleCommittedToInfoTech
ESDCONTROLPROGRAM
REVISION:
A
Date:
11/9/1999
PreparedBy:
______________________________
GyverLo
ApprovedBy:
______________________________
W.C.Wang
MITACINTERNATIONALCORP.
TAIPEIOFFICE:
8THFL.,NO.75,MINGSHENGE.RD.,SEC.3,TAIPEI,TAIWAN,R.O.C.TEL:
886-2-5018231TELEX:
11942TAIAUTOFAX:
886-2-5014265
FACTORY:
1,R&DROAD2.HSINCHUSCIENCE-BASEDINDUSTRIALPARK,HSINCHU,TAIWAN,R.O.C.TEL:
886-35-779250FAX:
886-35-776209
DOCUMENTCHANGESTATUS
REV
CHANGEDESCRIPTION
PREPARED
APPROVED
A
FirstRelease
GYVERLO
W.C.WANG
Contents
1ABSTRACT4
2REFERENCES5
3PROBLEMSTATEMENT6
4TEAMSTRUCTUREANDMEMBERLIST7
5ESDPROTECTIONEQUIPMENT9
6MEASURINGEQUIPMENT14
7ESDCONTROLCHECKINGITEMS16
8ESDCONTROLTRAININGPROGRAM21
9AUDITINGPROGRAM23
1ABSTRACT
ThisESDControlProgramestablishestheminimumrequirementsforElectrostaticDischarge
(ESD)controlmethodsandmaterialsusedtoprotectelectronicdevicesthataresusceptibleto
damageordegradationfromESD.Thepassageofastaticchargethroughanelectrostatic-
discharge-sensitive(ESDS)devicecanresultincatastrophicfailureorperformancedegradationof
thepart.
Inthefollowingsections,weimplementseveralESDprotectiveequipmentandsomemeasuring
equipmenttomaintaintheirfunctions.AlsoweimplementESDcontroltrainingprogramandESD
auditprogramtostrengthenandcheckourexecutionofESDControlProgram.However,the
effectivenessshouldbereliedonexactimplementationandpromptcorrectiveactions.
2REFERENCES
2.1WorkmanshipSpecificationforESDControlDocument,A-5951-1589-1,
RevisionH,ESDProgram,HPCorporate,1999.
2.2RequirementsforHandlingElectrostatic-Discharge-Sensitive(ESDS)Devices,
EIA-625,EIAStandard,EIA,1994.
2.3BasicsofElectrostaticDischarge,ESDAssociation,1998.
2.4ProtectionAgainstElectrostaticDamage,Sharp,1995.
2.5ESD/EOSFundamentalandAvoidance,INTEL,1996.
2.6靜電防制專業工程師訓練課程講義,工業技術研究院電子所,1999.
3PROBLEMSTATEMENT
AccordingtoStephenHalperin(GuidelinesforStaticControlManagement,Eurostat1990),averageproductlossesduetostaticrangefrom8%to33%(seeTable1).OthersestimatetheactualcostofESDdamagetotheelectronicsindustryasrunningintothebillionsofdollarsannually.Thecostofdamageddevicesthemselvesrangesfromonlyafewdollarsforasimplediodetoseveralthousanddollarsforcomplexhybrids.Whenassociatedcostsofrepairandrework,shipping,labor,andoverheadareincluded,clearlytheopportunitiesexistforsignificantimprovements.
ESDdamagetoelectroniccomponentsandassemblieshasbeenamajorproblemoftheelectronicsindustryinrecentyears,orinstallingESDsensitivedevices.Devicesthataren'tdestroyedduringhandlingareoftendamagedorimpaired.Thisdamageisknownas"latent"damageandoftenisnotdetectablebyroutinequalitytests,andcouldappearafterthedeviceisinstalledinitshostequipment.
Anelectrostaticchargealsomaybecreatedonamaterialinotherwayssuchasbyinduction,ionbombardment,photoelectriceffect,particlebeam,freezing,radioactivedecay,spray,fieldemissionorcontactwithanotherchargedobject.However,triboelectricchargingisthemostcommon.Table2showssomeexamplesthatcangeneratedifferentvoltagelevelsofelectrostaticcharges.
Table1
InformalSummaryof
StaticLossesbyLevel
StaticLossesReported
Description
Min
Loss
Max
Loss
Est.Avg.
Loss
Component
Manufacturers
4%
97%
16-22%
Subcontractors
3%
70%
9-15%
Contractors
2%
35%
8-14%
Users
5%
70%
27-33%
Source:
StephenHalperin."GuidelinesforStaticControlManagement"Eurostat1990.
Table2
ExamplesofStaticGeneration
TypicalVoltageLevels
MeansofGeneration
10-25%RH
65-90%RH
Walkingacrosscarpet
35,000V
1,500V
Walkingacrossvinyltile
12,000V
250V
Workeratbench
6,000V
100V
Polybagpickedupfrombench
20,000V
1,200V
Chairwithurethanefoam
18,000V
1,500V
4TEAMSTRUCTUREANDMEMBERLIST
4.1Structure
4.2MemberList
Position/DepartmentMission
Chairman/QAResponsibleforMiTAC'sESDcontrolprogram
Coordinator/QEDevelop,implementandmaintainESDcontrol
program
AuditController/IPQAResponsiblefortheauditingprogram
IQCResponsibleforIQC'sESDcontrolprogram
SMTlineResponsibleforSMT'sESDcontrolprogram
PCBAproductionlineResponsibleforPCBAproductionline'sESDcontrol
program
SystemassemblylineResponsibleforSystemassemblyline'sESDcontrol
program
WarehouseResponsibleforWarehouse'sESDcontrolprogram
OQAResponsibleforOQA'sESDcontrolprogram
MODResponsibleforMOD'sESDcontrolprogram
EngineeringDivisionAssisttheproductionlinetoexecuteandmaintain
theESDcontrolprogram
4.3ScheduleofTeamMeetings
4.3.1ThefirstESDControlmeetingwillbeheldat10:
10AM,Friday,5Nov99.
4.3.2ThesecondmeetingwillbeheldonThursday,Dec9,1999.
4.3.3ThethirdmeetingwillbeheldonThursday,Jan6,2000.
4.3.4Afterwards,meetingsshallbeheldquarterly.
5ESDPROTECTIONEQUIPMENT
5.1ESDWristStrapsandGloves
Typically,theprimarymeansofcontrollingstaticchargeonpersonneliswithawriststrap
andapairofgloves.Whenproperlywornandconnectedtoground,awriststrapkeepsthe
personwearingitneargroundpotential.Becausethepersonandothergroundedobjectsinthe
workareaareatornearthesamepotential,therecanbenohazardousdischargebetween
them.Inaddition,staticchargesaresafelydissipatedfromthepersontogroundanddonot
accumulate.Wriststrapshavetwomajorcomponents,thecuffthatgoesaroundtheperson's
wristandthegroundcordthatconnectsthecufftothecommonpointground.Mostwrist
strapshaveacurrentlimitingresistormoldedintothegroundcordheadontheendthat
connectstothecuff.Theresistormostcommonlyusedisa1MΩ,1/4Wwithaworking
voltageratingof250V.Theresistancefromawriststrapwearer'shandtogroundshallbe
~Ω.
5.2Shoes,HeelStraps
UsedincombinationwithESDprotectivefloormaterials,staticcontrolshoes,grounders,
castersandwheelsprovidethenecessaryelectricalcontactbetweenthepersonorobjectand
thefloormaterial.Insulativefootwear,castersorwheelspreventstaticchargesfromflowing
fromthebodytothefloortoground.Theresistancefromfingertiptogroundisthesameas
wriststrap.
5.3Smocks
Clothingmaterialscangenerateelectrostaticchargeswhentheycontactandseparatefrom
otherobjectsandtheclothingitself.Thesechargesmaydischargeintosensitivecomponents
orcreateelectrostaticfieldsthatmayinducechargesonthehumanbody.Althoughaperson
maybegrounded,thatdoesnotmeanthatinsulativeclothingfabricscandissipateachargeto
thatperson'sskinandthentoground.Clothingusuallyiselectricallyinsulatedorisolated
fromthebody.Staticcontrolgarmentsareintendedtominimizetheeffectsofelectrostatic
fieldsorchargesthatmaybepresentonaperson'sclothing.Smockssleevetosleeve
resistanceshouldbebetweenandΩafter20washings.
5.4WorkStationsandWorksurfaces
WorksurfacesandworkstationsareimportantpartsofanESDprotectiveprogram.Many
ESDSdevicesandassembliesarehandled,assembledorrepairedatworkstations.Thework
stationprovidesameansforconnectingallworksurfaces,fixtures,handlingequipment,and
groundingdevicestoacommonpointground.ThekeyESDcontrolelementscomprising
mostworkstationsareastaticdissipativeworksurface,ameansofgroundingpersonnel
(usuallyawriststrap),acommongroundingconnection,andappropriatesignageand
labeling.StaticprotectiveworksurfaceswitharesistancetogroundoftoΩ
provideasurfacethatisatthesameelectricalpotentialasotherESDprotectiveitemsinthe
workstation.Theyalsoprovideanelectricalpathtogroundforthecontrolleddissipationof
anystaticpotentialsonmaterialsthatcontactthesurface.Theworksurfacealsohelpsdefinea
specificworkareainwhichESDsensitivedevicesmaybesafelyhandled.Theworksurfaceis
connectedtothecommonpointground.
5.5ESDDissipativeChairs
ESDchairsshallbeconstructedofstaticdissipativematerials.Theresistancefromtheseat
cushion,backorarmreststogroundshallcontinuouslybewithintherequiredrangeofto
Ω.
5.6Ionizers
Aswehaveseen,theprimarymethodofstaticchargecontrolisdirectconnectiontoground
forconductors,staticdissipativematerials,andpersonnel.However,acompletestaticcontrol
programmustalsodealwithisolatedconductorsthatcannotbegrounded,insulatingmaterials
(e.g.,mostcommonplastics).Topicalantistatsoftenareusedtodissipatestaticchargesfrom
theseitemsundersomecircumstances.Morefrequently,however,airionizationcan
neutralizethestaticchargeoninsulatedandisolatedobjectsbychargingthemoleculesofthe
gasesofthesurroundingair.Whateverstaticchargepresentonobjectsinthework
environmentwillbeneutralizedbyattractingoppositepolaritychargesfromtheair.Because
itusesonlytheairthatisalreadypresentintheworkenvironment,airionizationmaybe
employedevenincleanroomswherechemicalspraysandsomestaticdissipativematerials
arenotusable.Airionizationisnotareplacementforgroundingmethods.Itisonecomponent
of