506
442703/B
AboutElectrostaticDischarge(ESD)
Electrostaticdischarge(ESD)isthesuddenowofelectricitybetweentwoelectrically
chargedobjects.Suchowcanbecausedbycontact,anelectricalshort,ordielectric
breakdown.Electrostaticdischarge(ESD)cancauseseriousdamagetoprintedcircuit
boardsandelectronicmodules.
BewareofElectrostaticDischarge(ESD)!
Note
Whenyouhandleelectroniccircuitboardsandmodules,youmustbewareofthedangers
ofelectrostaticdischarge(ESD),bothtoyourselfandtotheequipment.Inorderto
ensuresafetransportandstorage,circuitboardsandotherelectronicunitswillalways
bewrappedinaclearplasticprotectivebag,andthebagwillbesealed.
Forcorrectandsafehandlingofprintedcircuitboardsandelectronicmodules,youneed
asuitableworkingarea.Theworkingareamustbecoveredbyanapprovedconductive
servicematthathasaresistanceofbetween50kΩand2MΩ,andisconnecteddirectly
toareliableearthpointviaitsearthingcord.You-andallotherservicepersonnel
involved-mustwearawristbandindirectcontactwiththeskin.Thewristbandmustbe
electricallyconnectedtotheservicemat..
WhatisElectrostaticDischarge(ESD)?
ElectrostaticDischarge(ESD)isthetransferofanelectrostaticchargebetweentwo
bodiesatdifferentelectrostaticlevels,causedeitherbydirectcontactorinductionby
anelectrostaticeld.Thepassingofachargethroughanelectronicdevicecancause
localoverheating,anditcanalso"puncture"insulatinglayerswithinthestructureofthe
device.Thismaydepositaconductiveresidueofthevaporizedmetalonthedevice,
andthuscreateashortcircuit.ElectrostaticDischarge(ESD)mayresultinafailures
ordegradedperformanceofthedevice.
ESDcancreatespectacularelectricsparks(thunderandlightningisalarge-scale
ESDevent),butalsolessdramaticformswhichmaybeneitherseennorheard,
yetstillbelargeenoughtocausedamagetosensitiveelectronicdevices.Electric
sparksrequireaeldstrengthaboveapproximately4kV/cminair,asnotably
occursinlightningstrikes.OtherformsofESDincludecoronadischargefrom
sharpelectrodesandbrushdischargefrombluntelectrodes.
ESDcancausearangeofharmfuleffectsofimportanceinindustry,includinggas,
fuelvapourandcoaldustexplosions,aswellasfailureofsolidstateelectronics
componentssuchasintegratedcircuits.Thesecansufferpermanentdamage
whensubjectedtohighvoltages.Electronicsmanufacturersthereforeestablish
electrostaticprotectiveareasfreeofstatic,usingmeasurestopreventcharging,
suchasavoidinghighlychargingmaterialsandmeasurestoremovestaticsuchas
groundinghumanworkers,providingantistaticdevices,andcontrollinghumidity.
http://en.wikipedia.org/wiki/Electrostatic_discharge(January2014)
SimradST90InstallationManual
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