Simrad EK80 - Page 249

394149/C
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Thepassingofachargethroughanelectronicdevicecancauselocaloverheating,andit
canalso“puncture”insulatinglayerswithinthestructureofthedevice.Thismaydeposita
conductiveresidueofthevaporizedmetalonthedevice,andthuscreateashortcircuit.
Thismayresultinafailuresordegradedperformanceofthedevice.
ESDcancreatespectacularelectricsparks(thunderandlightningisalarge-scaleESD
event),butalsolessdramaticformswhichmaybeneitherseennorheard,yetstillbe
largeenoughtocausedamagetosensitiveelectronicdevices.Electricsparksrequire
aeldstrengthaboveapproximately4kV/cminair,asnotablyoccursinlightning
strikes.OtherformsofESDincludecoronadischargefromsharpelectrodesandbrush
dischargefrombluntelectrodes.
ESDcancausearangeofharmfuleffectsofimportanceinindustry,includinggas,fuel
vapourandcoaldustexplosions,aswellasfailureofsolidstateelectronicscomponents
suchasintegratedcircuits.Thesecansufferpermanentdamagewhensubjectedtohigh
voltages.Electronicsmanufacturersthereforeestablishelectrostaticprotectiveareas
freeofstatic,usingmeasurestopreventcharging,suchasavoidinghighlycharging
materialsandmeasurestoremovestaticsuchasgroundinghumanworkers,providing
antistaticdevices,andcontrollinghumidity.
http://en.wikipedia.org/wiki/Electrostatic_discharge(January2014)
PrecautionstopreventElectrostaticDischarge(ESD)
Sensitiveprintedcircuitboardsandelectronicmodulesmustalwaysbetransportedand
storedinprotectiveantistaticpackingbags.Thecircuitboardsandmodulesmustnotbe
transportedorstoredclosetostrongelectrostatic,electromagneticorradioactiveelds.
Ifitisnecessarytoopenandtouchtheprintedcircuitboardormoduleinsidetheprotective
bag,thefollowingprecautionsmustbetaken:
1Theworkingareamustbecoveredbyanapprovedconductiveservicematthathasa
resistanceofbetween50kΩand2MΩ,andisconnecteddirectlytoareliableearth
pointviaitsearthingcord.
2You-andallotherservicepersonnelinvolved-mustwearawristbandindirectcontact
withtheskin.Thewristbandmustbeelectricallyconnectedtotheservicemat.
3Printedcircuitboardsandelectronicmodulesmustbeplacedontheconductiveservice
matduringinstallationandmaintenanceoperations.
4If,foranyreason,itisnecessarytomovethecircuitboardfromtheconductiveservice
mat,itmustbeplacedinanapprovedantistatictransportationcontainer(forexamplea
staticshieldingbag)beforetransportation.
5Duringinstallationandservicing,allelectricalequipment(forexamplesolderingirons
andtestequipment)mustbeearthed.
Equipmenthandling