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1、WireBond/BallShearApplicationNoteP.1WirebondingWhatiswirebondingWirebondingisanelectricalinterconnectiontechniqueusingthinwireandacombinationofheat,pressureand/orultrasonicenergy.Wirebondingisasolidphaseweldingprocess,wherethetwometallicmaterials(wireandpadsur
2、face)arebroughtintointimatecontact.Oncethesurfacesareinintimatecontact,electronsharingorinterdiffusionofatomstakesplace,resultingintheformationofwirebond.Inwirebondingprocess,bondingforcecanleadtomaterialdeformation,breakingupcontaminationlayerandsmoothingouts
3、urfaceasperity,whichcanbeenhancedbytheapplicationofultrasonicenergy.HeatcanaccelerateInteratomicdiffusion,thusthebondformation.WirebondingprocessesWirebondingprocessbeginsbyfirmlyattachingthebacksideofachiptoachipcarrierusingeitheranorganicconductiveadhesiveor
4、asolder(DieAttach).Thewiresthenareweldedusingaspecialbondingtool(capillaryorwedge).Dependingonbondingagent(heatandultrasonicenergy),thebondingprocesscanbedefinedtothreemajorprocesses:thermocompressionbonding(T/C),ultrasonicbonding(U/S),andthermosonicbonding(T/
5、S),asshowninTable1-1.Table1-1.ThreewirebondingprocessesWirebondingPressureTemperatureUltrasonicenergyWireThermocompressionHigh300-500˚CNoAuUltrasonicLow25˚CYesAu,AlThermosonicLow100-150˚C*YesAu*DLIThermosonictemperature100-240˚CP.2WirebondingWirebondformsThere
6、aretwobasicformsofwirebond:ballbondandwedgebond,thecorrespondingbondingtechnique,bondingtoolandmaterialsarelistedinTable1-2.Currently,thermosonicgoldballbondingisthemostwidelyusedbondingtechnique,primarilybecauseitisfasterthanultrasonicaluminumbonding.Oncetheb
7、allbondismadeonthedevice,thewiremaybemovedinanydirectionwithoutstressonthewire,whichgreatlyfacilitatesautomaticwirebonding,asthemovementneedonlybeinthexandydirections.BallbondWedgebondTable1-2.WirebondformationWirebondBondingtechniqueBondingtoolWirePadSpeedBal
8、lbondT/C,T/SCapillaryAuAl,Au10wires/sec(T/S)WedgebondT/S,U/SWedgeAu,AlAl,Au4wires/secP.3WirebondingWirebondevaluationWirebondingevaluationcriteriavariesdependingontheapplicationreq