Wire Bonding.pdf

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1、ChapterA:WireBonding2Level2.Conclusionsandguideline2.1WirebondingtechniquesTherearetwobasicwirebondingtechniquesthatareusedinthermocompression(T/C),thermosonic(T/S)orultrasonic(U/S)bondingprocess:ballbondingandwedgebonding.Approximately93%ofallsemiconductorpackagesaremanufacturedusing

2、ballbondingmethod,whilewedgebondingisusedtoproduceabout5%ofallassembledpackages.2.1.1BallbondingInthistechnique,wireispassedthroughahollowcapillary,andanelectronic-flame-offsystem(EFO)isusedtomeltasmallportionofthewireextendingbeneaththecapillary.Thesurfacetensionofthemoltenmetalfroma

3、sphericalshape,orball,asthewirematerialsolidifies.Theballispressedtothebondingpadonthediewithsufficientforcetocauseplasticdeformationandatomicinterdiffusionofthewireandtheunderlyingmetallization,whichensuretheintimatecontactbetweenthetwometalsurfacesandformthefirstbond(ballbond).Theca

4、pillaryisthenraisedandrepositionedoverthesecondbondsiteonthesubstrate,apreciselyshapedwireconnectioncalledawireloopisthuscreatedasthewiregoes.Deformingthewireagainstthebondingpadmakesthesecondbond(wedgebondorstitchbond),havingacrescentorfishtailshapemadebytheimprintofthecapillary’sout

5、ergeometry.Thenthewireclampisclosed,andthecapillaryascendsonceagain,breakingthewirejustabovethewedge,anexactwirelengthisleftforEFOtoformanewballtobeginbondingthenextwire.Ballbondingisgenerallyusedinthermocompression(T/C)oroothermosonicbonding(T/S)process.Thistechniquerequiresahightemp

6、eratureragingfrom100Cto500Cdependingonbondingprocess.Heatisgeneratedduringthemanufacturingprocesseitherbyaheatedcapillaryfeedingthewireorbyaheatedpedestalonwhichtheassemblyisplacedorbybothdependingonthebondingpurposeandmaterials.Relativelysmallgoldwire(<75mm)ismostlyusedinthistechniqu

7、ebecauseofitseasydeformationunderpressureatelevatedtemperature,itsresistancetooxideformation,anditsballformabilityduringaflame-offorelectronicdischargecuttingprocess.Ballbondingisgenerallyusedinapplicationwherethepadpitchisgreaterthan100mm.However,theapplicationofthepitcheswith50mmhas

8、beenr