表面贴装焊接技术塑料包装的影响
Thisapplicationnoteisintendedtoinformandassist
thecustomersofMicrochipTechnologyInc.with
SurfaceMountDevices(SMD’s).Theprocessof
packagingasemiconductorinplasticbringstopassa
somewhatunlikelymarriageofdifferentmaterials.In
ordertominimizepotentialadverseeffectsofsurface
mountsoldertechniques,itisworthwhiletounderstand
theinteractionofthepackagematerialsduringthetime
theyaresubjectedtothermalstress.Understanding
boththelimitsofthermalstressingthatSMD’scan
withstandandhowthosestressesinteracttoproduce
failuresarecrucialtosuccessfullymaintaining
reliabilityinthefinishedproduct.Arecommended
Infrared(IR)solderprofileisprovidedasareference
later.
Theelectronicsindustryhasmovedtosmallerand
thinnersurfacemountpackagingintheprogress
towardminiaturizationofcircuits.Thistrendhas
necessitatedtheuseoflowerprofileandsmaller
footprintpackages.Therehasbeenanincreasein
reliabilityproblemscorrespondingwiththeshrinking
sizeofplasticSMD’s.Theseproblemsmanifest
themselvesinsuchwaysasmoisturesensitivity,
crackedpackages,openbondwiresandintermittent
continuityfailures.Problemsofthistypearenot
presentinthedevicespriortoassemblyontoprinted
circuitboardsbutaretheresultofthermallyinduced
stressingtothepartduringassemblyoranyrework
suchasdesoldering.AN598PlasticPackagingandtheEffectsofSurfaceMountSolderingTechniquesTheheatfromsolderingcausesabuildupofadditionalAuthor:JohnBarberstresseswithinthedevicethatwerenotpresentfromSurfaceMountTechnologyTeamthemanufacturingprocess.Boardlevelsolderprocesses,suchasIRreowandVaporphasereow,arewell-knownareaswheretemperaturescanreachPURPOSE
