雅达无铅工艺(1)

Lead-freePowerSupplyImplementationReferenceManualAPracticalGuidetoLead-FreeSoldering:Design,Material,Component,MachineandProcessIntroductionThismanualiswrittentoserveasworkingknowledgeandasaguidetoimplementalead-freemanufacturingsystem.Theinformationisbasedonthetrialresult,inputfromcustomerandsuppliertoworkoutthebasicrequirementforimplementingthelead-freeprocess.Introducinglead-freesolderingnormallyrequirestheusercopewithmoretighterprocesswindow,ifanysingleparametershiftedoutthelimit,itcanresultindramaticallyincreaseindefectrate.Soeverysingleparameter/item,whichincludedesign,material,component,machineandprocess,mustbeperfectlycontrolandmatchedinordertoleadtoasuccessivelead-freesolderingprocess.Thefollowingrequirementsjustprovideyouaguidelinefortheimplementation,thefinalsuccessoflead-freesolderingprocessdependsmajoroneverybodyfocustomaintaintheconsistenceofprocessTherearetwoDrivingForcesforAstectoimplementLead-freeSolder1.TheRoHSdirectiveareputintoforcesinceFeb20032.CustomerdrivenduetomarketandtechnologytrendContent1.LayoutRequirements2.MachineRequirements3.HandSolderingRequirements4.SolderingMaterials5.ComponentsandPCBSurfaceFinish6.QualificationTestforLead-freeSolder7.CommonProductionDefectGuide8.InspectionCriteria1)Layoutrequirementforlead-freewavesolderingprocess(Forreflowsoldering,nodifferencebetweentin-leadandlead-freeonlayoutrequirement)a)TeardropsolderresistopeningforAI/RIpad(Updateasgeneralforbothtin-leadandlead-free)Thisistominimizethepossibilityofpinhole/incompletesolderingduetohighviscositycharacteristicoflead-freesolderb)Norobberpadrequirement(Forlead-freeonly)Duetohigherviscosityoflead-freesolder,biggerlandsizecanpullmoresoldertobouncebackresultinshortsolderc)DoublesidedboardPTHannularringsizeoncomponentsideshouldbe0.3mmforall.Ifsolderpadislayoutonbigcopperarea,usesolderresistopeningtocontrolthepadsizetoholesize+0.6mm(Updateasgeneralforbothtin-leadandlead-free)Thesolderabilityoflead-freeisnotasgoodasthetin-lead,thereductioninannularringcanincreasetheflowofsolderfortopsidefilletd)Thermalreliefforbigcopperarea(Generalforbothtin-leadandlead-free)e)TeardropconnectionbetweenPTHandtracktoreducetheriskofbreakageandpadliftingduetocontractionoflead-freesolder(Applytobothtin-leadandlead-free)-Forholesize1.3mm-Widthoftrace1/2diameterofsolderpad-Extensionofteardrop=2/3diameterofsolderpadf)Thereisatendencythatlead-freesolderwillbepulledbackbybigsolderlandthatcreateshortsolderproblem,soforsolderpadlayoutonbigcopperarea,thesolderlandshouldbetrimmeddowntotheoriginalmacrosize(Applytobothtin-leadandlead-free)EasyshortareaSolderresistopeningSolderresistbridgetopreventshortTrimthesolderresistopeningtotheoriginalmacrosize2)Machinerequirementforlead-freesolderingprocess2.1WaveSoldering2.1.1SpecificationPreheat:-Duetohighersolidcontentfluxbeingused,alongerpreheatzonecanprovidesufficientenergytoactivatetheflux-ForlongtermwhereVOCfluxwillbeused,longerpreheatcanabletodrythefluxtopreventexplosionduringwavesoldering-Preheatlengthshouldbe1mlongminimumandconvectionheating(forVOCfluxrequirement)shouldbeused-IncaseofmultilayerPCBandheavyheatsinkbeingused,topsidepreheatingpanelshouldbeaddedSolderpotmaterial-Duetohightinalloybeingusedandhigherpottemperature,solderpotmaterialmustabletowithstandthehigherdissolutionrate.Potmaterialmustuseeitherstainlesssteel#316,ortitanium,orceramictopreventcorrosioninlongtermproductionDistancebetweenwaves-Inordertoreducethetemperaturedropbetweenthe1stand2ndwavetofacilitatethetopsidefilletrequirementforPTHPCB,thedistancebetween1stand2ndwavedistanceshouldbelessthanorequalto50mmDistancebetweenpreheatzoneandsolderpot-Toavoidthedropoftemperaturebetweenpreheatand1stsolderwavewhichaffectthedeltaT,thepreheatshouldbeascloseaspossibletothesolderpotsothedropshouldbelessthan5degreeCCoolingrequirement-Toachievethemaximumstrengthofsolderandtoavoidthefalseappearancereject(Cracklikesoldersurface),fastcoolingisnecessaryrightaftersoldering,thecoolingrateshouldbe5-6degreeCpersecondOthers:-Ifpossible,useofmagneticpumpsolderpotcanminimizethedrossformationrateandeliminatethepossiblewearoutofpropellersystemFailurestainlesssolderflowduct2.1.2ProfilerequirementAsageneralreferenceonly,therequirementmaychangebaseontypeoffluxuse,PCBandcomponentrequirementPreheat:4degC/secmaximumCooling:7degC/secmaximumDeltaT:lessthan100degCDwelltime:4.5secondsmaximumPreheattemp:110-140degCfor60-90seconds2.2ReflowSoldering2.2.1MachineSpecification-Noofheatingzone:minimum5(topandbottom),hotairforceconvectiontype.Forverycomplexboardwithlargecomponentsizevariation,7zones(orabove)convectiontypeovenshouldbeused-Deltaacrossconveyor:mustbelessthan2degC2.2.2ProfilerequirementAgeneralreferenceonly,therequirementmaychangebaseontypeoffluxuse,PCBandcomponentrequirementPreheat:Ramp3degC/secmax,130-170degCfor40-80secReflow:Peaktemperature245degC,timeabove217degCfor40-80sec3)HandSolderingrequirement3.1EquipmentandTooling3.1.1SolderironselectionandrequirementComponentTypeSolderTipTempTinLeadSolderTin-Silver-CopperSolderSmallDiscrete350+-10degC~2seconds~3