Reflow-Technology2(诺基亚SMT回流焊工艺)

ReflowSolderinginNitrogenAtmosphereTypicalapplications-finepitchcomponents-barecoppersurfaces-NoCleanDemandsonthereflowsystem-FastbuiltupoftheNitrogenatmosphere-Lowresidualoxygenlevel(10to100ppm)-Lownitrogenconsumption(10to25m³/h)-ConstantnitrogenatmosphereDemandsonNitrogenTechnology-finepitchcomponentsnitrogenavoidstheformationofdrossparticlesonthesolderjointsurfaceduringpreheatandpeak.Lessdrossparticleschangetheflowcaracteristicsofthesolderandreducestheriskforbridging.-barecoppersurfaces

underprotectivenitrogenatmosphere,barecuppersurfaceswillnotoxidizeandthesolderabilitywillbenotdecreased.-NoClean

duetolessoxidationundernitrogenatmosphere,thefluxmaterialhasto

reducelessoxidesontheboardandtheleads.Forthatreason,lessfluxcanbeusedintheprocess.usingnitrogenfor:nitrogeninletportinreflowzone20ppm-23-26m³/h50ppm-19-23m³/h100ppm-16-19m³/h500ppm-11-15m³/hwith250mmconveyorwidthopening15mmcomponentsheightMachineinworkingconditionsNitrogen5.0(purityO2<5ppm)typicalnitrogenvaluesleadfreesolderingLEADELIMINATION-WHY?•ENVIRONMENTALISSUES•MARKETINGISSUES•TECHNICALISSUESDriversforLeadFree•BanandTax-USA1993•WEEEDirective2001?implementation1.1.2008?•Japan-commitmentstoleadfreeinterconnectToshiba-2000Sony,Matshushita,Hitachi-2001NEC-2003WEEE-WastefromElectricandElectronicEquipmentWho’simpacted?•PCBsuppliers•componentsuppliers•equipmentsuppliers•manufacturers•contractmanufacturers•fluxandsoldersuppliers•recyclingcompanies•reworkandrepairworkshopsModificationsonsolderingequipmentReflowSolderM/C•convectionmodulesabletooperateathighertemperatures•newmaterialsforsealingsandbetterheatisolation•useofnitrogen?•differentlengthofpreheat-peak-andcoolingzoneERSASolderingMachinesDivision

ProcessRequirements„LeadFreeSoldering“ERSAGmbHUsingHightemperatureSolders–Liquidus217°C-227°C•Heat-upramp: 1°C-5°C/sec•Holdingzone: 60-120sec•Preheattemperature: 160°C-180°C•Reflowzone(doublezoneupper/lower)

ÞSoldertemperature: 235°C-240°C, at40-70secondsduration•Peaktemperatureovermeltingpoint: 15°Cto20°C•Maximumtemperature: approx.250°C,(5-10sec’s)•Temperatureinprocesschamber: >300°Cpossible•GapbetweenPCB-temperature

andsetvalues: assmallaspossible•∆Tinpeakzone: <10°C,lowmass/highmass•∆Tinacrossbelt: +/-1,5°C•Coolingzone: adjustable•Coolinggradiant: 3°C-5°Cpersec•Temperatureofboardatexitfromsystem: max.40°C-80°C30.03.00.CI/PR.kepage3ERSA.pptReflowtemperatureprofileforleadfreepasteReflowtemperatureprofileforleadfreepasteHotlow7NMP-VersionReflowtemperatureprofileforleadfreepasteHotflow7NMP-VersionReflowtemperatureprofileforleadfreepasteHotflow7TwinModuleleadfreesolderjointsbadwettingonbarecupperareaoncuttedleadborderlinelookslikeacrackleadfreesolderjointsSurfaceofthejointslooksdifferent.„freezinglines“or„orangepeeleffect“solderjointitself

isokleadfreesolderjointswettingisnotasgoodas

SnPbcornersofrectagularpadsarepreferedfornonwettingifsurfacesolderabilityisreducedBarrierstoLeadFree•costs•reliability•heateffectsonPCB’sandcomponents•supplychain•standards•reworkandrepair•outsourcing•LeadFreecomponentfinishConclusion•LeadFreeispossible•currentlynoacceptabledrop-inreplacementfortin-leadsolderfor