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1、ABSTRACTABSTRACTWiththerapiddevelopmentofmodernindustry,Micro-USBconnectorshavebeenanintegralpartofpeople'slives,sotheMicro-USBconnector’slifetimehasbeenhighlyputontheagenda.Becausethesolderjointisthebridgesoftheelectricalandmechanicalcharacteristics,oncethesolderjointfailu
2、rewilldirectlycauseMicro-USBconnector’sfailure.Sothepredictionofsolderjoint’slifeisofgreatsignificance.Underthecyclicaltemperature(-55℃to+125℃),thejointssolder’slifehasbeendescribedinthisthesis.Thesolderjoint’smaterialsisSn3.5Ag0.75Cuwhosemeltingtemperatureisabout217℃.Whent
3、hetemperaturereachesthemeltingpointof0.5,thesolderwillcreepandstressrelaxation,whichcaneffectivelypredicttheservicelifeofthesolderjointsunderextremeoperatingconditions.Underthecyclicaltemperature,thelifepredictionoftheMicro-USBconnectormainlytasksare:usingthe3Dmodelingsoftw
4、arePro/EestablishestheentitymodelMicro-USBconnectorwhichincludestheMicro-USBwholeconnectorbody,metalPin,wiresandSnAgCulead-freesolder,andremovingthesharppartiallywhichdonotimpacttheanalysis,thenimportingitintothefiniteelementanalysissoftwareANSYSforanalysis.Themechanicalbeh
5、aviorofthesolderjointsaredescribedbytheANANDunityconstitutiveequationmodelundercyclictemperatureloads.UsingcommandsofparametricdesignlanguageAPDLwritesthecyclictemperatureloadsandsimulatingthestressandstraindistributionsofsolderjointsbytheoreticalanalysis.Asthecoefficientof
6、thermalexpansionmismatchesamongallofthematerials,themaximumstress-strainhasbeenfoundatthelowtemperature.Andatthehightemperature,thethermalstress-strainisdecreased.Duringtheheatingorcoolingtemperature,thestress-strainofsolderjointschangesgreatest,whichresultsinthefinalsolder
7、crackinitiationatthisperiodthenfailure.UsingCoffin-Mansonempiricalformulabasedonplasticstraincalculatesthethermalfatiguelifeofsolderjointsunderthermalcyclingtemperatureeffects.Finalresultsshowedthatunderthecyclingtemperature,thesolderjointstheMicro-USBconnector’maximumstres
8、s-strainisfoundatthebottomofthesolderjointswheretouchonthemetalPin,whilethemiddles
