GNSSRandThermalDesign固态继电器.ppt

,SSR/HeatSinkAssemblyDesign,ProductPresentation,GNSERIESSOLIDSTATERELAYS,ReturntoMainMenu,InnovationInSolidStateTechnology,Ratingsto125Amps/660Vac,DirectBondCopperSubstrate,ImprovedPowerLeadFrameDesign,SurfaceMountTechnology,CastBasePlate,EMCCompliant(Level3),LargerSCRDie,OptionalIP20TouchSafeHousing,UL/cUL/CSARecognized,TUVApproved,CECompliant,InternalTransientProtection,InputStatusLEDIndicator,Features,Objectives,Developasolidstaterelaythatutilizesthelatesttechnologyandhasasmanyfeaturesaspossibleincorporatedintotheinitialdesign.,Designaback-to-backSCRassemblywithathermalefficiencythatissignificantlybetterthanourcompetitionsrelays.,Achievelevel3compliancewithallofthestandardssetforthbytheEuropeanCommunitiesEMCDirective.,Automatetheassemblylinetoincreasereliabilityandtoreducemanufacturingtime.,DevelopandimplementautomatedtestproceduresthatverifytheintegrityandfunctionalityoftheSSR.,AlloftheseobjectivesweremetbeforetheGNSSRswereintroducedintothemarket.,CompetetiveAnalysis,YesNoNoNoNoNoNoYesNo,NoNoNoNoNoNoYesYesNo,ThermalEfficiency,HeatistheprimarycauseofSSRfailuresinmostapplications.Ascurrentflowsthroughtherelay,theSCRsgenerateheatwhichmustbedissipatedthroughtheceramicsubstrate,throughthebaseplate,andintotheheatsink.Theheatsinkisthencooledbytheambientair.TheSSRsabilitytofunctionreliablyinanapplicationisdependentuponhowwellitcantransferheatfromtheSCRdietotheheatsink.IftheSSRisnotveryefficientintransferringheatthroughthebaseplate,thenthesizeoftheheatsinkmustbeincreasedtocompensateforthisortherelayand/orloadmaybedamaged.,SSRthermalefficiencyismeasuredindegreesCelsiusperwattbeinggeneratedbytheSCRs,orRjb.ThelowertheSSRsRjbrating,themoreefficientitis.Rjbisdeterminedbythetypeofceramicsubstrateused,thethicknessoftheceramic,andhowwelltheSCRdieandsubstrateareassembled.,DirectBondCopper(alsoknownasDirectCopperBondingorFusedCopper)hasamuchlowerthermalimpedancethantraditionalfoilsubstrates.Theceramicandcopperareheatedandpressedtoforma“bond”whichminimizesthethermalbarrierbetweenthetracesandthesubstrate.TheGNseriesSSRsalsoutilizeasubstratethatis40%thinnerthantraditionalceramicsubstrates,makingtheSSRevenmoreefficient.,DirectBondCopper,GNSERIESSOLIDSTATERELAYS,“Bussed”PowerLeadFrame,DirectBondCopperSubstrate,CastBasePlate,Reliability,GNSERIESSOLIDSTATERELAYS,RegulatedACNOTSOLDEREDTOBASEPLATEON25AAND50AMODELS,CARLOGAVAZZI,SMALLERBASEPLATEREDUCESTHEAVAILABLESURFACEAREAFORHEATTRANSFER,TRIACDRIVEROPTICALISOLATORS,INTERNALTRANSIENTPROTECTION,LEDINPUTSTATUSINDICATOR,CROUZET,CROUZET,“BUSSED”POWERLEADFRAME,DIRECTBONDCOPPER(DBC)SUBSTRATE,CASTBASEPLATE,BacktotheGNSSRPresentation,CROUZET,CORPORATION,SSRThermalDerating,ProperlyderatinganySSR-heatsinkassemblyiscriticaltothereliabilityoftheassemblyandoverallsatisfactionofthecustomer.Cost,Size,shape,color,oranyotherparticularrequirement,issecondarytoinsuringthattheheatgeneratedbytherelaywillbeadequatelydissipatedbytheheatsink.Lackofattentiontodetailwhendesigninganassemblymaysignificantlydecreasethelifeoftherelayorresultincatastrophicfieldfailures.,Essentialderatinginformation:AdditionalHelpfulInformation:AmbientTemperature(Tamb)AirFlow(CFMorLFM)LoadCurrent(I)DutyCycleSSROn-StateVoltageDrop(Vf)PanelVentilationSSRThermalImpedance(Rjb)SurroundingHeatSourcesHeatSinkThermalImpedance(Rs-a)SurgeCurrents,SSR/HeatSinkAssemblyDesign,Ascanbeseenfromtheformula,thetemperatureoftheSCRdieduringnormaloperationisasumoftheproductoftheambienttemperature,heatsinkefficiency,SSRthermalimpedance,andthetotalpowerbeingdissipatedbytherelay.IfthesumexceedsthemaximumtemperatureratingoftheSCRs,whichistypically125C,thenoneormoreofthevariablesmustbereducedinordertopreventafailureoftheSSR.IfthesumislessthanthemaximumtemperatureratingoftheSCRs,thenitissafetoproceedwithaverificationanalysisoftheassembly.,ITISALWAYSIMPORTANTTOVERIFYTHERESULTSOFTHEINITIALESTIMATE,ASTHEVARIABLESARENOTALWAYS100%ACCURATE!,Tdie=Tamb+(Rs-ax(IxVf)+(Rjbx(IxVf),GNSSR-SCR/BASEPLATEASSEMBLY,GNSERIESSOLIDSTATERELAYS,AstheloadcurrentflowsthroughtheSCRdie,heatisgeneratedproportionaltotheamountofthecurrentandtheVfoftheSCRs.ThetotalthermalimpedanceoftheSCR/baseplateassemblydetermineshowmuchofthisheatistransferredthroughtheDBCandbaseplate,andismeasuredindegreesCelsiusperWattbeinggenerated,orRjb.,Tocalculatethetemperaturedifferential,orDT,betweentheSCRdieandthebaseplate,wemultiplytheRjbbythetotalpowerbeinggenerated.,AssumetheSSRiscarrying50ampsofloadcurrentandhasaforwardvoltagedropof1.2Vpk.Thejunction-to-baseplatethermalimpedanceis.155C/W,DT=Rjbx(IxVf)DT=.155C/Wx(50Ax1.2Vf)DT=9.3C,WenowknowthattheSCRdieareoperating9.3ChotterthanthebaseplateoftheSSR.Alone,thisinformationisnotveryhelpful,asitonlygivesustheDT,andnottheactualtemperatureoftheSCRdie.,TodeterminetheactualtemperatureoftheSCRdie,wemustdeterminethetemperatureoftheSSRsbaseplate.,HeatTransfer,HeatTransfer,LFM=(CFM/(area/144)x70%(70%derateforbackpressure),LFM=(40/(9/144)x.7,LFM=(40/.0625)x.7,LFM=448(Deratedownto400LFM),OncetheapproximateLFMratingisknown,acorrectionfactorcanbeappliedtotheheatsinktodeterminethethermalimpedancewithairflow.,Velocity(LFM)CorrectionFactor100.757200.536300.439400.378500.338600.309700.286800.268900.2521,000.239,Soourheatsinkwouldhavea.378C/Wthermalimpedancewith400LFMofairflow.,ForcedAirv.ConvectionCooling,Todemonstratetheincreaseintheefficiencyoftheheatsinkprovidedbythe40CFMfan,wecancalculatehowmuchmorecurrent(I50Amps)theSSRwouldhavetocarryinordertoobtainthesame115.3Cdietemperatureasbefore.Toinsureadequatederating,wewillroundtheimpedanceoftheheatsinkto0.4C/W.,115.3C=Tamb+(Rs-ax(VfxI)+(Rjbx(VfxI),115.3C=40C+(.4C/Wx1.2X)+(.155C/Wx1.2X),115.3=40+.48X+.186X,75.3=.667X,X=112.9Amps(Increaseof62.9Amps),Alwaysevaluateanassemblythatistobecooledbyforcedairbeforethecustomerbeginsusingtheassemblyintheirproduction.ForcedaircoolingsystemsaretrickyatbestandSSRfailuremayresultfromaninadequateunderstandingofthesystemsparameters.Installingassembliesinthecustomersequipmentforthermaltestingisthebestwaytoinsureoverallreliability.,ForcedAirEfficiency,Astandardheatsinkprofilelistedinanextruderscatalogwilltypicallyhavethethermalimpedancespecifiedwhencuttoalengthofthreeinches.Aroughdeterminationoftheimpedanceofanextrusionprofilecutindifferentlengthscanbeobtainedwithacorrectionfactor.MultiplyingtheRs-a/3”bythecorrectionfactorforthedesiredextrusionlengthwillgivethethermalimpedanceofthatprofilewhencuttothatlength.Thisisavaluabletoolwhendesigningprototypeassemblies,butthecorrectionfactorwillvaryslightlyforeachprofileduetovariousspacingandlengthsofthefins.,ExtrusionLengthCorrectionFactor1”1.802”1.253”1.004”.875”.786”.737”.678”.649”.6010”.5811”.5612”.54,Cut-to-LengthExtrusions,2X+3Y=Z,ToCalculateHeatSinkThermalImpedance:Rs-a=(Tbp-Tamb)/PowerRs-a=(Tdie-(RjbxPower)-Tamb)/Power,ToCalculateBasePlateTemperature:Tbp=Tdie-(RjbxPower)Tbp=Tamb+(Rs-axPower),ToCalculateRjb:Rjb=(Tdie-Tbp)/Power,ToCalculateSCRTemperature:Tdie=Tamb+(Rs-axPower)+(RjbxPower)Tdie=Tbp+(RjbxPower),ToCalculateMinimumRequiredHeatSinkThermalImpedance:Rs-a-min=(Tdie-max-Tamb-(RjbxPower)/Power,ToCalculateMaximumAllowableCurrentGivenHeatSinkImpedance:Imax=(Tdie-max-Tamb)/(Rs-axVf)+(RjbxVf),E=hxf,ItsAllintheMath,Alwaysverifyanycalculation.Catastrophicfieldfailuresmayoccuriftheactualvalueofavariableshiftsevenaslightamountfromtheestimate.Evaluateeverynewassemblyinanenvironmentascloseaspossibletotheactualapplicationorintheactualequipmentforwhichitisintended.,Roundupeverynumberinthecalculationsandusemaximumvaluespecificationswhenever