Icepak高阶建模教程.ppt

AdvancedThermalModeling,AdvancedThermalModeling,CourseOutline,IntroductionCFDBasicsPrintedCircuitBoardsICPackagesHeatSinksInterfaceResistanceFans,ImpellersandBlowersAltitudeEffectsFlowResistancesRadiationHeatPipesJouleHeatingThermoelectricCoolersColdPlatesTransformersFlowBaffles,CourseOutline,WallEffectsExternalCoolers/HeatersCaseStudies:MeshRefinementModelingPBGASelectingHeatSinkSpreadingResistanceEffectofRadiationSealedSystemsModelingTECSelectingBafflesISelectingBafflesIIModelingDataCenter,Introduction,Introduction,TheCaseforThermalManagement,TheheatgeneratedinanelectroniccircuitisinverselyproportionaltotheefficiencyofthecircuitThepowerthatisnotconvertedtoperformusefulelectromagneticworkislostintheformofheattothesurroundingsThepowerwastedasheatincludes:Jouleheating(I2R)lossPowersupplyThereliabilityofasemiconductordeviceisdirectlyaffectedbyitsoperatingtemperature,TheCaseforThermalManagement,Virtuallyallelectronicfailuremechanismsareenhancedbytheincreaseinpackagetemperature:StressesduetoTCEmismatchCorrosionElectro-migrationOxidebreakdownCurrentleakage(whichdoubleswithevery10cinactivedevices)Degradationinelectricalperformance(duetochangeindeviceparameters),TheCaseforThermalManagement,TherateoffailureofelectronicpackagesisdirectlyproportionaltoheatandincreasesexponentiallywiththemaximumtemperatureofthepackageTherateoffailurecanbeexpressedas:F=Ae-E/KTwhere,F=failurerate,A=constantE=activationenergyinelectronvolts(eV)K=Boltzmannsconstant(8.63e-5eV/K),andT=junctiontemperatureinK,TheCaseforThermalManagement,TheCaseforThermalManagement,TheEffectofPackageTemperatureonFailure(Numberoffailuresafter1000hrofoperationpermillionunits),TheCaseforThermalManagement,MajorCausesofElectronicFailure,Source:U.S.AirforceAvionicsIntegrityProgram(Reynell,M.,1990),ICPackageTrends,PackagesaregettingthinnerNumberofleadsisgettinglargerPackagefootprintdecreasingtoapproachchipsizePackagepinpitchisdecreasingClockspeedisincreasingICchipsareperformingmorecomplextasksMovingtowardssystem-on-chiptechnologyPackagesaredissipatingmorepowerOperatingjunctiontemperatureremainsfixed55Cforcommodityandhandhelddevices125CforautomotivesystemsBudgetperwattofheatremovalisdecreasing,PackagingTrends,PackagePowerProjectionTrends(Watts),Commodity:Lowcost($300)consumerproductsHand-Held:Batterypowered($1000)productssuchascellular,etc.Cost/Performance:Maximumperformancewithcostlimit(20Largedifferencesinthermalconductivity,Multi-GriddingUserSpecification,DefaultsettingsArerobustforawiderangeofproblemsTypicallyshouldnotbechangedWhentooverridedefaultsettingstoaccelerateconvergenceConduction-onlysolutionswithverylargeratiosofconductivitychangeTemperaturetoVorW-cyclesetbothterminationcriteriaandresidualreductiontoleranceto1.0E-10,Ill-PosedProblems,InconsistentBoundaryConditionsEnsurethatamodelhasphysicallyplausibleboundaryconditionsinletandexhaustforflowheatrejectionpathsforallenergysourcesEnsurethatobjectshavenotbeenmistakenlyassignedashollowrecallthathollowobjectsareadiabaticEnsurethatobjectsaremeshed,especiallyfans,openings,vents,andresistancesnotgenerallyaproblem,butagoodideatocheckbeforestartingasimulationTransientversusSteadyProblemsSolvingatransientproblemassteadymaynotconvergeparticularlyimportantinnaturalconvectionproblemsinthetransitionalflowregime,AcceleratingConvergence,ConvergenceCanOftenBeAcceleratedSupplyagoodinitialconditiongiveastartingvelocityintheprimaryflowdirectionforforcedconvectionproblemsinterpolatefromaprevioussolutionifoneisavailableImprovethemeshqualityhigherqualitymeshesconvergefasterinmanycaseslargerrelaxationfactorscanbeusedexcessivelyhighvaluescanleadtodivergencePreventswappingifthesolverisswapping,reducethenumberofcellsinthemodelifpossible,AcceleratingConvergenceInitialGuess:EffectonConvergence,NaturalConvectionDefaultrelaxationfactorsPressure:0.7Momentum:0.3Initialguess:0.0m/sforz-velocity,AcceleratingConvergenceInitialGuess:EffectonConvergence,NaturalConvectionDefaultrelaxationfactorsPressure:0.7Momentum:0.3Initialguess:0.1m/sforz-velocity,IcepaksMesherHowitworks,FirstcombineadjacentobjectstogetherCreatessingle“macro”groupsofmultipleobjectsCreatethecoarsestcartesianmeshpossibleOnecellpergroupfacetodefinegeometryandextentsReplacethelocalcartesianmeshwithalocallyunstructuredmeshTheoriginalboundariesofthelocalcartesianmeshremainunchangedthemembersofeachgroupwillthenrecursivelycreateunstructuredmesheswithinthelargerunstructuredmesh,IcepaksMesherHowitworks,UnstructuredMeshingUtilizeangledcellsandflexibleconnectivitytoreducecellcountsbetterresolutionforsamenumberofcellsUnstructuredregionlocalizedwithinsub-domainsdefinedbytheO-grid(s)defaultsizeofeachO-gridisdeterminedbythegeometryinthemodelunlessotherwisespecified,O-gridsizescandifferfromobjecttoobjectThemore“unstructuredness”tothemesh,thesmallerthecellcount,O-grid,ReviewofMeshControlsGlobalControls,UserscancontrolthemesherwithglobalcontrolsMaximumcellfacesizeineachcoordinatedirectionMaximuminitialheightfromeachobjectsurface(includingthecabinet)Minimumnumberofcellsinfluidsgapsuselocalcontrolstogetmorethan3Minimumcellsontheedgesofsolids,cylinders,andtrianglesMaximumgrowthrateO-gridheightgroupO-griddingcanbedeactivated,ReviewofMeshControlsPer-ObjectControls:Blocks,Per-objectcontrolsforprismblocksCellcountineachofthecoordinatedirectionsInitialheightonthehighandlowsidesineachcoordinatedirectionGrowthrate(ratio)ofthecellsmovingawayfromtheobjectineachcoordinatedirectionHeightofthefirstcellgoingintotheobjectGrowthofcellsmovingintotheobjectfromtheedgesIcepakwillprovideatleastwhattheuserrequests,ifpossible,ReviewofMeshControlsPer-ObjectControls:2-DObjects,Per-objectcontrolsfor2-DobjectsCellcountineachofthetwodirectionsInitialheightonthehighandlowsidesineachdirectionHeightofthefirstcellgoingintotheobjectGrowthrate(ratio)ofthecellsmovingawayfromtheobjectineachdirectionGrowthofcellsmovingintotheobjectfromtheedgesIcepakwillprovideatleastwhattheuserrequests,ifpossible,ReviewofMeshControlsPer-ObjectControls:CircularObjects,Per-objectcontrolsforcircularobjectsNumberofcellsper1/4ofthecircumferenceInitialheightonthehighandlowsides,aswellastowardsandawayfromthecenterGrowthrate(ratio)ofthecellsmovingawayfromtheobjectineachdirection,aswellastowardsandawayfromthecenterIcepakwillprovideatleastwhattheuserrequests,ifpossible,ReviewofMeshControlsPer-ObjectControls:PolygonalObjects,Per-objectcontrolsforpolygonalobjectsNumberofcellspersideofthepolygonandalongits“extruded”heightInitialheightonthetopandbottom,aswellaseachsideGrowthrate(ratio)fromtheobjectonthebottom,top,andeachsideoftheobjectIfthemeshdoesnt“adhere”totheobject,per-sidecontrolswillhelpIcepakwillprovideatleastwhattheuserrequests,ifpossible,ReviewofMeshControlsDisplayMeshOptions,IcepakprovidesmanywaystodisplaycellsOnallobjects,currenttype,andcurrentobjectsurfaceandvolumecellswireframeandsolidCutplanescanalsobedefinedusingthemousehorizontalandverticalwithpoint/normaladvancedwith+and-buttonsorsliderbarcolorofthemeshcanalsobecontrolledkeepinmindthatplanecutsneednotconformtoactualcellfacesunstructuredinallthreedirections,ReviewofMeshControlsDiagnosticTools,ThediagnostictoolallowstheusertodeterminemeshqualityonacellbycellbasisUsetheminandmaxtonarrowrangeClickonthehistogrambar(s)tohighlightthecellswithaparticularcellcharacteristic(s)ItisalwaysagoodideatochecktheFaceAlignmentandVolumebeforestartingarun,ImprovingMeshQualityAlignment,IcepakhonorsthemodelgeometryWillnotmoveobjectswithinthedomainwithoutusersknowledgeandconsentAlignmentiscriticalUnintentionalorgeometricallyinsignificantmisalignmentscanmakethemeshlargerthanisrequiredcreateveryslendercellsinregionsofthedomaincreatecellswithpoorqualityFromameshingperspective,itsagoodideatoalignobjectsSettheMinimumobjectseparationtolimittheminimumallowabledistancebetweenmeshlines(inFile/Configure)Alldistancesorseparationsbelowthislimitwillbeignored,ImprovingMeshQualityPer-ObjectControls,Useper-objectcontrolstoflattenexpansionregionSetsmallerinwardheightandinwardratioforcircularobjectsSetsmallersidespecificationsandratiosforprismaticobjectsThisisthepreferredtechniqueItonlyaffectsthemeshlocally,resultingin:smallercellcountswontadverselyaffectotherregions,ImprovingMeshQualityFluidBlocks,Usefluidblocksto“mold”transitionregionCreateafluidblockwithsamediameterasfanandplacedirectlyonsurfacePutfluidblocksinregionswherethefacealignmentissmallerthan0.15ThisisaverypowerfultechniqueOnlyeffectsthemeshlocallyMayremovetheunstructurednatureofthemeshlocally,ImprovingMeshQualityGeometryModification,GivemorespaceforthemeshertotransitionMoveobjectsslightlytocreatelargergapAveryeffectiveapproachOftensmallchangescanremovetheproblem(1mm)Sometimesnotacceptablecanchangethephysicsoftheproblem,ImprovingMeshQualityGlobalControls,ReduceO-gridheighttoflattentransitionregionSetO-gridtoasmallnumber,1.0E-2to1.0e-6Thislimitstheangularexpansionofmeshlines“Sledge-Hammer”approachAffectsthemeshgloballyWillreducetheunstructurednatureofthemeshCancauseproblemsinotherregionsofthedomain,RecommendedProcedureBeforetheRunisSubmitted,Aftermodelisconstructed,butbeforegeneratingmeshEnsurethattheproblemiswellposedandthattheboundaryconditionsmakesenseCheckfancurvesforunitsandorderofinputsPeriodicallyusethealignmentcheckutilityidentifyandfixanyalignmentproblemsthiswillreducemeshsizeandpreventmanymeshqualityproblemsAftermeshisgeneratedUsingthediagnosticutility,checkfacealignmentandvolumeUsingthedisplaymeshoptionensurethatallobjectsaremeshedensureadequateresolutioninfluidgapsandregionswithpotentialsforhighgradientsClicktheResetbuttonintheSolverSetupdialogtosetthedefaultvaluesforrelaxationfactors,ChecklistforImprovingMeshQuality,UsethediagnosticutilitytodisplaycellswithpoorqualityTrytofixusingper-objectcontrols,likeinitialheightandgrowthrate(ratio)localcontrolswillnoteffecttheentiremeshCreatefluidblockstoprovidemeshcontrolblockscanbemadeinvisibletoretainpresentationqualityIfpossible,makesmallmodificationstothegeometrytomakeiteasieronthemesherprovidemorespaceforsmoothmeshtransitionReducetheO-gridheightwillresultinlargermeshcanremovethecocooningstructureofthemeshReplaceanydifficulttomeshobjectswithsimplerequivalentscircularobjectswiththeirpolygonalequivalents,ItStillDiverges-WhatNow?,Reverserelaxationfactors,ifappropriateSlowerconvergenceisbetterthannoconvergenceImproveinitialguessProvideagoodinitialguesstohelpthesolutionoutsolvealaminarproblemtouseasaninitialguessforaturbulentrunTerminatetherunassoonasdivergencehasoccurredIsovalueorplanecutofturbulenceviscosityratiowillindicatetheproblematicregion(s)inmostcasesimprovethemeshqualityinthisregionincreasethelocalresolutiontobetterresolvethephysicsCall/Emailasupportengineer,Summary,IcepakssolverisfinitevolumebasedSegregatedsolverrelaxationfactorsmulti-griddingConvergenceisdeclaredwhenresidualsdropbelowaspecifiedcriterionvaluesofquantitiesofinteresthavestoppedchangingMeshqualityisveryimportantinobtainingstableandaccurateresultsIfdivergenceoccursCheckthemodelforconsistencyEnsurethatthemeshqualityisacceptablemanytechniquestoimprovemeshqualityUsemoreappropriaterelaxationfactors,CaseStudy:MeshRefinement(I),CaseStudy:MeshRefinement(I),CaseStudy:MeshRefinement(I),Devicegenerating50W,0.5m/s(Laminar),HeatSinkModel,CaseStudy:MeshRefinement(I),Case1Cellheightnearsolids=0.06”Cellgrowthratio=2Meshcount=28,372,CaseStudy:MeshRefinement(I),Case1Cellheightnearsolids=0.06”Cellgrowthratio=2Meshcount=28,372,Mesharoundheatsink,CaseStudy:MeshRefinement(I),Case1Cellheightnearsolids=0.06”Cellgrowthratio=2Meshcount=28,372,Tmax79.1C,CaseStudy:MeshRefinement(I),Case2Cellheightnearsolids=0.03”Cellgrowthratio=2Meshcount=56,172,CaseStudy:MeshRefinement(I),Case2Cellheightnearsolids=0.03”Cellgrowthratio=2Meshcount=56,172,Mesharoundheatsink,CaseStudy:MeshRefinement(I),Case2Cellheightnearsolids=0.03”Cellgrowthratio=2Meshcount=56,172,Tmax82.9C,CaseStudy:MeshRefinement(I),Case3Cellheightnearsolids=0.006”Cellgrowthratio=2Meshcount=173,814,CaseStudy:MeshRefinement(I),Case3Cellheightnearsolids=0.006”Cellgrowthratio=2Meshcount=173,814,Mesharoundheatsinkfins,CaseStudy:MeshRefinement(I),Case3Cellheightnearsolids=0.006”Cellgrowthratio=2Meshcount=173,814,Tmax83.1C,CaseStudy:MeshRefinement(II),CaseStudy:MeshRefinement(II),CaseStudy:MeshRefinement(II),PCB,Components(Lumpedasthickplates),Inflow(5m/s),Outflow,Tele-rackModel,Fans,CaseStudy:MeshRefinement(II),Case1Cellheightnearsolids0.01Cellgrowthratio=3Meshcount=23,870,Coarsemesh:Onlyacoupleofelementsbetweencards,CaseStudy:MeshRefinement(II),Case1Cellheightnearsolids0.01Cellgrowthratio=3Meshcount=23,870,Tmax=61.8C,CaseStudy:MeshRefinement(II),Case2Cellheightnearsolids0.0035Cellgrowthratio=3Meshcount=77,096,CaseStudy:MeshRefinement(II),Case2Cellheightnearsolids0.0035Cellgrowthratio=3Meshcount=77,096,Mesharoundcards,CaseStudy:MeshRefinement(II),Tmax=50.6C,Case2Cellheightnearsolids0.0035Cellgrowthratio=3Meshcount=77,096,CaseStudy:MeshRefinement(II),Case3Cellheightnearsolids0.0008Cellgrowthratio=3Meshcount=146,040,CaseStudy:MeshRefinement(II),Case3Cellheightnearsolids0.0008Cellgrowthratio=3Meshcount=146,040,Mesharoundcards,CaseStudy:MeshRefinement(II),Tmax=40.6C,Case3Cellheightnearsolids0.0008Cellgrowthratio=3Meshcount=146,040,CaseStudy:MeshRefinement(II),Case4Cellheightnearsolids0.00035Cellgrowthratio=3Meshcount=253,946,CaseStudy:MeshRefinement(II),Case4Cellheightnearsolids0.00035Cellgrowthratio=3Meshcount=253,946,Mesharoundcards,CaseStudy:MeshRefinement(II),Tmax=38.7C,Case4Cellheightnearsolids0.00035Cellgrowthratio=3Meshcount=253,946,PrintedCircuitBoards,PCBs,PrintedCircuitBoards,Component-side(top)view,Source:Pixeldirect,PrintedCircuitBoards,Solder-side(bottom)view,Source:Pixeldirect,PrintedCircuitBoards,Aprintedcircuitboard(PCB)isgenerallyamulti-layeredboardmadeofadielectricmaterial(glass-reinforcedpolymerorFR4)andseverallayersofcopperplanesItservestowiremountedICchipsthatwouldotherwiseneedthousandsofpoint-to-pointwireconnectionsAsingle-layerboardhascomponentsmountedononesideandcopper(conductor)patternontheotherThecopperpatternisestablishedbyphoto-etchingacopperfoilpastedoverFR4Adouble-layerboardhascopper(conductor)patternaswellascomponentsonbothsidesAmulti-layerboardismadeofseveraldouble-sidedboardswithinsulatinglayersinbetween,PrintedCircuitBoards,Laminatesinamulti-layerPCB,PrintedCircuitBoards,HeatandpressureisappliedtolaminatethelayersintoarigidstructurecalledthePCBMulti-layerPCBsgenerallyhave4-10layersofcopperToestablishelectricalconnectionbetweenthedifferentcomponentsandcopperlayers,vias(smallholeslinedwithmetalplates)aredrilledthroughthethicknessofthePCBTheviasmaycutthroughtheentirethicknessofthePCBorconnectafewlayersonlyInamulti-layerboard,someofthecopperlayersareusedtoprovidegroundandpowersupplyvoltages,whiletheremaininglayersareusedtointerconnecttheICchips,PrintedCircuitBoards,Theareacoverageofthecopperlayerscanvarybetween10%to90%Thethicknessofonelayerofcopperisabout35micronor,asiscommonlyreportedintheindustry,itcontains1ozofcopperpersquarefootComponentsmaybemountedonaPCBusingThough-HoleTechnology(THT),orSurface-MountTechnology(SMT)InTHT,thelegs(pins)ofthecomponentspassthroughholesandaresolderedattheoppositesideofthePCBInSMT,thechipsaresolderedtothePCBandconnectedtotheconductorlayeronthesamesideofthePCB,PrintedCircuitBoards,TheconductivityofpureFR4is0.25W/mKTheconductivityofpurecopperis388W/mKFromthermalmodelingpointofview,aPCBmaybetreatedasahomogeneousmaterialwithnon-isotropic(direction-dependent)conductivityThePCBmodelmustbedefinedbyin-planeconductivityandnormal-to-planeconductivityThein-planeconductivityismuchlargerthanthenormal-to-planeconductivityThein-planeconductivityincreaseswiththenumberofcopperlayersofthePCBThenormalconductivityaPCBisnearlyconstantatabout0.3W/mK,PrintedCircuitBoards,Thein-planeandnormal-to-planeconductivityvaluesmaybecalculatedasfollows:kin-plane=S(kiti)/Sti)knormal=Sti/S(ti/ki)ki=fi*kcuorki=kFR4where,fi=fractionalcoverageofcopperk=conductivityofalayer(W/mK)t=thicknessofalayer(m)Whenhigheraccuracyisdesired,aPCBmaybemodeledusingmultipleplates:AconductingthickplatefortheFR4,andseveralconductingthinplatesforthecopperlayers,PrintedCircuitBoards,ExampleNumberofculayers=8Thicknessof1layerofcopper=1oz=3.5e-5mThicknessof1layerofFR4=1.453e-4mConductivityofcopper=388W/mKConductivityofFR4=0.25W/mKIn-planeconductivity:Kp=(8*388*3.5e-5)+(0.25*2.8e-4)/1.588e-3=68.6W/mKNormalconductivity:Kn=1.588e-3/(8*3.5e-5/388)+(9*1.453e-4/0.25)=0.303W/mK,PrintedCircuitBoards,PCBModeling,APCBmaybemodeledusingoneoftwoways:DetailedmodelCompactmodelTheDetailedPCBModelincludes:AnFR4plateorblock,andCopperlayersmodeledasconductingthinplatesTheCompactPCBModelincludes:ANon-isotropicplateIn-planeconductivityismuchhigherthanthenormalconductivityThecopperlayersarenotmodeledseparately,PCBModeling,CompactPCBModel,DetailedPCBModel,K(in-plane)=27W/mKK(normal)=0.34W/mK,FR4(K=0.3W/mK),Copperlayers,Non-Isotropicmaterial,PCBModeling,IcepakmenuforPCBcreation,ICPackages,ICPackages,ICPackages,ICPackages,AnICpackageisthehousingthatprotectsthechipfrom:EnvironmentalstresssuchashumidityandpollutionMechanicalstresssuchascrackingandoverheatingElectricaldischargeduringhandlingTheICpackagemustalsoprovide:InterfacefortestingElectricalinterconnectiontothenextlevelofpackagingAnICpackagemustsatisfytheaboverequirementswhilemeetingotherobjectssuchascost,qualityandreliabilityItisthefirstlevelofelectronicpackagingThesecondlevelbeingPackage-PCBassemblyAndthethirdlevelisPCBassemblytotheBackplane,LevelsofPackaging,System-levelAssembly,BackplaneAssembly,ICPackage,PCBAssembly,Chips,ICPackages,Packagesmaybeclassified(bymountingmethod)as:Through-holetype(THT)Surfacemounttype(SMT)SpecialpackagesTHTpackageshavepinsthatareinsertedintoholesdrilledacrossthethicknessofthePCBTheyareusedinpackagewhereboardspaceisnotpremiumExamplesareDIP,PGA,etc.SMTpackageshaveflatstructurewiththeleadpinssoldereddirectlyintotheconductorpatternonthesurfaceofthePCBTheyareusedinhighpindensitypackagesExamplesareQFP,QFJ,etc.,THTPackageExamples,ZIP(ZigzagIn-linePackage),DIP(DualIn-linePackage),SMTPackageExamples,QFP(QuadFlatPackage),SSOP(ShrinkSmallOutlinePackage),ICPackages,ICPackages,Specialpacka