Lecture 10 - Electronics Cooling Basics――FloEFD的培训

.184Lecture10ElectronicsCoolingBasics•Content•ModellingBoardsandComponents–Simpleandmoredetailed(Overlappingparts)–IDFImport–Thermalvias•EL-Module–PCBgenerator–2Rcompactcomponents–JouleHeating–PeltierElement•ForFlothermUsers:OperationaldifferencesbetweenFTandEFD.185EFDvs.FLOTHERM•Fairlyrectangulargeometries•Unrivaledfastcalculation•Manual&instantaneousmeshing•Semi-automaticormanualtransformationofCAD-Import•SpecificObjectsandparametricSmartParts•NoCADexperiencenecessary•HighproductivitybyattributesandCommandCenter•SpecializedforElectronicsCooling•Manualinputofcurrentonstraighttraces(only)•General(curved)geometries•3-5timelongerCPUtimesandmemoryconsumption•Automaticmeshingbyalgorithm•DirectCADimport•-•ConstructionviaandlikeCAD•-•GeneralFluidDynamicswithmorephysicalmodelling•3DelectricalsimulationwithJouleHeating.186FORFLOTHERMUSERSONLYOperationalDifferencesBetweenEFDandFLOTHERM•Objectsarenotkeypointed•Remeshingafterachangeofthemeshconnectivityisnecessaryevenifgeometryhasnotchanged,bute.g.materialassignmentschanged•Geometricalcopydoesnotcopyphysicalproperties•Overlappingofsolidsbyorderofmaterialandnotbyhierarchyofparts•Preprocessingnotpossiblewhilesolving•1sttimeopeningofwizardcantakehoursforveryextensivegeometries•Nomultiprocessingfacilities•Renamingofpartsbysaveasandreplace•EFDhasbetter2Dsources•Changingofapowervaluegivesareactionintemperaturemuchslowlier•2-resistormodelsneed2brickswithcorrectarea.187ThermalModelRequired•Inprinciple,anyCADdrawingcanbeusedforelectronicscoolingcalculations,however–amechanicaldrawingcontainstoomuchdetails–isusuallynotathermalmodel!–Simplificationsandenhancements/replacementsarenecessary–Removescrews,legs,pins,sealings,etc.–Closeholes–Replacefanbladegeometriesandextendedperforations–Createphysicalcomponentandboardmodels.188BoardModelling•Don‘tusejustEpoxy(k=0.2W/mK)•Level0:k=10W/mK•Level1:Orthotropicconductivity•Level2:Moredetailedwithindividuallayers•Level4:Allcircuits(traces).NotpossibleNormalConductivity(W/mK)NiiikdDk1nDdkkNiii1p.189IDFImport•IDFisaalmoststandardizedASCIIformattodecribeboardoutlinesandcomponents.–*brd,*bdf/*emn,*emp/*.bdf,*.ldf/other–Therearedialectsspoken–Specificationavailableondemand•FLOTHERMisreading–justtheboundigboxesveryquick–Sizeandnamefilteringpossible•EFD.labisreading–alldetailsveryslow.–nofiltering•IDFComponentsarejust“images”.190IDFRepair•Deleteunnecessarysmallcomponents–Smearouttheirtotalpowerontothewholeboard•Deletingoflegsandunnecessarydetails(holes)–later•Eventuallyreplacebricksbyacomponentmodel–2R–detailed.191PCBGenerator(ELModule)•Anyplatecanbedefinedasaboardbymanualinputofk•ExtensionbythePCBGenerator–Allowstoobtainthebi-axialthermalconductivityvalues,withthenormal(throughplane)andin-planethermalconductivitiesautomaticallyderivedfromthePCBstructureandthepropertiesofthespecifiedconductoranddielectricmaterials.–Theboardcanalsobearbitrarilyorientedwithrespecttotheglobalcoordinatesystem,–i.e.angledPCB’scanbemodelled..193ThermalVias•ViasaremodelledusingonesolidvolumewithaneffectiveconductivitynormaltothePCB•DetailedknowledgeaboutthelayerstackisneededdviadCudpitch2224)2(4pitchCuviaviaCundddd.194PackageModelling•ContentofaCADLibraryusuallyisnotathermalmodel•Transistormodelling–Level0:–Takejustthecopperflagasheatsourceand–deletetheauxiliaryequipment(legs,encaps)–Level1:–Addasilicondieandcopperinsideaplasticblock–Nestingofparts(seeDay3)–Level2:–Constructathermalmodelwithlegs,die,adhesiveetc..195•Other(logic)packages–Level0:brickwithlumpedconductivity–k=5to20W/mK–Indicatorforcasetemperature•Level1:2-ResistorCompactModels–Ifyouliketobelievedatasheets–Caution:theconceptofa2Rmodelisonlyvalidifthereisadominantheatfloweithertowardstheboardortowards„top“(„case“).Infifty-fiftysituationsalwaysbeindoubt..1962R-ComponentCompactModel(ELModule)•Thisisthesimplestpossiblenetworkcompactmodel,andconsistsofadefinedjunction-to-caseresistance(Rjc)andajunction-to-board(Rjb)resistance.•InEFD,thisdataisappliedtothedefinedpackagegeometryconsistingoftwoflatsolidbodiesrepresentingthejunctionandcase.•In-builtlibraryoftwo-resistormodelsofstandardJEDECpackageoutlines..198EFD:EL-ModuleFunctionalityListEnhancementJouleHeatingTwo-ResistorComponentCompactModelPerforatedPlateHeatPipeCompactModelPCBGeneratorEDB:ComponentTwoResistorModelLibraryEDB:PerforatedPlateLibrariesEDB:FanManufacturerLibrariesEDB:ComponentMaterialLibraryEDB:TECManufacturesLibrariesEDB:ElectronicsSolidMaterialLibraryEDB:InterfaceMaterialsEDB=EngineeringDatabase.199EFD:ElectronicsFeatureAccess•FlowAnalysisMenuUpdate•NewToolbarEntries•EngineeringDatabaseUpdate.200PerforatedPlate(ELModule)•Thiscompactmodelobjectcanbeusedtorepresentathinplatewithmultipleholes.Nomeshingoverhead,associatedwithexplicitrepresentationoftheholefeatures.•CanbeaddedasanadditionalconditiontotheopeningwiththeEnvironmentpressureboundaryconditionoraFanalreadyspecified.•TheperforatedplatesaredefinedbytheFreeAreaRatio,andtheshape(canberound,rectangularorregularpolygon)anddimensionsoftheholes.•Pressuredropcoefficientisautomati