Icepak高級培訓教材

AdvancedThermalModelingAdvancedIcepak高級建模Fluent.incCourseOutline1.Introduction簡介2.PrintedCircuitBoards(PCB板)3.ICPackages(IC封裝)4.HeatSinks散熱器5.InterfaceResistance接觸熱阻6.Fans,ImpellersandBlowers風扇，葉輪，離心風機7.AltitudeEffects高度的影響8.FlowResistances氣流阻尼9.Radiation幅射10.HeatPipes熱管11.JouleHeating電阻發(fā)熱12.ThermoelectricCoolers熱電冷卻CourseOutline13.ColdPlates冷板14.Transformers變壓器15.FlowBaffles氣流擋板16.WallEffects壁的效果17.ExternalCoolers/Heaters外部冷卻器/加熱器Exercises:

練習：1.PBGAModelPBGA模型2.SelectingaHeatSink選擇散熱器3.ModelingTEC

熱電冷卻器模型4.SelectingaBaffle選擇擋板5.ModelingExternalCoolers外部冷卻器建模IntroductionIntroduction簡介TheCaseforThermalManagementTheheatgeneratedinanelectroniccircuitisinverselyproportionaltotheefficiencyofthecircuit電子線路板產(chǎn)生的熱與它的效率成反比Thepowerthatisnotconvertedtoperformusefulelectromagneticworkislostintheformofheattothesurroundings沒有轉(zhuǎn)換成電磁功率的熱耗散到了周圍的環(huán)境Thepowerwastedasheatincludes:熱耗包括Jouleheating(I2R)loss電阻損失Powersupply電能提供Thereliabilityofasemiconductordeviceisdirectlyaffectedbyitsoperatingtemperature

工作環(huán)境的溫度直接影響到半導體設備的可靠性TheCaseforThermalManagementVirtuallyallelectronicfailuremechanismsareenhancedbytheincreaseinpackagetemperature:

實際上，所有電子失效的機理都是由于封裝溫度升高引起的StressesduetoTCE(=TotalCompositeError總綜合誤差）mismatch不匹配Corrosion腐蝕Electro-migration電子移動Oxidebreakdown氧化物崩潰Currentleakage(whichdoubleswithevery10cinactivedevices)電流泄漏Degradationinelectricalperformance(duetochangeindeviceparameters)電性能下降TheCaseforThermalManagementTherateoffailureofelectronicpackagesisdirectlyproportionaltoheatandincreasesexponentiallywiththemaximumtemperatureofthepackage

電子封裝失效的比例直接與熱成正比，而且與封裝的最高溫度成指數(shù)增長Therateoffailurecanbeexpressedas:

失效的比例可描述為：

F=Ae-E/KTwhere,F=failurerate,失效率

A=constant常數(shù)E=activationenergyinelectronvolts(eV)激活的電能K=Boltzmann’sconstant(8.63e-5eV/K),andT=junctiontemperatureinKTheCaseforThermalManagementTheCaseforThermalManagementTheEffectofPackageTemperatureonFailure(Numberoffailuresafter1000hrofoperationpermillionunits)

每百萬個元件工作1000hr失效的數(shù)目TheCaseforThermalManagementMajorCausesofElectronicFailure電子失效的主要原因Source:U.S.AirforceAvionicsIntegrityProgram(Reynell,M.,1990)ICPackageTrendsPackagesaregettingthinner封裝變薄Numberofleadsisgettinglargerleads數(shù)目增多Packagefootprintdecreasingtoapproachchipsize為滿足chip的尺寸，封裝的footprint降低Packagepinpitchisdecreasing封裝的pinpitch減少Clockspeedisincreasing時鐘速度提高ICchipsareperformingmorecomplextasks

ICchips功能更復雜Movingtowardssystem-on-chiptechnologyPackagesaredissipatingmorepower

功耗增加Operatingjunctiontemperatureremainsfixed工作的溫度保持不變55Cforcommodityandhandhelddevices生活用品55C125Cforautomotivesystems汽車系統(tǒng)125CBudgetperwattofheatremovalisdecreasing每watt的預算減少PackagingTrendsPackagePowerProjectionTrends(Watts)封裝功耗的發(fā)展趨勢Commodity:Lowcost(<$300)consumerproductsHand-Held:Batterypowered(<$1000)productssuchascellular,etc.Cost/Performance:Maximumperformancewithcostlimit(<$300)(Notebooks,etc.)HighPerformance:Performanceistheprimarydriver(Servers,Avionics,etc.)HarshEnvironment:Automotive,Military,etc.CoolingMethodsTypesofcoolingmethods:散熱方法種類：Naturalconvectionaircooling自然對流Forcedaircooling強迫對流Immersionliquidcooling浸潤冷卻Boiling蒸發(fā)冷卻Heatpipes熱管Coldplates冷板Thermoelectriccoolers熱電冷卻Microchannelcooling微通道冷卻Microjet微噴射冷卻Naturalconvectionaircoolingisusedforlowpowerapplications自然對流散熱主要用于低功耗ItisthesimplestandcheapestcoolingmethodavailableCoolingMethodsForcedaircooling（強迫對流）isusedforrelativelylargeloadsofheat主要用于相對大的熱耗Itrequiresafan,blower,etc.tomovetheairImmersioncoolingisusedtoremovelargeloadsofheatbyimmersingthecomponentsinsideinertdielectricfluidsuchasfluorocarbonorFreon浸潤主要用于大熱耗，通過將元件浸潤到惰性非導熱流體中，如碳氟化合物或氟利昂Typicalapplicationsincludemainframecomputers,supercomputers,high-powertransmitters,etc.Boilingheattransfer

（蒸發(fā)換熱）istheabsorptionofheatbyaboilingfluidandisusedforhighpowerapplicationsAcoldplate（冷板）

isablockofmetal,liquid-cooledbyforcedconvection,onwhichcircuitcardsorcomponentsaremountedTheyareusedinmilitaryandhigh-powerelectronicapplications

主要是軍用和高功耗電子設備CoolingMethodsMicrochannelCooling（微通道冷卻）

isatechnologydealingwithverysmallfinsthatareplacedextremelyclosetotheheatdissipatingelementthecoolantcanbeliquidorgasThermoelctriccoolers（熱電冷卻）

aresolidstateheatpumpsthatdonothaveanymovingpartsnoranyworkingfluidTheymoveheatfromonelocationtoanotherthroughthePeltiereffectHeatpipes

（熱管）aredevicesthatprovideapassivemethodoftransferringheatfromoneareatoanotherHeatisabsorbedatoneendthroughevaporationandisrejectedbycondensationattheoppositeendCoolingRoadmapNaturalConvectionModerateForcedAirAdvancedForcedAirLiquidCoolingCoolingRoadmapAirNaturalConvection+RadiationForcedAirConvectionImmersionNaturalConvectionFluorocarbonsImmersion-BoilingFlorocarbonsWaterForcedConvectionModesofHeatTransferThreemodelsofheattransfer:三種傳熱方式：Conduction傳導Convection對流Radiation幅射Conductionisaprocessinwhichheatflowsbetweentwomedia(solid,liquidorgas)thatareindirectcontactwithoneanother

傳導是發(fā)生在兩種直接接觸的介質(zhì)（固體，液體，氣體）Inconduction,energyistransferredthrough:

傳導過程中，能量通過以下方式傳遞Movementoffreeelectron自由電子運動latticevibration點陣振動Convectionisthetransferofthermalenergybetweenasurfaceandamovingfluidhavingsometemperaturedifference對流發(fā)生在有溫差的表面和運動流體間的傳熱ModesofHeatTransferConvectioncanbe:對流有如下兩種方式：Free(natural)convectionForcedconvectionRadiationisthetransferofheatbetweentwosurfacesthathavenodirectcontact:幅射發(fā)生在兩種沒有直接接觸的表面Energyisemittedthroughelectromagneticwaves

能量通過電磁波傳遞Allobjectattemperaturesabove0Kemitthermalradiation

所有物體大于0K均發(fā)生熱幅射Mostofthethermalradiationtakesplaceintheinfrared(紅外）wavelength(0.1to100micron)幾乎所有熱幅射發(fā)生在紅外波長范圍Therateofenergytransferdependsonsurfaceconditionsandtheviewbetweentheparticipatingbodies

能量傳遞率與表面條件及相關物體間的視角有關ConductionFourier’sLawofConduction:(1Dconduction)1D傳導Q=-k.A.DT/DXor,Q=DT/RA,T1A,T2DXConductionWhere,Q=heattransferT=temperatureA=cross-sectionalareak=thermalconductivityoftheslabDX=slabthicknessR=DX/(kA)=ConductionresistanceTheslabisassumedtoconductinonedirectionFourier’sLawofConduction:(1Dconduction)Conductionk1k2k3L1L2L3T1T2Q=(T2-T1)/RR=R1+R2+R3R1=L1/(A.k1)R2=L2/(A.k2)R3=L3/(A.k3)AAFourier’sLawofConduction:(1Dconduction)ConductionFourier’sLawofConduction:(1Dconduction)A1A2A3T1T2Q=(T2-T1)/R1/R=1/R1+1/R2+1/R3R1=L/(A1.k1)R2=L/(A2.k2)R3=L/(A3.k3)Lk1k2k3ConvectionConvectionmaybefreeorforced.對流可以是自然和強迫Infreeconvectiontheflowisinducedbydensitydifferencescausedbytemperaturevariationswithinthefluid.自然對流是由于溫度變化引起的流體內(nèi)部密度不同產(chǎn)生的Inforcedconvectiontheflowisgeneratedbyexternalmeanssuchasfan,blower,pump,wind,etc.強迫對流則是由于外部方式造成的氣流Flowsmayalsobeclassifiedasinternalflowsandexternalflows.氣流也可以分為內(nèi)流和外流Aninternalflowisflowthroughconfineddomainsuchasductsorchannels.內(nèi)流是發(fā)生在一定的空間內(nèi)，如管道等Anexternalflowisflowoversurfaceswhichcanbefullyorpartiallyunconfined.外流是全部或部分不在空間內(nèi)的氣流ConvectionFlowsmayalsobeclassifiedas氣流可以被分為：laminar,or層流或Turbulent湍流Alaminarflowisahighlyorderedflowwherefluidparticlesmovealongidentifiablepaths層流是很規(guī)則的氣流，氣流的流線軌跡比較一致Inturbulentflowsfluidmotionishighlyirregularandischaracterizedbyrandom,three-dimensionalmotion

湍流很不規(guī)則，比較任意，三維運動Itinvolvesstrongmixingandmorevigorousheattransferflowisinherentlytime-dependentMostreallifeflowsareturbulentflows大多數(shù)流動是湍流Flowsverynearsurfaces(ofobjects)areusuallylaminarflows離開物體表面很近氣流通常是層流ThisregioniswellwithintheboundarylayerItiscalledthelaminarsub-layerConvectionExternalFlow外流InternalFlow內(nèi)流ConvectionLaminarFlow層流TurbulentFlow湍流Convection:Newton’sLawofCoolingFlow(atTemperature=Tf)A,h,TwQ=h.A.(Tw-Tf)=DT/Rwhere,Q=totalheatflowfromthepatchtotheair小塊到空氣的全部熱量h=averageheattransfercoefficient平均傳熱系數(shù)A=areaofthepatch小塊的面積Tw=averagetemperatureofthepatch小塊的平均溫度Tf=averagefluidtemperaturenearthepatch小塊附近氣流的平均溫度R=thermalresistance=1/(hA)熱阻Convection:TypicalhvaluesRepresentativehandRvalues典型的h和R值Convection:FactorsAffectinghTheheattransfercoefficient,h,dependsonmanyfactors:傳熱系數(shù)取決于很多因素Turbulentflowshavelargerheattransfercoefficientthanlaminarflows湍流比層流

h值大Ingeneral,forcedconvectionflowshavehigherheattransfercoefficientthannaturalconvectionflows強迫對流比自然對流h值大Liquidflowshavelargerheattransfercoefficientthangasflows液體比氣體h值大Roughsurfaceshavelargerheattransfercoefficientthansmoothsurfaces(duetoflowturbulence)粗糙表面比光滑表面h值大Entry(undeveloped)flowshavelargerheattransfercoefficientthanfullydevelopedflows未展開氣流比完全展開氣流h值大Unsteadyflowstendtohavehigherheattransfercoefficientthansteadyones非穩(wěn)態(tài)比穩(wěn)態(tài)h值大PrintedCircuitBoardsPCBsPrintedCircuitBoardsComponent-side(top)viewSource:PixeldirectPrintedCircuitBoardsSolder-side(bottom)viewSource:PixeldirectPrintedCircuitBoardsAprintedcircuitboard(PCB)isgenerallyamulti-layeredboardmadeofadielectricmaterial(glass-reinforcedpolymerorFR4)andseverallayersofcopperplanesPCB是由FR4和幾層銅板構(gòu)成ItservestowiremountedICchipsthatwouldotherwiseneedthousandsofpoint-to-pointwireconnectionsAsingle-layerboardhascomponentsmountedononesideandcopper(conductor)patternontheother一層板的元件安裝在一邊，銅線（導熱器）在另一邊Thecopperpatternisestablishedbyphoto-etchingacopperfoilpastedoverFR4Adouble-layerboardhascopper(conductor)patternaswellascomponentsonbothsides兩層板有銅，兩邊都有元件Amulti-layerboardismadeofseveraldouble-sidedboardswithinsulatinglayersinbetween

多層板由幾個兩層板組成，在層與層之間有絕緣層PrintedCircuitBoardsHeatandpressureisappliedtolaminatethelayersintoarigidstructurecalledthePCB加熱和加壓而制成一種堅硬的結(jié)構(gòu)叫PCBMulti-layerPCBsgenerallyhave4-10layersofcopper多層PCBs通常有4-10層銅線Toestablishelectricalconnectionbetweenthedifferentcomponentsandthecopperlayers,vias(smallholeslinedwithmetalplates)aredrilledthroughthethicknessofthePCB

為了使不同元件和銅線層建立連接，通過在PCB厚度上打孔（vias）TheviasmaycutthroughtheentirethicknessofthePCBorconnectafewlayersonly

Vias可能穿透整個板或只連接幾層Inamulti-layerboard,someofthecopperlayersareusedtoprovidegroundandpowersupplyvoltages,whiletheremaininglayersareusedtointerconnecttheICchips

多層板中，有些銅線層會用來提供基礎和電流電壓，而其它的層用來提供ICchips間的連接PrintedCircuitBoardsLaminatesinamulti-layerPCBPrintedCircuitBoardsTheareacoverageofthecopperlayerscanvarybetween10%to90%銅線層的含量通常在10%到90%Thethicknessofonelayerofcopperisabout35micronor,asiscommonlyreportedintheindustry,itcontains1ozofcopperpersquarefoot一層銅的厚度約在35微米或每平方英尺含1oz的銅ComponentsmaybemountedonaPCBusing元件可以通過以下方式安裝到PCB上Though-HoleTechnology(THT),or穿孔型Surface-MountTechnology(SMT)表面安裝型InTHT,thelegs(pins)ofthecomponentspassthroughholesandaresolderedattheoppositesideofthePCBTHT方法，pins通過孔到PCB另一面焊接InSMT,thechipsaresolderedtothePCBandconnectedtotheconductorlayeronthesamesideofthePCBSMT方法，chips被焊接到PCB同一側(cè)PrintedCircuitBoardsTheconductivityofpureFR4is0.25W/mK純FR4的導熱率為0.25Theconductivityofpurecopperis388W/mK銅的導熱率為388Fromthermalmodelingpointofview,aPCBbetreatedasahomogeneousmaterialwithnon-isotropic(direction-dependent)conductivity從熱模型的角度來看，PCB應作為一種非正交導熱率的材料ThePCBmodelmaywillcontainin-planeandnormal-to-planeconductivityvaluesPCB應有面內(nèi)和法向?qū)嶂礣hein-planeconductivityismuchlargerthanthenormal-to-planeconductivity面內(nèi)值要比法向大得多Thein-planeconductivityincreaseswiththenumberofcopperlayersofthePCB面內(nèi)導熱率隨著銅線層的增加而增加ThenormalconductivityaPCBisnearlyconstantatabout0.3W/mK法向?qū)崧释ǔＴ?.3PrintedCircuitBoardsThein-planeandnormal-to-planeconductivityvaluesmaybecalculatedasfollows:

面內(nèi)導熱率可采用下面公式計算： kin-plane=S(kiti)/(Sti) knormal=Sti/S(ti/ki) ki=fi*kcu

where, fi=fractionalcoverageofcopper k=conductivityofalayer(W/mK) t=thicknessofalayer(m)Whenhigheraccuracyisdesired,aPCBmaybemodeledusingmultipleplates:如果還希望得到更準確的數(shù)值，PCB應采用多層板來建模AconductingthickplatefortheFR4,andseveralconductingthinplatesforthecopperlayersPrintedCircuitBoardsExample例如：Numberofculayers=8Thicknessof1layerofcopper=1oz=3.5e-5mThicknessof1layerofFR4=1.453e-4mConductivityofcopper=388W/mKConductivityofFR4=0.25W/mKIn-planeconductivity: Kp=((8*388*3.5e-5)+(9*0.25*1.453e-4))/1.588e-3 =68.6W/mKNormalconductivity: Kn=1.588e-3/((8*3.5e-5/388)+(9*1.453e-4/0.25)) =0.303W/mKPrintedCircuitBoardsPCBModelingAPCBmaybemodeledusingoneoftwoways:PCB可以采用如下的兩種方法建模：DetailedmodelCompactmodelTheDetailedPCBModelincludes:詳細PCB包括：AnFR4plateorblock,andCopperlayersmodeledasconductingthinplatesTheCompactPCBModelincludes:簡化PCB模型包括：ANon-isotropicplateIn-planeconductivityismuchhigherthanthenormalconductivityThecopperlayersarenotmodeledseparatelyPCBModelingIcepakmenuforPCBcreationPCBModelingCompactPCBModelDetailedPCBModelK(in-plane)=27W/mKK(normal)=0.34W/mKFR4(K=0.3W/mK)CopperlayersNon-IsotropicmaterialICPackagesICPackagesIC封裝ICPackagesICPackagesAnICpackageisthehousingthatprotectsthechipfrom:

IC封裝是為了保護的空間Environmentalstresssuchashumidityandpollution環(huán)境壓力如濕度，污染Mechanicalstresssuchascrackingandoverheating機械壓力如破裂，過熱Electricaldischargeduringhandling操作過程中的放電TheICpackagemustalsoprovide:IC封裝必須提供：Interfacefortesting用于測試的接觸面Electricalinterconnectiontothenextlevelofpackaging與PCB連接的電子連接面AnICpackagemustsatisfytheaboverequirementswhilemeetingotherobjectssuchascost,qualityandreliabilityIC封裝還應滿足其它要求如成本，質(zhì)量和可靠性Itisthefirstlevelofelectronicpackaging它是電子封裝的第一級ThesecondlevelbeingPackage-PCBassembly第二級是封裝-PCB裝配ThethirdlevelisPCBassemblytotheBackplane第三級是PCB與底板裝配LevelsofPackagingSystem-levelAssemblyBackplaneAssemblyICPackagePCBAssemblyChipsICPackagesPackagesmaybeclassified(bymountingmethod)as:

封裝可以分為（按安裝方法）：Through-holetype(THT)穿孔型Surfacemounttype(SMT)表面安裝型Specialpackages特殊類型THTpackageshavepinsthatareinsertedintoholesdrilledacrossthethicknessofthePCBTHT封裝的pins穿過PCB上的孔TheyareusedinpackagewhereboardspaceisnotpremiumExamplesareDIP,PGA,etc.SMTpackageshaveflatstructurewiththeleadpinssoldereddirectlyintotheconductorpatternonthesurfaceofthePCBSMT封裝的pins直接焊接在PCB的表面TheyareusedinhighpindensitypackagesExamplesareQFP,QFJ,etc.THTPackageExamplesZIP(ZigzagIn-linePackage)DIP(DualIn-linePackage)SMTPackageExamplesQFP(QuadFlatPackage)SSOP(ShrinkSmallOutlinePackage)ICPackagesICPackagesSpecialpackagesarepackagessuchas:

特殊類型封裝如：Chip-on-board(COP)packageswherethechipismountedandsealedonthePCBCOP封裝被安裝并密封在PCB上TapeCarrierPackages(TCP)帶載封裝Memorymodules記憶模塊Powerdissipationperchipisafunctionof:

每種芯片耗散功率是下列參數(shù)的函數(shù)：Frequency,f頻率Capacitance,C電容Voltage,V電壓Gatecount(I/Ocount)門數(shù)Morespecifically:即：

Power=F(f,C,V2,Gatecount)ICPackagesLogic(ASIC)chipshavemoregates(andhenceproducemorepower)thanmemorychips

邏輯芯片比記憶芯片有更多的門Thus,fromcoolingperspective,logicchipsaremoredifficulttocoolthanmemorychips

因此，從散熱的觀點來看，邏輯芯片比記憶芯片要難ExamplesofICPackagesPlasticBallGridArray(PBGA)LowConductingtop(~1W/m/K)頂部的導熱率低(~1

W/m/K)PCBtypeMaterialSubstratePCB材料型底部Smalldie(1/3ofpackagesize)小尺寸dieInterconnectisatthedietop,andsoisthepowerdie頂部與熱源內(nèi)部相連ExamplesofICPackagesTapeBallGridArray(TBGA)HighConductingTop(copper)頂部的導熱率高TapeSubstrate(thinnerthanPBGA)Substrate比PBGA薄Dieis1/3ofPackageInterconnectisatthediebottom,andsoisthepowerExamplesofICPackagesFinePitchBallGridArray(FPBGA)LowConductingtop(~1W/m/K)頂部的導熱率低(~1W/m/K)PCBtypeMaterialSubstrateChipScalePackage(CSP)(dieisabout70%ofpackagesize)Interconnectisatthedietop,andsoisthepowerModelisexactlythesameasPBGA模型與PBGA相似ExamplesofICPackagesFlipChipCeramicBallGridArray(Flipchip-CBGA)Exposeddie,optionalheatspreader,NowireBonds

外露的die,可選的散熱板，無線CeramicSubstrate(K~15W/m/K)陶瓷SubstrateInterconnectatdiebottom;Interconnectjunctionsisattachedtosolderbumps,whichinturnconnectssignaltracesModelisexactlythesameasPBGA模型與PBGA相似ExamplesofICPackagesPlasticQuadFlatPack(PQFP)LowConductingovermolding(~1W/m/K)頂部的導熱率低Dieisabout1/3ofpackage;NosubstrateInterconnectisatthedietop,andsoisthepowerConnectsperipherallytoPCBcircuitryviagoldwireleadsExamplesofICPackagesABGA(AdvancedBGA)PackagewithCeramicSubstrate(CBGA)ConductionPathsTypesofPackageModelsDetailedModels詳細的模型Detailsofthepackageareincludedinthemodel,suchassolderballs,leads,die,encapsulation,substrate,etc.UsedforPackageLevelModelingandmeasurementvalidationCompact(Semi-Detailed)Models簡化的模型(半詳細)ThemaincomponentsaremodeledusingThickorThinconductingplates,componentssuchasthedie,solderballs,substrate,etc.ThismodelisusedtoreducethemeshcountThereissomedropinaccuracyasaresultGoodforBoardandSub-systemLevelModelingTypesofPackageModelsNetwork(Resistance)Models網(wǎng)絡模型

PackagemodeledusingresistancenetworkThenetworkcanbetwo-resistornetwork,Starnetwork,Shuntnetwork,etc.TheusermustsupplytheresistanceValuesforthenetworkTheresistancevaluesmaybeobtainedfrommanufacturers,experiments,ordetailedpackagemodelsDetailedPackageModelMoldSolderBallsDieSubstrateWireBondCuTraceDiePadSemi-DetailedPackageModelContactResistanceDiePadMoldSolderBallsDetailedModelSemi-detailedModelNetworkPackageModelTwo-ResistorNetworkModelSix-Resistor(Star)NetworkModel393922Rjc=3Rjb=9Rjc=3Rjb=9Rjs=2DefinitionofPackageResistances

qjc=(Tdie–Tcase)/QcaseTdie=dietemperatureTcase=casetemperatureQcase=heatdissipatedthroughthecase

qjb

=(Tdie–Tbot)/QboardTbot=temperatureofpackagebottomQboard=heatdissipatedfromthepackagebottomtotheboardqja

=(Tdie–Tamb)/QcaseTamb=ambienttemperatureQdie=totalheatdissipatedfromthepackageFactorsAffectingChipResistancesqjadependson:與下列因素有關：DiepowerDie功耗Chipsize芯片大小Natureofconductionpaths(leadframes,etc.)傳導途徑Airvelocity氣流速度PCBtypeandpopulationPCB類型和數(shù)量qjadecreasesas:隨下列因素而降低chipsizeincreases芯片尺寸增大Airvelocityincreases氣流速度增加conductionpathsimprove傳導途徑改善Theresistancesmeasuredforasinglepackageonaboardareusuallylowerthanthoseobtainedonapopulatedboard,andmayonlyserveasalowerbound板上單個封裝測量的阻尼比很多封裝在板上測量的結(jié)果要低FactorsAffectingChipResistancesTypicalValuesof

qja

Source:NECPackagesTypicalValuesof

qja

Source:NECPackagesTypicalValuesof

qjaTheeffectofboardconfigurationonqja

Source:MotorolaDetailedvsNetworkModelsTcase~73-88CTcase~80CDetailedModelNetworkModelRjc=20Rjb=40Airvelocity=1m/s(Rja=44)(Rja=40)Exercise1:PBGAModelExercise1:練習1：PBGA模型Exercise1:PBGADetailedModel1.CreateaCabinet生成一個cabinetUnderModel/Cabinet,createacabinetwiththefollowingspecifications:(Alldimensionsinm)XS=-0.0375 XE=0.0375YS=-0.02 YE=0.0075ZS=-0.0375 ZE=0.0375Exercise1:PBGADetailedModel2.CreateanInletOpening生成一個入口UnderModel/Openings,createaninletopeningwiththefollowingdimensionsandvelocityspecification:Plane: X-YXS=-0.0375 XE=0.0375YS=-0.02 YE=0.0075ZS=-0.0375Zvelocity=0.3m/sInletOpeningExercise1:PBGADetailedModelOutletOpening3.CreateanOutletOpening生成一個出口UnderModel/Openings,createanoutletopeningwiththefollowingdimensions:XS=-0.0375 XE=0.0375YS=-0.02 YE=0.0075ZS=0.0375 Exercise1:PBGADetailedModel4.PCBMaterial材料UnderModel/Materials/Solid,createaPCBmaterialwiththefollowingspecifications:name: pcb-materialSub-type:otherConductivity:1.0W/m-KToggleonOrthotropic,

andassign:X=25W/m-K Y=0.3W/m-KZ=25W/m-KExercise1:PBGADetailedModel5.CreateaPlate生成一塊板UnderModel/Plates,createaplateusingthefollowingspecifications:(Alldimensionsinm)

Name: pcbPlane: X-ZXS=-0.0375 XE=0.0375YS=-0.009 ZS=-0.0375 ZE=0.0375Thermalmodel: ConductingthickThickness=0.0015mSolidmaterial: pcb-materialPlatecreationmenuExercise1:PBGADetailedModel6.CreateadetailedPBGA生成一個詳細的PBGAUnderModel/Macros/Packages,createaPBGApackage:Takeallthedefaultspecificationsasshowninthenextfourfigureswithoneexception:ChangethemodeltypefromCompacttoDetailed,thatis,underDimensions: Modeltype:Detailed(Seefiguresinthenextfourpages)Exercise1:PBGADetailedModelPBGAPackagecreationmenu:DimensionsExercise1:PBGADetailedModelPBGAPackagecreationmenu:SubstrateExercise1:PBGADetailedModelPBGAPackagecreationmenu:SolderBallsExercise1:PBGADetailedModelPBGAPackagecreationmenu:Die&MoldExercise1:PBGADetailedModel7.SpecifyMeshControls生成網(wǎng)格GotoModel/Meshandspecifythefollowingmeshcontrols:MaxX=0.007MaxY=0.003MaxZ=0.007Minelementsinfluidgap=2Minelementsonsolidedge=1MaxO-gridheight=3Exercise1:PBGADetailedModel8.GetaSolution求解1.GotoSolution/SolveandclickAccept2.Waituntilsolutionisfinished3.GotoPostandclickObjectfaceandselect:-Objecttype:group-Objectname:pbga.1

4.ToggleonContours5.ClickCreateExercise1:PBGANetworkModel9.CreateaPBGANetworkModel生成一個PBGA網(wǎng)絡模型1.MakeacopyofthePBGAdetailedmodelandnameitpbga-network2.GotoFile/Openandloadthenewmodel3.UnderModel/Groups,highlightthenamepbga.1andclickDeleteall;thisdeletesallthecomponentsofthedetailedPBGAmodelExercise1:PBGANetworkModel10.CreateaPBGANetworkBlock生成PBGA塊2.UnderModel/block,createaNetworkblockwiththefollowingspecifications:(Dimensionsinm)XS=-0.0075 XE=0.0075YS=-0.0075 YE=-0.0059ZS=-0.0075 ZE=0.0075Rjc=12C/W Rjb=25C/WJunctionpower=1WExercise1:PBGANetworkModel11.SpecifyMeshControls定義網(wǎng)格GotoModel/Meshandspecifythefollowingmeshcontrols:MaxX=0.007MaxY=0.003MaxZ=0.007Minelementsinfluidgap=2Minelementsonsolidedge=1MaxO-gridheight=3Maxinitheight=0.001Exercise1:PBGANetworkModel12.GetaSolution求解1.GotoSolution/SolveandclickAccept2.Waituntilsolutionisfinished3.GotoPostandclickObjectfaceandselect:-Objecttype:block-Objectname:Network-PBGA

4.ToggleonContours5.ClickCreateHeatSinksHeatSinks散熱器HeatSinksHeatSinksHeatsinksareusedtoenhanceheattransferfromacomponentbyextendingthesurfaceareaofheattransfer散熱器通過擴大散熱面積提高傳熱效果Newton’slawofcooling: Q=h.A.(Tw-Tf)Where,Q=totalheattransferfromthecomponentA=surfaceareaofthecomponentTw=surfacetemperatureofthecomponentTf=surroundingfluidtemperatureh=heattransfercoefficientTheaboveequationstatesthat,foragivenQ,handTf,thelargerthesurfacearea(A),thesmallerthesurfacetemperature(Tw)willbe上述公式說明，對于一個給定的Q，h和Tf,表面積越大，表面溫度越低HeatSinksThemostcommontypeofheatsinkisthefinnedheatsink最常用的散熱器是翅片散熱器Finsareformedbyextrusion,molding,machining,orAttachedbythermallyconductivematerialsThemostcommonheatsinkmaterialsusedarealuminumandcopper最常用的散熱器材料為鋁或銅Theyareoflowcost,andEasytomachinematerialsThethermalcoefficientofexpansion(TCE)forthesematerialsishigh這些材料的熱膨脹系數(shù)高Hence,theycannotberigidlyattachedtolowTCEpackagessuchasalumina;Forsuchapplications,wemayuseheatsinksmadeoflowTCE,orbondthemusingthermallyflexibleattachmentmaterials

因此，它們不能堅固地貼在低TCE封裝上；這種情況，我們必須使用低TCE的散熱器，或結(jié)合可變形附著材料使用TypesofHeatSinksTypesofHeatSinksavailable:現(xiàn)有的散熱器種類：Stampings沖壓Extrusions拉伸Bonded/Fabricated粘接Folded折疊Liquid-cooledcoldplates液體冷板Casting

鑄造StampingHeatSinks:沖壓散熱器aremadeofcopperoraluminumsheetmetallowcost,highvolumesolutionforlowpowerapplicationsExtrusionHeatSinks:拉伸散熱器maybeusedforlargewattageloadscanbelongitudinal,cross-cut,orserratedtypesLimitedbyheight-to-gapratioandfinthicknessthatcanbeachievedbymachiningTypesofHeatSinksBonded/FabricatedHeatSinks:粘接散熱器TheyarehighperformanceheatsinksNolimitationonheight-to-gapratioorfinthicknessFolded-FinHeatSinks:折疊-fin散熱器ThincorrugatedsheetmetalbondedorbrazedtobasemetalArelowprofileheatsinksLiquid-CooledColdPlates:液體冷板TubesinblockormilledpassagesUsedforheatloadsof500to30,000W/m2KCastingHeatSinks:鑄造散熱器Sand,lostcoreanddiecastingwith