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英文文献

南湖学院

毕业设计（论文）

外

文

翻

译

资

料

作者

彭泽诚

届别

2013届

系别

机械与电子工程系

专业

机械设计制造及其自动化

指导老师

刘伟香

职称

副教授

完成时间

2013年5月10日

原文：

RecentAdvanceinCoolingTechniquesforCPU

Abstract:

Withtheimprovementsonofthechipintegrationdensity,providingeffectiveheatremovalsolutionsforCPUisanessentialresearchprojectintheelectronicsindustry.TakingaimattheproblemcausedbyheatgenerationofCPU,thispapermainlydiscussedthecurrentdevelopments,principlesofheattrans2ferandperspectiveapplicationsofthethreenovelmicrocoolingmethods,includingheatpipe,microchannelandcoolchip.Advantagesandshortcomingsofthosemethodsandtherelativecriticalissueswereevalua2ted.Prospectinthechipcoolingareawasalsostated.

Keywords:

chipcoolingtechnique;heatpipe;microchannel;coolchip

Electroniccoolingconcernsthereliabilityandservicelifeofelectronicdevices,istodayabottleneckinthedevelopmentofelectronicindustry.Alongwithhighperformance,miniaturizationandintegrationofelectronicindustrydevelopmenttrendsof,thethermalproblemhasbecomeincreasinglyprominent.EspeciallyintermsofsensitivityhighCPUheatload,heatisaccumulatedatthechipswouldseriouslyaffectitsstabilityandservicelife.Studieshaveshownthatelevatedoperatingtemperature10

forasingleelectroniccomponents,theirreliabilityisreduced50%;55%CPUfailureiscausedbyoverheating.Atpresent,thehighfrequencyofPentium43.2ehadexceeded100wpowerconsumptionofmarkSmith2fieldcorePentiumddual-coreprocessor'spowerconsumptionisclimbingto130w.AccordingtoIntel'sChiefTechnologyOfficerPatRickGelsingerProjections,ifthenumberoftransistorsinachipatthepresentrateofgrowth,until2015,andashotasthesurfaceoftheSun[1],whichofcourseisunthinkable.Therefore,inordertoenabletheCPUtomaximizeperformanceandensureitsreliability,researchonpracticalandefficientchipcoolingmethodsarebecomingincreasinglyimportantandurgentissues.ThisarticleistoreviewtherecentadvancesinCPUheatsinktechnology..

1、CPUcoolingandexistingproblems

Accordingtothetheoryofelectronics,overheatingasaresultofthe"electronictransfer"[2]isadamagedCPUchipsinsidethemainreason."Electronictransfer"referstotheelectronicflowofmetalatomsasaresultofthemigrationphenomenon.Chiponthecurrentveryhighlevelsofmetalwire,amomentumofelectronsflowingtothemetalatom,oncewithametalatomcollisions,makesthemovemetalatomsfromthemetalsurface,resultsleadtoformationonmetalsurfacepit,ormound.Thisisapermanentandirreversibleharmifthischronicprocesscontinue,intheenditwillcausethecoreinternalcircuitforshortcircuitoropencircuitcompletelydamagetheCPU."Electronicmigration"becauseofthemanyfactorsandtemperaturefactorsplayedadecisiverole.Highertemperatureswillmakefree-electronkineticenergyhasgreatlyincreased,themetalatomcollisionsaremorestrongly.Atthesametime,withincreasingtemperature,thermalmotionofatomsofmetalhasincreased,electronictransfer,themoreprone.ThisiswhyCPUtemperatureismaintainedat50°cthefollowingreasons.

Aircoolingmethod.InstallingtheheatsinkontheCPUtoincreasethecoolingarea,andinstalledasmallfanontheheatsink,airforcedconvectionandtaketheheat.Advantageofthiscoolingmethodissimple,practical,andinexpensive.Butthedisadvantage:

①coolingefficiencyislow,canonlydrainCPUwasteheatofupto60%,thereforeonlyrelyonlawofconductionandconvectionaircoolingheatsinkthermalconductivityisclosetoitslimit;②asthepowerandspeedofthefanincreases,alsoincreasesthenoise;③fanismovingpartsmoreeasilydamaged.

Watercoolingmethod.Itissealinggoodsink（usuallymadeofaluminiumoraluminiumalloys）stickerontopofCPUsurface,andthenpassestothewatercirculationsystem,issuedbytheCPUheataway.Higherthermalefficiencythanthecoolingofthisapproach,butitrequiresmorecomplexwatercoolingsystemandinconvenience,installationproblems,andthere'sbeenleakageandcondensationproblems.

Semiconductorcoolingmethod.ItisbasedonthePALstickereffect[3]achieved,oftensemiconductorceramicpackageseries.Itworksinpracticeisathermaltransfer,whenturnontheDCcurrent,coldtemperaturesrapidlydecreaseinsemiconductor,evendownto-10°c,andarapidincreaseintemperatureontheotherside,soastoreducethesurfacetemperature.Advantagesofsemiconductorcoolingisnorefrigerant,longlife,easytoinstallandcanbecontrolledthroughcurrentforhigh-precisiontemperaturecontrol.Italsoexistsdisadvantages:

①refrigerationefficiencyislow;②technologynotmature...Highprices;③easyCPUcondensationduetocoldtemperatureistoolow,resultinginashortcircuit.

Therefore,withtheincreaseofconstantlydecreasingchipsize,CPUfrequencyandtherapidincreaseinheat,needanewCPUheatsinktoreplaceexistingcoolingtechnology.Followingintroduces3newCPUheatsinktechnology:

heat-pipecoolingtechnology,technologyofmicro-channelheatsinksandcoolingchiptechnology.

2、NewCPUcoolingtechnology

2.1Heatpipetechnology

Heatpipeisbasedonphase-changeheattransferenhancementtechnology,itclosedinvacuumtubematerial,repeatedboilingandcondensationtotransferheat.Typicalheatpipefollowedbyevaporation,thermalinsulationandcondensationcanbedividedintothreeparts（seeFigure1[4]）.Mountliquidknownasworkingfluidinapipe,istheheattransfermedium.First,theevaporationofboilingworkingfluidabsorbsheatfromtheoutsideair,andunderthedrivingforceoftheairpressuredifferenceaccesstocondensed,encounterscoolerpipewallwillcondensetoliquidandheat;Then,bysettingthewicktubeattheCenter,whichwiththeworkgeneratedbythesurfacetensionoftheliquidsuctionliquidbacktotheevaporatoragain.Repeatedtheaboveprocess,soastokeeptheevaporatorheattransfertothecondensingsection[6],andthendeliveredthroughtheheatsink.Asthetubeispassedthroughthelatentheatofphasetransformationheat,itsthermalconductivityishigh,orevendozensoftimesmorethandoubleofthesamesizecopperpipe,thereforesuitableforemissionofhighheatinasmallspace,hasbeenappliedinthelaptop.

Cotterfirstproposedtheconceptofmicroheatpipe.Thetextembeddedonthechipofmicroheatpipes,averagepipeline10~500μmindiameter,mmtoseveralcmlong.Thistubedoesnotneedtocapillariesstructures,polygonalshapeofcrosssectionthroughthecavityangleastheliquidrefrigerantreturnchannel,aswellasthroughTsimDistrictaxialcapillarypressuredifferenceoftheliquidrefrigerantfromthecondensingpressurebacktotheevaporator,soastocompletetherefrigerantcycle.BecauseofmicroheatpipecombinesadvantagesofMicroChannelcoolingandenhancedheatinasmallspacewasverypromising.Therehavebeenreports,usingICcablesmadeofmicroheatpipearray,thecoolingpowerofupto200W/cm

InventedbyMaidanikisanotherformofloopheatpipeheatpipe.Asitcaninthecaseofsmalltemperaturedifference,longdistancedeliveryalotofheat,sointermsofaerospacebroaderapplication,alsointheapplicationofcomputersandelectronicdeviceshaveaverybroadprospects.Sincetheexperimentforthefirsttimesince2001,manyhavecomearound50glHPheatsink,heatsinkofheatfluxin25~30w.Peoplealsotestedanewtypeof6mmindiameter•HPheatsink,itsmaximumthermalfluxisabout70w.ButsincelHPmainlydevelopednearly20yearsnewtechnology,theoreticalandappliedaspectsrequirefurtherin-depthstudy.Tosumup,ittubehastheadvantageofitsexcellentthermalconductivityandisothermalandthermalresponsespeed,lightweightandsimplestructure.Moreover,asheatpipeshavenomovingparts,reliable,durable,andcanworkinweightlessness,heatandlongdistanceandwithoutdirectionrestriction.Ofcourse,traditionalheatpipedesignisalsopresentonthecapillary,flying,boiling,Sonicandadhesiveonthelimit,whenthesizeandvariablehours,andphasechangeofsurfacetensiononconsideringthesmallsizeeffect,aswellasusingpolygonchannelstructuredesignedtoreplacethecurrentcommontrianglerunner,istheimportantsubjectofanalysisonheatpipedesign.

2.2Micro-Channelcoolingtechnology·

MicroChannelheatsinkconceptfirstbyTuckermanandthePeacein1981proposed[10,11],whichismadeupofmaterialswithhighthermalconductivity.AccordingtoRiddle,[12]research:

whentheflowmustberectangularchannelmidchannelandoverallheat-transfercoefficientofwaterisinverselyproportionaltothediameter[12].Asthechanneldiameterdecreases,increasedheattransfercoefficients,whilecoolingareaandvolumethanthesystemhassignificantlyincreased.Soalthoughthevolumecontinuouslydecreases,greatlyimprovingheatdissipation.FromFigure3inthecansee,twospecieshassamelengthandheightofmicro-channelsethotManager,dangmicro-pipelinewidthfor10μmShi,CPUtemperaturefor65℃,andDangwidthfor100μmShi,CPUtemperatureisupto85℃,apparentlywidthmoresmallonthermalmoreenabling,therefore,sizefactorsonmicro-channelthermalManagerofeffectiscriticalof,andthisanddirectlyeffecthasCPUofrunperformance.Intheareaofmicro-channelheatsinks,morematureshouldbeUnitedStatesCooligyintroduceditsproduct.Itswater-cooledchipsproduction,usingtheactivemicro-channelcoolingtechnology（ActiveMicro2ChannelCooling,AMCC）.Thisnewtechnologyconsistsof3mainparts:

micropi