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ID:40104812
大小:443.47 KB
页数:16页
时间:2019-07-21
《Thermal Design Consideration for Surface Mount Layouts 》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、ThermalConsiderationsforSurfaceMountLayoutsCharlesMauney,TexasInstrumentsABSTRACTThefocusofthispaperistopresentthetechniquesthatareeffectiveinremovingtheheatfromthesurfacemountedpowerICsandtransferringittothecoolersurroundings.Inthepastthethermaldesignwasassi
2、mpleasaddingthethetavalues(°C/W)ofthepowercomponent,thepadandtheheatsinktogetherandmultiplyingbythepowerdissipatedinthatcomponenttoarriveatthetemperaturerisebetweentheambientandthejunctionoftheIC.Today,withsurfacemounttechnologyandICswithpowerpadsthePrintedCi
3、rcuitBoard(PCB)hasbecomeanintegralpartforremovingtheheat.EveryPCBisdifferentandthetaskofmathematicallyderivingatemperatureprofileforthePCBandeachpowercomponentisbeyondthescopeofthispaper.HoweverthebasicconceptsofwhatmakesagoodthermallyconductivePCB,somefirsto
4、rdermodelingexamplesandevaluationsofanexistingEVMwillhelpthedesignerunderstandthetechniquesinproducingagoodthermallyconductivePCB.Therearethreebasicmethodstomoveheatawayfromthesource,conduction,convectionandradiationheattransfer.Conductionismovingtheheatthrou
5、ghamaterial(PCB)typicallyfromcoppertoFR4tocopperandsoon.Convectionisforremovingtheheatoffthesurfacematerialtotheair.Radiationisformovingtheheatfromonesurfacematerialtoanotherthroughair.TABLE1THERMALCONDUCTIVITYFACTORSI.HEATTRANSFERBYCONDUCTIONMaterialsK(W/m°K
6、)K(W/in°C)ConductionisimportantbecauseitistheCopper3559surfaceareathateventuallydissipatestheheatAluminum1754.44andonlythroughconductiondoestheheatFR40.250.0064spreadouttotherequiredsurfacearea.TheSolder63/67391trendistomigratetowardsmallerpackagesAir0.02750.
7、0007believingthatthedesignareacanbereduced.Therealityisthatasmallerfootprint,withtheAtfirstglanceattheunits,itappearsthatsamepowerdissipation,requiresabetterPCBonewouldmultiplytheThermalConductivityconductiondesignandasimilaramountofFactorbythethermalpathleng
8、thtogetW/°Csurfacearea,foragiventemperaturerise.(1/θ),butthisisnotcorrectsincethiswouldHeatconductionisbetterthroughsomeindicatethelongerthethermalpaththelargermaterials(Copper)thanothers
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