邹静(jing.zou@philips.com)GBULEDLampsandSystemsJune2010GeneralGuidetotheHeatsinkDesignforFortimomodulesConfidentialGBULEDLampsandSystems,June20102Nicetoknow:••网上有:•Productleaflet;•Design-inguide;•Opticalfiles;•Catalog;•Photometricfiles•Certificates•3DfilesuchasCADfileConfidentialGBULEDLampsandSystems,June20103LED模组会因为没有接散热器,过度受热而坏掉吗?ConfidentialGBULEDLampsandSystems,June20104LED模组会因为没有接散热器,过度受热而坏掉吗?不会,我们的模组有高温保护功能,一旦模组温度升到一定值,驱动器的输出电流会自动减小,这会阻止模组温度继续升高。ConfidentialGBULEDLampsandSystems,June2010•LEDPerformanceissue?Tj必须保持在特定的温度下,以免颜色飘移,或者光通的改变。5WhyBother?ConfidentialGBULEDLampsandSystems,June2010•LEDPerformanceissue?Tj必须保持在特定的温度下,以免颜色飘移,或者光通的改变。•Lifetimeconcern?焊点经历一定次数冷热循环后(热胀冷缩的循环)会产生脱节。一般来说,焊点的温度越高,脱节前经历的冷热循环数越低。6WhyBother?ConfidentialGBULEDLampsandSystems,June2010Tc对于模组来讲,只要Tc保持在650Cor550C,lifetime(B50L70)会在50000个小时左右。LLM模组由于具有CLO,所以lifetime不使用L70。7TcandLifetimeModuleTclife(0C)DLM65Lexel65SLM65LLM55Twistable55ConfidentialGBULEDLampsandSystems,June20108SpecialfeaturesFortimoLEDlinearConfidentialGBULEDLampsandSystems,June20109多少的功率(百分比)变成了热?ConfidentialGBULEDLampsandSystems,June201010Howmuchpoweristurnedintoheat?一般来说,有remotephosphor的模组,比如:2/3的模组消耗的功率(系统功率–驱动器的功率)转变成了热。ConfidentialGBULEDLampsandSystems,June201011Howmuchpoweristurnedintoheat?一般来说,有remotephosphor的模组,比如:2/3的模组消耗的功率(系统功率–驱动器的功率)转变成了热。RemotePhosphorTc(篊)POptical(W)Powermoduleonly[Watt]WPEOpen5514.6532.844.71%4000K559.2432.828.17%3000K558.5732.826.13%1-45%=55%的功率转换成热!1-26%=74%的功率转换成热!转换成光的效率ConfidentialGBULEDLampsandSystems,June201012Howmuchpoweristurnedintoheat?一般来说,有remotephosphor的模组,比如:2/3的模组消耗的功率(系统功率–驱动器的功率)转变成了热。RemotePhosphorTc(篊)submountPOptical(W)Powermoduleonly[Watt]WPEOpen5514.6532.844.71%4000K559.2432.828.17%3000K558.5732.826.13%Sidestory!ConfidentialGBULEDLampsandSystems,June201013Howtogetridofheat?被动散热主动散热Thermalmanagement:•Heatspreading(传热):把热传到一个更大的面积•Heatsinking(散热):通过convection(热对流)和radiation(热辐射)使热传到空气环境中。ConfidentialGBULEDLampsandSystems,June201014ThermalManagementHeatspreading•主要的传热机制(从模组到散热器)是conduction(导热);•为了增加模组和散热器之间的热传导,一般要使用thermalinterfacematerials(导热介质),比如导热胶,或者导热膜,甚至导热管.•散热器要用thermallyconductingmaterial(导热材料)–金属是比较好的导热材料–很多情况下铝是首选,因为造工比较方便,价格也比较合适。ConfidentialGBULEDLampsandSystems,June201015ThermalManagementHeatsinking(Convection)•影响热对流的因素如下:热对流系数Pconv=hc*Aeff*(Tc-Tamb),有效面积•热阻(Rth)如下:Rth=ΔT/Pheat=1/(h*Aeff*)热功率Tcase环境温度ConfidentialGBULEDLampsandSystems,June201016主动散热和被动散热的比较:热对流系数比较小相对大而重的散热器需要工具迫使空气对流,要消耗能量可能会产生一些噪音热对流系数相对较大相对小巧的散热器ComparisonbetweenpassiveandactivecoolingNaturalconvectionForcedConvection利用自然空气对流没有噪音ConfidentialGBULEDLampsandSystems,June201017ThermalmanagementHeatsinking(Radiation)•热辐射的影响因素也可以写成如下:Prad=hr*Aeff*(Tc-Tamb),热辐射系数热辐射因素和emissioncoefficient(放热系数)成正比,而emissioncoefficient和表面处理有关:ConfidentialGBULEDLampsandSystems,June201018ThermalmanagementHeatsinking(Radiation)•整个散热(热对流+热辐射):Pheat=h*Aeff*(Tc-Tamb),在我们模组的工作范围内,一般来说,热辐射在整个散热中占到20%-40%左右,整个的传热系数在2-10之间。ConfidentialGBULEDLampsandSystems,June201019HeatsinkExamplesPassivePassivePassivePassiveActiveActiveConfidentialGBULEDLampsandSystems,June201020要考虑的因素:•用导热性能好的材料铝是较好的选择•散热器的整个有效面积Aeff=1/(h*Rth)•散热片的摆放位置•散热片之间的距离•散热片的长度•散热片的厚度•用放热系数较大的表面处理铝一般用喷漆或者阳极•为了保证模组和散热器之间的热传导,要用导热介质ConfidentialGBULEDLampsandSystems,June201021Heatsinkverification:MeasuringTc(withheatsinkattached)•ThestabilizationtimeforTccanbebetweenhalfanhourupto3hours,whichdependsonthemeasurementenvironment.Ingeneral,ittakeslongertostabilizeinanenclosedenvironment,suchasasimulatedceilingenvironment.•ThermalcouplecanbeusedtomeasureTc.Ensuregoodcontactbetweenthethermalcoupleandthemodulebytaping(aluminumtape)orapplyingathinlayerofquickdryingglueandstringrelief•Thermalcouplehascertaindimensions,soitisnotrecommendedtoputthembetweenamoduleandaheatsinkdirectlyunlessthereisalreadyagroovemadeontheheatsink.However,Tccanalsobemeasuredtowardsthesideofthemodule,whichofcoursewillbeafewdegreeslessthanthetemperatureinthecenter.ConfidentialGBULEDLampsandSystems,June201022样例:模拟的天花板环境中Tc的测量Boxdimensions:1x1x1mHeightaboveceiling:0.35mAmbienttemperatureaboveceiling:35°CBoxtemperatureiscontrolledwithliquidcooledwallandathermostatbathTc等了1-2小时候才稳定;一般来讲,在一个封闭的环境中,Tc要等比较长的时间才可以稳定下来ConfidentialGBULEDLampsandSystems,June201023样例:Tc在敞开环境中的测量尽量避开空气流动比较大的地方!+100C56.80CT_ambientConfidentialGBULEDLampsandSystems,June201024ConfidentialGBULEDLampsandSystems,June201025DLM:在U型的边上测如果散热器安装在DLM的底部,边上的温度应该610C,只要可以基本保证Tc650CSimulationmadewithheatsinkattachedtothesides.ConfidentialGBULEDLampsandSystems,June201026散热器设计的流程•收集基本的一些信息,比如多少的热功率,以及设计上的一些形状或者大小的限制等等;•把以上信息输入到热学软件中,进行计算机模拟;•初步判断模拟结果对散热器设计进行修正;eg.•Mouldthefirstheatsinkanddoextensiverealtemperaturetesting.ConfidentialGBULEDLampsandSystems,June2010MeasurementresultsTESTPOINT#1(180024W/730)HS1experimentextropolateextrapolateheatsinkcenter(Tcase)5251.461.4Ambient(℃)25.62535Electricalpowermodule(W)24Thermalpowermodule(W)16Rth(K/Wth)1.7240mmx60mmx30mmConfidentialGBULEDLampsandSystems,June201028Whatish?A=0.24x0.03x9x2=0.13m2ΔT=52-25