Thermal Relief Design Guide for Your PCB - Altium's Resource

A thermal relief pad provides a way to keep heat confined to a pad for mounting a component to a printed circuit board with solder. Skiptomaincontent Mobilemenu PCBDesign AltiumDesigner World’sMostPopularPCBDesignSoftware AltiumNEXUS TheLastMileofDigitalTransformation CircuitStudio EntryLevel,ProfessionalPCBDesignTool CircuitMaker FreePCBdesignformakers,opensourceandnon-profits WhySwitchtoAltium SeewhyandhowtoswitchtoAltiumfromotherPCBdesigntools Parts&Data AltiumConcordPro CompleteSolutionforLibraryManagement Octopart Extensive,Easy-to-UseSearchEngineforElectronicParts Subscriptions Altium365 Resources&Support ExploreProducts FreeTrials Downloads Extensions FreeAltium365Tools OnlinePCBViewer Resources&Support AllResources SupportCenter Documentation AltiumCommunity Forum BugCrunch Ideas EducationPrograms ProfessionalTraining/Certification University/College Secondary/HighSchool Webinars Store SearchOpen Search SearchClose SignIn Home PCBLayout ThermalReliefDesignGuideforYourPCB ThermalReliefDesignGuideforYourPCB ZachariahPeterson |&nbspCreated:March22,2021 Fromrelativepermittivitytothermalexpansion,thereareplentyofthermalpropertiestoconsiderduringthedesignphase.Placingathermalreliefonpadscanaidassembly,butthisshouldbeconsideredalongsideothermethodsformanagingheattransportinyourboard.WiththerightPCBdesigntools,youcandesignthermalreliefpadsforimportantcomponentsandincorporateotherimportantheatmanagementfeaturesinyourboard.Altiumgivesyoutheseimportantdesigntoolsandmuchmoreinasingleprogram. ALTIUMDESIGNER AunifiedPCBdesignplatformthatintegratesadvancedPCBlayoutfeatureswithcomprehensiveviaandpaddesignfeatures. AlthoughFR4isapopularsubstrateduetoitslowcostandversatility,itcreatesproblemsforthermalmanagementduetoitslowthermalconductivity.Ascopperhashighthermalconductivity,itcanbedifficulttoheatpadstotherighttemperatureforapplyingsolder,bothinsomemanualprocessesandinwavesolderprocesses,especiallywhenpadsareconnectedtoaninternalplanewithavia.ManagingheatdistributionandeaseofassemblyinyourboardrequiresproperlydesigningthermalreliefpadsinyourPCBaswellasusingothermethodstomanageheat. Ifyou’rebuildingamultilayerPCB,thenyou’llneedtoincludecopperviastoroutebetweentheinnerlayersofyourboard,andyou’lllikelyplacesurface-mountcomponentsoncopperpadsonthesurfacelayer.Whileeverypadandthermalreliefdeviceisimportantforanelectricalandassemblystandpoint,theycanalsoplayaroleinheatregulationinyourboard.WiththerightPCBdesignandlayouttools,youcaneasilydesignthermalviasandthermalreliefdevicesinyourboard. WhatisThermalReliefDesign? Athermalreliefpadprovidesawaytokeepheatconfinedtoapadformountingacomponenttoaprintedcircuitboardwithsolder.Thepadforacomponentnormallypeaksthroughthesoldermask,allowingsoldertobeplacedonthepadduringassembly.Somecopperisremovedfromtheedgeofathermalreliefpad,allowingheattobeconfinedinthepadwhenapplyingsolderduringassembly. ThankstothelowthermalconductivityofFR4,heatiseasilyconfinedtoathermalreliefpadwhenapplyingsolder.Thisensuresastrongconnectioncanbeformedonacomponentduringmanualassembly.Thisisalsoimportantinwavesoldering,asapadwithoutathermalreliefcanquicklyremoveheatfromthesurfacewhenconnectedtoaninternalplanewithavia.Choosingwheretoplaceathermalreliefonapadwhilealsoincludingotherthermalmanagementmethodscanensurethatheatisproperlymanagedintheboardduringoperationwhileensuringtheboardcanbeeasilyassembled. ThermalReliefDesignandPCBs Thegoalinthermalreliefdesignistoremovesomecopperfromaroundthepadforathrough-holecomponent.Youcanalsousethermalreliefdesignonapadforasurface-mountcomponentaslongasthepadisanin-viapad.Inthiscase,theviafunctionsasthethermalreliefdevice.Thisisquiteimportantasthecopperpadforasurface-mountcomponentneedstomaintainsomeclearancearoundtheedgeofthepad,whereasyoucaneasilyremovesomecopperfromathrough-holepadwithoutaffectingtheabilitytoproperlymountthecomponent. Viasthatarenotintendedforuseaspadsforthrough-holecomponentsshouldnotincludethermalreliefpads.Infact,thermalviasarequiteusefulforremovingheatfromactivecomponentsthatgeneratesignificantamountsofheat.Itiscommontoplacethermalviasontheundersideofanactivecomponenttoregulateitstemperaturebytransportingheatintotheboard.Placingthermalviasinathermalreliefpadwillconnectaholetoaninternalplane,butspokesandvoidsareusedtorestrictthemetalareaintheinternalconnection.Ifyoutakealookattheimagebelow,you’llseewhatathermalrelieflookslike.Thesespokesandvoidsareimportantforsolderingthrough-holecomponentsinstandardthermalreliefpads. Athermalreliefpadisimportantbothfromanassemblyandthermalmanagementperspective.Learnmoreaboutdesigningacircuitboardwiththermalreliefpads. Yourinternalgroundandpowerplanesareimportantaspartoftheconnectiontothermalviasandyouroverallthermalmanagementstrategy. LearnmoreaboutdesigninggroundplanesinyourPCB. AspartofyourPCBdesignsoftware,polygonpourfeaturesareimportantfordesigningcopperregionsthatcanactasheatsinksinyourcircuitboard. LearnmoreaboutusingpolygonpoursinyourPCBlayout. ThermalpaddesignforpowerplaneconnectioninAltiumDesigner BeyondThermalReliefDevices:ComprehensiveThermalManagement InsomePCBs,highpowercomponentsandboardsthatusehighcurrentcangeneratesignificantamountsofheatduringoperation,andthelowthermalconductivityofFR4substratestrapsthisheatinspecificareasoftheboard.ThereareothermethodsinadditiontotheuseofthermalviasthatcanbeusedtodistributeandremoveheatfromaPCB. YourPCBsubstrateandstackupdeterminemanyimportantaspectsofyourPCB’sperformance,includingheattransportandmanagementinyourboard.Thethermalresistanceofyoursubstratewilldeterminewhetheryourboardcanquicklytransportheatthroughout,leadingtomoreeventemperaturedistribution.Whencoupledwiththermalvias,heatsinks,fans,andthermalreliefpads,youcanmoveheatawayfromcomponentsandpreventhotspotsfromforminginyourboardwhilestillensuringsoldercanbeeasilyappliedtoyourcomponentsduringassembly. OtherWaystoAidHeatManagement Usingathermalpadtoattachaheatsink,aswellastheuseoffans,aretwopopularwaystomoveheatawayfromcriticalactivecomponentsinyourPCB.Agroundorpowerplaneonaninnerlayerinyourboardwillalsohelpmoveheatlaterallythroughoutaboard,helpingtoproduceamoreeventemperaturedistributionawayfromactivecomponents.Finally,thethermalconductivityofyourcircuitboardsubstratedetermineshowquicklyyourboardwillconductheataroundaboard. Unlessyourboardismadefromaceramicmaterialorotheralternativesubstratematerial,yourstandardFR4boardwillhavelowthermalconductivity. Learnmoreaboutselectingtherighthighthermalconductivitysubstratematerial. HighpowercomponentslikebrightsurfacemountedLEDscanbenefitfromusinganaluminumsubstrateformitigatingheatgeneration. Learnmoreaboutworkingwithaluminumsubstrates. Asidefromusingalternativesubstratesandthermalvias,youcanhelpdecreasethetemperatureofyourboardbymountingaheatsinktoplanarcomponentswithathermalpadorthermalpaste.Learnmoreaboutselectingathermalpadorthermalpasteforusewithaheatsink. Yoursubstratematerialandyourstackupwilldeterminehowheattransfersthroughoutyourboard BestSoftwareforThermalReliefDesign Yourthermalreliefdesignfeaturesshouldn’tappearinyourPCBdesignsoftwareinisolation.You’llneedaccesstoacomprehensivesetofviaandpaddesignfeaturesthathelpyoudefinethegeometryofthermalreliefdevicesandyourlayerstack.Whentheseappearalongsideyourroutingfeatures,you’llhaveacompletesetofPCBdesignfeaturesforthermalreliefdesign. IntegratedThermalReliefDesignandStackupDesigninAltiumDesigner AltiumDesignerincludesCADtoolsthatallowyoutoeasilydefinepolygonpours,thermalvias,thermalreliefpads,andyourlayerstackinasingleprogram.YoucansimplifyyourPCBdesignprocessforthermalmanagementwiththeviadesign,paddesign,andplanedesignfeatures. AltiumDesigner’sintegrateddesignenvironmentunifiestheseimportantdesignfeaturesandmanymoreontopofasinglerules-drivendesignengine.Definingpadshapes,viashapes,yourstackup,andthermalreliefdevicesareeasywithAltiumDesigner.LearnmoreabouttheunifieddesignenvironmentinAltiumDesigner. ThePCBdesignrulesengineinAltiumDesignercanhelpensureyourthermalreliefdesignsareactuallymanufacturableandwillcomplywithimportantindustrystandards.Learnmoreabouttherules-drivendesignengineinAltiumDesigner. WithAltiumDesigner’smaterialsstackuplibrary,youcanchooseastandardsubstratematerialtouseaspartofacomprehensivethermalmanagementstrategy.LearnmoreaboutthematerialsstackuplibraryinAltiumDesigner. Thankstotheultra-accurateCADtoolsinAltiumDesigner,youcaneasilydefineyourthermalreliefpadsforimportantcomponentsanddesignalayerstackthataidsthermalmanagementinyourPCB.Withitshugemateriallibraryandintuitivestackupmanager,youhaveacompletesetoftoolsforthermalmanagementinasinglePCBdesignprogram.Byintegratingyourlayout,management,andsimulationfeaturesintoasingleplatform,you’llhavetheimportantdesignfeaturesyouneedtotakecontroloverallaspectsofyourproduct. HowtoCreateaPCBLayoutfromaSchematic BoardLayoutwithAltiumDesigner PCBLayoutandPlacementGuidelines PCBComponentPlacement(Webinar) Rules-BasedComponentPlacement AltiumNexusPCBLayoutCapabilities AboutAuthor AboutAuthor ZachariahPetersonhasanextensivetechnicalbackgroundinacademiaandindustry.Hecurrentlyprovidesresearch,design,andmarketingservicestocompaniesintheelectronicsindustry.PriortoworkinginthePCBindustry,hetaughtatPortlandStateUniversity andconducted researchonrandomlasertheory,materials, andstability.Hisbackgroundinscientificresearchspanstopicsinnanoparticlelasers,electronicandoptoelectronicsemiconductordevices,environmentalsensors,andstochastics.Hisworkhasbeenpublishedinoveradozenpeer-reviewedjournalsandconferenceproceedings,andhehaswritten1000+technicalblogsonPCBdesignforanumberofcompanies.HeisamemberofIEEEPhotonicsSociety,IEEEElectronicsPackagingSociety,AmericanPhysicalSociety,andthePrintedCircuitEngineeringAssociation(PCEA),andhepreviouslyservedontheINCITSQuantumComputingTechnicalAdvisoryCommittee. MorecontentbyZachariahPeterson RecentArticles UsinganIPC-2221PCBClearanceCalculatorforHighVoltageDesign UnsureofyourconductorspacingrequirementsinhighvoltagePCBs?AnIPC-2221calculatorcanhelp.PCBdesignandassemblystandardsaren’ttheretoconstrainyourproductivity.Instead,they’retheretohelpcreateuniformexpectationsofproductdesignsandperformanceacrossmultipleindustries.Withstandardizationcomesthetoolsforcompliance,suchascalculatorsforcertaindesignaspects,processesforauditingandinspection,andmuch ReadArticle IsThereanSPITraceImpedanceRequirement? ThereisnoSPItraceimpedancerequirementorterminationrequirement.Ifthissoundssurprising,readthisarticletoseewhy. 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