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JEDECSTANDARDAcceleratedMoistureResistance-UnbiasedHASTJESD22-A118DECEMBER2000JEDECSOLIDSTATETECHNOLOGYASSOCIATIONNOTICEJEDECstandardsandpublicationscontainmaterialthathasbeenprepared,reviewed,andapprovedthroughtheJEDECBoardofDirectorslevelandsubsequentlyreviewedandapprovedbytheEIAGeneralCounsel.JEDECstandardsandpublicationsaredesignedtoservethepublicinterestthrougheliminatingmisunderstandingsbetweenmanufacturersandpurchasers,facilitatinginterchangeabilityandimprovementofproducts,andassistingthepurchaserinselectingandobtainingwithminimumdelaytheproperproductforusebythoseotherthanJEDECmembers,whetherthestandardistobeusedeitherdomesticallyorinternationally.JEDECstandardsandpublicationsareadoptedwithoutregardtowhetherornottheiradoptionmayinvolvepatentsorarticles,materials,orprocesses.BysuchactionJEDECdoesnotassumeanyliabilitytoanypatentowner,nordoesitassumeanyobligationwhatevertopartiesadoptingtheJEDECstandardsorpublications.TheinformationincludedinJEDECstandardsandpublicationsrepresentsasoundapproachtoproductspecificationandapplication,principallyfromthesolidstatedevicemanufacturerviewpoint.WithintheJEDECorganizationthereareprocedureswherebyanJEDECstandardorpublicationmaybefurtherprocessedandultimatelybecomeanANSI/EIAstandard.Noclaimstobeinconformancewiththisstandardmaybemadeunlessallrequirementsstatedinthestandardaremet.Inquiries,comments,andsuggestionsrelativetothecontentofthisJEDECstandardorpublicationshouldbeaddressedtoJEDECSolidStateTechnologyAssociation,2500WilsonBoulevard,Arlington,VA22201-3834,(703)907-7560/7559or:PleaserefertothecurrentCatalogofJEDECEngineeringStandardsandPublicationsorcallGlobalEngineeringDocuments,USAandCanada(1-800-854-7179),International(303-397-7956)PrintedintheU.S.A.AllrightsreservedPLEASE!DON’TVIOLATETHELAW!ThisdocumentiscopyrightedbytheElectronicIndustriesAllianceandmaynotbereproducedwithoutpermission.Organizationsmayobtainpermissiontoreproducealimitednumberofcopiesthroughenteringintoalicenseagreement.Forinformation,contact:JEDECSolidStateTechnologyAssociation2500WilsonBoulevardArlington,Virginia22201-3834orcall(703)907-7559JEDECStandandNo.22-A118Page1TestMethodA118ACCELERATEDMOISTURERESISTANCE-UNBIASEDHAST(FromJEDECBoardBallotJCB-00-56,formulatedunderthecognizanceoftheJC-14.1SubcommitteeonReliabilityTestMethodsforPackagedDevices.)1PurposeTheUnbiasedHASTisperformedforthepurposeofevaluatingthereliabilityofnon-hermeticpackagedsolid-statedevicesinhumidenvironments.Itisahighlyacceleratedtestwhichemploystemperatureandhumidityundernon-condensingconditionstoacceleratethepenetrationofmoisturethroughtheexternalprotectivematerial(encapsulantorseal)oralongtheinterfacebetweentheexternalprotectivematerialandthemetallicconductorswhichpassthroughit.Biasisnotappliedinthistesttoensurethefailuremechanismspotentiallyovershadowedbybiascanbeuncovered(e.g.galvaniccorrosion).Thistestisisusedtoidentifyfailuremechanismsinternaltothepackageandisdestructive.2ScopeThistestmethodappliesprimarilytomoistureresistanceevaluationsandrobustnesstesting,andmaybeusedasanalternativetounbiasedautoclave.Samplesaresubjectedtoanon-condensing,humidatmosphere,similartotheJESD-22-A101,SteadyStateTemperature,HumidityandBiasLifeTest,butwithahighertemperature.Forthetemperaturelimitsdefinedbythisprocedure,thetestwilltypicallygeneratethesamefailuremechanismsasthoseinanunbiased85°C/85%RHSteadyStateHumidityLifeTest,butcautionmustbeusedifhighertemperaturesareconsideredsincenon-realisticfailuremodescanbegenerated.Theuseofanon-condensingenvironmentavoidsmanyirrelevantexternalfailures,e.g.,pin-to-pinleakageorleadcorrosion.However,becauseabsorbedmoisturetypicallydecreasesglasstransitiontemperatureformostpolymericmaterials,thecombinationofhighhumidityandhightemperature(Tg)mayproduceunrealisticmaterialfailures.Thus,cautionisneededifandwhenUnbiasedHASTisrequiredforreliabilityorqualificationpurposes.3ApparatusThetestrequiresapressurechambercapableofmaintainingaspecifiedtemperatureandrelativehumidityduringramp-upto,andramp-downfrom,thespecifiedtestconditions.JEDECStandandNo.22-A118Page2TestMethodA1183Apparatus(cont’d)3.1RecordsApermanentrecordofthetemperatureprofileforeachtestcycleisrecommended,sothestressconditionscanbeverified.Calibrationrecordsshallverifythattheequipmentavoidscondensationondevicesundertest(DUTs)hotterthan50°Cduringramp-upandramp-downforconditionsofmaximumthermalmassloading.Calibrationrecordsshallverifythat,forsteadystateconditionsandmaximumthermalmassloading,testconditionsaremaintainedwithinthetolerancesspecifiedin3.1.3.2DevicesUnderStressDevicesunderstressmustbeplacedinthechambertominimizetemperaturegradients.Devicesunderstressshallbenocloserthan3cmfrominternalchambersurfaces,andmustnotbesubjectedtodirectradiantheatfromheaters.Ifdevicesaremount