22-A118B

JEDECSTANDARDAcceleratedMoistureResistance-UnbiasedHASTJESD22-A118B(RevisionofJESD22-A118A,March2011)JULY2015JEDECSOLIDSTATETECHNOLOGYASSOCIATIONNOTICEJEDECstandardsandpublicationscontainmaterialthathasbeenprepared,reviewed,andapprovedthroughtheJEDECBoardofDirectorslevelandsubsequentlyreviewedandapprovedbytheJEDEClegalcounsel.JEDECstandardsandpublicationsaredesignedtoservethepublicinterestthrougheliminatingmisunderstandingsbetweenmanufacturersandpurchasers,facilitatinginterchangeabilityandimprovementofproducts,andassistingthepurchaserinselectingandobtainingwithminimumdelaytheproperproductforusebythoseotherthanJEDECmembers,whetherthestandardistobeusedeitherdomesticallyorinternationally.JEDECstandardsandpublicationsareadoptedwithoutregardtowhetherornottheiradoptionmayinvolvepatentsorarticles,materials,orprocesses.BysuchactionJEDECdoesnotassumeanyliabilitytoanypatentowner,nordoesitassumeanyobligationwhatevertopartiesadoptingtheJEDECstandardsorpublications.TheinformationincludedinJEDECstandardsandpublicationsrepresentsasoundapproachtoproductspecificationandapplication,principallyfromthesolidstatedevicemanufacturerviewpoint.WithintheJEDECorganizationthereareprocedureswherebyaJEDECstandardorpublicationmaybefurtherprocessedandultimatelybecomeanANSIstandard.Noclaimstobeinconformancewiththisstandardmaybemadeunlessallrequirementsstatedinthestandardaremet.Inquiries,comments,andsuggestionsrelativetothecontentofthisJEDECstandardorpublicationshouldbeaddressedtoJEDECattheaddressbelow,orreferto©JEDECSolidStateTechnologyAssociation20153103North10thStreetSuite240SouthArlington,VA22201-2107Thisdocumentmaybedownloadedfreeofcharge;howeverJEDECretainsthecopyrightonthismaterial.Bydownloadingthisfiletheindividualagreesnottochargefororreselltheresultingmaterial.PRICE:ContactJEDECPrintedintheU.S.A.AllrightsreservedPLEASE!DON’TVIOLATETHELAW!ThisdocumentiscopyrightedbyJEDECandmaynotbereproducedwithoutpermission.Forinformation,contact:JEDECSolidStateTechnologyAssociation3103North10thStreetSuite240SouthArlington,VA22201-2107orreferto(RevisionofTestMethodA118A)TESTMETHODA118BACCELERATEDMOISTURERESISTANCE-UNBIASEDHAST(FromJEDECBoardBallotJCB-00-56,JCB-11-17,andJCB-15-25,formulatedunderthecognizanceoftheJC-14.1SubcommitteeonReliabilityTestMethodsforPackagedDevices.)1ScopeThistestmethodappliesprimarilytomoistureresistanceevaluationsandrobustnesstesting,andmaybeusedasanalternativetounbiasedautoclave.Samplesaresubjectedtoanoncondensing,humidatmosphere,similartotheJESD22-A101,Steady-StateTemperature,HumidityandBiasLifeTest,butwithahighertemperature.Forthetemperaturelimitsdefinedbythisprocedure,thetestwilltypicallygeneratethesamefailuremechanismsasthoseinanunbiased85°C/85%RHSteady-StateHumidityLifeTest,butcautionmustbeusedifhighertemperaturesareconsideredsincenon-realisticfailuremodescanbegenerated.Theuseofanoncondensingenvironmentavoidsmanyirrelevantexternalfailures,e.g.,pin-to-pinleakageorleadcorrosion.However,becauseabsorbedmoisturetypicallydecreasesglasstransitiontemperatureformostpolymericmaterials,thecombinationofhighhumidityandhightemperature(Tg)mayproduceunrealisticmaterialfailures.Thus,cautionisneededifandwhenUnbiasedHASTisrequiredforreliabilityorqualificationpurposes.TheUnbiasedHASTisperformedforthepurposeofevaluatingthereliabilityofnonhermeticpackagedsolid-statedevicesinhumidenvironments.Itisahighlyacceleratedtestthatemploystemperatureandhumidityundernoncondensingconditionstoacceleratethepenetrationofmoisturethroughtheexternalprotectivematerial(encapsulantorseal)oralongtheinterfacebetweentheexternalprotectivematerialandthemetallicconductorsthatpassthroughit.Biasisnotappliedinthistesttoensurethefailuremechanismspotentiallyovershadowedbybiascanbeuncovered(e.g.,galvaniccorrosion).Thistestisisusedtoidentifyfailuremechanismsinternaltothepackageandisdestructive.2ApparatusThetestrequiresapressurechambercapableofmaintainingaspecifiedtemperatureandrelativehumidityduringramp-upto,andramp-downfrom,thespecifiedtestconditions.JEDECStandandNo.22-A118BPage2TestMethodA118B(RevisionofTestMethodA118A)2Apparatus(cont’d)2.1RecordsApermanentrecordofthetemperatureprofileforeachtestcycleisrecommended,sothestressconditionscanbeverified.Calibrationrecordsshallverifythattheequipmentavoidscondensationondevicesundertest(DUTs)hotterthan50°Cduringramp-upandramp-downforconditionsofmaximumthermalmassloading.Calibrationrecordsshallverifythat,forsteady-stateconditionsandmaximumthermalmassloading,testconditionsaremaintainedwithinthetolerancesspecifiedinTable1.2.2DevicesunderstressDevicesunderstressmustbeplacedinthechambertominimizetemperaturegradients.Devicesunderstressshallbenocloserthan3cmfrominternalchambersurfaces,andmustnotbesubjectedtodirectradiantheatfromheaters.Ifdevicesaremountedonboards,theboardsshouldbeorientedtominimizeinterferencewithvaporcirculation.2.3Ioniccontamination