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    HALT/HASS 英文资料

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    是个简单的介绍,有兴趣的人看看,有一些HALT/HASS基本概念:

    HALT/HASS—QualMark

    ————HASSFromConcepttoCompletionbyDavidRahe,QualMark

    Whenamanufacturerofpowerconditioningequipmentwantedtodeterminewhyproductswereexperiencing
    amajorfailuremodeinthefield,hecontactedoneofQualMark’sAcceleratedReliabilityTestCenters(ARTC)forhelp.AHASSprocesswasproposedandimplementedtoprovideasolution.
    ThegoalofHASSistodevelopascreenthatiseffectiveincausinglatentfailurestobecomeactualfailureswithoutremovingasignificantamountoftheproduct’slife.AtARTC,theHASSprocessusesrapidthermaltransitioningcombinedwithmultilevelvibrationperformedoverafrequencybandwidthfrom2Hzto10kHz.Inadditiontothesestresses,product-specificstresses,suchasvoltagemargining,frequencymargining,andpowercycling,areapplied.
    HALTpreviouslywasperformedonthisproductbyQualMarkARTC,andsubsequentlythecustomerrequested
    aHASSscreentobedeveloped.TheHASSprocessincludedbothHASSdevelopmentandproductionHASS
    andusedthesameacceleratedtechniquesasHALT,butderated.
    ProductDescriptionandChronology
    Thedetailsoftheuninterruptiblepowersupply(UPS)productwillnotbedisclosedtoprotectthecustomerandproductidentity.Theunitconsistedofametalchassiswiththemaincomponentsbeingaprintedcircuitboard(PCB),alargetransformer,andabattery.
    Thetopplateofthechassiswasleftofftoallowfasterthermalchangeratestotheproduct.ThePCBwasmountedtothechassisbaseviaseveralstandoffs.
    Thesystemtestedwasamatureproductwithmanyhundredsofunitsinthefield.Theproductwas
    experiencingrandomfailuresoccurringattheend-usersite.ThefailuremoderesultedinseveralFETs
    exploding,renderingtheUPSinoperable.
    AnESSprogramhadbeenperformedoneachUPSpriortoshipment.Theprogramconsistedofa50¥Cburn-inatalmostfulloutputloading.Thiswasineffectiveinprecipitatingthisfailuremodeorothers.
    HASSEquipmentTheHASSprofilewasdeveloped,tested,andproven(HASSdevelopment)inourlabusingtheOVS2.5HPHALT/HASSsystem.TheHASSdevelopmentprocessincludedfixturedesign,fabrication,qualification,profile
    development,andproof-of-screen.Afterthedevelopmentprocess,thescreenwasimplemented(production
    HASS)atthecustomer’sfacilityonitsOVS2.5HPsystem.
    2AdditionalfunctionaltestequipmentwasusedtoverifytheoperationoftheUPStoitsperformance
    specification.Thistestequipmentwaslocatedoutsideofthechamberandcabledviathechamberaccessporttotheunits-under-test.

    FixtureDesignandQualification
    TheHASSfixturewasdesignedandfabricatedtosupporttheproductthroughputtestingandprovidepropervibrationtransmissibility,thermaluniformity,andabalancedthermalrateofchange.Twofunctionalunitswere
    securedtothetwofixturelocationswiththermocouples,andaccelerometerswereattachedtoeachunittoperformthermalandvibrationsurveys(Figure1).
    ProfileDesignTheHASSprofilewasbasedontheHALTresults,alongwithotherproduct-relatedvariablessuchasfunctionaltestduration,thermallong-termdegradationeffects(long-termfailuremodesthatmayrequireareductionofstresslevels),product-specificstresses,andproductionthroughputtestrequirements.Theprofileconsistedof
    twocombinedenvironmentcyclesperformedwithintheproduct’soperatinglimits.TheUOL,LOL,andDLvalueswereacquiredfromtheHALTresults.

    Theinitialprofilelevels(rule-of-thumbestimates)were80%ofthecumulativerangeoftheUOLandtheLOL.
    Forexample,withanUOLof100°CandLOLof-70°Cequalinga170°Crange,85°Cand-53°Cwereused.
    X=[(LOL-UOL)(0.20)]/2
    Where:XequaledthemargintemperaturesubtractedfromboththeLOLandUOL.Vibrationsetpointlevels
    were50%oftheDL,butwithintheOL,asmeasuredontheproduct.Ifthe50%valuehadexceededtheOL,then80%oftheOLwouldhavebeenusedasthesetpoint.
    Vibrationwasmodulatedthroughout,beginningat3to5Grmsandslowlyrampedtothemaximumlevel.Thisprocesswasrepeatedinreverse,fromthemaximumlevelto3to5Grms.
    Dwelltimesateachtemperatureextremebeganwheretheproductsattainedthedesiredtemperature,and
    wereheldaminimumof5minutesduringwhichtimethefunctionaltestswererun.Thevibrationmodulationrampswereslow,witha5-minutedwellminimumrequirementatthemaximumvibrationlevel.
    Thesefactorswereconsideredinthedesignoftheprofile:
    ThermalUOL:100°C.
    ThermalUDL:100°C.
    ThermalLOL:-70°C.
    ThermalLDL:<-80°C. VibrationOL:50Grms. VibrationDL:50Grms. Functionaltestlength:2minutes. Productionthroughputrequirement:3unitsperhour. Powercycleateachthermalextremeduringthedwell. Plasticfront-panelchassiscover:softensatapproximately90°C. Consideringthesefactors,theinitialdesignedprofilelimitswereasfollows: Maximumprofiletemperature:83°C. Minimumprofiletemperature:-53°C. Maximumprofilevibration:30Grms. Profileduration:60minutes. ProductFunctionalTestRoutine Thefunctionaltestroutinewasperformedthroughouttheprofile.ThisconsistedofsupplyingavariableACinputtotheunitsandavariableloadontheoutputs.Thebatterychargeandbattery-lineswitchingcircuitsalsoweretested.Powercyclingwasperformedatthethermalextremes.

    Lv.4
    我是最棒的
    [b]Proof-of-Screen(POS)[/b] Proof-of-screenwasatwo-stepprocess.Itdeterminedhoweffectivethescreenwasindetecting manufacturingflawsandprovedthatthescreenhadnotremovedsignificantlifefromthescreenedproducts. ScreenEffectiveness Thescreen’seffectivenesswasmeasuredbyitscapabilitytoprecipitatelatentdefects,suchascomponentweaknesses,PCBflaws,circuittimingproblems,mechanicaltoleranceproblems,solderdefects,andothermanufacturingassembly-relatedissuesassociatedwiththemanufacturer’sorvendor’sprocessgoingoutofcontrol. Forthisprocess,unitsclassifiedasNTForparametricallymarginalfunctionalunitswouldhavebeenpreferred. SinceNTFunitswerenotavailable,productionunitswereused. Twofunctionalproductionunitswereseededwithflawsrepresentativeofthemanufacturingprocessgoingoutofcontrol,suchasapoorsolderprocessordamagedorincorrectcomponentinsertion.Theseededflawsweremicroprocessorpin24bentunderonbothunits,capacitorC618withaleadnickedonbothunits,andacoldsolderjointonathrough-holeleadofcapacitorC303onjustoneunit. Thescreenshoulddetecttheseflaws.Ifnot,itshouldbemodified(increaseordecreaseseveritylevels)untilitdoes. InitialScreenResults Theseededtestunitswerescreenedusingtheprogrammedprofile(Figure2).Thisprofilesubjectedtheunitstotemperaturecyclesfrom+83°Cto-53°Catanaveragetransitionrateof45°Cperminutecombinedwithvibration.Vibrationwasmodulatedfromasetpointof5Grmsto30Grms.Thisinitialscreenproducedthefollowingfailures: Theunitshadathermalfaultoccurringattemperaturesbelow-40°C,withtheunitlosingserial communications.ThefailurealsooccurredduringHALT,butwasnotcarefullyanalyzedduringtheroot-causeanalysis. ThefailurewasthoughttobecausedbyasmallPCBthatwasgoingtobereplacedwitharedesign.However,theresultsduringHASSdevelopmentindicatedthatthesourceofthisfailurewasnotthesmallPCB.Thiswasdeterminedbydisconnectingtheboardandverifyingthatthefailurecontinuedtooccur.Thetruerootcauseofthisfailurewasundeterminedatthistime. Inunit#1,thebatterychargecircuitwasnotfunctioning,andtheredLEDindicatedbatteryservicewasneeded.Thisoccurredduringtherampfrom-53°Cto+83°Catapproximately-35°Conthesecondcycle.Thishardfailureremainedevenat25°C. Theunitwasremovedandtestedwithabatteryonthebench.Onpower-up,itblewFETsQ6,Q11,Q22,andQ26,theidenticalfailurethatwasoccurringinthefield. Uponcompletionofthescreen,avisualinspectionrevealedthattheseededflawC303haddislodgedfromthethrough-holefilletatthecoldsolderjoint. Asaresultofthesefindings,thedamagedUnit#1wasreplacedwithUnit#3,andasecondscreenwas performedusingthesameprofile. SecondScreenResults ThesamethermalissuesoccurredonUnit#2astheydidduringtheinitialscreenat -53°C. TheloadLEDsonUnit#2wereflashingonandoffrandomlyat-53°Cduringthesecondcycle.Thiswasahardfailurethatremainedat25°Cwithnovibration.Avisualinspectionoftheunitrevealedthatametal-oxidevaristor(MOV)componenthadbrokenfreefromtheboard. ThedamagedUnit#2wasreplacedwithUnit#4,andathirdscreenwasperformedusingaslightlymodifiedprofile.Thisprofilewasprogrammedwithreducedlevels.Thethermallowerlimitwasincreasedto-30°C,andvibrationwasreducedto20Grms.Thisprofilesubjectedtheunitstotemperaturecyclesfrom+83°Cto-30°Catanaveragetransitionrateof45°Cperminutecombinedwithvibration.Vibrationwasmodulatedfromasetpointof5Grmsto20Grms. ThirdScreenResults Bothunitspassedthescreenwithnofailuresoranomalies. ProductLifeValuation ThisprocessdeterminedthedegreeofappreciableliferemainingintheproductsafterexposuretotheHASS profile.Theconceptwastorepeattheprofilemanytimes,withoutfailuresoccurring,toshowthatproductionunitsexposedtoonlyonepassoftheprofilewouldstillhave90%minimumoftheusefulliferemaining,or10%maximumofliferemoved.Forgreaterconfidence,additionalrepeatcyclescouldhavebeenperformedontheseunits;however,timedidnotallow. Production-levelunitswereusedforthisprocess,withbothfixturelocationspopulated.Thetestunitswerescreenedusingthelatestprofile,thenrepeated10times.Thisprofilesubjectedtheunitstotemperaturecycles from+83°Cto-30°Catanaveragetransitionrateof45°Cperminutecombinedwithvibration.Vibrationwasmodulatedfromasetpointof5Grmsto20Grms. ProductLifeValuationResults Aninspectionoftheunitsfollowingcompletionofthe20cycles(oneprofile=twocycles)revealedthattheMOVcomponentRV301hadbrokenfreefromtheboard(bothleadswerebrokenattheboard)ontheupperunit.Thisfailurewasnotconsideredofconsequencebecausethecustomerplanedtouseroom-temperaturevulcanizing(RTV)adhesivetosupporttheMOVonfutureproductionunits. SummaryTheHASSdevelopmenteffortbeganwithdesigningandqualifyingthefixturebymeasuringtheunit’sthermalandvibrationresponses.Then,theHASSprofilewasdevelopedusingtheunitlimitsdeterminedduringHALT,alongwithotherproduct-specificfactors.Remember,HALTwasrequiredbeforeHASScouldbeproperlyperformed. DuringthedevelopmentoftheHASSprofile,adjustmentsweremadetotheprofiletooptimizeitsefficiency. ThesechangeswerereflectedinthefinalprofileshowninFigure3. Thecoldthermalfaultproblemcausingtheunittoloseserialcommunicationsattemperaturesbelow-40°C neededmoreevaluationtodeterminetherootcause.Oncedetermined,theprofilewasexpandedandthe proof-of-screenrerun.ThesamewastrueregardingtheRTVadhesiveontheMOV.TheRTVhadtobeappliedbetweentheMOVandPCBandtheproductlifevaluationrerun. SuccessfulimplementationofHALTcandramaticallyreduceproductdevelopmentcycletimeandcostswhile providingtheanswersneededtoproduceamorerobustdesign.SuccessfulimplementationofHASScan eliminateinfantmortalityfailures,reduceproductsupportcosts,andincreasecustomersatisfaction. Asuccessfulmanufacturingprogramincludes: PerformHALTtounderstandandgaininformationoftheproduct’scapabilities. PerformrootcauseanalysisontheHALTfailuresandimplementcorrectiveaction. PerformHALTagainwiththenewfixesinplace. RepeatSteps2and3untiltheproblemsareresolvedsatisfactorily. PerformHASSdevelopment. PerformHASSonproductionproducts. ThemethodofHASSdevelopmentincludes: Designandbuildafixturethatsupportsthroughputandotherrequirements. Performfixturequalification. CreateaHASSprofileofthermalandvibrationstimulibasedontheHALTresults.Inadditiontothese stresses,applyotherproduct-specificstressesthatwilltestthefunctionalintegrityoftheproduct. Performaproof-of-screenprocess. Releasetheprovenprofiletobeginproductionscreening. MonitortheHASSeffectivenessovertime. HASSdevelopmentwasnotintendedtobearigidprocesswithanendpoint.Rather,itisalivingprocessthatmayneedmodificationoradjustmentoverthelifeoftheproduct.Asmoreislearnedabouttheproductovertime,includingtheHASSresults,theprofilemaychangeandevolveintoanevenbetter,moreeffectivescreen. Acknowledgment IwouldliketoacknowledgeDr.GregHobbsastheinventoroftheHALTandHASStermsandtechniques. AbouttheAuthor DavidRahe,directoroftechnicalsupportatQualMark,hasmorethan16yearsofexperienceinthe environmentaltestindustry.HejoinedQualMarkin1996asthemanagingengineeroftheDenverARTCand laterservedasdirectorofoperationsforfourwestern-regionARTCs.Mr.RahealsohasheldpositionsofengineeringmanagerandgeneralmanageratTest2.QualMark,AcceleratedReliabilityTestCentersDivision,1329W.121stAve.,Denver,CO80234,(303)254-8800. GlossaryofTerms DL—DestructLimit ESS—EnvironmentalStressScreening HALT—HighlyAcceleratedLifeTest HASS—HighlyAcceleratedStressScreen NTF—NoTroubleFound LDL—LowerDestructLimit LOL—LowerOperatingLimit OL—OperatingLimit ROC—RateofChange UDL—UpperDestructLimit UOL—UpperOperatingLimit
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