激活能的意义.doc

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1、激活能的懣义:激活能是晶休屮晶格点阵上的原子运动到另一点阵或间隙位毬时所需的能扯是反映温度应力对产阳寿命影响的•种指标。对产品而言•它从止常的来失效状态向失效状态转换的过程中行在希势这就是激活能C激活能越小.失效的物理过程越容易进行激活能越大.加速系数越大.越容易被加速而失效。激活能是不随温度变化的常数。也就是说.对应于某失效机理，激活能是不随温度变化的常数.这就保证了加速寿命试验的可行性。爭实上当温度大于500K时.激活能不再为常数。对于电子产品來说.温度应力•般不会500K超过。激活能会随产胡批次的不同和同批不同类的产胡而不同.此

2、外.同一产阳的不同失效模咒也会便激活能发生变化。因此，便用已公布的数值并不一定合适LettheDataSpeakAboutActivationEnergyLettheDataSpeakAboutActivationEnergyTherearemanyfactorstoconsiderwhenconductingananalysisofacceleratedtestdata.Onefactorthatisoftenoverlookedormisrepresentedistheactivationenergy.Whenconsiderin

3、gacceleratedlifetesLettheDataSpeakAboutActivationEnergyTherearemanyfactorstoconsiderwhenconductingananalysisofacceleratedtestdata.Onefactorthatisoftenoverlookedormisrepresentedistheactivationenergy.Whenconsideringacceleratedlifetests,theactivationenergyrepresentsthemagn

4、itudeofeffectthattheappliedstresswillhaveontheproductundertest.Alargeactivationenergyindicatesthattheappliedstresswillhavealargeeffectonthe1ifeoftheproduct.Understandingactivatioiienergyisonething,butobtaininganaccuratevalueisanother.Currently，thepublishedvaluesofactiva

5、tionenergyrelatetoaparticularmaterial,technology,orfailuremode,buthowthisvaluerelatestoaproduct,whichmaybecomposedofmanydifferentmaterials,isunknown.Onepossiblemethodtoal1eviatetheproblemofselectingthemostrepresentativeactivationenergyistoestimatethevaluebasedoncollecte

6、ddata.Utilizingmaximumlikelihoodtheory,theparameteTSoftheArrheniusmodelaresolvedwhileusingtheWeibulldistributionastheunderlyinglifedistribution.Oncetheparametershavebeenestimated,theactivatioiienergyandaccelerationfactorcanbeeasilycalculated.ArrheniusRelationTheArrheniu

7、slife-stressrelationshipisgivenby:EawhereCisaparametertobeestimated,E“istheactivationenergyandKisBoltzmannsconstant(8.617385*10-5eV/K).The2一parameterWeibullpdfisgivenby:0一1Thescaleparameter(characteristiclife)ish.TheArrhenius-Weibu11pdfisobtainedbysettingh=L(T).However,

8、theactivationenergy,mustbeknownaprioriandthisisrarelythecase.Soanotherparameter,B,isintroduced,where:TheArrhcn