激活能的意义.docVIP

激活能的意义:激活能是晶体中晶格点阵上的原子运动到另一点阵或间隙位置时所需的能量, 是反映温度应力对产品寿命影响的一种指标。对产品而言, 它从正常的未失效状态向失效状态转换的过程中存在着势垒, 这就是激活能。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。事实上, 当温度大于500K时, 激活能不再为常数。对于电子产品来说, 温度应力一般不会500K超过。激活能会随产品批次的不同和同批不同类的产品而不同,此外, 同一产品的不同失效模式也会使激活能发生变化。因此, 使用已公布的数值并不一定合适 Let the Data Speak About Activation Energy Let the Data Speak About Activation Energy There are many factors to consider when conducting an analysis of accelerated test data. One factor that is often overlooked or misrepresented is the activation energy. When considering accelerated life tes 　　Let the Data Speak About Activation Energy There are many factors to consider when conducting an analysis of accelerated test data. One factor that is often overlooked or misrepresented is the activation energy. When considering accelerated life tests, the activation energy represents the magnitude of effect that the applied stress will have on the product under test. A large activation energy indicates that the applied stress will have a large effect on the life of the product. Understanding activation energy is one thing, but obtaining an accurate value is another. Currently, the published values of activation energy relate to a particular material, technology, or failure mode, but how this value relates to a product, which may be composed of many different materials, is unknown. One possible method to alleviate the problem of selecting the most representative activation energy is to estimate the value based on collected data. Utilizing maximum likelihood theory, the parameters of the Arrhenius model are solved while using the Weibull distribution as the underlying life distribution. Once the parameters have been estimated, the activation energy and acceleration factor can be easily calculated. Arrhenius Relation The Arrhenius life-stress relationship is given by: where C is a parameter to be estimated, Ea is the activation energy and K is Boltzma