# A particular type of IC has two different failure modes, both of which can be accelerated by…

19.9. A particular type of IC has two different failure modes, both of which can be accelerated by increasing temperature. The random failure time of Mode 1 is TM, and the random failure time due to Mode 2 is TM2. In a unit, suppose that the IC fails at T = min(TM, , TM2). Failure mode M, has an activation energy of Ea = 1.4 electron volts and failure mode M2 has an activation energy of Ea = .7. The physical nature of the failure mechanisms suggests that TM, and TM2 are independent. The engineers involved believe that both TM, and TM2 have a lognormal distribution. At the proposed highest test temperature of 120°C, with failure time measured in hours, assume that = 6.9, ir, = .6, µ2 = 9.0, and u2 = .8. (a) Assuming an Arrhenius ALT model, plot the median of the failure-time distribution versus temperature for failure mode M, and also for failure mode M2. Plot using temperatures between the use temperature of 40°C and 120° C. (b) Plot the .1 and .9 quantiles of the mode M, failure-time distribution and of the mode M2 failure-time distribution, as a function of temperature. (c) Use the plots to help describe potential dangers of using a temperature-accelerated life test on a component, ignoring failure mode differences, when the different failure modes have vastly different activation ener-gies.

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