Based on previous experience with similar products, the

18.2. Based on previous experience with similar products, the failure time of a particular field effect transistor on a monolithic microwave GaAs integrated circuit, operating at 100°C (channel temperature), is expected to have a lognormal distribution with a median time to failure of 30 years. The primary failure mode is caused by a chemical reaction that has an activation energy of Ea = .6 eV. The value of the lognormal scale parameter for this failure mode is expected to be a = .7. (a) What are the lognormal parameters and a- if time is recorded in hours? (b) For operation at 100°C channel temperature, what is the time at which 5% of the units would fail? 10%? 90%? (c) Calculate the time-acceleration factor for testing at 250°C, 200°C, and 150°C channel temperature. Use Table 18.2 and Figure 18.3 and check with equation (18.2). (d) Obtain an expression for the temperature at which 100p% of tested units would be expected to fail in a 6000-hour test. Use this expression to compute the temperatures at which 90% and 10% would be expected to fail18.3. Refer to Exercise 18.2. Obtain an expression for the (average) FIT rate (in standard units of failures per hour in parts per billion) for the first 10 years of operation at 100°C? How much would this improve if the operating channel temperature is changed to only 90°C?