Usage temperature has a significant effect on reliability as illustrated on this slide. This effect is based on chemistry’s Arrhenius equation, which is typically used to model the acceleration of temperature dependent on physical process that lead to functional wear out. In this equation: CR is the “Process Rate Coefficient”; M is an experimentally determined constant specific to the materials/methods used; e is Euler’s number (2.718281), the base of the natural log; Ea is the activation energy for the processes that lead to failure (typ. 0.8eV to 1.0eV); k is the Boltzmann constant 8.617x10-5 evK-1; and T is temperature (°K), typically at ambient room temperature (25°C / 298°K). The effect of a given temperature change on a component’s projected life can be measured using a small modification to calculate the acceleration factor as highlighted in the second equation above where T1 is the reference temperature (e.g. 85°C / 358°K), T2 is the actual use temperature and M is eliminated as it is the same at both temperatures.