JEDEC JESD 85:2014

The methods described in this document apply to failure modes and mechanisms whose failures exhibit a constant failure rate, e.g., an Arrhenius behavior characterized by an activation energy
for failure. If data on the distributions of failure with time exist, these activation energies can be
assumed from prior knowledge or failure analysis signatures. If the default activation energies are not known or can't be determined, an activation energy can be used as a default. Refer to JEP122 Activation Energies for Failure Mechanisms to obtain initial estimates. The purpose of this method is to provide a reference to the way failure rates are calculated in FITs.