Meaning
Multiplicative coefficient relates the observed failure rate under extreme laboratory conditions to the expected failure rate in the end-user environment. Calculating the field acceleration factor allows reliability engineers to compress years of field life into hundreds of hours of testing. This value is derived from physical models of degradation such as the Arrhenius equation for temperature.
It acts as the bridge between destructive testing and the warranty commitments made to the customer.
Stress Level
Differences between test parameters and operational parameters define the magnitude of the result. A higher field acceleration factor implies that the test is much more aggressive than the actual use case. Designers must ensure that the stress applied does not trigger failure modes that would never occur in the field.
Model Accuracy
Fitting data to a specific mathematical distribution is necessary for a valid projection. The field acceleration factor relies on the assumption that the same failure mechanism is active at both high and low stress levels. If a new mechanism appears during accelerated testing, the calculated factor is no longer valid.
Lifetime Prediction
Multiplying the test duration by the calculated constant yields an estimate of the product service life. This field acceleration factor is specific to each failure mode, such as dielectric breakdown or solder joint fatigue. A single component might have different factors for different environmental stressors.
