Early Failure Rate (EFR)
The EFR is obtained by accumulating the test-results of SHTL and DHTL stresses over a period of 12-months, with readpoints upto 170 hours of stress. The "fpm" figures are calculated with a 60% Confidence Level (Poisson statistics).
Components typically have an initially high, but rapidly decreasing, failure rate. The Early Failure Rate (EFR), sometimes referred to as Infant Mortality Failures (IMF) or Early Life Failures (ELF), represents this small fraction of the population of components which contain defects that do not immediately fail but will fail in a relatively short time interval.
The formula for calculating the Early Failure Rate, expressed in Failures-Per-Million (FPM), is:
EFR = nc(n) * 106
It is often useful to normalize the Early Failure Rate based upon die area, especially for large die. This methodology allows for scaling of Early Failure Rate FPMs based upon die area as follows:
EFRN = nc(n) * 106 * AN
Σ[(N1*A1) + … + (Nn*An)]