This paper addresses the question under what conditions bum-in can be eliminated. Based on data of more than 30 million sold devices, the effect of screening of latent defects at electrical test on product reliability has been investigated. The results are combined with the yield-reliability relation and an experimentally determined failure rate time evolution, yielding a model that allows to determine the sense or non-sense of bum-in or screens at electrical test quantitatively. The model predictions are in good agreement with experimental data. Furthermore for typical operating conditions high yielding batches show a better long term reliability than low yielding batches even if the latter have been subjected to bum-in. It is also shown that voltage stresses, distribution tests and Iddq screens can be good alternatives to burn-in. Transition period -Voltage screen &Distribution testing * No screen Month Fig. 2: Defect density trend of the Bipolar-BiCMOS waferfab.