Lot uniformity and small sample sizes in hardness assurance

Recent standard radiation test procedures allow wafer-level lot acceptance testing using as few as two or four parts with no failures. Such tests guarantee a high survivability of the accepted part only when the parts within a wafer exhibit a highly uniform response to radiation and when a large fraction of the wafers pass the test. The author points out the need for validating these tests, suggests techniques for doing so, and recommends modifications to current test procedures