When The Test Cell Lies

Key Takeaways: A marginal test result can be electrically valid and still diagnostically misleading because the socket, load board, and thermal loop are now part of the measurement. Separating device drift from test-cell drift depends on tracking margins, variance, and calibration trends rather than bins alone. In advanced packages, a false pass destroys value downstream, a false failure discards it early, and a false downgrade hides the loss inside normal binning. The first problem with a margi