A leak in an enclosure of an integrated circuit package is detected by the steps of: filling the enclosure with a first gas at the time the enclosure is sealed; subsequently enveloping the integrated circuit package with a second gas that is different than the first gas; holding the second gas at a constant...http://www.google.com.au/patents/US4893499?utm_source=gb-gplus-sharePatent US4893499 - Method and apparatus for detecting leaks in IC packages by sensing package deflections
