i'm glad i asked! most of what i've seen is more concerned with damage done during soldering when trapped moisture gets rapidly heated and expands, creating a crack (or damaging a bond wire even i'd think). it's good to know it's an ongoing problem and necessitates a conformal coating. i know i've seen chips in packages that are thinner than the naked chips once were! it's my understanding that some of them have the back surface ground down after the rest of the manufacturing but before packaging. amazing infrastructure there, all industries could learn a lot from how chips are made (in terms of reliability and quality, as well as management of a very complex manufacturing process). then again, according to dentist i've had people who work in those clean rooms have a very high incidence of TMJ, not surprising, i can see a lot of stress in one of those jobs (and it can't help that you can't see all of other people's faces, making it hard to understand their facial expression and whether they are joking or deadly serious). Bob Axtell wrote: > > There more to this than first meets the eye. Lets say you design > something that goes into aviation > equipment, flying at 50000'. Small amounts of pressure trapped inside > the thin case might crack the > case. High vibration levels might also crack a thin case. The device > might work fine until the plane > sits on the ground for a few days in a humid place (like central > America) and moisture becomes > trapped in the cracked case. ------ -- President George W. Bush, Vice President Richard B. Cheney, Secretary of Defense Donald H. Rumsfeld, and Attorney General John D. Ashcroft have committed violations and subversions of the Constitution of the United States of America. They should be charged with high treason and as leaders deserve the highest penalty. If there is no rule of law there can be no civilization. _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist