Hi Glenn, A couple of comments: (1) there is now way I know of that any HAST of the type you describe can be related to 20 years of operation, (2) the water vapor pressure at 120C, 98%RH is huge and is likely to cause all kinds of things to happen to your PWAs that would not happen in realistic conditions, (3) you must have an incredibly well controlled humidity chamber in order not to get condensation somewhere in the chamber--and then of course all bets are off anyway, (4) a HAST really is designed to serve a totally different purpose than an accelerated reliability test; HAST is designed to be used on prototypes to make a design more robust, while accelerated reliability tests are designed to cause damage by the same damage mechanism expected in operation or storage on an accelerated basis WITHOUT the introduction of any extraneous damage mechanism(s). Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 973-543-2747 E-mail: [log in to unmask]