Hi Bev, Brian is correct on all points, and just because people (that is who write Nortel or Telecordia or Bellcore or IPC specs, after all) established definitions does not make it a "fait accompli"; only sloppy use of language and a perfect source for miscommunication. Also, please do not misquote 'almost' ancient (I was part of it) work by Bell Labs; there indeed was a significant difference how one ramped up--the temperature increase had to precede the humidity increase and conversely, the humidity had to be decreased before the temperature was reduced. Crazy data resulted when condensation occurred. In both SIR and ECM it is very important, that only the areas to be measured contribute to the reduction in resistance. It thus becomes very important how the test leads are attached to the test vehicles and how much distance there is between attachment points. We have found, that for boards for which CAF paths are created PTH-to-PTH during T/RH/V exposure, such path are also created even if no bias is applied during the T/RH exposure; this path turn quickly into CAF upon application of the sensing voltage. One other thing we found was, that unless we supplied water to the internal wet-bulb reservoir via a peristaltic pump rather than an external refill reservoir, the internal reservoir can run dry. All in all, this is a rather complex subject matter. Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 904-437-8747, Fax: 904-437-8737 E-mail: [log in to unmask], Website: www.engelmaier.com ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################