Hi Richard , I sure am getting tired of all the acronyms floating around, particularly since they are hardky ever properly defined and/or applied. What you described as your ESS procedure in not ESS, but a burn-in. ESS has to be much more severe to screen-out (bring to failure) latent defects, whiule at the same time not significantly damage good product. What you describe as HARASS', is thermal shock—any procedure involving rates of change above about 40C/min, note: not 40C/sec, is dominated by thermal shock which involves the loading of your product by severe warping due to the large thermal gradients. It certainly will fail bad solder joints, but—depending on the T extremes—also good ones. The best ESS for solder joints is vibration, preferably at cold temperatures like -40C. Latent defects in solder joints means inadequate wetting—in essence no real solder joint with a metalurgical bond has been formed. Most other so-called (latent) defects have no significant impact on reliability. In all ESS testing of solder joints, the monitoring for failures has to be done during loading, because the opens are intermittent and the fractured/separated surfaces make typically good electrical contact at rest. 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] ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################