Hi Paul, You ask whether cracks could be found by interpolating the known good tolerances program against the tested resistivity variances. I doubt that you would have sufficient sensitivity or actual differences. Some 15 years back, there was a study by IBM-Minneapolis, that showed that you needed about a physical separation of 80% of the fracture surfaces to have a 10% increase in resistance for a single solder joint instrumented with a 4-point probe. On the other hand, high-speed signals should show signal reflections and deterioration of rise times, that should be detectable. 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 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################