Ed You are touching a point where some solder reliability folks don't agree (at least I don't agree with some reliability folks). In my opinion there is no link because tin deforms with two deformation mechanisms ( Grain Boundary Sliding, GBS, and Dislocation Climb, DC ). How much of each mechanism is activated in tin depends on the temperature as well as on the deformation rate. Since each deformation mechanism has its own degradation law one can not compare tests where different ratios of DC/GBS are activated. This is the reason, why I have the opinion that the design of accelerated tests should be done with care and why I think that thermal shock tests are useless unless shocks occur in the use of the electronics tested. Guenter ################################################################ 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 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 ################################################################