Hi Jason, The "large grain structure, yielding a low fatigue resistance" is a red herring, since the grain structure of solder is unstable and coarsens with time and temperature. True, if you fatigue cycle fine grained solder in an accelerated test you get about twice the life as compared to coarse grained solder, but for actual product this is immaterial since within a years time the initial fine grained solder is virtually indistinguishable from initially coarse grained solder. You ask: "will the invar layers help with TCE mismatch issues and/or board warpage". The CTE (not TCE--coefficient of thermal expansion) mismatch is not the issue in solder joint reliability, it is the thermal expansion mismatch. That is not quite the same thing for real product (it is for temperature cycling in a chamber). And the answer is : It depends. It depends on the type of components (materials) you are using, whether the run much hotter than the PCB, and whether they are attached with compliant leads. 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 ##############################################################