TechNet team, I have an application where a LCCC (CTE = 7.6 ppm/°C) is to be soldered on to a Rogers Corp Duroid substrate (CTE = 24 ppm/°C). I know how to do the length differential calculation over temperature, but what criteria do I use to say whether the differential is OK or not OK? I could also do a stress calculation on the solder joints, but I don't have a value for Young's Modulus of the solder to plug in. If you have rules of thumb or past experience to share, I'd appreciate hearing from you. Thanks, Rich MacConnell Mechanical Engineer Northrop-Grumman --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------