Hi Werner, I agree with your comment and your method completely. I would consider reviewing Young's modulus and a variable for degradation in the STII due to thermal excursions for inclusion in your STII value. What if we were to take a sample of a PWB, make our measurements, calculate the STII to use as our control? Then expose similar samples to 3, and 6 thermal excursions (260°C) to simulate assembly and assembly/rework. I bet the STII would change based on those thermal excursions. The degree of STII change would be a reflection of material robustness through assembly and rework. Best regards, Paul ________________________________ From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, September 02, 2008 11:11 AM To: Paul Reid; [log in to unmask] Subject: Re: [TN] TMA result Hi Leo & Paul, With Pb-free, you need to consider Td, Tg and CTE for reliability in combination---that is why I developed the STII (Soldering Temperature Imact Index)-parameter. Also, you also need to consider that you get different CTE's in the x and -direction (about 2 ppm/C), not to say anthing about the diagonal. Werner ************** It's only a deal if it's where you want to go. Find your travel deal here. (http://information.travel.aol.com/deals?ncid=aoltrv00050000000047) --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 -----------------------------------------------------