Hi Dave, We use a thermal mechanical analyzer (TMA). The amount of change is so small I think TMA is the only reasonable method for an accurate readings. With TMA you can measure CTE before and after Tg and the overall change of thickness at any temperature. Most labs, our company included, can perform the test. The real question is ... Why do you want to know CTE? The CTE measurement is straight forward. The implication of the measurement, particularly on reliability and the like, is very much convoluted. Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. 235 Stafford Rd., West, Unit 103 Nepean, Ontario Canada, K2H 9C1 613 596 4244 ext. 229 Skype paul_reid_pwb [log in to unmask] <mailto:[log in to unmask]> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Connitt Sent: Wednesday, January 21, 2009 6:34 AM To: [log in to unmask] Subject: [TN] method of calculating CTE of a rigid flex circuit board Hello, Does anyone know of a reasonably accurate way of calculating the overall CTE of a 4 layer rigid flex circuit board? Thanks, Dave Connitt CID+ Printed Circuit Designer L3 Fuzing & Ordnance Systems A Wholly Owned Subsidiary of: L3 Communications 3975 McMann Road Cincinnati, Ohio 45245 Ph. 513- 943-2010 Fax 513-943-2288 --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------