Hi Brian, Indeed, measuring technique has an influence on the Tg, or for that matter, any other property measurement. Let us also not forget that there are 3 different ways to measure Tg, with the method giving the most important value for reliability being TMA. We need to differentiate between laminate and prepreg layers. The prepregs closer to the platens will have a higher degree of cure and different Tg's than the layers near the PCB center; on the other hand, laminate layers will be the same throughout. But the prepreg layers will not only be different in Tg's, but also resin content, CTE [alpha 1 and alpha 2]; and they will be different from each other, but even more so from the laminate layers. That is the reason why barrel fracture invariably will be at barrel locations with prepreg layers not laminate layers. Werner --------------------------------------------------- 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 847-615-7100 ext.2815 -----------------------------------------------------