I'm just following along on this exchange which is interesting, but Brian in this scenario wouldn't the "middle" start a very short distance from the edge? I wouldn't have thought the extra outlet path provided by the thickness of material would be significant over any great distance compared to the surface area of the two faces of the sheet.. Mike ----- Original Message ----- From: Brian Ellis <[log in to unmask]> To: <[log in to unmask]> Sent: Friday, June 09, 2000 9:21 AM Subject: Re: [TN] Baking of boards Tim Thanks for this info. Interesting. First time I've heard of non-aqueous solvents having the same effect, although it is not unreasonable. However, this leads me to another question. To make the prepreg, the glass cloth is run through a solution of resin, which is then dried in the treater ovens. There is always some solvent (I think ca. 1%) left in the prepreg. During pressing, this will certainly vapourise, but it has nowhere to go, especially in the middle of the sheets. Does this mean that samples taken from the middle of a sheet of laminate will have a lower Tg than from the extreme edge???? The 5 deg C Tg range measured seems very small. I would opt for 10 or more being more typical, as this is a function of the MW of each molecule, which is very variable. A small range implies that the average MW is quite small, which may not offer the best electrical properties, as I understand it. ############################################################## 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 Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################