Mike Yes: that is why I used the term "extreme edge" because I have no idea how much diffusion through the material could be expected in the pressing time. Brian Mike Fenner wrote: > 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 > ############################################################## ############################################################## 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 ##############################################################