Earl, I was talking not so much about the resin to glass ratio, which will affect primarily dielectric constant and dissipation factor, but as to the butter coat of resin. How much or how thick a layer of pure resin is present on the top and bottom of the glass reinforcement. If that layer is compromised, you have weave exposure, and thence susceptibility to contaminant absorption. With the drive to get to thinner and thinner laminates, that resin layer often is the area that gets minimized. Doug --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------