This is likely poor glass wet-out of the package during lamination - cores or final lam of the board.  During the laminate cycle, the resin on the glass fabric enters the liquid state briefly and wets to the glass fibers in the pre-preg, then cures into the C stage of the resin system (this is GEL Time).  This allows the resin to become the bonding agent for the package and cure into the required dielectric layer.  The fibers become encapsulated in the resin providing good thermal/mechanical strength as intended.  When this wet out is impacted by low resin content, gel time, pressure and possibly other rheology issues, the glass is not bonded into the package.  This will produce a substrate shows the fibers a lighter than the resins with the weave properties visible.  Impacts are electro-mechanical performance deltas in a host of areas, which also vary by extent of the wet out issue.  

Jeffrey Bush
BAE Systems Incorporated 
IS&R - Space Products and Systems
P.O. Box 868, MER24-116A
Nashua, NH 03061-0868
Office +1 603.885.8137
Mobile +1 603.318.8056
Fax +1 603.885.5258

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Friday, November 16, 2012 8:14 AM
To: [log in to unmask]
Subject: [TN] Laminate, Resin recession-dry glass bundle

Fellow TechNetters:

   Can any of the gurus out there comment on the above terminology and perhaps share a photo.   What is the worse than can occur within the laminate with such artifacts.

"X"

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