Ok, my turn to try and give back here...(thanks to all who replied to my
question about availablity of cap arrays). 7781 E-glass means  E=
Electrical. E-glass is an aluminosilicate glass.  7781 = the yarn style
(yarn, warp x fill and weight). "7781" just refers to the yarn style, not
the finished material and sizes available or application.  In your
comparison shopping for "7781 E-glass" for PCB use you want to look for
resin-compatibility as this varies from mfgr. to mfgr. depending on how the
material is processed.  Before weaving the yarn is sized with a binder or
coating to maintain strand integrity and protect the fibers during the
weaving process. After weaving the fabric is "desized" to permit adhesion
between the glass fiber and chrome or silane finishing agents. Finally, the
fabric is finished to give desired resin compatibility. There are
conventional processed E-glass PCB yarns (usually with an oily starch) and
there are some with newer coatings available now that are supposed to help
eliminate heat cleaning ( a problem with the oil starch used for "sizing"),
improve hydrolytic stability and increase overall laminate strength and
stiffness among other things. Take a look at websites for Owens Corning,
PPG Industries, Nippon among others for more info.
-eom-

At 11:52 AM 8/10/01 -0400, Steve Telgen wrote:
>Hi, everyone,
>Does anyone know what 7781 E glass is?  It's supposed to be a type of
>fiberglass material for PCBs.
>TIA
>Steve Telgen
>IGK Industries

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