I would guess that 7781 is the yarn type, and E-glass is the standard glass
type used for FR-4 and most rigid PCB laminate materials.
According to Electronic Packaging Materials and Their Properties (Pecht et
al.), E-glass is 54.5% SiO2, 14.5-15-2% Al2O3, 17.2% CaO, 4.7% MgO, 8.0%
B203 and smaller amounts of some other compounds. Has a dielectric constant
of 6.3, density of 2.54 g/cc, CTE of 5.5 ppm/C. There is also S-glass,
D-glass, and quartz--all less common.
I don't see 7781 listed as a yarn type, but I do see 55.51, 5111, 5221,
6331, 7221, 9681 and 9991. I think the number relates to the number of glass
strands and how they are spun together.
Tim Reeves


-----Original Message-----
From: Steve Telgen [mailto:[log in to unmask]]
Sent: Friday, August 10, 2001 8:52 AM
Subject: Material specification


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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