Structural Specification
Fiberglass reinforcement fabric is the mechanical foundation of rigid printed circuit board laminates. This light woven material, designated as 1080 woven glass, consists of fine glass yarns woven into a plain pattern with a typical nominal thickness of about two thousandths of an inch. Yarn counts and thread spacing define this grade, yielding a highly flexible glass cloth that prepreg manufacturers coat with epoxy resin.
It creates a thin, uniform insulating layer. This uniform layer is required for multi-layer board build-ups that require precise dielectric thickness control, protecting internal circuits from physical deflection and ensuring dimensional stability during high-temperature thermal cycling.
Resin Absorption
High resin content characterizes the finished prepreg sheets produced with this thin fabric style. Because the open structure of 1080 woven glass provides large gaps between the yarns, the fabric holds a higher percentage of resin by weight than heavier, more tightly woven fabrics such as 7628 style glass. This high resin percentage ensures complete filling of copper patterns during the multi-layer lamination process.
Circuit boards with complex, fine-line copper tracks rely on this flow to eliminate micro-voids between adjacent tracks.
Dielectric Performance
Signal integrity in high-frequency circuit boards depends on the ratio of glass to resin in the cured dielectric layers. Since the glass filaments have a higher dielectric constant than the cured epoxy resin, laminates made with 1080 woven glass exhibit a lower overall dielectric constant due to the higher resin fraction. This lower dielectric constant supports faster signal propagation speeds.
It reduces signal attenuation. High-speed digital designs use this characteristic to control impedance.
