Evaluating Spread Prepreg Styles for Timing Jitter Reduction in PAM4 Signal Lines
Spread prepreg styles flatten glass yarns to eliminate dielectric window voids, reducing differential phase skew below 1.5 ps per inch in PAM4 signal lines.
Style 1080
Glass Reinforcement
Lightweight woven fiberglass fabric serves as a thin structural substrate layer in high-density interconnect and high-speed printed circuit board laminates. Identified by standardized glass industry specifications, style 1080 uses fine yarn counts in both warp and fill directions to yield nominal fabric thicknesses near one and a half mils. The open plain weave pattern accepts high resin content, enabling laminate manufacturers to achieve low effective dielectric constants.
Thin dielectric core materials and prepreg bonding sheets frequently incorporate this style to achieve tight layer stackup dimensions. High yarn counts per inch provide uniform mechanical support for small microvia structures.
Physical Profile
Fine glass filament bundles arranged in forty-seven warp strands and forty-seven fill strands per inch create a symmetrical mesh structure. Low aerial weight permits thorough resin impregnation, reducing internal void formation during vacuum lamination cycles. However, open windows between narrow glass yarns create localized dielectric constant variations across short spatial distances.
Laser drilling operations penetrate thin filaments cleanly, forming smooth microvia sidewalls suitable for direct electroless copper plating. Board fabricators utilize this fabric style in build-up layers requiring tight thickness control and high resin fill capacity.
Electrical Impact
Localized dielectric constant shifts between glass bundle intersections and resin-rich openings induce phase skew in differential signal pairs. Trace routing strategies utilize angled layouts or spread glass variations to mitigate phase timing errors over long interconnect paths.