Laminate Glass Weave Selection for High Speed Differential Pair Routing
Selecting spread glass fabric styles with tight yarn pitch eliminates differential skew and preserves PAM4 channel margins without complex trace routing.
Glass Fabric Style 3313
Weave Geometry
Fiberglass reinforcement materials engineered for medium-range laminate thicknesses provide enhanced dimensional stability during PCB fabrication. Characterized by a yarn count of sixty ends per inch in the warp and fill directions, glass fabric style 3313 has a nominal thickness of 3.3 mils. This style sits between lightweight fabrics and heavy power-plane laminates, offering a balanced compromise for multi-layer builds.
Lamination Behavior
The thicker yarn bundles of glass fabric style 3313 increase the mechanical stiffness of the resulting laminate sheet. This rigidity helps prevent warpage during sequential build-up cycles where asymmetric copper distributions might otherwise warp the assembly. Laminators utilize this fabric to maintain flatness across large panel sizes while ensuring that the resin content remains high enough to prevent resin starvation around thick copper traces.
The increased glass mass also provides better resistance against conductive anodic filament growth along the glass-resin boundary.
Signal Integrity
Routing high-speed traces over this style requires careful consideration of the weave structure. Although the yarns are thicker, the fabric style 3313 can produce significant fiber-weave skew if the weave is not mechanically spread during laminate manufacturing. Selecting spread versions of this fabric minimizes the localized dielectric variations that disrupt high-speed signal pathways.