Definition

Fiber weave effect refers to the signal integrity impact of periodic dielectric constant variation in glass-reinforced laminates. Glass fiber bundles have different Dk (~6) than the surrounding resin (~3), creating a pattern of Dk variation. Traces routed over glass bundles see different impedance than traces over resin-rich regions. This causes timing skew between differential pair legs and impedance ripple. Mitigation includes rotating the board relative to the trace direction, using spread glass materials, or non-woven reinforcement for critical applications.