Statistical analysis of fiber weave effect over differential microstrips on printed circuit boards

Fiberglass and epoxy-based dielectric substrates are ubiquitous in manufactured printed circuit boards. Their construction usually involves various woven fiberglass fabrics saturated with epoxy resin. These two materials have different electrical properties, hence as data rate increases and structure feature size decreases, the fiber weaves in the substrates can have profound impacts on the effective dielectric constants of printed circuit boards, which can cause unforeseen degradations in signal integrity. This paper proposes a systematic way of modeling fiber weave effect on high-speed interconnects over low-cost substrates, and also presents a statistical analysis of the impact of fiber weave effect on intra-pair skew of differential microstrip lines.