A study on fibre weave effect on intra-pair skew of differential lines using analytical approach

As differential lines at very high speed are electrically long, fibre weave effect on intra-pair skew of differential lines will affect the signal integrity (SI). Due to the geometrical constraints of the printed circuit board (PCB) substrate's fibre weaving, the effective dielectric constant of the positive signal trace differs with the effective dielectric constant of the negative signal trace. When the difference is large, it will result in signal skew. This paper serves to provide some insights on the conditions on how to handle the fibre weave effect.