  Delay Deviation Exceedance (DDE) and Differential Skew Exceedance (DSE)
measures are proposed to quantify delay uncertainty in single-ended and
differential PCB interconnects arising from Fiber Weave Effect (FWE). DDE and
DSE are constructed with 3D EM analysis of traces over inhomogeneous dielectric
with glass fiber bundles in resin. Measurements or 3D EM models for FWE are
usually used for observations of delay or impedance dependency on position of
traces over fiber bundles with the purpose to find the worst case scenario.
This paper turns the results of 3D EM analysis into probabilistic measures of
possible delay or skew uncertainty - probability to have delay deviation in
single-ended interconnects over allowed limit (DDE measure) or to have skew
over allowed limit in differential interconnects (DSE measure). The introduced
measures allow formalizing the laminate selection process for parallel as well
as for serial PCB interconnects.
