Effect of Fiber Weave Structure in Printed Circuit Boards on Signal Transmission Characteristics

Abstract

In this paper, we characterized and compared signal transmission performances of traces with different specifications of fiber weave. Measurements demonstrated that the dielectric constant, impedance fluctuation, and differential skew were all affected by fiber weave style. For flattened fiber weaves, the dielectric constant fluctuation reached 0.18, the impedance fluctuation amplitude was 1.0 Ω, and the differential skew was 2 ps/inch. For conventional fiber weaves, the three parameters were 0.44, 2.5 Ω, and 4 ps/inch respectively. Flattened fiber weave was more favorable for high-speed signal control. We also discussed the other methods to improve the fiber weave effect. It turned out that NE-glass (new electronic glass) fiber weave also had better performance in reducing impedance fluctuation and differential skew. Furthermore, made the signal traces and fiber weave bundles with an angle or designing the long signal line parallel to the weft direction both are simple and effective methods to solve this problem.

Validation of the Reference Impedance in Multiline Calibration With Stepped Impedance Standards

“…Accordingly, combining the results of ( 10) and (11) and inserting them into (9), we have the general sensitivity equations of | S ij | with respect to Γ given by For calibration verification, we require a standard that is most sensitive to mismatch error. Such a standard allows us to identify the error in the reference impedance of the calibration.…”

“…On the other hand, establishing traceable standards with PCB technology is more challenging. PCB manufacturing mostly uses composite materials made from reinforced fiberglass with epoxy resin, which can introduce significant delay skew depending on the location of the transmission lines on the substrate [10], [11]. Manufacturing : tolerances of PCBs are also much higher than those in onwafer applications [12], [13].…”

“…9. Previous studies have also presented crosssectional images of fiberglass dielectric substrates [11], [14]. The calibration comparison method [15], [16] is a widely used approach for validating on-wafer multiline TRL calibration.…”

An Impedance Transition Method to Verify the Reference Impedance of Multiline TRL Calibration

“…Millimeterwave (mm-wave) measurements performed on PCB are affected by uncertainties in the manufacturing process [9], [10]. Furthermore, dielectric materials based on fiberglass and epoxy resin can introduce a significant delay skew depending on the location of the transmission lines on the substrate [11], [12]. An illustration of microstrip lines on a PCB based on a fiberglass and epoxy resin mixture is depicted in Fig.…”

Mitigating differential skew by rotating meshed ground for high-density layout in flexible printed circuits

“…There is known a problem with the differential skew, such as the differential skew occurring in the differential transmission lines on a printed circuit board because of dielectric problems with the board's glass cloth [20,21,22,23]. It has been reported that the differential skew becomes a relatively small value when the angle between the trace of the differential transmission lines and the thread of the glass cloth is around 40 • [24].…”