Low Loss Hybrid-Plane PCB Structure for Improving Signal Quality in High-Speed Signal Transmission

Abstract

Due to the inherent loss characteristics of transmission lines today, the challenges in signal transmission are increasing. Typically, the most widely used printed circuit boards (PCBs) in transmission lines employ FR-4 as the insulation material due to its advantages in electrical insulation and cost-effectiveness. Nevertheless, PCBs that rely solely on FR-4 for the entire insulation layer are unsuitable for high-speed circuits due to significant dielectric losses. Efforts have been made to reduce losses by researching hybrid-stackup PCBs that stack low loss dielectric materials vertically. However, due to the high cost of these low loss dielectric materials, they have mainly been applied in high-end and high-speed applications. Therefore, in this paper, we propose a hybrid-plane PCB structure that uses low loss dielectric materials only in the planes adjacent to high-speed signal traces, minimizing the use of expensive low loss dielectric materials while achieving similar enhancements in signal quality compared to previously researched hybrid-stackup each PCB was modeled using Ansys Q2D Extractor, and S-parameters and eye diagrams were extracted for each to compare their electrical characteristics and signal quality. The simulation results confirm that the proposed hybrid-plane PCB structure in this paper has been found to exhibit improved electrical characteristics compared to PCBs constructed solely with an FR-4 insulation layer. Furthermore, various low loss dielectric thicknesses were compared to interpret the optimal thickness of the low loss dielectric for the hybrid-plane PCB, based on the signal integrity assurance rate.

Keywords

• High-speed
• low loss dielectric material
• PCB
• signal integrity (SI)
• signal loss