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Method for the use of carbon materials for signal coupling across plane splits on PCBs

IP.com Disclosure Number: IPCOM000009598D
Publication Date: 2002-Sep-04
Document File: 4 page(s) / 44K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the use of carbon materials for signal coupling across plane splits on printed circuit boards (PCBs). Benefits include improved design flexibility and improved ease of manufacturing.

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Method for the use of carbon materials for signal coupling across plane splits on PCBs

Disclosed is a method for the use of carbon materials for signal coupling across plane splits on printed circuit boards (PCBs). Benefits include improved design flexibility and improved ease of manufacturing.

Background

        � � � � � High-speed signals that cross splits in adjacent reference planes (power/ground) generate electromagnetic (EM) radiation because of the electrical discontinuity caused by the plane split. This radiation can lead to issues with electromagnetic containment (EMC) and signal integrity (SI). Additionally, the increased electrical path length around the plane split creates increased loop inductance and reduces frequency response. To avoid these problems, high-speed signals typically are not routed over plane splits. However, this practice adds routing constraints for PCB designers.

� � � � � High-speed signal routing limitations imposed by power/ground plane splits are conventionally addressed through the addition of stitching capacitors across plane splits (see Figure 1). The capacitors provide AC signal coupling that reduces EM radiation at plane splits and subsequent EMC/SI effects. However, this approach requires at least one stitching capacitor for each signal trace crossing a plane split and is costly from the component and PCB surface area usage aspects. As a result, the stitching capacitor solution becomes undesirable, when a large number of signal traces are crossing a plane split.

General description

        � � � � � The disclosed method is the addition of a conductive material layer, such as carbon or metalization in a printed circuit board stack-up to enhance signal coupling across power/ground plane splits. The conductive layer may overlap just the split in the plane or be an entire layer.

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved performance due to reducing EM radiation and EMC/SI effects across a broad frequency spectrum without resorting to the use of stitching capacitors

•        � � � � Improved design flexibility due to relaxing the signal routing constraints currently imposed by power/ground plane layouts

•        � � � � Improved ease of manufacturing due to more efficient use of PCB surface area

•        � � �...