PCB Air Gap Pedestals Reduce High-Speed Noise Coupling
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Solution Overview
Problem
High-speed digital systems experience poor signal integrity due to cross-talk noise coupling between adjacent nets on printed circuit boards, which existing techniques fail to adequately address without complex digital signal processing and filtering.
Innovation Solution
A printed circuit board design featuring a core layer with copper sheets, a pre-preg layer with a mold-mat thickening agent, and a core insulating layer, where high-speed signal traces are supported by pedestals created by etching trenches in the core and pre-preg layers, resulting in air gaps between adjacent traces to reduce capacitive and inductive coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex digital signal processing and filtering techniques are used to reduce noise coupling, then noise isolation is improved, but device complexity increases
Solution Approach 1:
The patent extracts the harmful dielectric material between adjacent signal traces by creating air gaps through etching trenches. This removes the source of capacitive coupling at its origin, eliminating the need for complex digital signal processing to compensate for noise, thereby resolving the contradiction between noise isolation and device complexity
Solution Approach 2:
The patent introduces air gaps as an intermediary medium between adjacent signal traces. Air serves as a mediator with minimal dielectric properties, replacing the harmful solid dielectric material and reducing capacitive coupling without requiring complex processing systems
2Object-affected harmful factors
If trace spacing is increased to reduce cross-talk noise coupling, then noise isolation is improved, but area of the circuit board increases
Solution Approach 1:
The patent applies local quality modification by creating air gaps only in specific regions between adjacent signal traces where capacitive coupling occurs, rather than uniformly increasing the spacing between all traces. This localized approach reduces cross-talk noise coupling while maintaining compact overall board area
Solution Approach 2:
The patent addresses the spacing issue by moving from a two-dimensional spacing problem to a three-dimensional solution. Instead of only increasing horizontal trace spacing, the invention creates vertical air gaps by etching trenches and filling with air, adding a vertical dimension to the isolation strategy and reducing the required planar area
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces cross-talk noise coupling between adjacent nets on PCBs, maintaining signal integrity without increasing trace spacing and utilizing air gaps to minimize capacitive coupling, as demonstrated by simulation results.
Implementation Method 1
cross-talk noise coupling from adjacent nets on PCBs is reduced... utilizing air gaps to minimize capacitive coupling
Implementation Method 2
reduces cross-talk noise coupling between adjacent nets on PCBs... to reduce capacitive and inductive coupling
Data Source
AI summary
An apparatus having reduced noise coupling includes a core layer having an upper and lower surface, the upper and lower surface each including a copper sheet layer, a pre-preg layer having an upper surface and a lower surface, the upper surface of the pre-preg layer coupled to the lower surface of the core layer, a core insulating layer having an upper surface and a lower surface, the upper surface of the core insulating layer coupled to the lower surface of the pre-preg layer, a return current reference layer disposed on the lower surface of the core insulator layer and high-speed signal traces disposed on the upper surface of the core insulating layer, each of the high speed signal traces disposed on a pedestal defined by a section of the pre-preg layer and the core insulating layer, each pedestal being separated by an air gap disposed between adjacent pedestals.