Golden Finger Ground Loop for Impedance Discontinuity
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Solution Overview
Problem
Golden finger connectors on riser boards in server systems cause impedance discontinuity and signal reflections due to the absence of a ground plane under the edge region, leading to reduced signal margin and potential failure, especially with short trace lengths that are constrained by server height limitations.
Innovation Solution
A ground ring or loop is integrated under the golden finger connectors on the circuit board, extending from the ground plane to reduce impedance discontinuity and signal reflections, fabricated from conductive materials like copper, and connected to the ground plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the ground plane is cut out under the edge region with golden finger connectors to increase impedance, then the impedance is increased, but signal reflections and impedance discontinuity worsen
Solution Approach 1:
The patent applies local quality by creating a ground loop structure specifically under the golden finger connectors rather than extending the ground plane under the entire edge region. This localized ground loop provides the necessary impedance control and signal reference only where the connectors are present, maintaining signal integrity without unnecessarily reducing overall ground plane area.
Solution Approach 2:
The ground plane is segmented into a main ground plane area and a separate ground loop structure. The ground loop is specifically positioned under the golden finger connectors to address impedance discontinuity locally, while the main ground plane remains intact for overall system grounding. This segmentation allows targeted impedance management without compromising overall signal integrity.
2Reliability
If the ground plane is extended under the edge region to reduce impedance, then impedance discontinuity is reduced, but the ground plane area increases
Solution Approach 1:
Instead of extending the ground plane under the entire edge region, the patent implements a ground loop structure specifically under the golden finger connectors. This localized approach provides the necessary signal reference and impedance control only where connectors are present, avoiding unnecessary ground plane extension and preserving board space for other components or routing.
Solution Approach 2:
The patent transitions from a two-dimensional ground plane extension approach to a three-dimensional ground loop structure that contours around the connector area. This dimensional change allows the ground reference to follow the connector geometry closely, providing effective impedance control with minimal ground plane area consumption.
3Reliability
If the trace length between golden finger connectors and sockets is increased to reduce reflections, then signal reflections are reduced, but the board height increases
Solution Approach 1:
The patent applies preliminary anti-action by implementing a ground loop structure under the golden finger connectors before signals can reflect from impedance discontinuity. This preemptive grounding structure counteracts potential reflections by providing a stable impedance reference, eliminating the need for increased trace length to mitigate reflections.
Solution Approach 2:
The ground loop is positioned to preemptively address impedance discontinuity at the connector interface before signals propagate along the traces. By establishing proper impedance control at the source, the patent prevents reflections from occurring in the first place, eliminating the need for longer traces to allow reflections to decay.
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 ground loop reduces signal reflections and channel loss, achieving a 2.2 dB margin gain compared to traditional designs, with improved signal integrity and reduced impedance deviation, as demonstrated by probe measurements and frequency analysis.
Implementation Method 1
there is typically impedance discontinuity caused by the golden finger connectors on a riser or linkage board of a server system
Implementation Method 2
These discontinuities cause multiple reflections when signals are transmitted over the golden finger connectors
Implementation Method 3
A ground loop is formed on the second opposite surface under at least two of the plurality of connectors
Data Source
AI summary
A connector assembly is disclosed to reduce discontinuity impedance between golden finger connectors and components on a circuit board. The assembly includes a circuit board including a connector edge. A plurality of connectors is formed on the connector edge on a first surface of the circuit board. A ground plane is formed on part of the circuit board on a second opposite surface of the first surface. The ground plane leaves the second opposite surface under the connector edge exposed. A ground loop is formed on the second opposite surface under at least two of the plurality of connectors.