Overlapping Ground Planes for High-Speed Board-to-Board Signal Integrity
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Solution Overview
Problem
High-speed data transmission systems face significant challenges in maintaining signal integrity due to cross-talk between signal lines, which is exacerbated by the close proximity of high-frequency signals and the lack of effective shielding in conventional board-to-board connections, leading to signal distortion and degradation.
Innovation Solution
The electrical connection interface incorporates overlapping ground plane layers with strategically placed clearances and grounding webs to reduce cross-talk, while maintaining a compact form factor and cost-effective construction, using solder balls or press fit pins for connecting conductive leads and ensuring impedance matching to prevent signal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground plane layers are connected using ground-to-ground interconnecting leads extending over the ground plane free gap, then electrical connection between ground planes is established, but the connector size becomes significant (1200 μm per differential pair) and cross-talk reduction is insufficient
Solution Approach 1:
The patent transitions from a planar ground connection approach to a three-dimensional stacked configuration. Ground plane layers are positioned on opposite sides of the substrate at different vertical levels, connected through vertical vias rather than horizontal leads spanning large gaps. This vertical stacking reduces the horizontal footprint while maintaining electrical connectivity and shielding effectiveness.
Solution Approach 2:
The ground plane layers are nested within the substrate structure at different depths, with the first ground plane layer positioned below the first signal layer and the second ground plane layer positioned below the second signal layer. This nested arrangement allows compact integration of grounding structures without increasing the overall connector dimensions.
2Reliability
If conventional board-to-board connections are used without internal ground layers in the soldering region, then impedance compensation can be applied, but cross-talk between signal lines is not effectively eliminated
Solution Approach 1:
The patent introduces ground plane layers as intermediary shielding structures positioned between adjacent signal lines. The first ground plane layer is positioned between the first and second signal lines, while the second ground plane layer is positioned between the second and third signal lines. These ground planes act as electromagnetic shields that reduce cross-talk while allowing impedance compensation at the connection interface.
Solution Approach 2:
The ground plane layers are strategically positioned at specific locations where cross-talk is most problematic - between adjacent signal lines. The first ground plane layer is located between the first and second signal lines, and the second ground plane layer is located between the second and third signal lines. This localized grounding approach provides targeted cross-talk suppression without requiring ground layers throughout the entire connector.
3Length of stationary object
If signal lines are placed closer together to reduce connector size, then form factor is improved, but electromagnetic coupling and cross-talk increase
Solution Approach 1:
Ground plane layers are introduced as intermediary shielding structures between closely spaced signal lines. The first ground plane layer is positioned between the first and second signal lines, and the second ground plane layer is positioned between the second and third signal lines. These ground planes act as electromagnetic barriers that reduce coupling between adjacent signals while allowing the signal lines to be positioned close together for compact form factor.
Solution Approach 2:
The patent utilizes the space between signal lines, which would normally be a source of cross-talk, by positioning ground plane layers in these gaps. The first ground plane layer fills the space between the first and second signal lines, while the second ground plane layer fills the space between the second and third signal lines. This converts the harmful electromagnetic coupling region into a beneficial shielding structure that reduces cross-talk while maintaining compact dimensions.
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
This design effectively suppresses cross-talk and maintains signal integrity at high data rates, achieving improved insertion loss and crosstalk ratios, even at frequencies up to 40 GHz, while allowing for a compact and cost-effective high-speed board-to-board connection.
Implementation Method 1
cross-talk is caused by electromagnetic coupling between signal lines. Therefore, cross-talk is a particular problem for high-speed, high-density interconnection systems
Implementation Method 2
The traces transmit electrical signals across the respective first and second printed circuit boards
Implementation Method 3
A first printed circuit board has traces and pads on at least one of its surfaces, wherein particular contact pads are to be contacted by being soldered to mating contact pads on a second printed circuit board
Data Source
AI summary
An electrical connection interface is provided. The electrical connection interface includes a first ground plane layer, a second ground plane layer, a first substrate and a second substrate. The second ground plane layer is positioned to overlap the first ground plane layer. The first substrate includes a first substrate conductive lead with a first interface region connected to and electrically insulated from the first ground plane layer. The second substrate includes a second substrate conductive lead with a second interface region connected to the first substrate conductive lead and the second ground plane layer. The second substrate conductive lead is electrically insulated from the second ground plane layer.