PCB Ground Plane Segmentation for Impedance Control
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Solution Overview
Problem
Current printed circuit boards (PCBs) face challenges in achieving precise signal impedance adjustment, minimizing leakage currents, and reducing electromagnetic interference due to high electronic component density and high-speed data transfer requirements, which often result in uncontrolled impedance and increased thickness.
Innovation Solution
A PCB design featuring conductive layers separated by insulation material with a ground plane layer that includes openings between conducting stripes crossing signal lines at an angle of 30°-60°, preferably 45°, allowing for adjustable impedance and defined return current paths without splitting the ground plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between signal lines and ground plane is increased to achieve higher impedance, then impedance control is improved, but PCB thickness increases
Solution Approach 1:
The ground plane is segmented into conducting stripes separated by openings, creating a structured ground plane. This segmentation allows control of the effective ground area to achieve precise impedance matching without increasing the distance between signal lines and ground plane, thus maintaining thin PCB thickness while achieving 90-100 ohm impedance requirements
Solution Approach 2:
The ground plane structure is locally optimized with conducting stripes positioned and dimensioned specifically to control impedance characteristics. The openings are strategically placed to adjust the effective ground area beneath each signal line, enabling precise local impedance control without affecting overall PCB thickness
2Reliability
If a continuous ground plane is used to provide return current paths, then signal integrity is improved, but electromagnetic interference increases
Solution Approach 1:
The continuous ground plane is divided into conducting stripes with openings between them. This segmentation reduces the ground plane's antenna effect and electromagnetic radiation while maintaining sufficient return current paths through the striped structure, thereby reducing electromagnetic interference while preserving signal integrity
Solution Approach 2:
The ground plane is designed with a porous-like structure of conducting stripes separated by openings. This allows the ground plane to provide necessary electrical reference and return paths while reducing the continuous conductive area that would otherwise act as an antenna, thus minimizing electromagnetic interference
3Manufacturing precision
If additional conductive layers are added to achieve required impedance, then impedance control is improved, but device complexity increases
Solution Approach 1:
Instead of adding more conductive layers to achieve impedance control, the invention segments the existing ground plane into conducting stripes with openings. This approach achieves the required 90-100 ohm impedance in tight HDI areas without introducing additional layers, thereby avoiding increased device complexity while maintaining manufacturing precision
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 achieves stable signal performance with adjustable impedance, reduced signal loss, and minimized electromagnetic interference, maintaining a thin PCB thickness even in high-frequency regions.
Implementation Method 1
a conductive layer associated to and extending along the at least one signal line is provided with openings therein. According to the invention the openings are spaces between adjacent conducting stripes, extending, seen from above, across the at least one signal line
Data Source
Figure 1~3
AI summary
A printed circuit board (9) comprising conductive layers (11,15, 21 ) separated by insulation layers (14, 16) of dielectric material, at least one conductive layer (11, 15) being patterned and having at least one signal line (12, 13) embedded in an insulation material (10, 14, 16 ), whereby a conductive ground plan layer (15), separated by the insulation material and lying in a predetermined distance (d) from the at least one signal line includes a ground plane area (17) associated to and extending along the at least one signal line, the conductive layer (15) associated to and extending along the at least one signal line (12, 13) is provided with openings (18) therein. Preferably the openings (18) are spaces between conducting stripes (19), extending, seen from above, across the at least one signal line, the conducting stripes being integrally connected with the conductive remainder (20) of the conductive layer (15).