Segmented Ground Via Structure for High-Speed Signal Integrity
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Solution Overview
Problem
Conventional coaxial vias in circuitry suffer from signal reflection and distortion due to impedance mismatch between signal conductors and transmission wires, especially at high speeds, limiting the quality of signal transmission in densely packed substrates.
Innovation Solution
A via structure comprising a ground conductor, a floated conductor, and a signal conductor, where the ground conductor is coupled to a reference potential, and the floated conductor is insulated from the ground conductor, with dielectric members between the conductors to adjust impedance and reduce signal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the dimension of the coaxial via is reduced to fit limited substrate space, then the area occupied is reduced, but the impedance of the signal conductor becomes smaller than the transmission wire impedance, causing signal reflection and distortion
Solution Approach 1:
The ground conductor is segmented into two separate conductors: a first ground conductor and a second ground conductor. These segmented ground conductors are positioned at different radial distances from the signal conductor, allowing independent optimization of their positions to achieve both compact via dimensions and proper impedance matching for high-quality signal transmission.
Solution Approach 2:
Different regions of the via structure are assigned different functional qualities. The first ground conductor is positioned closer to the signal conductor for impedance control, while the second ground conductor is positioned farther away for additional shielding and reference potential stability. This local differentiation of ground conductor positions enables simultaneous optimization of impedance matching and signal integrity within a compact area.
2Area of stationary object
If the dimension of the coaxial via is reduced to fit limited substrate space, then the area occupied is reduced, but signal reflection and distortion occur due to impedance mismatch
Solution Approach 1:
The ground conductor is segmented into two separate conductors: a first ground conductor and a second ground conductor. These segmented ground conductors are positioned at different radial distances from the signal conductor, allowing independent optimization of their positions to achieve both compact via dimensions and proper impedance matching for high-quality signal transmission.
Solution Approach 2:
A dielectric member is introduced as an intermediary between the signal conductor and the ground conductors. This dielectric member provides electrical insulation while its permittivity characteristics enable precise control of the impedance matching between the transmission wire and the via structure, thereby reducing signal reflection and distortion within a compact area.
3Device complexity
If a conventional coaxial via structure is used, then the structure is simple, but the impedance mismatch causes serious signal distortion at high speeds
Solution Approach 1:
The ground conductor is segmented into two separate conductors: a first ground conductor and a second ground conductor. These segmented ground conductors are positioned at different radial distances from the signal conductor, allowing independent optimization of their positions to achieve both compact via dimensions and proper impedance matching for high-quality signal transmission.
Solution Approach 2:
The impedance characteristics of the via structure are optimized by adjusting multiple parameters: the radial positions of the first and second ground conductors relative to the signal conductor, the permittivity and thickness of the dielectric member, and the dimensions of the conductors. These parameter adjustments enable impedance matching with transmission wires while maintaining a relatively simple overall via structure suitable for high-speed signal transmission.
Data Source
AI summary
A via structure includes a ground conductor, a floated conductor and a signal conductor. The ground conductor is electrically coupled to a reference potential. The floated conductor is electrically insulated from the ground conductor. The signal conductor is located between and insulated from the ground conductor and the floated conductor.