Backplane Footprint Using Shadow Vias for High-Speed Differential Pairs
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Solution Overview
Problem
High-density, high-speed electrical connectors face challenges with electrical interference and crosstalk due to the close proximity of signal conductors, which affects the overall electrical performance of interconnection systems.
Innovation Solution
The incorporation of shadow vias, which are conductive structures extending through the layers of a printed circuit board, positioned between signal vias of a differential signal pair, helps reduce crosstalk and improve electrical properties by altering the electromagnetic environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of signal conductors is increased to achieve higher data transmission capacity, then the data transmission capability is improved, but electrical interference and crosstalk between adjacent conductors worsens
Solution Approach 1:
Ground conductors are introduced as intermediary elements between signal conductors. These ground conductors act as mediators that provide a reference potential and shield the signal conductors from mutual interference, thereby enabling higher data transmission capacity while reducing crosstalk between adjacent signals
Solution Approach 2:
The connector is divided into multiple independent signal pairs, each surrounded by its own ground conductors. This segmentation isolates each signal pair's electromagnetic field, preventing interference between different signal channels while maintaining high overall data transmission capacity through parallel operation of multiple pairs
2Quantity of substance
If signal conductors are placed closer together to achieve higher density, then the connector density is improved, but crosstalk between adjacent signal conductors increases
Solution Approach 1:
Ground conductors are positioned between closely spaced signal conductors to serve as electromagnetic shields. This intermediary structure allows signal conductors to be placed closer together for higher density while the ground conductors block the electromagnetic coupling that would otherwise cause crosstalk between the dense signal arrangements
3Reliability
If shield members are added between signal conductors to reduce crosstalk, then electrical properties are improved, but the complexity of the connector structure increases
Solution Approach 1:
The ground conductors perform multiple functions simultaneously: they provide a reference potential for differential signaling, act as shields between signal conductors to reduce crosstalk, and maintain mechanical structure integrity. This multi-functionality improves electrical properties without proportionally increasing structural complexity, as the same elements serve multiple purposes
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 use of shadow vias effectively reduces crosstalk between signal vias in high-density connectors, enhancing the electrical performance at high frequencies, including improved differential mode and common mode performance.
Implementation Method 1
The incorporation of shadow vias, which are conductive structures extending through the layers of a printed circuit board, positioned between signal vias of a differential signal pair, helps reduce crosstalk and improve electrical properties by altering the electromagnetic environment
Data Source
AI summary
A printed circuit board includes a plurality of layers including attachment layers and routing layers; and columns of via patterns formed in the plurality of layers, wherein via patterns in adjacent columns are offset in a direction of the columns, each of the via patterns comprising: first and second signal vias forming a differential signal pair, the first and second signal vias extending through at least the attachment layers; and at least one conductive shadow via located between the first and second signal vias of the differential pair. In some embodiments, at least one conductive shadow via is electrically connected to a conductive surface film.