PCB Differential Trace Segmentation for Signal Integrity
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Solution Overview
Problem
Current PCB design methods complicate layout routing, increase development costs, and result in inconsistent Signal Integrity (SI) performance between differential traces due to dielectric constant differences and structural limitations, especially in limited spaces.
Innovation Solution
A layout routing structure and method using a PCB made of glass cloth and epoxy resin, with staggered and offset differential traces routed on alternating materials to ensure equal transmission speeds and reduce noise conversion, employing specific angles and lengths for segments to maintain consistent signal delay and reduce impedance and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all high-speed traces are routed as oblique traces with an angle of 10° to reduce DK difference influence, then consistency of transmission delays is improved, but layout routing complexity increases and design cycle is prolonged
Solution Approach 1:
The differential traces are divided into multiple segments (first segments and second segments) with different routing paths. First segments are routed on glass cloth regions while second segments are routed on epoxy resin regions, allowing each segment to compensate for DK differences in its respective region, thereby maintaining transmission delay consistency without requiring complex oblique routing
Solution Approach 2:
Different segments of the differential traces are routed through different material regions (glass cloth vs. epoxy resin) according to their local DK characteristics. This local adaptation allows the routing to optimize for transmission delay consistency in each specific region rather than applying a uniform oblique angle throughout the entire board
2Ease of manufacture
If conventional board structure is used without pressure process, then development cost is reduced, but DK difference between points on the board increases affecting SI performance
Solution Approach 1:
The board is conceptually divided into glass cloth regions and epoxy resin regions, and the differential traces are segmented to route through both types of regions. This segmentation allows the design to work with the inherent DK differences rather than requiring a pressure process to eliminate them, reducing development cost while maintaining SI performance
Solution Approach 2:
The routing design changes the path parameters of differential traces to alternate between glass cloth and epoxy resin regions, compensating for DK differences through strategic routing rather than through material processing changes, thereby maintaining performance without additional manufacturing steps
3Manufacturing precision
If oblique traces are routed in limited structure space, then routing difficulty increases and time investment is required, but SI transmission requirement must be met
Solution Approach 1:
By segmenting the traces into first segments (on glass cloth) and second segments (on epoxy resin), the routing becomes more manageable in limited spaces compared to continuous oblique traces. The segmented approach allows for easier navigation around obstacles while maintaining SI performance through material-based compensation
Data Source
AI summary
A layout routing structure and a layout routing method for improving an SI performance of a signal are provided. Each of two positive and negative differential traces on a PCB includes multiple segments D1, multiple segments D2 and multiple segments D3. In each of the two differential traces, the segment D1 and the segment D2 are staggered and parallel to each other, the segment D2 is routed between any two segments D1, and any two adjacent segments D1 and D2 are connected by the segment D3. In one of the two differential traces, all of the segments D1 are routed on the glass cloth, and all of the segments D2 are routed on the epoxy resin. In the other of the two differential traces, all of the segments D1 are routed on the epoxy resin, and all of the segments D2 are routed on the glass cloth.