PCB Trace Offset Layout for Fiber Weave Skew Control
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Solution Overview
Problem
The propagation characteristics of signals on printed circuit boards (PCBs) are affected by the routing of traces along fiber glass weave patterns, leading to skew and undesirable electrical coupling, which impacts signal integrity and synchronization.
Innovation Solution
Routing traces on PCBs with offset segments that align with corresponding layouts of the fiber glass weave pattern, reducing skew and minimizing electrical coupling by maintaining consistent impedance and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traces are routed along fiber glass weave patterns, then signal propagation is enabled, but skew and electrical coupling occur that degrade signal integrity
Solution Approach 1:
The patent applies local quality by varying the trace routing strategy based on the local fiber glass weave pattern. Traces are routed to align with the weave direction in certain regions to minimize skew, while in other regions they are positioned to avoid dense fiber areas that cause electrical coupling. This localized adaptation to the weave pattern's characteristics resolves the contradiction between enabling signal propagation and avoiding skew and coupling effects.
Solution Approach 2:
The patent changes geometric parameters of trace routing, including offset distances from fiber bundles, trace widths, and routing angles, to optimize signal propagation. By adjusting these parameters based on the fiber glass weave pattern, the design achieves consistent impedance and minimizes skew and electrical coupling, thereby improving signal integrity while maintaining functional connectivity.
2Reliability
If trace segments are offset to align with fiber glass weave pattern, then skew is reduced, but PCB space utilization is reduced
Solution Approach 1:
The patent applies partial offsetting rather than complete alignment for all trace segments. By offsetting trace segments partially to align with the fiber glass weave pattern only where necessary for signal integrity, and maintaining closer spacing where the weave pattern allows, the design achieves adequate signal synchronization while improving space utilization compared to full alignment approaches.
3Speed
If trace impedance is maintained consistent along fiber glass weave, then signal propagation speed is stabilized, but trace routing flexibility is reduced
Solution Approach 1:
The patent changes trace geometric parameters such as width, spacing, and layer selection to compensate for variations in the fiber glass weave pattern. By adjusting these parameters, the design maintains consistent impedance and stable signal propagation velocity while retaining sufficient routing flexibility to accommodate different circuit design requirements and adapt to various weave patterns.
Data Source
AI summary
A method of manufacturing a printed circuit board (PCB) includes arranging a first trace segment of a trace on a substrate of the PCB, the substrate being composed of fiber glass strands that define a fiber glass weave pattern, and arranging a second trace segment of the trace on the substrate at a position that is fractionally offset from the first trace segment along an axis by a distance that is less than a ball grid array (BGA) pitch of a BGA based on the fiber glass weave pattern. The BGA pitch is a separation distance along the axis between a center of a first via of the BGA of the PCB and a center of a second via of the BGA.