Grid Array Pattern for Crosstalk Reduction in PCB Assemblies
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Solution Overview
Problem
High-speed signal integrity disturbances, such as far-end crosstalk (FEXT), occur in printed circuit board (PCB) assemblies due to the close proximity of differential signal pairs, leading to reduced network performance as speeds increase, and existing solutions like increasing ground vias reduce signal throughput.
Innovation Solution
Implementing a Grid Array (GA) space design pattern that routes high-speed differential signals through interconnects to delay match and cancel FEXT by routing one signal away from and the other towards the victim signal, using interconnects of specific lengths to ensure equal propagation time and offset differences in via length and diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed differential signal pairs are routed close together to increase signal density, then signal throughput increases, but crosstalk between adjacent signals increases
Solution Approach 1:
The patent converts the harmful crosstalk effect into a beneficial cancellation mechanism by routing one signal away from the victim signal and the other toward it, creating equal and opposite crosstalk effects that cancel each other out, allowing high signal density without proportional increase in crosstalk
Solution Approach 2:
The patent applies asymmetric routing where the two signals in a differential pair are routed differently relative to the victim signal - one routed away and the other routed toward - creating intentional asymmetry in physical proximity that results in symmetric crosstalk cancellation when combined with the differential signaling
2Object-affected harmful factors
If ground vias are increased to reduce crosstalk, then crosstalk reduction is achieved, but signal throughput is reduced
Solution Approach 1:
Instead of using additional ground vias to suppress crosstalk (which would reduce throughput), the patent converts the crosstalk itself into a beneficial effect by routing signals to create opposing crosstalk paths that cancel each other, achieving crosstalk reduction without adding more ground vias or reducing signal density
3Object-affected harmful factors
If interconnect lengths are adjusted to delay match signals, then crosstalk cancellation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent adjusts the physical length parameter of interconnects to achieve delay matching, where one interconnect is made longer than the other to compensate for routing differences and ensure that signals arrive at the victim signal location at the same time, optimizing crosstalk cancellation
Data Source
AI summary
A printed circuit board (PCB) assembly may include a component capable of sending or receiving high-speed differential signal pairs, a package that is connected to the component, and a PCB connected to the package. The PCB assembly may be used to support a first high-speed differential signal pair that includes a first differential signal and a second differential signal. The first differential signal may be capable of causing crosstalk onto a particular differential signal, of a second high-speed differential signal pair, while propagating through the PCB assembly. A set of interconnects may be used to intelligently route the first differential signal pair within the package and/or within the PCB. The set of interconnects may include a first interconnect to route the first differential signal away from the particular differential signal and a second interconnect to route the second differential signal toward the particular differential signal.