PCB Trace Shield Structure With Voids for SerDes Crosstalk Reduction

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Solution Overview

Problem

High-speed serializer/deserializer (SerDes) links in printed circuit boards (PCBs) are susceptible to attenuation and crosstalk due to electromagnetic interference between adjacent parallel traces, which worsens with increasing data rates and package density.

Innovation Solution

The method involves forming trenches between traces on a PCB, filling these trenches with conductive material to create vertical walls, and then forming voids between these vertical walls to disrupt electromagnetic field lines and divert electromagnetic energy away from adjacent traces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high-density parallel traces are used to increase I/O density, then productivity and device functionality improve, but electromagnetic interference and crosstalk between traces worsen

Engineering Contradiction:

ImproveI/O densityVSAvoidcrosstalk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The continuous conductive layer is segmented into discrete ground shields positioned between adjacent traces. These segmented shields create electromagnetic isolation zones that prevent crosstalk while maintaining high trace density. The shields are selectively placed only where needed between specific trace pairs, optimizing the balance between signal isolation and I/O density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Ground shields made of conductive material are introduced as intermediary elements between signal-carrying traces. These ground shields act as electromagnetic mediators that redirect and contain electric field lines, preventing them from coupling between adjacent traces. The ground shields serve as a protective intermediary layer that maintains signal integrity in high-density configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional shielding methods are used to reduce crosstalk, then signal quality improves, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvesignal qualityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ground shields serve multiple functions simultaneously: they provide electromagnetic shielding between traces, act as reference planes for impedance control, and serve as attachment points for via structures. This multi-functionality eliminates the need for separate shielding layers and complex manufacturing processes, reducing overall device complexity while maintaining signal quality.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The shielding effectiveness is achieved by changing the geometric parameters of the ground shields (width, spacing, height) and their electrical connection parameters (via density, via diameter) rather than changing the fundamental shielding approach. These parameter optimizations provide effective crosstalk reduction using standard PCB manufacturing techniques, avoiding the need for specialized or expensive shielding materials and processes.

Inventive Principle:

Principle #35Parameter changes

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

This approach effectively reduces attenuation and crosstalk between traces without requiring high-cost materials, thereby enhancing signaling performance in high-speed channels and applications with high input/output density.

Implementation Method 1

the void extends between the first trace and the second trace... disrupt electromagnetic field lines and divert electromagnetic energy away from adjacent traces

Methodology Applied

Scientific EffectElectromagnetic field disruption: Electric Field

Implementation Method 2

filling these trenches with conductive material to create vertical walls... divert electromagnetic energy away from adjacent traces

Methodology Applied

Scientific EffectElectromagnetic energy redirection: Electromagnetic Induction

Data Source

PatentUS12207392B2Electronic component comprising first and second conductive traces and a void formed in an insulative layer between the first and second traces providing crosstalk reduction

Publication Date: 2025.01.21 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An electronic component includes a first trace configured to transmit a first signal and a second trace configured to transmit a second signal. The electronic component further includes a layer of conductive material separated from the first and second traces by a layer of insulative material. The electronic component further includes a first vertical wall formed in direct contact with the layer of conductive material. The electronic component further includes a second vertical wall formed in direct contact with the layer of conductive material. The second vertical wall is separated from the first vertical wall by a void, and the void extends between the first trace and the second trace.