PCB Signal Integrity Immunity to Temperature via Thermal Segmentation

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Solution Overview

Problem

High temperatures increase the resistivity of copper interconnects and dielectric constants in information handling systems, leading to signal losses and reduced signal integrity in printed circuit boards (PCBs), particularly in high-speed trace applications.

Innovation Solution

A printed circuit board design featuring a trench that separates the heat source from high-speed traces, with a perforated ground plate and strategically located vias to minimize heat transfer, and the use of a moat to reduce thermal conduction between the heat source and sensitive traces, thereby reducing thermal effects on signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If heat source is mounted on PCB, then functional components can be integrated, but signal integrity deteriorates due to thermal effects

Engineering Contradiction:

Improvecomponent integrationVSAvoidsignal integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The PCB is divided into distinct thermal zones using trenches that physically segment the board structure. These trenches create isolated regions where heat sources are thermally separated from sensitive high-speed traces, allowing both functional integration and signal integrity to coexist through spatial segmentation of thermal pathways.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Trenches filled with low thermal conductivity material act as thermal intermediaries or barriers between heat sources and sensitive traces. These intermediary structures block direct thermal conduction pathways while maintaining the structural integrity and electrical functionality of the PCB, enabling heat source mounting without compromising signal integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of moving object

If temperature increases, then component operation continues, but resistivity of Cu interconnects increases causing signal loss

Engineering Contradiction:

Improvecomponent operationVSAvoidsignal loss

Core Design Contradiction:

Duration of action of moving objectVSLoss of energy

Solution Approach 1:

Thermal management features such as trenches and heat sinks are pre-configured in the PCB design before operation. These preliminary structural arrangements establish low thermal conductivity pathways that prevent heat accumulation in advance, maintaining stable resistivity of Cu interconnects during extended operation and reducing signal loss over time.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If trench is formed to separate heat source from traces, then signal integrity is protected, but device complexity increases

Engineering Contradiction:

Improvesignal integrityVSAvoidPCB structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Trenches are strategically positioned only in specific local regions where thermal interference occurs between heat sources and high-speed traces. Rather than uniformly complicating the entire PCB structure, the trenches are locally applied to critical areas, providing signal integrity protection while minimizing overall structural complexity and manufacturing overhead.

Inventive Principle:

Principle #3Local quality

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 design significantly reduces heat transfer and maintains signal integrity by minimizing thermal effects on PCBs, ensuring robust performance even at elevated temperatures.

Implementation Method 1

A trench may be formed partially in the dielectric material, wherein at least one layer of the plurality of layers is continuous over the length of the dielectric material, the trench has a depth less than the thickness of the dielectric material, and the trench divides a set of the plurality of layers into a first side and a second side such that the heat source is mounted on the first side of the trench and the high-speed trace is formed on the second side of the trench

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

Joule heating takes place due to current flow in the conductor, while environmental heating is due to the ambient temperature

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

Joule heating takes place due to current flow in the conductor, while environmental heating is due to the ambient temperature. Resistivity of Cu interconnects increases with increase in temperature

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11665811B2Printed circuit board with signal integrity immunity to temperature

Publication Date: 2023.05.30 DELL PROD LP

AI summary

A system for providing signal temperature immunity to a printed circuit board (PCB) comprises moating a set of reference planes, forming a trench between a heat source and a stripline trace and positioning a perforated section of a plane on a reference plane opposite the heat source. Moating the reference planes increases thermal resistance, the trench removes dielectric material and replaces it with air and the perforated section causes heat to travel in a non-linear path. Vias positioned at the ends of the PCB route heat along the outer surfaces of the PCB to transfer heat to the ambient environment.