PCB Conductor Surface Roughness and Insertion Loss Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional printed circuit boards (PCBs) with rough conductor surfaces attached to dielectric layers suffer from increased insertion loss, compromising signal integrity, especially at high frequencies, which requires additional engineering measures and increased costs to maintain reliability.

Innovation Solution

A smooth conductor layer with a surface roughness of less than two microns is adhered to the dielectric layer using a perfluoroalkoxy copolymer adhesive, reducing insertion loss while maintaining sufficient peel strength through the use of adhesive layers between conductor and dielectric layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the conductor layer surface is made rough to increase adhesion to the dielectric layer, then the peel strength is improved, but the insertion loss increases significantly

Engineering Contradiction:

Improvepeel strengthVSAvoidinsertion loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

An adhesive layer is introduced as an intermediary between the conductor layer and dielectric layer. This adhesive layer provides the necessary adhesion strength while allowing the conductor layer surface to remain smooth, thus resolving the contradiction between peel strength and insertion loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bonding function is separated from the conductor layer surface. Instead of relying on the conductor layer surface roughness for adhesion, the bonding function is transferred to a dedicated adhesive layer, allowing the conductor layer to maintain its smooth surface for low insertion loss.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If conventional rough conductor surfaces are used to ensure adhesion, then manufacturing simplicity is maintained, but signal integrity deteriorates at high frequencies

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidsignal integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The adhesive layer acts as a mediator that enables reliable bonding without requiring rough conductor surfaces. This allows the use of smooth conductor layers which maintain signal integrity at high frequencies, while the manufacturing process remains relatively simple through the use of standard adhesive application techniques.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 significantly reduces insertion loss by up to 14% at higher frequencies, maintaining high peel strength and eliminating the need for costly materials or signal repeaters, thus enhancing signal integrity and reducing overall costs.

Implementation Method 1

a conductor layer (typically copper foil) is adhered to an underlying dielectric layer using an adhesive layer

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS10827627B2Reduction of insertion loss in printed circuit board signal traces

Publication Date: 2020.11.03 INTEL CORP

AI summary

A printed circuit board, according one embodiment, includes a reference layer; a dielectric layer disposed on the reference layer; and a conductor layer adhered to the dielectric layer with an adhesive layer disposed between the dielectric layer and the conductor layer. The conductor layer has a smooth surface facing the dielectric layer having a roughness (Rz) of less than two microns.