Surface-Treated Copper Foil for Low-Loss Flexible Circuits
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Solution Overview
Problem
Existing flexible copper-clad laminates (FCCLs) face challenges in achieving high peel strength and low conductor loss for high speed/high frequency applications, with current solutions increasing magnetic permeability and electric resistance, leading to signal loss and reliability issues.
Innovation Solution
A surface-treated copper foil with controlled grain size, surface roughness, and specific non-copper metal elements, combined with a dielectric layer of polymeric material, to enhance adhesion and reduce conductor loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the surface roughness of the copper foil is reduced to lower conductor loss, then the conductor loss is reduced, but the adhesion strength of the copper foil to the dielectric layer is weakened
Solution Approach 1:
The invention applies different surface treatments to different regions of the copper foil. The surface treatment layer is formed only on the side facing the dielectric layer, while the other surface maintains its original properties. This localized treatment allows optimization of adhesion at the interface without compromising the overall surface roughness needed for low conductor loss.
Solution Approach 2:
The invention creates a composite structure by forming a surface treatment layer on the copper foil. This layer comprises copper and non-copper elements in specific ratios, combining the electrical conductivity of copper with the adhesion-enhancing properties of non-copper elements, thus resolving the contradiction between conductor loss and adhesion strength.
2Strength
If non-copper elements such as nickel or silane are added to increase peel strength, then the peel strength and thermal resistance are improved, but the magnetic permeability and electric resistance increase leading to increased insertion loss
Solution Approach 1:
The invention precisely controls the composition parameters of the surface treatment layer, specifying that non-copper elements must be 5 wt% or less and copper must be 95 wt% or more. This parameter control ensures that the surface treatment provides adequate peel strength while minimizing the impact on electrical conductivity and insertion loss.
Solution Approach 2:
The surface treatment layer is applied only on the side of the copper foil that contacts the dielectric layer, localizing the non-copper elements to where they are most needed for adhesion. This localized approach minimizes the overall amount of non-copper elements in the copper foil structure, thereby reducing magnetic permeability and electric resistance effects.
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
The solution provides a flexible copper-clad laminate with improved peel strength and reduced conductor loss, enabling high speed/high frequency signal transmission with minimal signal loss and reliability issues.
Implementation Method 1
Under the high speed/high frequency conditions, the current of signal transmission is mainly conducted across the surface of copper conductor which is a well-known phenomenon named skin effect.
Data Source
AI summary
Disclosed are surface-treated copper foils having at least one treated surface that exhibit high conductivity and a set of surface properties. Also provided are flexible copper-clad laminates and printed circuits made therefrom. The present printed circuits exhibit low insertion loss and are suitable for use in high speed/high frequency applications.