Surface-Treated Copper Foil for Low Signal Loss and High Adhesion

Solution Overview

Problem

Conventional copper-clad laminates face challenges in maintaining adhesion strength between the conductive lines and the board while minimizing signal transmission loss, especially at high frequencies, due to the skin effect, which often results in peeling of conductive lines during solder floating processes.

Innovation Solution

A surface-treated copper foil with a peak extreme height of 0.4 to 3.0 μm and a diffraction peak ratio of at least 60% for the (111) plane to the sum of (111), (200), and (220) planes, after heating at 200°C for 1 hour, is used, incorporating a surface treatment layer to enhance adhesion and reduce signal loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the surface of the conductive line is flattened to reduce signal transmission loss caused by skin effect, then the signal transmission loss is reduced, but the adhesion strength between the conductive line and the board is reduced

Engineering Contradiction:

Improvesignal transmission lossVSAvoidadhesion strength

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The invention applies different surface qualities to different regions: the drum side surface is kept relatively flat (peak extreme height 0.03-0.5 μm) for low signal loss, while the deposited side surface is made rougher (peak extreme height 0.4-3.0 μm) for high adhesion strength. This local differentiation resolves the contradiction between smooth surface for signal transmission and rough surface for adhesion.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of making the entire surface flat to reduce signal loss (conventional approach), the invention inverts the approach by making the board-contact surface (deposited side) rough while keeping the signal transmission surface (drum side) smooth. This inversion allows simultaneous achievement of low signal loss and high adhesion.

Inventive Principle:

Principle #13The other way round (Inversion)

2Strength

If a roughening process is applied to the drum side to improve adhesion strength, then the adhesion strength is improved, but the signal transmission loss increases

Engineering Contradiction:

Improveadhesion strengthVSAvoidsignal transmission loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The invention applies different surface qualities to different regions: the drum side surface is kept relatively flat (peak extreme height 0.03-0.5 μm) for low signal loss, while the deposited side surface is made rougher (peak extreme height 0.4-3.0 μm) for high adhesion strength. This local differentiation resolves the contradiction between smooth surface for signal transmission and rough surface for adhesion.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If the surface is made too flat to reduce signal transmission loss, then the signal transmission loss is reduced, but the conductive lines are easily peeled off from the board

Engineering Contradiction:

Improvesignal transmission lossVSAvoidpeel resistance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The invention applies different surface qualities to different regions: the drum side surface is kept relatively flat (peak extreme height 0.03-0.5 μm) for low signal loss, while the deposited side surface is made rougher (peak extreme height 0.4-3.0 μm) for high adhesion strength. This local differentiation resolves the contradiction between smooth surface for signal transmission and rough surface for adhesion.

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

The solution maintains high adhesion strength and reliability between the copper foil and the board, while keeping signal transmission loss low, ensuring the copper-clad laminate's integrity during solder floating and high-frequency signal transmission.

Implementation Method 1

the demand for copper foils and copper-clad laminates is also increasing. Generally, the circuit of a copper-clad laminate is carried by the insulating board, and the electrical signals may be transmitted to a predetermined region along a predetermined path within the layout of the circuits. In addition, for the copper-clad laminate used for transmitting high-frequency electrical signals (for example, higher than 10 GHz), the circuit of the copper-clad laminate must be further optimized to reduce the signal transmission loss caused by a skin effect.

Methodology Applied

Scientific EffectSkin effect: Skin Effect

Implementation Method 2

When the surface-treated copper foil is heated at a temperature of 200° C. for 1 hour, the ratio of the integrated intensity of diffraction peak of (111) plane to the sum of the integrated intensities of diffraction peaks of (111) plane, (200) plane, and (220) plane of the treating surface is at least 60%.

Methodology Applied

Scientific EffectX-ray diffraction: Bragg Diffraction

Data Source

PatentUS12060647B2Surface-treated copper foil and copper clad laminate

Publication Date: 2024.08.13 CHANG CHUN PETROCHEMICAL CO LTD

AI summary

A surface-treated copper foil includes a treated surface, where the peak extreme height (Sxp) of the treating surface is 0.4 to 3.0 μm. When the surface-treated copper foil is heated at a temperature of 200° C. for 1 hour, the ratio of the integrated intensity of diffraction peak of (111) plane to the sum of the integrated intensities of diffraction peaks of (111) plane, (200) plane, and (220) plane of the treating surface is at least 60%.