Surface-Treated Copper Foil for High-Frequency Circuits

Solution Overview

Problem

Conventional copper foils for high-frequency circuits face challenges in achieving low transmission loss while maintaining good adhesion, thermal resistance, and chemical resistance.

Innovation Solution

A surface-treated copper foil with a treatment layer comprising oxides of molybdenum and zinc, chromium oxide, and a coupling agent layer, applied without any roughening treatment, resulting in a low surface roughness and improved mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the surface of the copper foil is roughened to enhance adhesion to the resin layer, then adhesion characteristics are improved, but transmission loss at high frequencies increases due to scattering effects

Engineering Contradiction:

ImproveadhesionVSAvoidtransmission loss

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The invention applies different surface treatments to different sides of the copper foil. The first side (adhesive side) is roughened with nodular treatment to enhance adhesion to the resin layer, while the second side (signal transmission side) is kept smooth to minimize transmission loss. This local differentiation allows each side to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The copper foil is divided into two distinct sides with different surface properties. The first side undergoes roughening treatment while the second side remains smooth, creating segmented functional zones that address both adhesion and signal transmission requirements independently.

Inventive Principle:

Principle #1Segmentation

2Loss of energy

If a smooth surface is used to minimize transmission loss, then transmission characteristics are improved, but adhesion to the resin layer deteriorates

Engineering Contradiction:

Improvetransmission lossVSAvoidadhesion

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The copper foil is divided into two distinct sides with different surface properties. The first side undergoes roughening treatment while the second side remains smooth, creating segmented functional zones that address both adhesion and signal transmission requirements independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies different surface treatments to different sides of the copper foil. The first side (adhesive side) is roughened with nodular treatment to enhance adhesion to the resin layer, while the second side (signal transmission side) is kept smooth to minimize transmission loss. This local differentiation allows each side to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

3Strength

If conventional roughening treatments are applied to ensure bondability, then adhesion is improved, but surface roughness increases to several μm impacting high-frequency transmission

Engineering Contradiction:

ImproveadhesionVSAvoidsurface roughness

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The copper foil is divided into two distinct sides with different surface properties. The first side undergoes roughening treatment while the second side remains smooth, creating segmented functional zones that address both adhesion and signal transmission requirements independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies different surface treatments to different sides of the copper foil. The first side (adhesive side) is roughened with nodular treatment to enhance adhesion to the resin layer, while the second side (signal transmission side) is kept smooth to minimize transmission loss. This local differentiation allows each side to optimize for its specific function.

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 surface-treated copper foil achieves minimal transmission losses at high frequencies, maintains excellent adhesion, and exhibits improved thermal and chemical resistance, making it suitable for applications like 5G communication.

Implementation Method 1

a first layer comprising oxides of molybdenum and of zinc deposited on said first side

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 2

a second layer of chromium oxide

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 3

preferably a coupling agent layer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS20250168969A1Surface-treated copper foil for high-frequency circuit and method for producing the same

Publication Date: 2025.05.22 CIRCUIT FOIL LUXEMBOURG SARL

AI summary

A surface treated copper foil for a High-Frequency circuit as well as a corresponding method of treating a copper foil, the copper foil including two opposite sides, where a first side is coated with a treatment layer including, in this order: a first layer including oxides of Mo and of Zn deposited on the first side, where the first layer is free of Ni; a second layer of Cr oxide; and a coupling agent layer; where the first layer includes the oxides of Mo and of Zn in a quantity of between 5 and 30 mg/m2 calculated as Mo and Zn; where the treatment layer has a roughness Rz JIS of 0.7 μm or less; and where the first side is free of roughening treatment.