Surface-Treated Copper Foil for High-Frequency Circuit Boards
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Solution Overview
Problem
Current copper foils for high-frequency circuit boards face challenges in minimizing transmission loss and require enhanced acid resistance, particularly during the soft etching process in their production.
Innovation Solution
A surface-treated copper foil with a surface treatment layer containing Ni, where the Ni content ratio is 8% by mass or less and the ten-point average roughness Rz is 1.4 μm or less, is used to reduce transmission loss and improve acid resistance, with optional inclusion of Co and additional layers like heat resistant, rust preventing, or silane coupling layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a roughening treatment layer is formed on the copper foil surface to improve adhesion, then adhesion strength is improved, but transmission loss increases due to increased surface roughness
Solution Approach 1:
The invention controls the surface roughness parameters (Rz ≤ 1.4 μm, Ra ≤ 0.2 μm) of the roughening treatment layer to optimize the balance between adhesion strength and transmission loss. By precisely controlling these parameters, the invention achieves sufficient adhesion while minimizing the impact on high-frequency signal transmission.
Solution Approach 2:
The invention creates a composite surface structure consisting of a copper foil base layer and a roughening treatment layer with controlled morphology. This composite structure provides both the adhesion benefits of surface roughness and the transmission loss reduction through controlled roughness parameters, effectively resolving the contradiction between adhesion and signal transmission.
2Loss of energy
If the copper foil surface is made smoother to reduce transmission loss, then transmission loss decreases, but adhesion strength deteriorates
Solution Approach 1:
The invention optimizes the surface roughness parameters within specific ranges (Rz ≤ 1.4 μm, Ra ≤ 0.2 μm) to achieve the best compromise between transmission loss and adhesion strength. These controlled parameter changes ensure that the surface is smooth enough for low transmission loss but rough enough for sufficient adhesion.
3Reliability
If Ni content in the surface treatment layer is increased to improve acid resistance, then acid resistance is improved, but transmission loss increases due to higher metal content
Solution Approach 1:
The invention controls the Ni content ratio in the surface treatment layer to be 8% by mass or less. This parameter control achieves sufficient acid resistance for the soft etching process while minimizing the impact on transmission characteristics, effectively balancing chemical resistance with electrical performance.
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 effectively decreases transmission loss and enhances acid resistance, enabling its use in high-frequency circuit boards while maintaining excellent transmission characteristics and resistance to etching solutions.
Implementation Method 1
The conductor loss of a high frequency signal is mainly caused by decreasing the cross sectional area, through which an electric current flows, due to the skin effect, in which an electric current having a higher frequency flows only the surface of the conductor
Implementation Method 2
the roughened surface of the rolled surface after subjecting to the roughening treatment by electrolytic plating has an arithmetic average roughness (which may be hereinafter referred to as Ra) of from 0.02 μm to 0.2 μm and a ten-point average roughness (which may be hereinafter referred to as Rz) of from 0.1 μm to 1.5 μm
Data Source
AI summary
To provide a surface-treated copper foil that can favorably decrease the transmission loss even used in a high frequency circuit board, and has improved acid resistance. A surface-treated copper foil containing a copper foil, and a surface treatment layer containing a roughening treatment layer on at least one surface of the copper foil, wherein the surface treatment layer contains Ni, the surface treatment layer has a content ratio of Ni of 8% by mass or less (excluding 0% by mass), and an outermost surface of the surface treatment layer has a ten-point average roughness Rz of 1.4 μm or less.