Surface-Treated Copper Foil for High-Frequency LCP Substrates
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Solution Overview
Problem
Current copper foils for flexible printed wiring boards face challenges in achieving high-frequency signal transmission efficiency due to increased conductor loss and low peel strength when laminated with liquid crystal polymer substrates, particularly at frequencies exceeding 1 GHz.
Innovation Solution
A surface-treated copper foil with controlled amounts of Si and N adhesion, ranging from 3.1 to 300 μg/dm² and 2.5 to 690 μg/dm² respectively, is developed to enhance adhesive strength and reduce surface roughness, utilizing silane treatment and other surface modifications to improve peel strength and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the surface roughness of copper foil is reduced to minimize conductor loss at high frequencies, then transmission efficiency improves, but peel strength when laminated with liquid crystal polymer substrates deteriorates
Solution Approach 1:
The invention applies different surface treatments to different regions or aspects of the copper foil surface. The copper foil surface is treated to have low roughness (Rz ≤ 0.8 μm) for minimizing conductor loss, while simultaneously forming a specific chemical composition profile (Si: 0.1-5.0 μg/cm², N: 0.1-10.0 μg/cm²) that enhances peel strength. This local differentiation of surface properties resolves the contradiction between smooth surface for electrical performance and surface characteristics for mechanical bonding.
Solution Approach 2:
The invention changes the chemical and physical parameters of the copper foil surface through controlled treatment processes. By adjusting the surface composition to specific ranges (Si: 0.1-5.0 μg/cm², N: 0.1-10.0 μg/cm²) and controlling surface roughness (Rz ≤ 0.8 μm), the invention optimizes both electrical and mechanical properties. This parameter optimization allows the surface to simultaneously achieve low conductor loss and high peel strength.
2Strength
If silane treatment is applied to increase peel strength, then adhesive properties improve, but surface roughness increases causing higher conductor loss
Solution Approach 1:
The invention optimizes the parameters of silane treatment to achieve the desired balance. By controlling the Si content to 0.1-5.0 μg/cm² and N content to 0.1-10.0 μg/cm² on the copper foil surface, and limiting surface roughness to Rz ≤ 0.8 μm, the invention achieves sufficient peel strength while minimizing the impact on conductor loss. This precise parameter control allows the treatment to be effective without excessive roughening.
Solution Approach 2:
The invention creates a composite surface structure on the copper foil by combining multiple treatment effects. The surface comprises a base copper layer with controlled roughness, overlaid with a thin silane-based treatment layer containing specific amounts of Si and N. This composite structure provides both the adhesive benefits of silane treatment and the electrical performance of a relatively smooth surface.
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 increased peel strength and reduced transmission loss, enabling high-frequency circuit applications beyond 1 GHz with improved adhesive properties when laminated with liquid crystal polymer substrates.
Implementation Method 1
the amount of adhesion of Si on a copper foil surface is from 3.1 to 300 μg/dm2, and the amount of adhesion of N on a copper foil surface is from 2.5 to 690 μg/dm2
Data Source
AI summary
This surface-treated copper foil is characterized in that the amount of adhesion of Si on the copper foil surface is from 3.1 to 300 μg/dm2, and the amount of adhesion of N on the copper foil surface is from 2.5 to 690 μg/dm2. The objective of the present invention is to obtain a copper foil having improved peel strength in providing a copper foil for a flexible printed substrate (FPC), in which a copper foil is laminated to a liquid crystal polymer (LCP) suitable for high-frequency applications.