Zn-Clustered Copper Foil Surface for High-Temperature PCB Adhesion
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Solution Overview
Problem
Existing copper foils for high-frequency circuits face challenges in maintaining high adhesive strength and long-term high-temperature reliability due to the use of heat-resistant resin substrates, which often result in decreased etching rates and increased transmission loss.
Innovation Solution
A surface-treated copper foil with a primary particle layer of Cu or Cu alloy particles and a secondary particle layer of Zn particle clusters, along with an optional anti-rust layer, providing enhanced adhesive strength and high-temperature reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alloy layers are used to enhance heat resistance, then adhesive strength at high temperature is improved, but etching rate decreases and transmission loss increases
Solution Approach 1:
The invention changes the chemical composition parameters of the surface treatment layer by specifying precise ranges of Sn (0.1-5 mass%), Zn (0.1-5 mass%), and Ag (0.1-5 mass%) elements, along with controlled particle sizes (0.1-10 μm) and particle density (10^4-10^6 particles/mm²). These parameter optimizations enable the surface layer to provide adequate heat resistance and adhesive strength without the need for traditional alloy layers that would harm etching rate and transmission loss.
2Reliability
If alloy layers are used to enhance heat resistance, then adhesive strength at high temperature is improved, but transmission loss increases
Solution Approach 1:
The invention optimizes the surface treatment layer composition with controlled concentrations of Sn, Zn, and Ag elements within 0.1-5 mass% each, along with specific particle size (0.1-10 μm) and particle density (10^4-10^6 particles/mm²). These parameter changes enable the surface layer to provide heat resistance and adhesive strength while maintaining low transmission loss, avoiding the use of alloy layers that would increase transmission loss.
3Strength
If roughening particles are attached to enhance adhesive strength, then adhesive strength is improved, but surface roughness increases which is unsuitable for high-frequency circuits
Solution Approach 1:
The invention applies local quality by creating a surface treatment layer with specific local characteristics: particle size of 0.1-10 μm, particle density of 10^4-10^6 particles/mm², and controlled element distribution (Sn, Zn, Ag at 0.1-5 mass% each). This localized particle layer provides adequate adhesive strength through anchoring effect while maintaining overall surface smoothness (Rz ≤ 3.0 μm) suitable for high-frequency circuits.
Data Source
AI summary
Disclosed is a surface-treated copper foil having long-term high-temperature reliability and being suitable for use in high-frequency circuits due to a low transmission loss, wherein the surface-treated copper foil has a surface treatment layer, the surface treatment layer including: a primary particle layer containing Cu or Cu alloy particles formed on at least one surface of an original copper foil; and a secondary particle layer containing Zn particles formed on the primary particle layer, the secondary particle layer being composed of particle clusters formed by clustering of a plurality of Zn particles.