Surface-Treated Copper Foil Adhesion and Conductor Loss
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Solution Overview
Problem
Existing surface-treated copper foils face challenges in maintaining high adhesion to low-dielectric-constant resin base materials and interlayer adhesion in multilayer printed wiring boards, especially at high temperatures, due to insufficient surface area ratio and nickel content in the metal treatment layer, leading to increased insertion loss and delamination.
Innovation Solution
A surface-treated copper foil with a finely roughened layer of copper particles (10 nm to 110 nm) and a heat-resistant-treatment layer containing nickel and phosphorus, achieving a surface area ratio of 5.1 or more and a nickel coating mass of 2 mg or more per square meter, along with optional chromate and silane-coupling-agent treatment layers, to enhance anchoring effect and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a roughened layer is formed on copper foil to increase surface area ratio for better adhesion, then adhesion to resin base material is improved, but conductor loss increases due to surface irregularities
Solution Approach 1:
The patent applies local quality by creating a roughened layer with specific particle size distribution (10 nm to 110 nm) only on the copper foil surface where adhesion is needed, while maintaining smooth surface characteristics in the bulk copper layer to minimize conductor loss. The roughened layer occupies only a thin portion of the total foil structure, localized exactly where the adhesion function is required.
Solution Approach 2:
The patent changes the surface area ratio parameter to a specific range (5.1 or more per 1 m2 of two-dimensional area) and controls the arithmetic mean deviation Sa within 0.02 μm to 0.35 μm. These parameter optimizations balance the adhesion enhancement from increased surface area while limiting the conductor loss that would result from excessive surface irregularities.
2Temperature
If metal treatment layer with nickel is applied to prevent oxidation at high temperatures, then heat resistance is improved, but adhesion to low-dielectric-constant resin base materials deteriorates due to insufficient nickel content
Solution Approach 1:
The patent optimizes the nickel coating mass to a specific parameter range (2 mg or more per 1 m2 of surface area, but not exceeding 60 mg) and controls the surface area ratio within specific bounds. This parameter optimization ensures sufficient nickel content for oxidation prevention while maintaining adequate adhesion to low-dielectric-constant resin base materials.
Solution Approach 2:
The patent creates a composite structure combining the roughened copper particle layer with a metal treatment layer containing nickel and phosphorus. This composite material approach allows the roughened layer to provide adhesion through physical anchoring while the nickel-containing metal treatment layer provides chemical protection against oxidation at high temperatures.
3Strength
If surface area ratio is increased to enhance anchoring effect, then adhesion is improved, but insertion loss increases
Solution Approach 1:
The patent precisely controls the surface area ratio parameter to be 5.1 or more per 1 m2 of two-dimensional area while limiting the arithmetic mean deviation Sa to 0.02 μm to 0.35 μm. This optimized parameter combination provides sufficient anchoring effect for high adhesion while keeping surface irregularities within bounds that minimize insertion loss for high-frequency signal transmission.
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 exhibits strong adhesion to low-dielectric-constant resin base materials, suppresses insertion loss, and maintains high interlayer adhesion in multilayer printed wiring boards, even at elevated temperatures, while maintaining transmission characteristics similar to unroughened copper foils.
Implementation Method 1
a treated surface having a three-dimensional structure formed of a plurality of fine copper particles connected together, and having a high surface area ratio per 1 m2 of the two-dimensional area to provide a strong anchoring effect
Implementation Method 2
the surface-treated copper foil includes a heat-resistant-treatment layer containing different metals of nickel and phosphorus, hence the copper particles are less likely to be oxidized even upon exposure to high temperatures for a long time
Implementation Method 3
the roughened layer is a finely roughened layer formed of copper particles in which primary particles have a particle size of 10 nm or more and 110 nm or less... the surface-treated copper foil has good transmission characteristics similar to those of unroughened copper foils
Data Source
AI summary
A surface-treated copper foil includes, on at least one surface of an untreated copper foil, a finely roughened layer formed of copper particles in which primary particles have a particle size of 10 nm to 110 nm or less, and a heat-resistant-treatment layer containing nickel and phosphorus, wherein a treated surface has a surface area ratio of 5.1 or more per 1 m2 of a two-dimensional area, the surface area ratio being calculated from a specific surface area measured by a krypton gas adsorption BET method, and a coating mass of the nickel is 2 mg or more per 1 m2 of a surface area.