Micro-roughened Copper Foil for High-Frequency Circuit Insertion Loss
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Solution Overview
Problem
Copper foil substrates face a challenge in maintaining high peel strength while achieving good insertion loss performance at high frequencies, as reducing surface roughness improves insertion loss but compromises bonding strength.
Innovation Solution
A micro-roughened electrodeposited copper foil with a specific surface texture, characterized by a multiplication value of arithmetic mean height and vertex density within certain ranges, is developed, which includes mountain-shaped and recessed structures to enhance bonding strength and reduce signal transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the surface roughness of the copper foil substrate is decreased, then the insertion loss performance is improved, but the peel strength between the copper foil and the substrate is reduced
Solution Approach 1:
The patent applies local quality by creating a specific micro-rough surface structure with mountain-shaped protrusions and recessed structures at the copper foil surface. This localized micro-structure provides mechanical interlocking for strong bonding while the overall controlled roughness maintains good insertion loss performance. The surface is not uniformly smooth or rough, but has specific local features that simultaneously achieve both objectives.
Solution Approach 2:
The patent changes the surface morphology parameters by controlling the multiplication value of arithmetic mean height (Sa) and vertex density (Spd) to be 100,000 μm/mm² to 300,000 μm/mm², and arithmetic mean undulation (Wa) to be 0.05 μm to 1.0 μm. These parameter changes create an optimal balance between surface roughness for bonding and smoothness for signal transmission, resolving the contradiction between peel strength and insertion loss.
2Strength
If the surface roughness is optimized for bonding strength, then the peel strength is maintained, but the insertion loss performance deteriorates
Solution Approach 1:
The patent uses local quality by implementing specific micro-structures (mountain-shaped protrusions and recessed structures) that provide localized bonding sites for high peel strength, while the overall surface maintains controlled roughness characteristics that prevent excessive signal loss. The local micro-features enable bonding without requiring the entire surface to be highly rough.
Solution Approach 2:
The patent optimizes surface parameters by controlling Sa×Spd within 100,000-300,000 μm/mm² and Wa within 0.05-1.0 μm. These parameter ranges are specifically selected to achieve the dual objective of maintaining peel strength above 4.0 lb/in while keeping insertion loss below 0.20 dB/in at 10 GHz, thus resolving the contradiction between bonding strength and 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 micro-roughened copper foil achieves a balance between maintaining high peel strength and minimizing signal transmission loss, ensuring optimal electrical properties and circuit performance.
Implementation Method 1
a copper-containing electrodeposition solution and performing an electrodeposition roughening treatment on a surface of the raw foil
Data Source
AI summary
The present disclosure provides a micro-rough electrolytic copper foil and a copper clad laminate. The electrolytic copper foil has a micro-rough surface formed with mountain-shaped structures and recessed structures. A multiplication value of an arithmetic mean height (Sa) and a vertex density (Spd) of the mountain-shaped structures measured according to ISO 25178 is between 150000 μm/mm2 and 400000 μm/mm2. An arithmetic mean undulation (Wa) of the mountain-shaped structures measured according to JIS B0601:2001 is between 0.06 μm and 1.5 μm. Therefore, the electrolytic copper foil with good binding strength and electrical properties can be obtained.