Printed Circuit Board Signal Line Adhesion via Local Quality
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Solution Overview
Problem
High-frequency signal transmission loss in printed circuit boards increases with frequency, and existing materials like liquid crystal polymer struggle to provide sufficient adhesion strength and mechanical stability, especially when bent, leading to potential signal line breakage and degradation of transmission properties.
Innovation Solution
A printed circuit board design featuring a first dielectric layer with a higher specific conductivity metal foil pattern for signal lines and a lower specific conductivity metal foil pattern for ground layers, embedded in adhesive layers with controlled thickness and surface roughness, and made of liquid crystal polymer, to reduce transmission loss and enhance mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If liquid crystal polymer is used for the dielectric layer to reduce signal transmission loss, then dielectric properties are improved, but adhesion strength and mechanical stability deteriorate
Solution Approach 1:
The patent applies different surface roughness characteristics to different metal foil patterns based on their function: the signal line metal foil pattern has a first surface roughness (Ra ≤ 1.0 μm) to maintain high specific conductivity and reduce signal loss, while the ground layer metal foil pattern has a second surface roughness (Ra > 1.0 μm) to enhance adhesion strength. This local differentiation resolves the contradiction between dielectric properties and adhesion strength by optimizing each component's surface characteristics according to its specific functional requirements.
2Loss of energy
If liquid crystal polymer is used for the dielectric layer to reduce signal transmission loss, then dielectric properties are improved, but mechanical stability deteriorates
Solution Approach 1:
The patent implements local quality differentiation by assigning distinct surface roughness values to different metal foil patterns: the ground layer metal foil pattern exhibits higher surface roughness (Ra > 1.0 μm) providing enhanced mechanical anchoring and stability, while the signal line metal foil pattern maintains lower surface roughness (Ra ≤ 1.0 μm) to preserve electrical conductivity and minimize signal transmission loss. This resolves the contradiction between dielectric properties and mechanical stability.
3Adaptability or versatility
If the printed circuit board is bent to achieve flexibility, then adaptability is improved, but signal line integrity deteriorates
Solution Approach 1:
The patent applies local quality differentiation to metal foil patterns where the ground layer metal foil pattern has higher surface roughness (Ra > 1.0 μm) providing superior mechanical anchoring that prevents delamination during bending, while the signal line metal foil pattern maintains lower surface roughness (Ra ≤ 1.0 μm) to preserve electrical conductivity. This resolves the contradiction between flexibility and signal line integrity by strengthening the ground layer's mechanical bond without compromising the signal line's electrical performance.
Data Source
AI summary
Provided is a printed circuit board which includes: a first dielectric layer including a first principal surface and a second principal surface on a side opposite to the first principal surface; a first adhesive layer formed on the first principal surface; a first metal foil pattern formed on the first adhesive layer and forming a signal line; and a second metal foil pattern formed on the second principal surface and forming a ground layer, in which the first metal foil pattern has a higher specific conductivity than a specific conductivity of the second metal foil pattern.