Resin Multilayer Substrate Using Asymmetric Foil Roughness
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Solution Overview
Problem
Existing resin multilayer substrates face issues with separation of the upper and lower resin layers due to differential adhesion strengths between the metal foil layer and resin layers, leading to potential transmission loss in electric signals.
Innovation Solution
The metal foil layer is designed with one smooth main surface in contact with the upper resin layer and one roughened main surface in contact with the lower resin layer, along with a specific side surface configuration to enhance adhesion and prevent separation, while minimizing transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If both main surfaces of the metal foil layer are roughened to prevent separation of resin layers, then adhesion strength between metal foil and resin layers is improved, but transmission loss of electric signals increases
Solution Approach 1:
The patent applies different surface qualities to different regions of the metal foil layer. The first main surface has a first surface roughness while the second main surface has a second surface roughness that is smaller than the first. This local differentiation allows the first surface to provide sufficient adhesion strength to prevent resin layer separation, while the second surface maintains smoothness to minimize signal transmission loss when the conductor layer is formed on it.
2Stability of the object's composition
If both main surfaces of the metal foil layer are fixed to resin substrate layers, then separation of upper and lower resin layers is prevented, but complexity of manufacturing process increases
Solution Approach 1:
The patent employs asymmetric surface treatment where the first main surface of the metal foil layer is roughened to a greater extent than the second main surface. This asymmetry creates different adhesion characteristics on each side, allowing the structure to achieve stable layer bonding with a simpler manufacturing process compared to treating both surfaces equally, while still preventing separation of the resin layers.
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
This design effectively prevents separation of resin layers and reduces transmission loss, ensuring stable signal transmission in flexible high-frequency applications.
Implementation Method 1
a lower main surface of the metal foil layer having a surface roughness greater than a surface roughness of an upper main surface of the metal foil layer
Data Source
AI summary
A metal foil layer includes a metal foil layer upper main surface, a metal foil layer lower main surface with a surface roughness greater than that of the metal foil layer upper main surface, and a metal foil layer side surface that is a surface of the metal foil layer excluding the metal foil layer upper main surface and the metal foil layer lower main surface. The metal foil layer upper main surface is in contact with an upper resin layer. The metal foil layer lower main surface is in contact with a lower resin layer. A portion of a lower main surface of the upper resin layer and a portion of an upper main surface of the lower resin layer are in contact with each other to define a layer interface. In a cross section of the metal foil layer, the metal foil layer side surface includes an outer point and an inner point where the upper resin layer is in contact with the side surface, and the inner point is below the outer point and inward of the outer point.