Flexible Circuit Board Bonding Layers for Low Dielectric Loss
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Solution Overview
Problem
Circuit boards made of polyimide materials have high dielectric loss factors and constants, making it difficult to satisfy requirements for high-frequency signal transmission.
Innovation Solution
A flexible circuit board is manufactured using a base layer with bonding layers formed from a specific adhesive solution, copper layers for signal lines, and insulating layers, with through holes electroplated for conductive vias, resulting in reduced dielectric loss and improved signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polyimide material is used for circuit board, then flexibility is achieved, but dielectric loss factor and dielectric constant become high
Solution Approach 1:
The patent uses a composite structure consisting of a polyimide base layer combined with low-dielectric-loss adhesive layers (containing fluorinated compounds or hollow micropheres). This composite approach maintains the flexibility advantage of polyimide while compensating for its high dielectric loss through the low-loss adhesive material.
Solution Approach 2:
The patent modifies the dielectric properties by changing the chemical composition and physical structure of the adhesive layer. Specific parameters such as adding fluorinated compounds (reducing dielectric constant) or incorporating hollow glass/silicon micropheres (reducing dielectric loss) alter the effective dielectric characteristics of the bonding layer to achieve lower transmission loss.
2Adaptability or versatility
If polyimide material is used for circuit board, then flexibility is achieved, but signal transmission quality deteriorates at high frequency
Solution Approach 1:
The patent creates a composite bonding system where polyimide adhesive is combined with low-dielectric-loss additives (fluorinated compounds or hollow micropheres). This composite material maintains the flexibility and adhesion properties of polyimide while introducing low-loss characteristics that improve high-frequency signal transmission reliability.
Solution Approach 2:
The patent applies local quality improvement by specifically modifying the adhesive layer (which has lower signal impact than the base layer) with low-dielectric-loss materials. This localized modification targets the critical bonding regions while preserving the overall flexibility of the circuit board structure.
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 method achieves a flexible circuit board with low transmission loss and enhanced dielectric properties, suitable for high-frequency signal transmission by optimizing the bonding layers and copper structures.
Implementation Method 1
A bonding solution is applied on each of opposite surfaces of the base layer. The bonding solution is dried to form two corresponding bonding layers
Implementation Method 2
An inner wall of the through hole is electroplated to form a conductive via
Data Source
AI summary
A flexible circuit board includes a substrate including a base layer and a bonding layer formed on each of opposite sides of the base layer. Each of the two bonding layers is formed by coating a bonding solution and drying the bonding solution. The bonding solution is composed of an adhesive and a solvent. A viscosity of the adhesive is 5000 millipascal-seconds. The adhesive is composed of a precursor having a mass fraction of 35%-65%, carboxyl modified polyphenylene oxide having a mass fraction of 10%-15%, bisphenol-F-epoxy resin having a mass fraction of 10%-15%, a silane coupling agent having a mass fraction of 0%-1.5%, silica filler having a mass fraction of 5%-20%, and a flame retardant filler having a mass fraction of 10%-20%.