Flexible PCB Substrate with Reinforcing Layers for Low Loss
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Solution Overview
Problem
Flexible printed wiring boards face challenges in achieving low transmission loss for high frequency signals due to high relative permittivity and dielectric loss tangent in existing insulating base materials, and securing adhesiveness between fluororesin and other materials is difficult, leading to separation issues.
Innovation Solution
A method involving a laminated body formation with reinforcing resin layers having a lower coefficient of thermal expansion than fluororesin, stacked through thermosetting adhesives, and integrated at a temperature below the fluororesin's melting point to ensure dimensional stability and adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fluororesin is used as insulating base material to reduce relative permittivity and dielectric loss tangent, then transmission loss is reduced, but adhesive force with conductor layers and other insulating layers is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the fluororesin by incorporating specific fluorinated monomers (VF6, HFP, PTFE) in controlled ratios to achieve optimal balance between dielectric properties and adhesiveness. The copolymer composition is precisely controlled to maintain low permittivity while improving adhesive force.
Solution Approach 2:
The patent creates a composite fluororesin material by copolymerizing multiple fluorinated monomers (tetrafluoroethylene, VF6, HFP, and PTFE) to combine the low dielectric loss properties of PTFE with the adhesiveness provided by VF6 and HFP components, resulting in a composite material that achieves both low transmission loss and sufficient adhesive strength.
2Strength
If fluororesin layer is heated at high temperature for integration, then adhesive strength is improved, but dimensional stability deteriorates due to large coefficient of thermal expansion
Solution Approach 1:
The patent modifies the thermal processing parameters by implementing a multi-stage heating process with controlled temperature progression. The integration is performed at optimized temperature and time parameters that activate the adhesive properties of VF6 and HFP components without causing excessive thermal expansion or deformation of the fluororesin layer.
Solution Approach 2:
The patent applies local quality enhancement by incorporating specific fluorinated monomers (VF6 and HFP) at controlled concentrations within the fluororesin copolymer structure. These localized compositional variations provide targeted adhesive functionality at the bonding interfaces while maintaining the overall dimensional stability of the fluororesin layer during thermal processing.
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 provides a substrate with high dimensional stability, capable of transmitting high frequency signals effectively while suppressing delamination and maintaining adhesive strength, reducing transmission loss and ensuring handleability.
Implementation Method 1
a first and second reinforcing resin layers having a coefficient of thermal expansion smaller than that of the fluororesin layer are respectively stacked on an upper surface and a lower surface of a fluororesin layer through a first thermosetting adhesive
Implementation Method 2
the laminated body is heated and integrated at a temperature not lower than a curing temperature of the first and second thermosetting adhesives and lower than a melting point of the fluororesin layer
Data Source
AI summary
Provided is a method for manufacturing a substrate for flexible printed wiring board, comprising a laminated body forming step and an integration step, wherein in the laminated body forming step, on an upper surface and a lower surface of a fluororesin layer having a modified surface, a first and second reinforcing resin layers having a coefficient of thermal expansion smaller than that of the fluororesin layer are respectively stacked through a first thermosetting adhesive, on the first reinforcing resin layer and/or the second reinforcing resin layer, a conductor layer is stacked through a second thermosetting adhesive, to form a laminated body, and in the integration step, the laminated body is heated and integrated at a temperature not lower than a curing temperature of the first and second thermosetting adhesives and lower than a melting point of the fluororesin layer.