Multilayer Circuit Board Lamination for Moisture-Resistant Adhesion
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Solution Overview
Problem
Existing circuit boards using liquid crystal polymers and fluoropolymers for radio-frequency applications suffer from reduced adhesion and impaired dielectric properties due to moisture absorption, particularly in laminated sheets where fluorine-based resins are used as a dispersion, and in multilayer bodies where moisture absorption affects the adhesion between insulating layers.
Innovation Solution
A circuit board design incorporating a first insulating layer of liquid crystal polymer and a second insulating layer of fluoropolymer with a polyimide resin content of 0.5 to 20 parts by weight, ensuring high adhesion and maintaining dielectric properties by using a solvent-soluble polyimide resin with an imidization rate of 90% or more, which acts as a binder, and optionally including inorganic fillers to adjust permittivity and expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-based resin is used as a dispersion in the adhesive layer, then dielectric properties are improved, but moisture absorption increases and adhesion deteriorates
Solution Approach 1:
The patent extracts the fluorine-based resin from the adhesive layer composition and uses it as a separate insulating layer material. This allows the adhesive layer to use conventional low-moisture-absorption materials while the fluorine-based resin layer provides the desired dielectric properties, thus resolving the contradiction between dielectric performance and moisture resistance.
Solution Approach 2:
The patent creates a composite structure where fluorine-based resin is combined with other materials in the insulating layer to achieve both low dielectric loss and low moisture absorption. The composite material approach allows synergistic effects where the fluorine-based resin provides excellent dielectric properties while the composite formulation maintains low hygroscopicity.
2Reliability
If liquid crystal polymer and fluoropolymer layers are laminated together, then dielectric properties are improved, but adhesion between layers deteriorates due to moisture absorption
Solution Approach 1:
The patent introduces an intermediary adhesive layer between the liquid crystal polymer insulating layer and the fluoropolymer insulating layer. This adhesive layer acts as a mediator that maintains strong adhesion between the two insulating layers while being resistant to moisture absorption, thus preventing adhesion deterioration while preserving the dielectric properties of both insulating layers.
3Strength
If polyimide resin content is increased to improve adhesion, then adhesion between layers improves, but dielectric properties deteriorate
Solution Approach 1:
The patent applies local quality by using different materials with different properties in different layers. The adhesive layer uses polyimide resin for strong adhesion, while the insulating layers use liquid crystal polymer and fluoropolymer for excellent dielectric properties. This localized material selection allows each layer to optimize its function without compromising the overall performance.
Solution Approach 2:
The patent uses composite material formulation in the adhesive layer, combining polyimide resin with other materials to achieve both adequate adhesion and acceptable dielectric properties. The composite approach allows balancing the conflicting requirements of adhesion strength and dielectric performance within the adhesive layer itself.
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 design maintains high adhesion and dielectric properties before and after moisture absorption, enhancing production efficiency and mechanical strength while allowing for miniaturization of antenna substrates by adjusting permittivity and expansion coefficients.
Implementation Method 1
the polyimide resin being present in an amount of about 0.5 parts or more by weight and less than about 20 parts by weight per 100 parts by weight of the fluoropolymer, and the polyimide resin is a solvent-soluble polyimide resin
Implementation Method 2
a polyimide resin with an imidization rate of about 90% or more
Data Source
AI summary
A circuit board includes, in order in a stacking direction, a first insulating layer, a second insulating layer in contact with the first insulating layer, and a conductor layer, the first insulating layer includes a liquid crystal polymer as a main component, and the second insulating layer includes a fluoropolymer including at least one of polytetrafluoroethylene and a perfluoroalkoxy alkane and includes a polyimide resin with an imidization rate of about 90% or more, the polyimide resin being present in an amount of about 0.5 parts or more by weight and less than about 20 parts by weight per 100 parts by weight of the fluoropolymer.