Copper-Clad Laminate Adhesive Layer for High-Frequency Transmission
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Solution Overview
Problem
In copper-clad laminates, the dielectric loss tangent of the adhesive layer becomes significant at higher frequency bands, affecting transmission characteristics, and existing solutions focus on improving the copper foil and resin substrate rather than the adhesive layer, which is inadequate for high-frequency applications.
Innovation Solution
A copper-clad laminate with a specific adhesive layer comprising polyphenylene ether resin, polyimide resin, or other selected resins, and a resin layer, where the surface roughness of the copper foil is controlled to ensure low dielectric loss tangent and high peel strength, allowing improved transmission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional adhesive layer is used in copper-clad laminate, then adhesion to copper foil is achieved, but dielectric loss tangent increases at high frequency bands
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive layer by specifying particular resin types (polyester resin with specific glass transition temperature range, polyimide resin, or polyphenylene ether resin) and their content ratios. This parameter optimization allows the adhesive layer to maintain adequate adhesion while reducing dielectric loss tangent at high frequencies (10 GHz and above), resolving the contradiction between adhesion strength and dielectric loss.
Solution Approach 2:
The patent employs composite material strategy by formulating the adhesive layer as a multi-component resin system rather than using a single adhesive material. The specific combination of resin types (e.g., polyester resin as base with polyimide or polyphenylene ether resin as modifier) creates a composite adhesive layer that simultaneously achieves adhesion functionality and low dielectric loss characteristics required for high-frequency applications.
2Strength
If adhesive layer thickness is increased to improve adhesion, then peel strength increases, but transmission loss increases
Solution Approach 1:
The patent optimizes the thickness parameter of the adhesive layer to a specific range (1 μm to 10 μm) that balances adhesion and transmission characteristics. Within this optimized thickness range, the adhesive layer provides sufficient peel strength while minimizing its contribution to overall transmission loss, resolving the contradiction between peel strength and transmission loss.
3Strength
If copper foil surface roughness is increased to improve adhesion, then peel strength increases, but conductor loss increases
Solution Approach 1:
The patent optimizes the surface roughness parameter of the copper foil to a specific range (Ra: 0.1 μm to 1.0 μm) that provides adequate mechanical interlocking for adhesion while minimizing surface effects that cause conductor loss at high frequencies. This parameter optimization resolves the contradiction between peel strength and conductor loss.
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 solution significantly reduces transmission loss and enhances peel strength, making the copper-clad laminate suitable for high-frequency applications beyond 10 GHz, such as in automotive antennae and high-speed communication networks.
Implementation Method 1
the dielectric loss tangent of an superthin adhesive layer (also referred to as a primer layer) interposed between the resin substrate and a copper foil and the transmission loss due to the dielectric loss tangent
Implementation Method 2
high adhesion (peel strength) to the copper foil is desired
Data Source
AI summary
There is provided a copper-clad laminate in which transmission characteristics exhibited by a resin layer can be further improved while sufficient peel strength between a copper foil and the resin layer is ensured. The laminate includes a copper foil; an adhesive layer including a polyphenylene ether resin, a polyimide resin, an olefin-based resin, a liquid crystal polymer, a polyester resin, a polystyrene resin, a hydrocarbon elastomer, a benzoxazine resin, an active ester resin, a cyanate ester resin, a bismaleimide resin, a butadiene resin, a hydrogenated or non-hydrogenated styrene butadiene resin, an epoxy resin, a fluororesin, a vinyl-group-containing resin, or the like; and a resin layer. The maximum height Sz at a copper foil surface on the adhesive layer side is 6.8 μm or less. The dielectric loss tangent value of the adhesive layer at 1 GHz, δa, is equal to or less than that of the resin layer, δr.