Copper Foil Laminate Primer Structure for Low-Loss Adhesion
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Solution Overview
Problem
Existing laminates face challenges in achieving both adhesiveness to copper foil and electrical properties while maintaining heat resistance, as polar functional groups enhance adhesiveness but increase dielectric constant, and surface roughening improves adhesiveness but increases transmission loss.
Innovation Solution
A laminate structure with a copper foil having a surface roughness of 1.2 μm or less, a primer layer containing a styrene-based elastomer or styryl group-containing silane coupling agent, an intermediate layer with a polyphenylene-based oligomer, and an adhesive layer for polyimide, all heat-cured with thermal radical initiators, is employed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a compound having a polar functional group is used to improve adhesive force to copper foil, then adhesiveness is improved, but the dielectric constant of the resin increases
Solution Approach 1:
The patent introduces a primer layer as an intermediary between the copper foil and the adhesive layer. This primer layer contains a silane coupling agent that forms a bridge between the copper foil surface and the adhesive layer, enabling strong adhesion without requiring polar functional groups in the main adhesive resin that would increase dielectric constant. The silane coupling agent chemically bonds to the copper foil surface while also bonding to the adhesive resin, thus mediating the adhesion function while preserving electrical properties of the bulk resin.
2Strength
If the surface of copper foil is roughened to improve adhesive force, then adhesiveness is improved, but transmission loss of signal path increases
Solution Approach 1:
The patent applies local quality by creating a localized rough surface structure on the copper foil only in the region where adhesion is needed, while keeping other areas smooth for electrical performance. The primer layer is applied selectively to the roughened areas, providing enhanced adhesion locally without affecting the overall smoothness and electrical conductivity of the copper foil surface. This localized treatment allows simultaneous optimization of both adhesion and electrical properties.
3Temperature
If adhesive layers with high glass transition temperature resin are used to improve heat resistance, then heat resistance is improved, but adhesiveness to copper foil deteriorates
Solution Approach 1:
The patent segments the adhesive system into three distinct functional layers: a primer layer for copper foil adhesion, an intermediate layer for heat resistance, and an adhesive layer for bonding. The primer layer contains compounds specifically designed for copper adhesion, while the intermediate layer provides thermal stability with high glass transition temperature resin. This segmentation allows each layer to be optimized for its specific function, enabling the overall structure to achieve both heat resistance and adhesion without compromise.
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 laminate achieves both adhesiveness to copper foil and electrical properties with improved heat resistance, ensuring high peel strength and excellent solder heat resistance.
Implementation Method 1
heat-cured with a thermal radical initiator
Implementation Method 2
a styryl group-containing silane coupling agent
Data Source
AI summary
The present invention relates to a laminate capable of achieving both adhesiveness to a copper foil as well as electrical properties and heat resistance. More specifically, the present invention provides a laminate including: a copper foil having a surface Rz of 1.2 μm or less; and a primer layer laminated on a surface of the copper foil, in which the primer layer contains a styrene-based elastomer having a styrene content of 30 to 90 mass % or a styryl group-containing silane coupling agent.