Copper Foil Laminate with Styrene-Based Primer 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 adhesion but increase dielectric constant, and surface roughening improves adhesion but increases signal transmission loss.
Innovation Solution
A laminate structure with a copper foil having a surface roughness (Rz) of 1.2 µm or less, a primer layer containing a styrene-based elastomer with 30 to 90% styrene content or a styryl group-containing silane coupling agent, and an intermediate layer with a polyphenylene-based oligomer, all heat-cured with a thermal radical initiator, is used to improve adhesion and electrical properties.
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:
A primer layer comprising a styrene-based polymer is introduced as an intermediary between the copper foil and the main resin layer. This primer layer provides adhesion to the copper foil without containing polar functional groups that would increase the dielectric constant, thus resolving the contradiction between adhesiveness and electrical properties
Solution Approach 2:
The resin layer is segmented into two distinct parts: a primer layer in direct contact with the copper foil that provides adhesion, and a main resin layer that provides electrical properties. This segmentation allows each layer to be optimized for its specific function without compromising the other
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 styrene-based polymer primer layer acts as an intermediary that can adhere to both rough copper foil surfaces and smooth resin layers. It provides sufficient adhesion without requiring excessive surface roughness, thereby reducing signal transmission loss while maintaining bond strength
3Strength
If adhesive layers with high adhesion are used to bond laminate to polyimide resin, then bonding strength is improved, but heat resistance deteriorates
Solution Approach 1:
The adhesive layer uses a thermoplastic polymer with carefully controlled glass transition temperature (Tg) parameters. By selecting polymers with Tg between -50°C and 100°C and controlling the ratio of low-Tg to high-Tg components, sufficient bonding strength is achieved while maintaining adequate heat resistance for the application
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 strong adhesion to copper foil and excellent electrical properties with heat resistance, ensuring high peel strength and improved solder heat resistance.
Implementation Method 1
is heat-cured with a thermal radical initiator
Data Source
Figure 1~2
Figure 3
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.