Metal-Clad Polymer Films with Low-Roughness Polyimide Interfaces
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Solution Overview
Problem
Existing metal-clad laminates for electronic devices face issues with poor thermal reliability, low peel strength, and electromagnetic interference (EMI) due to challenges in adhesion between copper and polyimide films, especially when using electroless copper plating, and the need for effective EMI shielding.
Innovation Solution
A metal-clad polymer film with a thermoplastic polyimide layer derived from specific monomers, including a dianhydride with ether functionality and a diamine with hydrogen bonding, and a process involving electroless and electrolytic plating to achieve high peel strength and EMI shielding, with a root-mean-square roughness of less than 1 μm and a metal layer thickness of 12 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If electroless copper plating is used to produce metal-clad laminates, then the signal loss is improved, but the peel strength decreases and thermal reliability deteriorates
Solution Approach 1:
The patent introduces a specialized polyimide film as an intermediary layer between the copper layer and the substrate. This film contains specific functional groups (carboxylic acid, hydroxyl, or amine groups) that act as chemical mediators to enhance adhesion to the electroless copper plating, thereby maintaining high peel strength while allowing the use of electroless plating for low signal loss
Solution Approach 2:
The patent modifies the chemical parameters of the polyimide film by incorporating specific functional groups with defined concentrations (0.1-5.0 mmol/g for carboxylic acid, 0.1-5.0 mmol/g for hydroxyl, or 0.1-5.0 mmol/g for amine groups). These parameter changes enable the film to achieve optimal chemical bonding with electroless copper while maintaining thermal stability and adhesion properties
2Loss of energy
If electroless copper plating is used to produce metal-clad laminates, then the signal loss is improved, but the thermal reliability decreases
Solution Approach 1:
The functionalized polyimide film serves as a thermal and chemical intermediary that protects the substrate from direct exposure to plating chemistry while providing stable thermal performance. The film's specific functional groups create a stable interface that maintains reliability under thermal aging conditions
Solution Approach 2:
The patent creates a composite structure combining the polyimide film with specific functional groups embedded within its matrix. This composite material approach allows the system to exhibit both the low signal loss characteristics of electroless copper plating and the high thermal reliability of chemically-resistant polyimide materials
3Device complexity
If a thin metal layer is used for EMI shielding, then the device complexity is reduced, but the shielding effectiveness decreases
Solution Approach 1:
The patent optimizes the metal layer thickness parameter to 12 μm or less while maintaining effective EMI shielding. This is achieved by combining the thin metal layer with the functionalized polyimide film that enhances the overall shielding performance through its dielectric properties and interface characteristics
Solution Approach 2:
The patent creates a composite shielding structure consisting of a thin metal layer (12 μm or less) combined with the functionalized polyimide film. This composite approach maintains EMI shielding effectiveness while reducing the overall thickness and complexity compared to using thicker metal layers alone
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 enhances peel strength to greater than 5 N/cm after 168 hours at 150°C and provides effective EMI shielding, addressing thermal reliability and adhesion issues while maintaining thin metal layer thickness.
Implementation Method 1
forming a first metal layer on the first thermoplastic layer by electroless plating followed by electrolytic plating
Implementation Method 2
forming a first metal layer on the first thermoplastic layer by electroless plating followed by electrolytic plating
Implementation Method 3
0.1 to 30 mol % of a second diamine having hydrogen bonding
Data Source
AI summary
In a first aspect, a metal-clad polymer film includes a polymer film adhered to a first metal layer. The root-mean-square roughness (Sq) of the interface between the polymer film and the first metal layer is less than 1 μm. The peel strength between the polymer film and the first metal layer is greater than 5 N/cm after 168 hours of aging at 150° C. when tested for a polymer film having a thickness in the range of from 25 to 75 μm and a first metal layer having a thickness of 18 μm in accordance with IPC-TM-650 test methods. The thickness of the first metal layer is 12 μm or less. The polymer film includes a first thermoplastic polyimide layer. In a second aspect, an electronic device includes the metal-clad polymer film of the first aspect. In a third aspect a process includes for forming a double-sided metal-clad polymer film.