Adhesive-Free Polyimide Metal Laminated Plate for FPCB
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Solution Overview
Problem
Conventional polyimide metal laminated plates for flexible printed circuit boards (FPCBs) suffer from reduced heat resistance, flame resistance, anti-chemical properties, and dimensional stability due to the use of adhesive layers like epoxy resin or acrylate resin, which also hinder the thinning trend of FPCBs and lead to delamination and whitening issues.
Innovation Solution
A polyimide metal laminated plate is developed without an adhesive layer, featuring a structure with a first metallic film, a first thermoplastic polyimide film, a first thermosetting polyimide film, and a second thermoplastic polyimide film, where the thermosetting and thermoplastic polyimide films have a water vapor transmission rate of at least 170 g-μm/m2-day, preventing delamination and whitening, and maintaining good heat resistance, flame resistance, and dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesive layer made of epoxy resin or acrylate resin is used to laminate copper foils on the polyimide film, then the copper foils can be firmly attached to the substrate, but the heat resistance, flame resistance, anti-chemical properties, and dimensional stability of the FPCB deteriorate
Solution Approach 1:
The invention extracts and removes the adhesive layer from the FPCB structure, eliminating the source of degraded heat resistance and flame resistance. Instead of using epoxy or acrylate resin adhesives, the patent directly laminates copper foils onto the polyimide film surface, achieving firm attachment through the polyimide-copper interface alone, thus preserving the inherent high-performance properties of the polyimide substrate
Solution Approach 2:
The invention employs a composite structure where the polyimide film itself serves as both the substrate and the bonding medium for copper foils. By utilizing the polyimide material's inherent adhesion properties and forming a direct metal-polyimide interface, the structure achieves strong attachment while maintaining the excellent thermal and chemical resistance characteristics of the polyimide composite material
2Strength
If an adhesive layer is used to laminate copper foils on the polyimide film, then the copper foils can be attached to the substrate, but the FPCB thickness increases and cannot meet the thinning tendency
Solution Approach 1:
The invention removes the adhesive layer that adds unnecessary thickness to the FPCB structure. By eliminating this intermediate layer and achieving direct lamination of copper foils to the polyimide film, the overall thickness of the FPCB is reduced, meeting the industry's thinning requirements while maintaining adequate attachment strength through the direct interface
3Reliability
If the water vapor transmission rate of the polyimide film is too low, then the barrier performance is improved, but delamination and whitening occur
Solution Approach 1:
The invention changes the water vapor transmission rate parameter of the polyimide film to an optimal range that balances barrier performance and layer stability. By controlling the WVTR within a specific range, the film achieves sufficient moisture barrier protection while allowing adequate water vapor transmission to prevent delamination and whitening, thus maintaining both protection and structural integrity
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 provides a polyimide metal laminated plate with enhanced heat resistance, flame resistance, and dimensional stability, while meeting the thinning requirements of FPCBs, and prevents delamination and whitening by ensuring adequate water vapor transmission rates in the polyimide film layers.
Implementation Method 1
the first thermosetting polyimide film has a water vapor transmission rate equal to or more than 170 g-μm/m2-day; and a second thermoplastic polyimide film laminated on a surface of the first thermosetting polyimide film distal from the first thermoplastic polyimide film, wherein the second thermoplastic polyimide film has a water vapor transmission rate equal to or more than the water vapor transmission rate of the first thermosetting polyimide film
Data Source
AI summary
A polyimide metal laminated plate has a first metallic film, a first thermoplastic polyimide film laminated on a surface of the first metallic film, a first thermosetting polyimide film laminated on a surface of the first thermoplastic polyimide film distal from the first metallic film, and a second thermoplastic polyimide film laminated on a surface of the first thermosetting polyimide film distal from the first thermoplastic polyimide film. The polyimide metal laminated plate has no adhesive layer, so the polyimide metal laminated plate not only has good heat resistance, flame resistance, anti-chemical properties, and dimensional stability, but also meets the thinning tendency of FPCB. In addition, by the first thermosetting polyimide film and the second thermoplastic polyimide film having a water vapor transmission rate equal to or more than 170 g-μm/m2-day, the delamination and whitening of the polyimide metal laminated plate is prevented.