Multi-Layer Polyimide Substrate Curl Reduction
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Solution Overview
Problem
Flexible polyimide substrates with thicknesses greater than 30 microns are difficult to handle due to internal mechanical stresses and curling, making them challenging for use in flexible electronics without damaging the deposited thin films.
Innovation Solution
A method involving the sequential coating and curing of polyimide and metal layers on a carrier, followed by mechanical de-bonding without laser ablation, to create a multi-layered polymer film with reduced curl and improved handling properties, using techniques like spin coating and chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the polyimide substrate thickness is increased to resist wrinkling, then the substrate becomes easier to handle in terms of wrinkling resistance, but internal mechanical stresses cause noticeable curl which makes the substrate difficult to handle
Solution Approach 1:
The polyimide substrate is segmented into multiple thin layers (first polyimide layer and second polyimide layer) with a metal layer deposited between them. This segmentation allows each layer to be thinner and more flexible while the combined structure provides the necessary wrinkle resistance, eliminating the curling problem associated with thick single-layer substrates.
Solution Approach 2:
The invention creates a composite structure by depositing a metal layer (such as molybdenum) between two polyimide layers. This composite material combination provides both the mechanical strength needed for wrinkle resistance and the flexibility needed to minimize curling, resolving the contradiction between thickness-related strength and handling ease.
2Ease of manufacture
If laser ablation is used to de-bond polyimide from carrier, then de-bonding can be achieved, but the process is complex and requires expensive equipment
Solution Approach 1:
The metal layer is deposited between the polyimide layers and the carrier during the fabrication process, creating a natural de-bonding interface in advance. This preliminary action allows for simple mechanical de-bonding later without requiring complex laser ablation equipment or processes.
Solution Approach 2:
The metal layer serves as an intermediary between the polyimide substrate and the carrier substrate. This intermediary layer provides a controlled adhesion interface that enables easy mechanical de-bonding, replacing the need for complex laser ablation processes while maintaining manufacturing capability.
3Adaptability or versatility
If thin polyimide films are used, then the substrate remains flexible, but films thinner than 30 microns are difficult to handle without creasing or bending which is catastrophic to deposited thin films
Solution Approach 1:
The substrate is divided into multiple thin polyimide layers rather than using a single thick layer. This segmentation maintains the flexibility advantages of thin films while the multi-layer structure with embedded metal layer provides the mechanical strength needed for safe handling without creasing or bending that would damage deposited thin films.
Solution Approach 2:
By creating a composite structure with multiple polyimide layers and an embedded metal layer, the substrate achieves both the flexibility of thin films and the handling robustness needed to prevent damage to deposited thin films, resolving the contradiction between flexibility and handling ease.
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 method results in a flexible, thick polyimide substrate with minimal curl, enabling easier handling and fabrication of devices like flexible displays and x-ray detectors, while maintaining the necessary adhesion for thin film transistors and reducing the risk of damage during processing.
Implementation Method 1
curing the first layer of polyimide by subjecting the first layer of polyimide to an elevated temperature
Implementation Method 2
depositing a first layer of metal onto the cured first layer of polyimide
Data Source
AI summary
A method for coating a multi-layered polymer film is disclosed including coating a first layer of polyimide onto a carrier, curing the first layer of polyimide by subjecting the first layer of polyimide to an elevated temperature, depositing a first layer of metal onto the cured first layer of polyimide, coating a second layer of polyimide onto the first layer of metal, and curing the second layer of polyimide by subjecting the second layer of polyimide to an elevated temperature. A flexible electronic device is also disclosed, including multiple interposed layers of polyimide and layers of metal, a dielectric barrier layer disposed on the top layer of polyimide, and a thin film transistor-based device disposed on the dielectric barrier layer. The flexible electronic device has little to no curl.