Flexible LED Transfer via Anisotropic Conductive Film
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Solution Overview
Problem
Conventional methods for fabricating flexible electronic devices, such as inorganic light emitting diodes (LEDs), face challenges in transferring high-performance electronic devices from rigid substrates to flexible substrates with high yield and stability, due to alignment issues and limitations in reducing substrate thickness, leading to spatial errors and lower efficiency.
Innovation Solution
A method involving the formation of inorganic LED multilayers on a mother wafer, isolation of individual LED chips, temporary attachment to a carrier substrate, and transfer onto a flexible target substrate using a transferring element like anisotropic conductive film (ACF) for electrical connection and adhesion, with bonding under high pressure and temperature, enabling flexible LED devices as individual chips or arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional wet etching method is used to separate devices on a flexible substrate, then device isolation is achieved, but alignment problems and procedural errors occur leading to reduced manufacturing precision
Solution Approach 1:
The patent applies preliminary action by pre-forming protrusions on the flexible substrate before device fabrication. These protrusions are prepared in advance to serve as precise alignment features during subsequent transfer processes, eliminating alignment issues that would otherwise occur during wet etching separation.
Solution Approach 2:
The patent introduces an intermediary approach by using a transfer process with a transfer substrate as a mediator between the rigid mother wafer and the flexible substrate. This intermediary transfer mechanism avoids direct wet etching on the flexible substrate, thereby preventing alignment problems and procedural errors.
2Quantity of substance
If anisotropic conductive film is used for connection between circuitry and LED on flexible substrate, then electrical connection is achieved, but the thickness of the flexible substrate cannot be reduced
Solution Approach 1:
The patent merges the electrical connection function with the adhesive bonding function by using a transferring element that provides both adhesion for device attachment and electrical connection through conductive particles. This combination eliminates the need for separate anisotropic conductive film layers, enabling substrate thickness reduction while maintaining connection feasibility.
Solution Approach 2:
The patent changes the parameters of the bonding interface by using high pressure and temperature bonding conditions that enable direct metal-to-metal or metal-to-conductive-adhesive bonding without requiring thick anisotropic conductive film layers. This parameter change allows both thin substrate construction and reliable electrical connection.
3Manufacturing precision
If conventional transfer methods are used for moving LED chips to flexible substrate, then device transfer is achieved, but spatial errors occur reducing manufacturing precision
Solution Approach 1:
The patent applies preliminary action by pre-forming protrusions on the flexible substrate and designing corresponding recesses on the transfer substrate. These pre-formed geometric features ensure precise spatial alignment during the transfer process, eliminating spatial errors while maintaining high transfer stability through the complementary fit.
4Adaptability or versatility
If iterative transferring processes are used to fabricate flexible devices, then flexibility is achieved, but process complexity increases reducing productivity
Solution Approach 1:
The patent merges multiple separate processes into a single integrated transfer operation. By combining device isolation, transfer substrate attachment, and flexible substrate bonding into one coordinated transfer step using pre-formed protrusions and recesses, the process achieves flexibility without requiring multiple iterative transfers, thereby improving productivity.
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
This approach allows for stable and efficient transfer of flexible LED devices with improved yield and stability, enabling applications in flexible displays, wearable devices, and bio-integrated systems, and facilitates mass production suitable for commercialization.
Implementation Method 1
the transferring element enables electrical connection and adhesion between the carrier substrate and the target substrate
Implementation Method 2
bonding under high pressure and temperature on a carrier substrate and a target substrate aligned vertically with a transferring element interposed between the carrier substrate and the target substrate
Data Source
AI summary
A laminating structure of an electronic device using a transferring element according to the present disclosure includes a target substrate, a bottom electrode formed on the target substrate, an electronic device which is bonded to the bottom electrode, a top contact formed on the electronic device, a transferring element which is placed between the bottom electrode and the electronic device on the target substrate, and a top electrode connected to the electronic device, wherein the transferring element attached to the carrier substrate comes into contact with the electronic device, and is then transferred onto the target substrate.