Micro-LED Transfer Using Photosensitive Polymer Intermediary
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Solution Overview
Problem
The mass production of micro LED display apparatuses is hindered by the difficulty in transferring numerous small micro LEDs onto a circuit board due to differences in thermal expansion coefficients between the wafer and the circuit board, making conventional die bonding technologies inefficient.
Innovation Solution
A method involving the transfer of micro LEDs onto a first carrier substrate with a first adhesive material layer, followed by curing to reduce adhesiveness, then onto a second carrier substrate with a higher adhesiveness, and finally bonding them to a circuit board using a metal bonding layer, while separating the second carrier substrate, ensuring precise placement and minimizing thermal expansion issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is used to transfer micro-LEDs, then transfer precision and positioning accuracy are improved, but the risk of damaging the laser head and increasing device complexity increases
Solution Approach 1:
A photosensitive polymer layer is introduced as an intermediary between the laser beam and the micro-LEDs. The laser writes patterns on this polymer layer which then guides the transfer process, allowing precise positioning without the laser directly interacting with the micro-LEDs or requiring complex laser head positioning systems
Solution Approach 2:
The invention creates a master pattern on a photosensitive polymer layer that serves as a template. This pattern is then used to guide the transfer of multiple micro-LEDs, replacing the need for complex real-time laser positioning systems with a simple copying process
2Manufacturing precision
If conventional transfer methods are used, then device complexity is reduced, but transfer precision and positioning accuracy deteriorate
Solution Approach 1:
The pattern for micro-LED placement is created in advance on a photosensitive polymer layer before the actual transfer process. This preliminary patterning step enables high positioning accuracy during transfer without requiring complex real-time control systems
Solution Approach 2:
The invention moves the precision requirement from the transfer mechanism to the pattern layer. By creating a 2D patterned layer that guides the 3D transfer process, the system achieves high precision through the pattern geometry rather than through complex transfer mechanics
3Manufacturing precision
If direct laser writing on micro-LEDs is performed, then transfer precision is improved, but the risk of damaging micro-LEDs and increasing loss increases
Solution Approach 1:
The photosensitive polymer layer acts as a protective intermediary that receives the laser writing instead of the micro-LEDs. This prevents laser-induced damage to the micro-LEDs while still enabling precise pattern transfer for accurate positioning
Solution Approach 2:
The laser writes a pattern on the photosensitive polymer layer rather than directly on the micro-LEDs. This copying approach transfers the positional information without exposing the micro-LEDs to damaging laser energy
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 enables efficient and precise transfer of micro LEDs onto a circuit board, reducing bonding failures and facilitating mass production by managing thermal expansion differences and adhesiveness levels effectively.
Implementation Method 1
a photosensitive polymer layer is provided on the substrate, the photosensitive polymer layer comprising a pattern formed by photopolymerization
Data Source
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AI summary
A micro-LED transfer method according to one embodiment comprises: preparing a substrate on which a plurality of micro-LEDs are formed; transferring the plurality of micro-LEDs onto a first carrier substrate having a first adhesive material layer; curing the first adhesive material layer, thereby reducing the adhesive strength of the first adhesive material layer; transferring the plurality of micro-LEDs, which are placed on the first carrier substrate, onto a second carrier substrate having a second adhesive material layer; bonding at least some of the plurality of micro-LEDs, which are placed on the second carrier substrate, to pads on a circuit board by using a metal bonding layer; and separating the second carrier substrate from the micro-LEDs bonded onto the circuit board.