Self-aligning Optical Structures for Random Micro-LED Arrays
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Solution Overview
Problem
Existing methods are impractical for precisely positioning optical structures, such as lenses or phosphors, directly over randomly located microscopic LEDs in a high-speed manufacturing process, especially in roll-to-roll manufacturing, due to the small size and random arrangement of the LEDs.
Innovation Solution
The technique involves printing LEDs with tall, narrow anode electrodes and wide, bottom cathode electrodes to ensure proper orientation, followed by the application of a thin dielectric layer and a conductive layer with bumps, and then using an omniphobic liquid to self-align optical materials over the exposed conductive bumps, allowing the optical materials to adhere only to these areas and form structures like lenses or diffusers directly above each LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional printing methods are used to deposit LEDs on a substrate, then high-speed manufacturing and flexibility are achieved, but the LEDs are randomly positioned making precise alignment of optical structures impractical
Solution Approach 1:
The system uses self-alignment mechanisms where optical structures automatically position themselves over LEDs through capillary action and surface tension forces during the printing process, eliminating the need for complex external alignment systems while maintaining both high speed and precision
Solution Approach 2:
A specially designed printing ink or adhesive layer acts as an intermediary medium that facilitates the self-alignment of optical structures with LEDs through controlled fluid dynamics, enabling precise positioning without sacrificing manufacturing speed
2Manufacturing precision
If precise positioning of optical structures over each LED is attempted using conventional alignment methods, then positioning accuracy improves, but the process becomes incompatible with high-speed roll-to-roll manufacturing
Solution Approach 1:
Optical structures self-position over LEDs through physical forces inherent in the printing process itself, such as capillary action in narrow gaps and surface tension at liquid interfaces, enabling precise alignment at high speeds without external intervention
Solution Approach 2:
The patent replaces complex mechanical alignment systems with fluid-based self-alignment mechanisms, using the printing ink's flow and surface properties to automatically position optical structures correctly over LEDs during high-speed manufacturing
3Ease of manufacture
If optical structures are positioned to cover areas between LEDs, then alignment is simplified, but light extraction efficiency decreases due to light being blocked in inter-LED regions
Solution Approach 1:
The printing process deposits optical structures with locally optimized coverage that precisely matches the LED array pattern, ensuring light extraction efficiency is maximized in inter-LED regions while maintaining simplified alignment through the self-aligning mechanism
Solution Approach 2:
The system uses dynamic control of the printing process parameters, such as ink viscosity and deposition speed, to achieve optimal optical structure placement that balances alignment simplicity with light extraction efficiency in real-time during manufacturing
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 method enables precise and efficient self-alignment of optical structures over randomly arranged LEDs, facilitating high-speed manufacturing and allowing for customizable light diffusion or wavelength conversion, suitable for roll-to-roll processes, while maintaining the LEDs' electrical connectivity and optical performance.
Implementation Method 1
an omniphobic liquid to self-align optical materials over the exposed conductive bumps
Implementation Method 2
allowing the optical materials to adhere only to these areas
Data Source
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AI summary
Printed micro-LEDs have a top metal anode electrode that is relatively tall and narrow and a bottom cathode electrode. After the LED ink is cured, the bottom electrodes are in electrical contact with a conductive layer on a substrate. The locations of the LEDs are random. A thin dielectric layer is then printed between the LEDs, and a thin conductive layer, such as a nano-wire layer, is then printed over the dielectric layer to contact the anode electrodes. The top conductive layer over the tall anode electrodes has bumps corresponding with the locations of the LEDs. An omniphobic liquid is then printed which only resides in the "low" areas of the top conductive layer between the bumps. Any optical material is then uniformly printed over the resulting surface. The printed optical material accumulates only on the bump areas by adhesion and surface tension, so is self-aligned with the individual LEDs.