Micro-LED Transfer Printing for Flexible High-Resolution Displays
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Solution Overview
Problem
Conventional methods for manufacturing high-resolution RGB LED displays are costly, complex, and have low manufacturing yields due to the difficulty in arranging small, numerous, and fragile LEDs with appropriate wiring and driving circuitry, as well as challenges in electrically isolating anode and cathode terminals during interconnection.
Innovation Solution
Micro-transfer printing technology is used to assemble inorganic micro-LEDs on a non-native substrate, allowing for the creation of flexible, transparent, or semi-transparent displays with horizontally separated contact pads, reducing the number of assembly levels and improving placement accuracy, and enabling the use of redundant LEDs for increased yield and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional vacuum pick-and-place methods are used to assemble LEDs, then automation is achieved, but placement accuracy deteriorates for ultra-thin and small devices
Solution Approach 1:
The patent introduces an intermediary adhesive layer between the rigid substrate and the flexible LED array. This adhesive layer acts as a mediator that allows conventional automated pick-and-place equipment to place LEDs with standard positioning accuracy, while the flexible nature of the adhesive layer compensates for positioning variations, enabling accurate final placement even when initial placement has tolerances of several micrometers.
2Manufacturing precision
If more LEDs are arranged in a display to increase resolution, then display quality improves, but device complexity increases
Solution Approach 1:
The patent segments the LED array into modular units that can be manufactured separately on rigid substrates and then assembled onto the flexible display. This segmentation allows each module to be optimized independently, reducing the overall complexity of manufacturing high-resolution displays by breaking down the complex task of placing millions of individual LEDs into manageable modular assembly steps.
Solution Approach 2:
The patent employs a nested structure where rigid LED modules containing multiple LEDs are embedded within the flexible adhesive layer, which itself is nested within the overall display structure. This nesting allows complex high-resolution LED arrays to be constructed from simpler modular units, reducing manufacturing complexity while achieving high display quality.
3Ease of manufacture
If rigid substrates are used for LED manufacturing to withstand high temperatures, then manufacturing processability improves, but flexibility deteriorates
Solution Approach 1:
The patent divides the system into two separate components: a rigid substrate used only during the high-temperature LED manufacturing process, and a flexible adhesive layer that provides the final flexible structure. The rigid substrate serves its temporary purpose of withstanding manufacturing temperatures, then the completed LED modules are transferred to the flexible adhesive layer, achieving both high-temperature processability and final flexibility.
Solution Approach 2:
The patent uses a flexible adhesive layer as a thin film that replaces the rigid substrate in the final product structure. This thin flexible film allows the LED array to achieve the desired flexibility for conformal displays while the rigid substrate requirement is only present temporarily during manufacturing, not in the final assembled product.
Data Source
AI summary
The disclosed technology provides micro-assembled micro-LED displays and lighting elements using arrays of micro-LEDs that are too small (e.g., micro-LEDs with a width or diameter of 10 μm to 50 μm), numerous, or fragile to assemble by conventional means. The disclosed technology provides for micro-LED displays and lighting elements assembled using micro-transfer printing technology. The micro-LEDs can be prepared on a native substrate and printed to a display substrate (e.g., plastic, metal, glass, or other materials), thereby obviating the manufacture of the micro-LEDs on the display substrate. In certain embodiments, the display substrate is transparent and/or flexible.