Micro-LED Transfer Printing for Flexible Transparent 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 reliability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional vacuum pick-and-place tools are used to assemble LEDs, then automated assembly is achieved, but placement accuracy and reliability deteriorate due to difficulty in picking up ultra-thin and small devices
Solution Approach 1:
The patent segments the assembly process into two distinct stages: (1) pickup stage using vacuum grippers that engage with the larger pickup pad on the LED背面, and (2) placement stage using a compliance mechanism that allows precise positioning. This segmentation enables automated assembly while maintaining high placement accuracy by optimizing each stage for its specific function.
Solution Approach 2:
The patent introduces a compliance mechanism as an intermediary between the vacuum gripper and the LED device. This intermediary component absorbs positioning errors and allows fine-adjustment during placement, enabling the system to achieve high placement accuracy while maintaining automated operation through the vacuum gripper.
2Measurement precision
If more LEDs are arranged in a display to increase resolution, then display quality improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple functions into the substrate: the substrate serves as both the structural support and the integrated circuit board containing driving circuitry. Additionally, the compliance mechanism merges positioning and attachment functions. This merging reduces overall system complexity despite high LED counts by consolidating control functions into the substrate rather than requiring separate complex wiring harnesses.
Solution Approach 2:
The patent transitions from planar LED arrangement to three-dimensional compliance-based positioning. The compliance mechanism introduces vertical and rotational degrees of freedom, allowing LEDs to be positioned and accommodated in three dimensions rather than strictly on a two-dimensional plane, simplifying the interconnection architecture for high-resolution displays.
3Ease of manufacture
If rigid substrates are used for LED manufacturing to withstand high-temperature processes, then manufacturing feasibility improves, but display flexibility and transparency deteriorate
Solution Approach 1:
The patent segments the manufacturing process into two separate stages performed on different substrates: (1) LED fabrication on a rigid substrate that can withstand high temperatures, and (2) LED attachment on a flexible, transparent display substrate using the compliance mechanism. This segmentation allows each substrate to be optimized for its specific function without compromise.
Solution Approach 2:
The patent introduces the compliance mechanism as an intermediary that couples the rigid LED (manufactured on high-temperature substrate) to the flexible display substrate. This intermediary component allows the rigid LED to be attached to the flexible substrate without requiring the display substrate itself to withstand high manufacturing temperatures, enabling both rigid LED fabrication and flexible display characteristics.
4Area of moving object
If vertically stacked LED terminals are used to reduce footprint, then area efficiency improves, but electrical isolation difficulty increases
Solution Approach 1:
The patent employs asymmetric LED packaging where the anode and cathode are positioned asymmetrically on the LED housing rather than vertically stacked. This asymmetric arrangement naturally provides electrical isolation pathways and simplifies the interconnection architecture, allowing compact footprint without the complexity of vertical isolation structures.
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.