Micro LED Mass Transfer Using Adhesive Bonding
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Solution Overview
Problem
Conventional methods for integrating micro LEDs with pixel driver circuitry are inefficient, costly, and prone to reliability issues due to thermal mismatch and light cross-talk, especially in multi-color display panels where different color micro LEDs are grown on incompatible substrates.
Innovation Solution
The mass transfer of micro structures using adhesives, where micro LEDs are first transferred to an intermediate substrate with a compatible thermal expansion coefficient, allowing for bonding to pixel drivers without the original substrate, thereby overcoming thermal mismatch and enabling efficient integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If micro LEDs are bonded to pixel drivers while both remain on their original substrates, then the fabrication process is simpler, but thermal mismatch between substrates generates stress causing reliability issues
Solution Approach 1:
The patent segments the fabrication process into distinct stages: first bonding micro LEDs to pixel drivers on separate substrates, then removing original substrates, and finally bonding the combined structure to a new common substrate. This segmentation resolves thermal mismatch by eliminating the incompatible original substrates while maintaining manufacturing feasibility through staged processing.
Solution Approach 2:
The patent performs preliminary bonding of micro LEDs to pixel drivers before substrate removal. This preliminary action establishes the electrical and mechanical connections early in the process, allowing subsequent substrate removal and re-bonding to proceed without compromising the integrity of the LED-driver interface.
2Ease of manufacture
If the original substrate is retained in the final product, then the manufacturing process is simpler, but the substrate causes light cross-talk
Solution Approach 1:
The patent extracts and removes the original substrates from the final device structure through chemical etching or other removal techniques. This extraction eliminates the source of light cross-talk while the micro LEDs and pixel drivers remain functional, achieving both manufacturing simplicity and optical performance.
3Adaptability or versatility
If conventional picking and placing methods are used to integrate micro LEDs with pixel drivers, then substrate compatibility is not an issue, but the fabrication process is inefficient and costly
Solution Approach 1:
The patent merges multiple micro LEDs and pixel drivers into a single integrated structure through wafer-level bonding processes. This combining approach enables parallel processing of thousands of devices simultaneously, dramatically improving productivity compared to individual picking and placing, while the staged substrate removal and re-bonding ensures compatibility between different substrate types.
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 improves the efficiency and reliability of micro LED display fabrication by allowing for the integration of micro LEDs with pixel drivers on a thermally compatible substrate, reducing stress and light cross-talk, and facilitating the production of multi-color displays.
Implementation Method 1
The micro LED array is transferred to an intermediate substrate (e.g., silicon) by use of an adhesive
Implementation Method 2
The intermediate substrate is then separated from the micro LED array by releasing the adhesive
Data Source
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AI summary
Mass transfer of micro structures are effected from one substrate to another using adhesives. In the context of an integrated micro LED display, a micro LED array is fabricated on a native substrate and corresponding CMOS pixel drivers are fabricated on a separate substrate. The micro LED substrate (e.g., sapphire) and the CMOS substrate (e.g., silicon) may be incompatible. For example, they may have different thermal coefficients of expansion which make it difficult to bond the micro LEDs to the pixel driver circuitry. The micro LED array is transferred to an intermediate substrate (e.g., silicon) by use of an adhesive. This intermediate substrate may be used in a process of bonding the micro LED array to the array of pixel drivers. The intermediate substrate is separated from the micro LED array by releasing the adhesive.