Micro LED Bonding via Adhesive Layer Shift
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Solution Overview
Problem
In the manufacturing process of display modules, micro LEDs often deviate from their predetermined positions or are not properly contacted with electrodes due to non-uniform pressure, leading to defects in the bonding process.
Innovation Solution
A method involving a substrate with a pixel region and a peripheral region, where the peripheral region has a higher surface energy than the pixel region, allowing for the pre-curing of an adhesive layer to shift from the pixel region to the peripheral region, creating a thicker adhesive layer on the peripheral region, which enhances the bonding of micro LEDs to electrodes, and includes a hydrophilic layer on the peripheral region and a hydrophobic layer on the pixel region to improve positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If uniform pressure is applied during bonding, then bonding strength is improved, but micro LED positioning accuracy deteriorates due to deviation and spacing from electrodes
Solution Approach 1:
The adhesive layer is designed with non-uniform thickness distribution, being thicker at the peripheral region and thinner at the pixel region. This local variation in adhesive layer properties allows different regions to serve different functions: the thicker peripheral region provides bonding strength and pressure distribution, while the thinner pixel region maintains micro LED positioning accuracy and ensures proper contact with electrodes.
2Reliability
If adhesive layer is made thicker to improve bonding, then bonding reliability is improved, but micro LED positioning accuracy deteriorates due to increased deviation
Solution Approach 1:
The adhesive layer thickness is locally optimized with a gradient distribution: thicker at the periphery for bonding reliability and thinner at the pixel region for positioning accuracy. This spatially varying thickness resolves the contradiction by providing different thickness values in different locations based on functional requirements.
3Manufacturing precision
If pressure is reduced to improve positioning accuracy, then micro LED positioning is improved, but bonding strength deteriorates due to insufficient contact
Solution Approach 1:
The adhesive layer is designed with local thickness variation where the peripheral region has greater thickness to provide bonding strength through pressure distribution, while the pixel region maintains smaller thickness to ensure positioning accuracy. This allows the system to achieve both strong bonding and accurate positioning simultaneously.
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 improves the accuracy and stability of micro LED positioning, reducing defects by minimizing pressure on the LEDs during bonding and ensuring proper contact with electrodes, thus enhancing the overall quality and reliability of the display module.
Implementation Method 1
A surface energy of the peripheral region is higher than a surface energy of the pixel region
Implementation Method 2
The hydrophilic layer is formed of a self-assembled monolayer
Implementation Method 3
The providing the substrate includes forming a hydrophobic layer on a surface of the pixel region by chemical vapor deposition
Data Source
AI summary
A method of manufacturing a display module is provided. The method may include providing a substrate including a pixel region on which a plurality of electrodes are disposed and a peripheral region that is a region other than the pixel region on the substrate; forming an adhesive layer on the pixel region of the substrate; transferring a plurality of micro light emitting diodes (LEDs) onto the adhesive layer; pre-curing the adhesive layer to shift the adhesive layer on the pixel region to the peripheral region; and bonding the plurality of micro LEDs to the plurality of electrodes.