Micro LED Unit Pixel Pad Overlap for Stable Mounting
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Solution Overview
Problem
Conventional micro LED displays face challenges in mounting small light emitting diodes (LEDs) due to their tiny size, leading to irregularities and stress on the pixel structure, which can result in cracks and peeling of thin layers, affecting the reliability and appearance of the display.
Innovation Solution
A unit pixel design featuring a transparent substrate with light emitting devices, connection layers, and bonding pads that are partially overlapped with the LEDs, increasing the contact area and using a concave-convex pattern to improve light extraction efficiency and uniform viewing angle, along with a light blocking layer and adhesive layer to enhance adhesion and prevent light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick photosensitive solder resist (PSR) protection layer is used, then the protection layer provides sufficient protection during transfer processes, but pressing marks and cracks occur on the protection layer, and large stress causes peeling of thin layers
Solution Approach 1:
The patent changes the thickness parameter of the protection layer from thick to thin (10-50 μm), and changes the material from PSR to a different protective material that provides sufficient protection without causing stress-related defects. This parameter change resolves the contradiction by maintaining protection functionality while eliminating pressing marks and cracks.
Solution Approach 2:
The patent uses a thin, disposable protection layer that is removed after the transfer process. This thin protection layer provides sufficient protection during transfer without causing stress accumulation, and is discarded after serving its purpose, avoiding the long-term stress issues of thick PSR layers.
2Length of moving object
If micro LEDs are made very small (100 μm or less), then the display resolution is improved, but handling difficulty increases and direct mounting becomes difficult
Solution Approach 1:
The patent segments the micro LEDs into arrays on separate transfer substrates before final mounting. This allows the micro LEDs to be handled and transferred as groups rather than individually, making it feasible to handle extremely small LEDs (100 μm or less) that would be impossible to manipulate one by one.
Solution Approach 2:
The patent introduces transfer substrates as intermediary carriers that hold the micro LEDs during fabrication and transfer processes. These substrates enable handling of tiny micro LEDs by providing a larger, easier-to-manipulate platform, which is then transferred to the final display substrate.
3Strength
If the protection layer is relatively thick, then protection during transfer is sufficient, but large stress causes cracks in micro LED devices or thin layers
Solution Approach 1:
The patent changes the thickness parameter of the protection layer from thick to thin (10-50 μm), fundamentally altering the stress characteristics. This thin protection layer provides adequate protection during transfer while eliminating the stress accumulation that causes cracks and peeling in the micro LED devices and thin layers.
Data Source
AI summary
A unit pixel includes a transparent substrate, a plurality of light emitting devices arranged on the transparent substrate, connection layers electrically connected to the light emitting devices, and bonding pads disposed over the connection layers and electrically connected to the connection layers. The bonding pads are partially overlapped with at least one of the light emitting devices in a vertical direction, respectively.