Micro LED Overcoat Structure for Clean Transfer Fracture Control
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Solution Overview
Problem
The issue of residual holding structures remaining on the peripheral surface of micro LEDs after transfer, which affects light emission and device quality, is a challenge in micro LED transfer processes.
Innovation Solution
A micro device structure is designed with a sacrificial portion of the holding structure contacting an extension portion of the overcoat layer, defining a predetermined fracture region to prevent residual holding structure adhesion during transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the holding structure contacts the peripheral surface of the micro LED to secure it during transfer, then the micro LED can be easily picked up and transported, but residual holding structure remains on the peripheral surface after transfer, affecting light emission
Solution Approach 1:
The holding structure is divided into a contact portion that interfaces with the micro LED and a sacrificial portion that is designed to break away. The contact portion maintains grip during transfer while the sacrificial portion is positioned to fracture at a predetermined location, separating the functional holding element from the residual element that would otherwise contaminate the micro LED surface.
Solution Approach 2:
The harmful residual holding structure is extracted from the system by designing a sacrificial portion that is intentionally removed through controlled fracture. The break line is positioned such that the sacrificial portion separates from the micro LED assembly during or after transfer, eliminating the source of contamination while preserving the light-emitting properties of the micro LED.
2Strength
If the contact surface area between the holding structure and the micro LED is increased to improve holding strength, then the micro LED is more securely held during transfer, but the residual holding structure becomes more difficult to remove completely
Solution Approach 1:
The holding structure is segmented into a contact portion with sufficient surface area for strong adhesion to the micro LED, and a sacrificial portion with reduced surface area that is designed to fracture away. This segmentation allows the contact portion to provide the necessary holding strength while the sacrificial portion minimizes residual contamination.
Solution Approach 2:
The sacrificial portion acts as an intermediary element between the contact portion and the micro LED. It provides the necessary mechanical connection for strong holding while being designed to fracture at a controlled break line, thereby mediating between the need for strong adhesion and the need for clean release without residual contamination.
3Reliability
If the holding structure is designed to fully cover the peripheral surface for maximum security, then the micro LED is securely held, but complete removal of the holding structure becomes difficult and leaves residues
Solution Approach 1:
The holding structure is segmented into a contact portion that covers the necessary area for reliable holding of the micro LED, and a sacrificial portion that extends beyond the contact portion but is designed to fracture away. This segmentation enables the contact portion to provide reliable holding while the sacrificial portion is easily removed through controlled fracture.
Solution Approach 2:
The holding structure is pre-configured with a predetermined break line in the sacrificial portion during the manufacturing process. This preliminary design ensures that when the holding structure is subjected to stress during or after transfer, the fracture occurs at the predetermined location, automatically removing the sacrificial portion without requiring additional manual intervention.
Data Source
AI summary
A micro device includes an epitaxial structure, an overcoat layer, and a first light-guiding structure. The epitaxial structure has a top surface and a bottom surface opposite to each other and a peripheral surface connecting the top surface and the bottom surface. The insulating layer covers at least the bottom surface and part of the peripheral surface of the epitaxial structure. The overcoat layer includes a contact portion and an extension portion. The contact portion conformally covers the insulating layer and the peripheral surface and the bottom surface of the epitaxial structure, and the extension portion connects the contact portion and extends in a direction away from the peripheral surface. The display apparatus includes a circuit substrate and a plurality of the above-mentioned micro devices. The micro devices are disposed and are correspondingly electrically connected to the first pads and the second pads of circuit substrate.