Microchip Surface Roughness for Directional Self-Assembly
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Solution Overview
Problem
The productivity of micro LED display apparatus manufacturing decreases as micro LED sizes shrink and display sizes increase, due to inefficiencies in the laser lift off or pick and place method used for transferring micro LED chips.
Innovation Solution
A microchip structure is designed with a first surface having lower surface roughness than the electrode layer, enhancing van der Waals forces for alignment in fluidic self-assembly methods, allowing for improved directional alignment and easier transfer of microchips onto a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser lift off or pick and place method is used for transferring micro LED chips, then the micro LED chips can be transferred to the display apparatus, but the productivity decreases as the micro LED size becomes smaller and the display size increases
Solution Approach 1:
The patent replaces the mechanical laser lift off or pick and place method with a fluidic self-assembly method. Microchips are transferred by flowing a liquid medium through the display apparatus, allowing the chips to settle into designated positions through fluid dynamics rather than mechanical manipulation. This substitution dramatically improves productivity for small-sized micro LEDs and large display areas.
Solution Approach 2:
The patent implements self-service through directional alignment features on the microchips (such as asymmetric patterns or geometric shapes) that enable the chips to automatically orient and position themselves correctly during fluidic flow. The chips self-align and self-assemble into the desired configuration without requiring complex external positioning mechanisms, thereby improving transfer efficiency and productivity.
2Manufacturing precision
If the size of micro LED becomes smaller, then the display resolution increases, but the alignment precision becomes more difficult to achieve
Solution Approach 1:
The patent employs asymmetric directional alignment features on the microchips (such as non-symmetric patterns, geometric shapes, or surface structures) that create a preferred orientation during fluidic flow. This asymmetry ensures that even sub-100-micron micro LEDs automatically align in the correct direction as they settle, maintaining high alignment precision despite the reduced chip size and enabling high-resolution displays.
3Productivity
If fluidic self assembly method is used for transferring microchips, then the productivity increases, but the alignment accuracy must be ensured through proper surface roughness control
Solution Approach 1:
The patent applies local quality by differentiating the surface roughness characteristics of different microchip surfaces. The first surface (contacting the substrate) is engineered with a specific roughness range (0.3-3 nm RMS) to optimize van der Waals adhesion and alignment accuracy, while the second surface (opposite side) may have different characteristics. This localized surface engineering ensures high alignment precision while maintaining the efficiency benefits of the fluidic self-assembly method.
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 increases the probability of microchips aligning correctly in one direction, enhancing the manufacturing efficiency of micro LED display apparatus by leveraging the van der Waals forces for stable and controlled chip placement.
Implementation Method 1
a surface roughness of the first surface is smaller than a surface roughness of an upper surface of the electrode layer such that van der Waals force between the first surface and an external contact surface are greater than van der Waals force between the electrode layer and the external contact surface
Data Source
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AI summary
Provided is a microchip including a chip body having a first surface and a second surface facing the first surface, and an electrode layer on the second surface, wherein a surface roughness of the first surface is smaller than a surface roughness of an upper surface of the electrode layer such that van der Waals force between the first surface and an external contact surface are greater than van der Waals force between the electrode layer and the external contact surface.