Surface Mount Micro-LEDs with Bottom Contacts for High Fill Factor Assembly
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Solution Overview
Problem
Current technologies for large area displays, such as LCDs and OLEDs, face inefficiencies and reliability issues, while inorganic micro-LED displays are cost and time prohibitive due to complex fabrication processes and low emission area fill factors in fluidic assembly.
Innovation Solution
A surface mount emissive element configuration using inorganic micro-LEDs with top and bottom electrical contacts simplifies electrical connections and fabrication, allowing for high dynamic range displays with improved reliability and cost-effectiveness through fluidic assembly on a sapphire substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional fluidic assembly is used to distribute LED micro structures randomly, then assembly automation is improved, but manufacturing precision deteriorates due to random distribution requiring extra tolerances
Solution Approach 1:
The patent applies preliminary action by pre-forming protrusions on the LED micro structures before assembly. These protrusions engage with corresponding recesses in the substrate, ensuring precise positioning and orientation of each LED before the fluidic assembly process begins. This pre-positioning mechanism maintains high emission area fill factor while enabling automated assembly.
2Device complexity
If conventional inkjet printing or robotic pick-and-place is used, then manufacturing complexity is reduced, but productivity deteriorates due to time and cost prohibitions for large displays
Solution Approach 1:
The patent employs hydraulic principles by using fluidic assembly to transport and deposit LED micro structures. The fluidic system enables high-speed, parallel assembly of millions of LEDs across large display areas, dramatically improving productivity compared to robotic methods while maintaining process simplicity.
3Device complexity
If top contact LED configuration is used, then device complexity is reduced, but manufacturing precision deteriorates due to misalignment tolerances reducing emission area
Solution Approach 1:
The patent inverts the conventional top-contact configuration by using bottom-contact LED micro structures. The protrusions extend from the bottom surface to engage with substrate recesses, reversing the contact geometry. This inversion enables precise positioning without the alignment tolerance issues that plague top-contact configurations, maintaining high emission area fill factor.
4Reliability
If blue GaN LEDs are used for direct emission, then reliability is improved with over 50,000 hours operation, but use of energy deteriorates due to lower efficiency compared to other technologies
Solution Approach 1:
The patent applies parameter changes by optimizing the LED micro structure geometry, including size, shape, and arrangement density. By carefully controlling these parameters and using bottom-contact configuration with protrusions, the system maximizes the intrinsic efficiency of blue GaN LEDs while maintaining their superior reliability, achieving both high efficiency and long operational life.
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
The surface mount configuration enables efficient and reliable large area displays with high emission area fill factors, reducing fabrication complexity and costs, and allowing for active matrix driving to power uLEDs nearly 100% of the time.
Implementation Method 1
A surface mount light emitting diode (SMLED) includes a first electrical contact, formed exclusively on a top surface... a multiple quantum well (MQW) layer interposed between the first semiconductor layer and the second semiconductor layer
Data Source
AI summary
A surface mount emissive element is provided with a top surface and a bottom surface. A first electrical contact is formed exclusively on the top surface, and a second electrical contact is formed exclusively on the top surface. A post extends from the bottom surface. An emissive display is also provided made from surface mount emissive elements and an emissions substrate. The emissions substrate has a top surface with a first plurality of wells formed in the emissions substrate top surface. Each well has a bottom surface, sidewalls, a first electrical interface formed on the bottom surface, and a second electrical interface formed on the bottom surface. The emissions substrate also includes a matrix of column and row conductive traces forming a first plurality of column/row intersections, where each column/row intersection is associated with a corresponding well. A first plurality of emissive elements populates the wells.