Micro-LED Light Module Backplane for Fine Contacts and Low Voltage Drop
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Solution Overview
Problem
The challenge in creating high-resolution micro-LED displays lies in achieving precise contact size and positioning, reducing seam visibility between modules, ensuring flatness, and managing high driving currents due to the limitations of traditional substrates and contacting methods, particularly with micro-LEDs requiring micrometer-scale precision and smaller pixel pitches.
Innovation Solution
A light emitting module design featuring a third backplane with cavities and copper layers on top of a thin film transistor layer, allowing for reduced voltage drop, finer tracks, and side contacts, along with metalized cavities for power and ground connections, which also provides EMI shielding and optical enhancements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional PCB substrates are used for micro-LED displays, then manufacturing is easier, but contact precision and positioning accuracy deteriorate due to wire dimensions being larger than micro-LEDs themselves
Solution Approach 1:
The patent transitions from traditional PCB substrates to TFT (thin-film transistor) technology on glass or ceramic substrates. This parameter change enables precise lithographic definition of contact pads and routing layers at micrometer scale, matching the dimensions of micro-LEDs. The TFT process allows for single-sided contacts and processing with high precision positioning capabilities that PCB technology cannot achieve.
Solution Approach 2:
The patent replaces the mechanical PCB wiring system with a lithographically defined TFT circuit system. Instead of using physical wires and traces on PCB that are too large for micro-LEDs, the invention uses TFT-based conductive layers that can be precisely patterned at the required micrometer scale, enabling proper electrical connection between micro-LEDs and driving components.
2Manufacturing precision
If glass substrates are used to achieve high precision contact positioning, then contact precision improves, but device complexity increases due to lack of Cu routing layers and need for TFT integration
Solution Approach 1:
The patent makes the glass substrate with TFT layer serve multiple functions simultaneously: it provides the mechanical support structure, defines the precise contact pad positions through lithography, creates the conductive routing layers, and enables single-sided processing. This multi-functionality reduces the need for additional separate components and simplifies the overall device architecture despite the advanced TFT technology required.
Solution Approach 2:
The patent segments the display into modular light emitting modules that can be independently manufactured and then assembled. Each module contains its own TFT-driven micro-LED array with integrated routing, allowing for precise contact positioning within each module while simplifying the overall system assembly and reducing complexity at the system level.
3Manufacturing precision
If pixel pitch is reduced to achieve higher resolution, then display resolution improves, but seam visibility between modules increases
Solution Approach 1:
The patent extracts the driving electronics from the front view of the display by implementing backside driving architecture. The TFT circuits and control electronics are positioned on the backside of the glass substrate, away from the viewer's perspective. This extraction eliminates visible seams and bezels at the edges of the display, allowing for seamless high-resolution images even with reduced pixel pitch.
Solution Approach 2:
The patent moves the driving components from the two-dimensional front plane to the three-dimensional backside of the display. By placing TFT circuits and routing on the backside of the glass substrate, the design eliminates visible seams at the module edges from the viewer's perspective, enabling higher resolution displays without compromising aesthetic appearance.
4Manufacturing precision
If micro-LEDs with smaller size are used to improve display resolution, then display resolution improves, but power routing capability deteriorates due to higher driving currents required
Solution Approach 1:
The patent utilizes the third dimension (depth/thickness of glass substrate) to create wide Cu routing layers on the backside of the display. These thick copper layers provide low-resistance power distribution paths that can handle the high driving currents required by micro-LEDs, while the front surface maintains high resolution with small pixel pitch. The power routing is separated from the light-emitting plane, resolving the contradiction between resolution and power capability.
Data Source
AI summary
A light emitting module for a light emitting display, including a first backplane and a third backplane arranged in a stackup. The first backplane includes a thin film transistor (TFT) layer deposited on a first substrate, the TFT layer further including a plurality of light emitting elements, associated contact pads and conducting tracks. The third backplane is provided on top of the light emitting elements, includes cavities at the locations of the light emitting elements and includes at least a ground layer and a power layer. The upper and lower layers of the third backplane are provided by alternatively the ground layer and the power layer for contacting the light emitting elements.