Micro-LED Display Redundancy for High-Yield Assembly
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Solution Overview
Problem
Current LED display manufacturing techniques face challenges in achieving high yields due to low wafer manufacturing yields, complex assembly processes, and the need for precise testing of small, micron-sized LED dies, which are time-consuming and costly, especially for smaller displays like wearables.
Innovation Solution
The method involves using multiple micro-LED dies per pixel with electrodes on the same side for easy testing and integration, employing a non-selective pick-up tool for assembly, and implementing redundancy schemes to achieve high display yields by repeating pick, place, and test cycles, allowing for in-process testing and repair, and utilizing excess emitters as solar cells for energy harvesting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple micro-LED dies are placed at the same sub-pixel location through multiple placement cycles, then display yield is improved and defect rates are reduced, but manufacturing complexity and process time increase
Solution Approach 1:
The patent applies preliminary action by performing pick-up and placement of multiple LED dies at each sub-pixel location before final testing. By pre-placing redundant dies and only testing after all placements are complete, the process avoids the complexity of selective pick-up tools while still achieving high display yield through in-process testing and repair capabilities.
2Reliability
If multiple micro-LED dies are placed at the same sub-pixel location, then redundancy is increased and functional pixels are improved, but assembly time and manufacturing cost increase
Solution Approach 1:
The patent merges multiple placement operations into a single unified process flow. Instead of performing separate placement cycles for each die with intermediate testing, all multiple dies are placed at each sub-pixel location in one continuous process, followed by a single testing phase. This combining of operations reduces total assembly time while maintaining the functional yield benefits of redundancy.
Solution Approach 2:
The patent skips intermediate testing steps between placement cycles by placing all redundant dies first and then performing testing only after completion. This rushing through the placement phase without interruption significantly reduces assembly time while the subsequent comprehensive testing ensures high functional pixel yield through efficient defect identification.
3Area of moving object
If micron-sized LED dies are used to reduce pixel size for portable displays, then display resolution and portability are improved, but testing difficulty and manufacturing precision requirements increase
Solution Approach 1:
The patent applies self-service by designing the micro-LED dies with electrodes positioned on the same side, enabling the components to be tested directly after placement without requiring complex flip-chip bonding or specialized testing equipment. The dies essentially test themselves through their own electrode configuration, simplifying the detection and measurement process for such small components.
4Productivity
If wafer-level manufacturing is used to produce LED dies, then production efficiency is improved, but manufacturing yield remains low due to process defects
Solution Approach 1:
The patent changes the fundamental parameter approach by shifting from attempting to achieve high yield at the wafer level to achieving high display level yield through redundancy. Instead of optimizing manufacturing parameters to reduce defect rates, the invention accepts the low wafer yield and compensates through multiple die placement and in-process testing, transforming the yield optimization problem from component level to system level.
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 significantly reduces the number of assembly cycles, increases display yield, and lowers defect rates, making the manufacturing process more efficient and cost-effective for small displays by enabling high-yield production with minimal defects and extended battery life through energy harvesting.
Implementation Method 1
each sub-pixel configured to provide light of a given wavelength... The first LED dies may include a first LED die including at least one LED emitter
Implementation Method 2
utilizing excess emitters as solar cells for energy harvesting
Data Source
AI summary
Methods and apparatus for use in the manufacture of a display device including pixels. Each pixel includes a plurality of sub-pixels, each sub-pixel configured to provide light of a given wavelength. The method may include: performing, using a pick up tool (PUT), a first placement cycle comprising picking up first light emitting diode (LED) dies, and placing a first LED die on a substrate of the display device at a location corresponding to a sub-pixel the display device. The method further includes performing one or more subsequent placement cycles comprising picking up a second LED die, and placing the second LED die on the substrate of the display device at a second location corresponding to the sub-pixel of the display device. Multiple first and second LED dies may be picked and placed during each placement cycle to populate each pixel of the display device to provide redundancy of LED dies at each sub-pixel.