The firm has also announced that a fluidic assembly tool from a display panel tool maker is operational at an eLux prototype fab located in Taiwan.
eLux's assembly technique is based on moving microLEDs from wafer to target substrate using a liquid rather than a pick and place process. The process uses wells built into the substrate that the LEDs fall into, as a self-assembly process.
The 12.3-inch display consisted of 518,400 GaN microLEDS and was assembled in 10 minutes giving an assembly rate of 3.1 million devices per hour. The unit had a 99.987 percent natural yield. So 34 failing subpixels of which 33 could be laser repaired.
This is approaching the quality level required for 4K television screens, which have 8.3 million pixels.
The assembly tool has demonstrated automatic cassette-to-cassette fluidic assembly of ten display panels up to 15-inches diagonal. The tool has provisions for capture and recycle of microLEDs and assembly fluids to minimize operating costs, and two additional modules can be added to the main frame for increased capacity. The manufacturing process includes automated inspection at the assembly, clean-off, recycling and drying stages for throughput optimization and yield enhancement. Unlike mass transfer equipment, fluidic assembly can be scaled up to substrates much larger than 15” so this tool will be used to develop equipment modules and processes for a proposed Gen 3.5 fluidic assembly tool.
Inspection and selective harvest techniques developed by eLux prevent defective microLEDs from entering the fluidic assembly process, so displays are fabricated using only known-good microLEDs. Fluidic assembly randomizes the microLEDs in liquid, which prevents the mosaic patterns caused by epi-wafer non-uniformity.
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