Described in a paper titled “48x48 pixelated addressable full-color micro display based on flip-chip micro LEDs” published in the Applied Optics journal, the LED-on-Silicon (LEDoS) micro display can be addressed at individual red, green and blue pixel level, the metallization pattern was designed and fabricated on the silicon substrate using standard photolithography and magnetron sputtering, before the individual microLEDs were transfer-printed on top of the substrate as flip-chip structures.
Removing the wire-bonding not only makes the display more rugged and reliable, it also reduces the full-colour pixel size and increases the manufacturing speed. The LEDoS micro display reported in the paper consisted of 48x48x3 (3 for RGB) pixels with a full-colour pixel size of 250x480um distributed at a pitch of 500um on a single silicon substrate. The researchers anticipate such LEDoS micro displays could find their way in applications such as augmented reality, virtual reality, head up displays and wearables, all requiring a high brightness and good image visibility.
In their design, the 48x48 RGB array is surrounded by a series of pads on each side of the array, including VCC common anodes on the top of the array and red, green, and blue electrodes on the right, left, and bottom of the array, respectively. The series pads are connected to the control units with the micro LED array so the pixels in the array can be addressed individually.
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