Full-color high brightness Micro-LED displays with high bonding yield realized via photosensitive conductive polymeric bumps
Micro light-emitting diode (Micro-LED) display technology is a promising next-generation display technology due to its high brightness, high contrast, low power consumption, long life, and fast response. However, aggressive downscaling of Micro-LEDs to a few microns makes lift-off fabrication of metal bumps for soldered joints between Micro-LEDs and driver substrates increasingly difficult, challenging high-yield bump arrays under high-density conditions. This study innovatively replaces conventional metal bumps with a photosensitive conductive polymer (PCP), enabling fabrication of polymeric micro-bump arrays via well-established photolithography, bypassing complex lift-off processes and reducing short-circuit risk. Isopropyl alcohol regulates developer wettability for optimal development, yielding bump arrays with bump size 20 μm × 12 μm and height (1.9288 ± 0.0213) μm on thin-film transistor (TFT) drivers with yield over 99.99%. The issue of low bonding yield from polydimethylsiloxane (PDMS) thermal expansion was resolved by adjusting chip spacing on the temporary substrate, achieving bonding yield exceeding 99.8%. A 0.99-inch full-color Micro-LED display with density 114 pixels per inch (PPI) and brightness 5537 cd/m² was fabricated. High-yield bump arrays, Micro-LED arrays, and high bonding yield are highly reproducible, promoting development of Micro-LED displays and related fields.