A LED Micro-Display with 90x90 Pixels on a 80 mu m Pitch

作者：Akhter Mahbub^*; Lee Jun Su; Maaskant Pleun P; Rensing Marc; Nudds Noreen; O'Brien Peter; Degenaar Patrick; Corbett Brian

来源：20th European Microelectronics Packaging Conference And Exhibition (EMPC), 2015-09-14 to 2015-09-16.

We report on the flip-chip packaging of 90x90 arrays of addressable microLEDs onto CMOS circuitry by a solder reflow process. The substrate emitting microLEDs were parabolically shaped and fabricated on free-standing GaN. The individual emitters were 15 mu m in diameter with an array pitch of 80 mu m where all bond pads were given a gold finish. The solder balls were dispensed onto the CMOS pads with an automated PacTech solder dispenser that dispensed 50 mu m diameter solder spheres with a composition of Sn (96.5%)-Ag-(3%)-Cu (0.5%). After alignment of the LED array on top of the CMOS chip, the solder was reflowed at a temperature of 260 degrees C in nitrogen ambient. The completed assemblies form micro-displays that can display computer generated patterns designed for the stimulation of neural cells. The displays were designed to be mounted on the camera port of a microscope to project the emitted light onto neural tissue.