Application of laser-assisted bonding in micro-LED display technology

Micro-LED is considered as the new generation of display with the long-lifetime, high contrast and brightness, splicing capability, and so forth. Mass transfer is the bottleneck that limits the manufacturing of Micro-LED display at large volume, due to factors such as laser-lift off, pick-up, and metal bonding. Metal bonding between the Micro-LED chip and the substrate is one of the most important factors to the light-up yield. To solve the key thermal mismatch issue between the backplane and Micro-LED donor during heating, the laser-assisted bonding process could be a viable solution. We present a study in metallic element Au/Sn with high productivity, capability and low cost, as well as good thermal and electrical conductivity, excellent bonding strength, and low sensitivity to surface roughness. The result is presented in a 62 × 78 pixels full-color Micro-LED display, with reliable metal electrical connection between microscale LED devices and the backplane that can be achieved under 250°C without any damage to the backplane. In conclusion, the micromorphology and formation mechanism of different alloy phase compositions of welded metal elements have been thoroughly studied, and a feasible technological methodology has been developed for the upcoming mass production of Micro-LED display modules.