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

Abstract 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.