Process Window of Mini-LED Display Panel Packaging using Laser Assisted Bonding Technology

Abstract

For high-resolution display panels using mini-LEDs, high alignment accuracy and high yield of LED transfer and bonding technology are very important parameters of packaging technologies. These parameters of packaging technologies are highly dependent on the interconnection material and bonding process. The use of laser assisted bonding (LAB) technology and epoxy-based interconnection materials has been introduced in mini-LED display panel packaging to improve bonding accuracy and yield. The bonding process of the entire display panel was performed by a tiling SITRAB process because the laser irradiation area is smaller than the LED bonding area on the substrate. For the SITRAB process, an epoxy-based SITRAB material to remove oxide on the surface of solder bump has been developed as a solvent free material. For good wetting of the solder bump during the SITRAB process, the temperature of the solder bumps must be higher than the melting temperature of solder. In general, the stage temperature of the laser process is determined to be around 100C in order to minimize the laser power. However, if the stage temperature is high, the initial properties of the SITRAB material (such as low viscosity and deoxidation function) may be lost due to the high temperature. In this study, the process window of the SITRAB material was determined for a stable SITRAB process. The process window was identified according to three different pot lifes: room temperature pot life (RPL), stage pot life (SPL), and laser pot life (LPL).