Laser-assisted bonding strategy enabling enhanced bonding strength and reliability for Mini-LED packaging

To address the limitations of conventional reflow bonding such as insufficient solder joint strength and substrate warpage in advanced Mini-LED packaging, this study proposed an optimized laser-assisted bonding (LAB) method. A finite element thermodynamic simulation model for Mini-LED bonding was established, utilizing a movable rectangular near-infrared laser beam. The optimal parameters for LAB were determined through thermal simulations, ensuring reliable bonding with small warpage and without thermal damage to the chips. The LAB and reflow soldering experiments were conducted using the optimized parameters. Interface characterizations and shear strength tests reveal that LAB joints exhibited a ‌tough fracture mode‌ with fewer voids and cracks, resulting in higher bonding strength‌ compared to reflow soldering. The atomic diffusion phenomena at the bonding interface for LAB joints was investigated. Furthermore, the stability of the intermetallic compound (IMC) for LAB joints under thermal cycling was evaluated. Results indicate that the LAB strategy outperforms the conventional reflow method with processing time, higher precision, and greater reliability. The present work integrates three-dimensional transient thermal simulation, simulation-guided process window determination, experimental benchmarking against reflow bonding, and thermal cycling reliability assessment to establish a relationship among process, microstructure, and reliability, for Mini LED solder interconnections.