Realization of precise alignment and high reliability in metal interconnects for ultra-high pixel density micro-LED arrays based on laser-assisted bonding

Laser-assisted bonding (LAB) technology offers advantages in localized thermal management, making it a promising approach for micro-LED integration. However, the stringent requirements of large-scale micro-LED arrays pose significant challenges in achieving high bonding accuracy and reliability, particularly in minimizing bonding misalignment and void formation. In this work, an optimized LAB process was developed by combining line-shaped laser beam bonding (L-LAB) with thermally matched substrate materials. Multidimensional process optimization was also introduced to further enhance solder-joint reliability. This approach reduced post-bonding misalignment by up to 28.6% relative to planar-shaped laser-beam bonding (P-LAB), and lowered the void rate to below 0.3%. It also effectively suppressed the formation of brittle intermetallic compounds at Sn/Au/Ni interfaces through rapid laser quenching. COMSOL-based simulations further validated the experimental results and elucidated the mechanisms underlying the observed performance improvements. Based on this novel process, a high-resolution head-up display (HUD) module with a 58.88 μm pixel pitch and >99.99% yield was successfully fabricated, demonstrating the effectiveness of such a proposed process. These results establish a practical bonding strategy that significantly improves the optical and structural performance of micro-LED displays, paving the way for high-reliability, large-scale micro-LED integration.