Abstract: In order to increase the lead-free laser soldering speed, the laser parameters, properties of solder and substrate, laser soldering system and other influencing factors of the lead-free laser soldering are studied. The research shows that once the laser, the solder and the substrate are given, a laser soldering system equipped with two galvanometer scanners and an f-theta lens has obvious advantages in soldering speed as compared with the traditional laser soldering system with moving worktable or laser head, because the reflection of the laser beam through the scanning galvanometers overcomes the restriction of the mechanical inertia of the laser head and worktable. In addition, the path that laser beam has scanned in the process of soldering is optimized. The optimization can greatly sho