LEAD-FREE SOLDERING METHOD AND DEVICE THEREOF

PROBLEM TO BE SOLVED: To improve solder-wicking property and to reduce appearance deficiencies of solder of a board with high through holes by using lead-free solder. SOLUTION: The soldering device performs soldering of a MID board 10 in one solder bath 5 in the atmospheric. When a board housing 30 held by a robot is transferred to above a nozzle 51 of the solder bath 5, the bath 5 makes a turbulent flow region and jets solder liquid from the underside of the MID board 10. The board housing 30 is consecutively conveyed forward in the turbulent flow region for 3.5-4 sec. by the robot. In this way, the solder jet onto the MID board 10 rises in a through-hole 14 in the MID board 10. After the completion of the forward conveyance, the solder bath 5 turns to a laminar flow region and the board housing 30 is conveyed backward in the laminar flow region. Consequently, the solder is cut back without waste, and the occurrence of solder bridges, icicle-like solder or the like is reduced.