| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for soldering by which high junction reliability can be obtained by effectively preventing the occurrence of solder bridging phenomena at the time of performing flow soldering by using lead-free solder. SOLUTION: In the method of soldering electronic components to wiring boards by using molten lead-free solder, the solder composition in a molten solder bath is managed so that the contents of copper element and lead element may fall within the ranges of 0.5-0.05 wt% and 300-3,500 ppm, respectively. The management of the solder composition in the solder bath is performed by fractionating the solder from the solder bath, and performing elemental analysis on the fractionated solder after the operating hour of the solder bath reaches a prescribed value or the number of wiring boards dipped in the solder bath reaches a prescribed number. When at least either the copper element or lead element deviates from a prescribed range, the components of the solder bath is adjusted, so that the composition of the solder bath may fall within a prescribed range. COPYRIGHT: (C)2004,JPO
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