| 摘要 |
PROBLEM TO BE SOLVED: To provide a cheaper solder alloy having a best soldering feature by improving the wettability of a Sn-Cu base lead-free solder alloy poorer than that of a Sn-Ag base lead-free solder alloy while better in cost effectiveness. SOLUTION: In the soldering method, P of 0.001-0.1 percent by mass is added independently or together with Ge of 0.001-0.1 percent by mass to Sn-Cu of 0.1-3 percent by mass base lead-free solder alloy. Additionally as a strength improving element, either 4 or less percent by mass in the total of Ag and/or Sb, or 0.5 or less percent by mass in the total of one or more type selected from among groups comprising Ni, Co, Fe, Mn, Cr and Mo, may be added. Also as a melting point depressing element, 5 or less percent by mass in the total of at least one type among Bi, In and Zn may be added.
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