| 摘要 |
PROBLEM TO BE SOLVED: To form a thin thread solder of even an alloy poor in mechanical properties, to manufacture a resin flux-cored solder of the alloy composition low in melting point of a lead-free solder, and to achieve the solder repair which is inexpensive in cost and high in quality reliability by providing a flux in a concentric center part, and providing a first alloy layer on an outer layer, and a second alloy layer on its outer layer. SOLUTION: A first alloy layer Sn-Zn alloy 1 is provided around a flux 3 to remove an oxide film at a part to be soldered to improve the wettability. A second alloy layer Sn-Bi alloy 2 is provided therearound to form a concentric resin flux-cored solder 4. The melting point of the first alloy layer is preferably higher than that of the second alloy layer. After the Sn-Zn alloy 1 is rolled thin, its outer circumference is covered by the Sn-Bi alloy 2. When the concentric resin flux-cored solder 4 is melted by a soldering iron, a new alloy Sn-Zn-Bi is formed to enable the soldering at a low temperature.
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