| 摘要 |
A wired circuit board includes an insulating layer, a conductive pattern made of copper formed on the insulating layer and a covering layer made of an alloy of copper and tin to cover the conductive pattern. An existing ratio of tin in the covering layer increases in accordance with a distance from an inner surface adjacent to the conductive pattern toward an outer surface being not adjacent to the conductive pattern. An atomic ratio of copper to tin in the outer surface of the covering layer is more than 3.
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