| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of weak adhesive properties between a nickel plating layer and a gold plating layer covering a surface o a wiring layer. SOLUTION: A circuit board comprises a nickel-boron plating layer 6 exposed on the surface of the wiring layer 2 formed on an insulating base 1 and a gold plating layer 7 to be sequentially covered. In this case, an opening diameter of each of air gaps A formed on a surface of the layer 6 covered with the layer 7 is 3μm or less. The overall opening area of the gaps A is 5% or less to a surface area of the layer 6.
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