Patent ID: 8338716

Claim:
A circuit board comprising: an insulating substrate; and a circuit formed on the insulating substrate, wherein the circuit comprises: a undercoat layer with a circuit pattern formed by irradiating a metal thin film covering a surface of the insulating substrate with a laser along an outer shape of the circuit so as to partly remove the metal thin film along the outer shape of the circuit; a Cu plating layer, a Ni plating layer and a Au plating layer formed by metal plating and sequentially provided on a surface of the undercoat layer; and a first middle plating layer and a second middle plating layer provided between the Ni plating layer and the Au plating layer, wherein the first middle plating layer includes metal with a less noble standard electrode potential with respect to Au and is in contact with the Au plating layer, and wherein the second middle plating layer includes metal with a noble standard electrode potential with respect to the metal in the first middle plating layer and is in contact with the first middle plating layer, wherein the first middle plating layer is composed of Rh.