Patent ID: 8431029

Claim:
A method of manufacturing a circuit board, the method comprising: forming a first pad portion, a second pad portion, and a lead line portion of a metal on an insulating substrate, wherein the lead line portion is connected to the first pad portion, and the second pad portion has no lead line; forming resist to cover the second pad portion on the substrate wherein the resist is the only layer above the second pad portion, relative to the substrate, during the forming of the resist; forming a conductive layer only on the first pad portion and the lead line portion, wherein the conductive layer has an upper surface comprising gold; removing the resist; forming an etching mask on the conductive layer to cover the second pad portion and the first pad portion, and to expose a portion corresponding to the lead line portion in the conductive layer; etching a portion of the lead line portion exposed by the etching mask and a portion of the conductive layer corresponding to the lead line portion using an etching solution containing an acid; and removing the etching mask.