PURPOSE: To eliminate the separation of a lead from a circuit board (causing an open circuit) in a component mounting operation by a method where in a pad includes a wide part in the length-wise direction and a solder bump is formed on a solder layer of the wide part of the pad.

CONSTITUTION: A solder layer 3 having a thickness required to solder a component lead is formed on a pad 2 formed on an insulating board 1 by pattern- etching a copper foil. In this case, the pad 2 includes a wide part in the length wise direction of the pad, and a solder bump 3a is formed on the wide part 2a. Thereby, the position of the solder bump 3a can be formed in a predetermined part, the thickness and the shape of the solder layer are made uniform in each pad, and a solder amount on the pad 2 can be increased. Since the solder layer 3 is swollen locally, it is possible to prevent the solder layer from being swollen and to eliminate an open defect.