A conductive bump structure of a circuit board includes at least one composite conductive bump formed in at least one bump preservation region on a conductive layer of the circuit board. The composite conductive bump includes a raised portion and a conductive pillar. The raised portion is raised from a top surface of the conductive layer by a height. A bottom of the conductive pillar is in contact with and is combined with a curved top surface of the raised portion, and a top of the conductive pillar is raised upwards to protrude beyond the top planar surface of the conductive layer by a protrusion height.