Abstract: A circuit board structure and its forming method are provided. The circuit board structure includes a dielectric layer and a first wiring layer embedded in the dielectric layer. The first wiring layer includes a plurality of conductive contact pads exposed on the upper surface of the dielectric layer. The circuit board structure also includes a plurality of metal pillars. Each of the metal pillars is formed on and is in direct contact with one of the conductive contact pads. The circuit board structure also includes a first insulating passivation layer and a second insulating passivation layer formed on the upper surface and the lower surface of the dielectric layer. The first insulating passivation layer includes a first opening exposing the metal pillars and the conductive contact pads, and the second insulating passivation layer includes a second opening.