A semiconductor package substrate includes a body having an upper surface and a lower surface opposite to one another, a plurality of circuit layers formed in the body, a plurality of solder pads formed on the upper surface of the body, and a plurality of solder ball pads formed on the lower surface of the body. Each of the solder pads is electrically connected to one of the solder ball pads via the circuit layers and conductive structures disposed between the circuit layers, wherein the circuit layers and conductive structures are configured to expand outwardly in a fan-out manner so as to provide more space between the circuit layers closer to the lower surface of the body such that part of the solder pad-solder ball pad electrical connections can comprise a plurality of parallel connected conductive structures formed in the space, thereby enhancing the heat conducting passageway and the effect of heat-dissipation without having to dispose more solder pads on surface of the substrate.