The present disclosure is directed to systems and methods for improving the impedance matching of semiconductor package substrates by incorporating one or more magnetic build-up layers proximate relatively large diameter, relatively high capacitance, conductive pads formed on the lower surface of the semiconductor package substrate. The one or more magnetic layers may be formed using a magnetic build-up material deposited on the lower surface of the semiconductor package substrate. Vias conductively coupling the conductive pads to bump pads on the upper surface of the semiconductor package substrate pass through and are at least partially surrounded by the magnetic build-up material.