Abstract: A method and structures are provided for implementing customizable dielectric printed circuit card traces. A void is defined near selected signal traces. The void is then filled with a dielectric material having a predefined dielectric property. The dielectric material is selected to alter at least one predefined electrical property of the selected signal traces, such as, coupling, propagation delay and attenuation. In one embodiment, an outer layer of a printed circuit card includes a plurality of signal traces and a mating circuit card layer including a plurality of matching signal traces is attached to the outer layer of the printed circuit card to create a cavity near selected signal traces. The cavity is filled with the selected dielectric material. In another embodiment, dielectric material is selectively removed near signal traces on an outer layer of the printed circuit card to define a void near selected signal traces.