A method for fabricating an integrated circuit array supporting substrate having coaxial transmission lines formed about a core means in proper position for electrically connecting integrated circuit chips. After determining the position and function of the integrated chips mounted upon the core means, the substrate is fabricated by properly positioning insulated conductors in a frame designed to retain the conductors in a desired arrangement, folding the frame about the core, plating the insulated conductors, core and frame with metallized layers to form coaxial cables of the insulated conductors, encapsulating the device, and exposing the ends of the coaxial lines.