Flat embedded-shield multiconductor signal transmission cable, method of

Abstract

A flat embedded-shield multiconductor signal transmission cable includes an embedded conformal shield interposed between adjacent conductors to significantly reduce cross-talk by as much as several orders of magnitude over conventional techniques. The shield is forced to a shape in which it is interposed between adjacent conductors by pinch rolling a sandwich of the conductors, insulation and shield between heated rollers, in which the top and bottom sets of conductors are forced inwardly to lie one beside the other with the shield in between. Uniform termination impedance is achieved because the embedded shield is protected during cable stripping. In an alternative embodiment, external shielding may be utilized to completely circumferentially surround the conductors. For improved pitch control, both heated pinch rollers are identical and are provided with resilient surfaces. Additionally, improvement in pitch control is obtained through the use of cylindrical wire guides in which the wires are pulled over cylindrical surfaces and then over a portion of the cylindrical heated pinch roller prior to pinch rolling, with the wires being preheated prior to arriving at the nip of the pinch rollers. This permits added dwell time for preheating of the wires and therefore greater peel strength and dimensional stability. Alternatively, pitch control is achieved through the utilization of a wire guide having a floor portion which is slanted towards one edge or the other of the guide such that when the wires are pulled downwardly through the guide, they move toward the wire guide edge having the lower portion of the sloped floor adjacent thereto.