High-density high-performance flexible cables for digital applications

In this paper we investigate the range of usage for high-density flexible cables in high-performance applications. We characterize the electrical performance of a test vehicle containing several flexible transmission line structures built on a Kapton film. The results of time-domain measurements with a novel short-pulse propagation technique are presented. 15 ps and 35 ps risetime sources are launched on the experimental structures. This broad-band measurement technique is used to determine frequency-dependent characteristics up to 25 GHz. It is shown that in order to compete with coaxial cables or optical interconnections, an asymmetrical shielded triplate design needs to be used for flexible-film cables. Such a structure offers very low crosstalk, controlled impedance, no radiation and relatively inexpensive fabrication. Based on the experimentally developed models, it is predicted that flexible-film cables can transfer data at 1 Gb/s rates, with lengths of up to 83-165 cm when the line widths are in the range of 55-212 μm