Impact of Transistors on Military Electronics Design

POLYSTRIP Cable is a thin, multiple-conductor, flexible cable. It consists of a number of parallel fiat copper wires sandwiched between polyester plastic layers. The cable occupies little volume, having a thickness of 0.009 inch and is flexible enough to fit into irregular spaces. It can reduce cable weight by as much as 80 percent in many applications. All conductors are prepositioned in the same plane permitting simultaneous stripping, termination, or dip soldering to printed wiring boards and connectors. The conductors are evenly spaced 0.100 inch center-to-center in order to conform with EIA Standards for printed wiring boards. The maximum number of conductors is 51; any smaller number can be readily fabricated. Lengths up to 1000 feet are produced. The weight of this cable is 0.64 lb per 1000 conductor feet. The design tensile strength is 4 lbs per conductor, with an elongation of 0.5 per cent. With proper design the flexing life is over 500,000 cycles. Tests at low temperatures have shown that when the cable was bent around a 3/16 inch mandrel at -78°C, no changes in tensile strength or cracking occurred. The cable is not attacked by dilute acids or alkalies. There was a slight reversible increase in weight on exposure to gasoline and carbon tetrachloride. Polystrip Cable is rated at a maximum of +85°C, hot-spot temperalure. It can withstand higher temperatures for short periods of time, and can be dip soldered. The insulation will support combustion. It is rated at 1 ampere per conductor in air at 25°C. The continuous operating rating is 600 volts. The breakdown voltage is in excess of 4 kv. Leakage resistance is 1.5 X 10
¹³
ohms per conductor-foot. Insulation can be readily stripped with commercially available wire strippers. Branches or tapped-off conductors can be fabricated at any position. Standard connectors are available. A conductor in Polystrip Cable may be electrostatically shielded by grounding the adjacent conductors. External shielding may be secured by applying pressure-sensitive aluminum or copper tape to the outside of the cable, and grounding the metal tape. Cables with a larger number of conductors, or with more complete shielding may be made by stacking Polystrip Cable. Conductors of different dimensions or spacing can be made to special order. Polystrip Cable has been used to interconnect printed wiring boards and flexible connectors between chassis parts. It may be of interest for use with large selector switches, telemetering circuits, and with multiple sensing devices. With wires of special alloys, it has been used for thermocouple circuits. A limitation of Polystrip Cable for some applications is its inability to withstand high ambient temperatures for long periods of time. At the present, development work is underway aimed at a cable capable of operation at temperatures of 200°C or higher.