Abstract:

Pressure-tolerant ATM and Ethernet network interface cards (NICs) were developed for towed array data acquisition and telemetry. The card functions include sensor signal conditioning, analog-to-digital conversion, network protocol processors, and network interface transceivers. Design and fabrication techniques were developed to achieve space constraints, power constraints, and operation at 2500-psi pressure in oil or saltwater submersion without the use of pressure vessel housings. The development included the testing of candidate electronic components and NIC assemblies for pressure, temperature, and oil tolerance. Components and assemblies which failed testing were analyzed, and design rules were established for future designs. Generally, the elimination or minimization of voids by proper component selection and fabrication was found to be critical. Pressure-tolerant fabrication techniques were developed such as temperature cycle screening, encapsulation in low-viscosity polyurethane, pressurized curing, and compression sealed wires. High-density printed circuit boards and minimalist circuit designs were used to minimize NIC size. Low-voltage components, selective component location, and thermally conductive packaging were used to minimize operating temperatures. Commercially available components and open standard interfaces were used to minimize costs.