A new reduced-oxide soldering activation method

This article describes a new reduced-oxide soldering activation (ROSA?) process that removes oxides from tin, tin-lead, and copper surfaces without the use of a flux. In this process, surface oxides are electrolessly reduced back to the metallic state by a highly reducing vanadous ion solution that is non-corrosive to most metals and is regenerated electrochemically. The electroless reduction and redox regeneration cycles form a closed loop such that oxygen gas is the only effluent. Wetting time and surface analysis data show that a ten-second exposure to the vanadous ROSA solution completely reduces all tin-lead oxides that would normally be encountered on production components. The ROSA treatment has a wide operating window, provides soldering performance comparable to that attainable with a fully-activated rosin flux, and offers the promise of providing low soldering defect rates without the use of CFC solvents.     

Dependence of optical receiver sensitivity, in a 147-Mbit/sheterodyne DPSK system, as a function of optical and electricalparameter variations

Measurements of the changes in optical receiver sensitivity are described. They are caused by (a) the effect of bandpass and low-pass filtering, (b) the dependence on integer and noninteger values of the intermediate-frequency-to-bit-rate ratio, (c) the influence of the local oscillator power, and (d) the impact of deviation from ideal π phase-shift modulation. The studies were conducted at λ=1.523 μm and at a bit rate of 147.75 Mb/s, using external-cavity lasers with negligible phase noise. The results demonstrate the conditions for optimum DPSK system performance in the absence of laser phase noise. The receiver degradation observed for deviations from optimal electrical and optical conditions have been measured and found to be in good agreement with earlier theoretical calculations of microwave phase modulated schemes