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.