A NEW REDUCED OXIDE SOLDERING ACTIVATION METHOD

This article describes a new reduced-oxide soldering activation (ROSA( TM)) process that removes oxides from tin, tin-lead, and copper surfac es without the use of a flux. In this process, surface oxides are elec trolessly reduced back to the metallic state by a highly reducing vana dous ion solution that is noncorrosive to most metals and is regenerat ed 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 o ffers the promise of providing low soldering defect rates without the use of CFC solvents.