New reflow process for indium bump

Abstract

A new reflow method for indium bump of hybridized HgCdTe IRFPA is proposed using H<SUB>2</SUB> plasma. Twenty micrometer height indium bump is easily achieved with this method. In the new method, H<SUB>2</SUB> plasma makes the indium bump surface clean with removing the oxidized indium by H radical chemical reaction. Simultaneously, H<SUB>2</SUB> plasma increases the temperature of indium bump above 160 degrees Celsius. This sphere shaped bump is easily deformed plastically with relatively small force. Force of 2 g/bump changes the 20 micrometer height bump to 10 micrometer. The flip-chip bonding technique using the new reflow method is characterized with shear strain strength measurement. It is found that bonding reliability can be improved owing to increased height and smooth surface.