Corrosion of Pb-50In flip chip interconnections exposed to harsh environment

Lead-indium alloys are an alternative to lead-tin solders commonly used for interconnections in the electronics industry. Lead-indium alloys with 25 to 50 wt.% In provide the advantage of a substantially lower process temperature and overall exhibit a much lower tendency to scavenge gold compared to Pb-Sn solders with high Pb content. However, a corrosion problem has been identified in connection with Pb-50In solders, an alloy of interest owing to its thermal-fatigue resistance property. The author presents the results of a study conducted to gain a fundamental understanding of the nature and path of corrosion in Pb-50In flip-chip connections exposed to an accelerated hostile-environment test simulating harsh industrial ambients. The key events in the corrosion process are identified and discussed