Insights into sulfur and hydrogen sulfide induced corrosion of sintered nanocopper paste: A combined experimental and ab initio study

The power semiconductor joining technology through sintering of copper nanoparticles is well-suited for die attachment in wide bandgap (WBG) semiconductors, offering high electrical, thermal, and mechanical performances. However, sintered nanocopper will be prone to degradation resulting from corrosion in sulfur-containing corrosive environments such as offshore areas. In this study, experiments, including aging test and corrosion characterization, and simulations based on density functional theory (DFT) studies were conducted to explore the corrosion behavior and mechanism of elemental sulfur (S₈) and hydrogen sulfide (H₂S) on sintered nanocopper. The experimental results indicated that loose corrosion products were observed on the sintered nanocopper during the ageing process involving S₈, and compact layered corrosion products formed during the ageing process involving H₂S. Furthermore, similar corrosion product compositions (Cu₂O, Cu₂S, CuO, CuS, and potentially Cu₂SO₄ or CuSO₄) were observed in both the S₈- and H₂S-ageing processes. However, the S₈-ageing process exhibited more noticeable corrosion penetration. This was explained in simulations results: the unsaturated Cu sites on the oxide layer [Cu₂O(1 1 1)] of the sintered nanocopper could adsorb both H₂S and S₈, while the saturated Cu sites only exhibited the potential to adsorb S₈.