Understanding Electrochemical Migration Behavior in Fe₂O₃-Enhanced SAC Lead-Free Alloys

The effect of ferric oxide $\left(\mathrm{Fe}_{2} \mathrm{O}_{3}\right)$ nanoparticle incorporation on the reliability of SAC305 solder alloy, in terms of electrochemical migration (ECM) behavior, was studied using water drop (WD) tests performed in a $0.1 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}$ solution with a 10 VDC. The incorporation of Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> nanoparticles at different weight percentages ($\mathbf{0. 1 \%}$ and 0.25%) into SAC305, referred to as nanocomposite SAC305-x $(0.1,0.25$ wt. $\% \mathrm{Fe}_{2} \mathrm{O}_{3}$), resulted in a significant shorter mean time to failure (MTTF) compared to pure SAC305. This result indicates that the SAC305 alloy with incorporated Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> nanoparticles exhibits lower ECM resistance than undoped SAC305. A comprehensive surface analysis was conducted on the dendrites formed during the WD test for nanocomposite solders in various solutions, including $0.1 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}, 10 \mathrm{mM} \mathrm{H} \mathrm{O}_{2}, 10 \mathrm{mM} \mathrm{HCl}$, and $10 \mathrm{mM} \mathrm{HNO}_{3}$. In all cases, the dendrite morphology predominantly displayed straight, perpendicular branching, resembling a fishbone-like structure. Elemental composition analysis consistently identified Sn as the dominant element in the dendrites, indicating that the ECM behavior of the nanocomposite solders is still primarily governed by the dissolution of Sn.