On the role of complexing agents in co-electrodeposition of SnAg alloy with uniform composition

This study investigated the effect of different Ag complexing agents on the co-electrodeposition of SnAg alloys. The reduction onset potentials of Ag and Sn electrodeposition solutions were determined using electrochemical measurements in the presence of the complexing agents thiourea (TU), 1-(2-dimethylaminoethyl)-5-mercapto-1,2,3,4-tetrazole (DMT), and 4,4′-thiodiphenol (TDP). TDP was found to be the most effective at decreasing onset reduction potential compared to TU and DMT, leading to a more uniform deposition process and smoother surface morphology of the SnAg bump. The molecular structures and energy levels of the complexing agents were analyzed to gain insights into their complexation behaviors. The results suggest that TDP has a higher reactivity towards metal ions and is more likely to form stable complexes with Ag ions. By elucidating the intricate interplay between complexing agents and the electrodeposition process, this research contributes to the advancement of knowledge in this field and holds promising implications for optimizing the fabrication of SnAg alloys in various technological applications.