Corrosion Behavior of Sn-3.0Ag-0.5Cu Lead-Free Solder in Potassium Hydroxide Electrolyte
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INTRODUCTION
Sn-Ag-Cu solders have been widely used in electronic industries as promising replacements for Sn-Pb solders. Corrosion of Sn-Ag-Cu mostly contributed to the exposure of corrosive media and moisture absorption in application. However, the susceptibility of Sn-Ag-Cu to corrosion is a main issue that needs to be solved. Moreover, insufficient information is available on the corrosion properties of these lead-free solders. Currently, the corrosion behavior of the Sn-Ag-Cu solders is mainly studied using sodium chloride (NaCl) electrolyte to simulate the seawater condition. The authors in all of these studies[1–5] employed the potentiodynamic polarization test to qualify the corrosion behavior of these lead-free solders. Li et al.[1] investigated the corrosion resistance of Sn-Pb and several candidates of the lead-free solders in 3.5 wt pct NaCl electrolyte through potentiodynamic polarization. The results showed that lead-free solders have better corrosion resistance than that of the SnPb solders. This phenomenon occurred because of the lower passivation current density and lower corrosion current density obtained by the lead-free solder after the passivation film breakdown, which signified a more stable passivation film on the surface. Rosalbino et al.[2] investigated the corrosion behavior of Sn–3Ag–3Cu (at. pct) alloy in 0.1 M NaCl electrolyte using the similar corrosion test and compared the results with that of the Sn-3.0Ag-0.5Cu (SAC305) solder. The Sn-3Ag-3Cu alloy showed a passivation process, whereas no passive behavior was observed for the SAC305 alloy. The Sn-3Ag-3Cu alloy has lower MUI CHEE LIEW, IBRAHYM AHMAD, LIU MEI LEE, and MUHAMMAD FIRDAUS MOHD NAZERI, Students, HABSAH HALIMAN, Research Officer, and AHMAD AZMIN MOHAMAD, Lecturer, are with the School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia. Contact e-mail: [email protected] Manuscript submitted December 5, 2011. Article published online May 9, 2012 3742—VOLUME 43A, OCTOBER 2012
pseudopassivation current density and a larger pseudopassivation range compared with that of the SAC305 alloy. This observation revealed that the corrosion resistance of Sn-3Ag-3Cu is somewhat better than that of SAC305 alloy. However, no current data in literature exist on the corrosion properties of SAC305 in alkaline environment. Alkaline solution is widely used in batteries as electrolyte. Given that batteries are is included inside different devices and in contact with electrical circuits, the leakage of electrolyte could be catastrophic to the circuit. Thus, the corrosion and electrochemical behavior of SAC305 solder alloy in 6 M potassium hydroxide (KOH) electrolytes was studied in the current article through the potentiodynamic polarization analysis. Surface morphology, elemental composition, and phase compositional analyses were also conducted to assist in the interpretation of the obtained polarization curves.
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EXPERIMENTAL
The SAC305 solder wire (Kester 48; Kester, Inc., Itasca, IL) wa
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