The development of the next generation lead-free solders presents an important task for material scientists due to health and environmental concerns induced mainly by the lead content of conventional solders. During soldering of copper (Cu), its interaction with liquid Pb-free Sn-based solder alloys is accompanied with the formation of complex interface structure composed of different intermetallic compounds, depending on the type and amount of alloying additions in the solder. The corrosion resistance of solder joints, affected by its heterogeneous structure and, particularly, its complex interfaces, is one of the key factors responsible for their reliability.
This research focuses on the comparative studies of the effect of Zn content on the reactivity between liquid Sn-Zn alloys and Cu, corresponding structure and properties of Sn-Zn/Cu interfaces and their influence on corrosion resistance of solder joints. The Sn-Zn/Cu couples were produced at 230°C for 5 min contact in air under flux. The corrosion resistance tests were performed by means of electrochemical measurements and the detailed analysis of polarization curves recorded for sulfate solution of various pH. The special attention was paid to the role of the solder/Cu interface structure and chemistry responsible for the mechanism of electrochemical processes in the examined couples.
The research was performed in frame of EU COST ACTION MP0602 with financial support from the Ministry of Science and Higher Education of Poland.