Polarization and EIS studies to evaluate the effect of aluminum concentration on the corrosion behavior of SAC105 solder alloy

This paper presents an investigation on corrosion behavior of Sn-1.0Ag-0.5Cu-XAl (X = 0, 0.1, 0.5, 1.0) by means of polarization and electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt.% NaCl solution. The results show that addition of aluminum into SAC105 shifts the corrosion current density and passivation current density towards more positive values. It is also found that with an increase in aluminum concentration in SAC105 solder alloy, the corrosion current density increases and polarization resistance decreases. This suggests that SAC105 with the highest concentration of Al has the lowest corrosion resistance. In this case, the corrosion behavior seems to be attributed to anodic dissolution of aluminum and Sn-matrix.

Effect of Boron on Microstructure and Properties of Sn-1.0Ag-0.5Cu Low-Silver Lead-Free Solder

In this work, B (boron) was added into Sn-1.0Ag-0.5Cu (SAC105) solder alloy using mechanical alloying method in order to develop a new low-silver lead-free solder, Sn-1.0Ag-0.5Cu-xB, where B ranges from 0wt% to 0.2wt%. The melting characteristics, wettability, mechanical properties of welded joints, and microstructure of this solder were studied. The results showed that with adding B into SAC105 alloy, the melting point and melting range was not obviously changed. Although the wettability decreases with the B content increasing, the solder joints exhibited higher shear strength. As a result, the shear strength was the highest at the B content of 0.2wt%. For example, the shear strength of the Sn-1.0Ag-0.5Cu-0.2B solder was 35.12MPa, while that of the B free SAC105 solder was only 28.94MPa. Furthermore, adding B had a significant effect on grain refinement on the SAC105 solder . Observations on solder matrix and weld joints by SEM showed that the IMC thickness of solder joints with the addition of B was less than the SAC105 lead-free solder. Moreover, with the addition of B, the solder grains were refined obviously which had the effect of refining straitening, and the growing rate of brittle IMC in solder joint could be effectively reduced during soldering and aging process. Thus solder joint performance can be improved significantly.

Impact of aluminium addition on the corrosion behaviour of Sn–1.0Ag–0.5Cu lead-free solder

(a) Al provides an enhanced passivation capability over SAC105 solder alloy. (b) Corrosion products on the surface consist of Al2CuO4, Al2O3, SnO and SnO2. (c) Al-added SAC105 is less susceptible to corrosion.