Corrosion reliability of lead-free solder systems used in electronics

Corrosion reliability of five Sn-Ag-Cu (SAC) based lead-free solder alloys under humid and corrosive conditions has been investigated to understand the microstructure effects on corrosion performance. Electrochemical experiments such as potentiodynamic and potentiostatic tests were conducted in 3.5 wt% sodium chloride electrolyte at room temperature. Microstructure of the solder alloys and corrosion surface morphology was evaluated using light optical microscope (LOM) scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). During the potentiostatic tests, the cathodically active Bi phase in No. 5 alloy introduced pitting in the Sn phase nearby, whereas Ag
₃
Sn phase prompted pitting on the adjacent to β-Sn phase in No. 1-4 solder alloys (Table 1.).