Dynamics of corrosion on mechanical and electrical reliability of SAC305 solder joints during salt spray test

Abstract

This paper, concerns the impact of a corrosion evolution on mechanical and electrical reliability of solder joints during salt spray tests. Focus is made in test vehicle resistors (1210) soldered with a SAC305 lead-free solder. Solder joints resistors were electrically and mechanically tested and aged from 24 to 96 h in a salt spray chamber with one salinity of 5 % NaCl at five temperatures ranging from 25 °C to 45 °C. The shear strengths of SAC305 solder joints decreased with increasing temperature and corrosion time. No electrical failure was observed. However, the solder joints deterioration is visible by cross-section after 72 h at 25 °C, 60 h at 30 °C, 48 h at 35 °C, 36 h at 40 °C and 24 h at 45 °C. Moreover, the corrosion has a significant effect on the mechanical strength of lead-free solder joints. A relationship between the mechanical behaviour and the dynamics of corrosion of the solder joints has been established. In addition, although the corrosion product remains the same, the corrosion dynamics of the solder material (alloy) and the solder joint (assembly) are very different: the corrosion kinetics is significantly less in the solder material than in the solder joints.