Morphological and Structural Properties of Sn-Bi Lead-Free Solder in 6 M Potassium Hydroxide

Abstract

Sn-based lead-free solder alloys have been explored extensively as an alternative to the conventional Sn–Pb solder alloys. While the miniaturization of electronic devices and the growth of appliance area, the corrosion resistance of solder alloys play a crucial element in the reliability of electronic devices in a prolonged period of service. This paper determines the corrosion effect of Sn-Bi solder lead-free solder, particularly immersed in alkaline solution which is potassium hydroxide. Morphological and elemental analyses reveal the formation of oxides on the surface after immersion after using a scanning electron microscope, dispersive energy X-ray and X-ray diffraction. The result of morphology reveals that the Sn matrix in plateau indicated dark contrast while Bi-rich in the lamellar eutectic structure indicated in light contrast appearance. In addition, phase and elemental analyses revealed the formation of mixed corrosion products of SnO, SnO2 and Bi2O3 on the surface after testing. It is hoped that this finding will provide some helpful evidence in clarifying the corrosion progress of lead-free solder alloys. Furthermore, the remaining corrosion potential and current of Sn-Bi in 6 M potassium hydroxide solutions in this research are proposed.