The effects of temperature and humidity on the growth of tin whisker and hillock from Sn5Nd alloy

• Published in: Journal of alloys and compounds 2013-02, Vol.550, p.231-238
• Main Authors: Li, Cai-Fu, Liu, Zhi-Quan, Shang, Jian-Ku
• Format: Article
• Language: English
• Subjects: Crack propagation; Cracks; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Extrusion; Extrusions; Growth mechanism; Hillock; Humidity; Materials science; Methods of crystal growth; physics of crystal growth; Molds; Morphology; NdSn3; Oxidation; Physics; Tin; Tin whisker
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.09.092

► Tin whiskers and hillocks grow from Sn5Nd alloy due to oxidation. ► Temperature and humidity can affect the oxidation and the growth diversities. ► Growth models of whiskers and hillocks were proposed upon microstructural study. ► The proposed models can explain the characteristics of whiskers and hillocks. The effects of exposure time, temperature and humidity on the growth of tin whisker and hillock from Sn5Nd alloy were investigated via scanning electron microscopy. It was found that tin whiskers grew from NdSn3 compound, while hillocks grew from the tin matrix around the NdSn3 compound, which was induced by the oxidation of NdSn3 compound by oxygen and water vapor in the ambient. More tin whiskers and/or hillocks were extruded from the substrate with longer exposure time, higher temperature and higher humidity. This resulted in the formation of various morphologies of tin extrusions at different storage conditions, including thread-like, spiral, flute-like, claw-like, sprout-like, chrysanthemum-like and rod-like whiskers, as well as hillocks. Tin whisker was extruded from the crack of the surface Nd(OH)3 layer which serves as the mold of tin whisker growth. And the proposed growth models of tin whisker and hillock on Sn–Nd alloy can explain the diversity of the whisker morphology.