Investigation of mechanism for spontaneous zinc whisker growth from an electroplated zinc coating

Zinc (Zn) whiskers are tiny hair-like electrically conductive filaments of Zn that sometimes grow from Zn coated surfaces (e.g., electroplated, hot dip). Zn coatings are commonly used as anti-corrosion coatings for iron (Fe) based structures. One of many common applications for Zn coated Fe is found on raised-floor tiles and support structures utilized in computer data centers. The formation of Zn whiskers threatens the reliable operation of electronic equipments due to the electrical shorting hazard they present. As with tin whiskers (much more broadly researched than Zn whiskers), the mechanism of formation is still not clear. This work investigated the Zn whisker growth mechanism for an electroplated Zn coating above carbon steel substrate from a raised floor tile using recent technology methods. Iron-zinc (Fe-Zn) Intermetallics and Zn oxides were identified by X-ray diffraction analysis (XRD). EDS (energy disperse spectroscopy) and EPMA (electron probe micro analysis) identified Fe-Zn intermetallic compounds on the surface of the Zn layer in addition to the interface between Zn coating and carbon steel substrate. Zn oxides formed primarily on the surface of Zn coating. Consequently, we speculate that Fe-Zn intermetallic compounds and Zn oxide formation can be the source of compressive stress effect on Zn whiskers growth on electroplated Zn coating above carbon steel substrate.