Issue Date: May 26, 2014
Metal Whisker Growth Clarified
So-called whiskers growing out of metal surfaces commonly cause current leaks or short circuits, resulting in electronics failures in satellites, power plants, and even pacemakers. Although reports of whiskers date back to the 1940s, the mechanism behind their growth is poorly understood. The answer may lie in electric field formation just above metal surfaces, according to a theoretical analysis by Victor G. Karpov of the University of Toledo (Phys. Rev. Appl. 2014, DOI: 10.1103/physrevapplied.1.044001). Metal surface defects, such as oxide formation, chemical contamination, local stresses, or interfacial boundaries, can generate a strong electric field within 1 μm of the surface. That electric field induces nucleation of needle-shaped metal filaments, about 100 nm long and 1 nm in diameter, Karpov suggests. Electric fields may also influence whiskers’ growth rates, lengths, and diameters, as well as how many appear in a particular location. Previous observations indicate that whiskers grow from their bases by adding material obtained through long-range surface diffusion. More work is necessary to determine the chemical nature of whisker development and how whiskers correlate with specific surface imperfections.
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