Abstract
We have investigated the impact of strong (∼104 V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.
Highlights
INTRODUCTIONSimilar to other metal whiskers (amply described in the available literature databases1,2), Zn whiskers are tiny electrically conductive filaments unpredictably developing on Zn coatings deposited by various methods, such as electroplating or hot dip
Similar to other metal whiskers, Zn whiskers are tiny electrically conductive filaments unpredictably developing on Zn coatings deposited by various methods, such as electroplating or hot dip
We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we used (4) the electric field produced by a Van der Graaf generator
Summary
Similar to other metal whiskers (amply described in the available literature databases1,2), Zn whiskers are tiny electrically conductive filaments unpredictably developing on Zn coatings deposited by various methods, such as electroplating or hot dip. Their practical significance is due to the fact that Zn is commonly used as anti-corrosion coatings for Fe-based structures; one common application is found on raised-floor tiles and support structures utilized in computer data centers. We present data showing that the Zn whisker development from a raised floor tile can be greatly accelerated by the external electric field, a conclusion consistent with the electrostatic theory of metal whiskers[10,11,12,13] and recent observations of the field induced development of metal whiskers.[14,15,16,17]
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