Electric field stimulated growth of Zn whiskers

Abstract

We have investigated the impact of strong (∼10 4 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. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Whisker growth on Sn thin film accelerated under gamma-ray irradiation

“…Comparing the obtained results with those previously measured for tin and zinc samples under high-energy electron beams, 5,18 we point out roughly 4 times lower values of acceleration factor observed under photon irradiation here. We attribute it to the lower dose rate of the gammaray source, resulting in longer irradiation times to achieve the same dose and charge density levels.…”

Gamma- and x-ray accelerated tin whisker development

“…We attribute the dose rate dependence to the radiation charging capacity, resulting in lower sustained electric fields during irradiation with lower dose rate sources. The final achieved total dose levels are close to 30kGy in all three experiments (∼ 26 kGy under the 20-hour electron beam irradiation of reference 9,10 ). From a practical standpoint that acceleration means growing whiskers under high-energy photon (gamma-or x-ray) or electron sources should take one-two weeks rather than years.…”

“…Such field-induced accelerated whisker growth has been observed in multiple experiments. [7][8][9] A related effort was devoted to acceleration of whisker growth under ionizing radiation sources, such as 6 MeV electrons 9,10 and 0.4 MeV gamma-rays 11 capable of inducing electric fields by electrically charging a substrate (glass or acrilic holder) supporting tin or zinc films. We note that radiation effects on whisker growth have been observed ∼60 years ago and remained unexplained.…”

Whiskers growth and self-healing in Ti-based metallic glasses during ion irradiation

“…Whiskers growth has been widely reported in other materials, such as, Sn or Zn crystal solders [21,22]. Whiskers growth in Sn solders can be interpreted as an atomic diffusion process where stress generation and relaxation simultaneously occurs.…”