Tin Whisker Growth Suppression Using NiO Sublayers Fabricated by Dip Coating

Whiskers are small crystalline growths, which can grow from certain metals or alloys. Reaching up to several millimeters long, whiskers have the potential to cause device failures due to short circuits and contamination by debris. Tin (Sn) is one such metal that is particularly prone to whisker development. Until the 2006 RoHS Initiative, lead (Pb) was added to tin in small amounts (up to 2%) to greatly reduce the growth of whiskers. Since then, however, industry has switched to lead-free tin solders and coatings, and the issue of whisker growth on tin has attracted new interest. A reactive-sputtering-deposited nickel oxide sublayer was shown recently to strongly suppress the growth of whiskers from an overlaying tin layer. This paper reports on using nickel oxide films, obtained by a sol–gel dip coating method, as whisker suppressing sublayers. The proposed method is simple, low-cost, and can easily be scaled up for manufacturing purposes. The properties of the sol–gel deposited nickel oxide film were examined using SEM, EDS, and Raman spectroscopy. Samples containing the nickel oxide sublayer were observed through SEM periodically over several months to examine the surfaces for whisker development, and the results show that such layers can be very effective in suppressing whisker growth.

Enhanced Electrochromic Performance by Anodic Polarization in Nickel Oxide Films

Nickel oxide (NiO) is considered to be the best candidate for the compensatory layer of WO3-based smart windows. In this article, we demonstrate that a facile anodic polarization can dramatically improve the electrochromic performance. Unambiguous evidence of performance enhancement was demonstrated by both in situ optical response and cyclic voltammetry. Benefiting from this treatment, the quantity of voltammetric charge increased by ∼43.8% under the same test conditions, enhancing the corresponding electrochromic modulation by ∼17.6 %. The improved performance is due to the newly exposed high-valence Ni3+ ions during anion-dependent anodization. These results offer a novel strategy for the preparation of high-performance NiO films and provide valuable insights into the underlying mechanism in the electrochromic process.