Study of Hillock and Zinc Whisker Evolution in Five Different Cable Tray Coatings

The main objective of this work is the study of the hillock and zinc whisker evolution of five different commercial zinc coatings applied on the same base steel wires of the patented EASYCONNECT system cable trays manufactured by VALDINOX Ltd.: white zinc alkaline electrolyte, yellow zinc trivalent electrolyte, acid zinc electrolyte, hot dip galvanized, and zinc nickel coating. The limited literature on the subject is summarized, and then the coating thickness, chemical composition, hardness and surface rugosity are characterized. The hillock and whisker density evolution are evaluated over a period of 12 months, considering the presence of compression bending stresses. It is concluded that the white alkaline and yellow trivalent coatings are the most affected, while the zinc-nickel shows the best behavior with no presence of whiskers; the acid zinc electrolyte also shows good results despite the delayed appearance of whiskers from the ninth month; the hot-dip galvanized coating does not show any presence of zinc whiskers or hillocks.

Relation of Sn whisker formation to intermetallic growth: Results from a novel Sn–Cu “bimetal ledge specimen”

Sn whisker formation was studied in a “bimetal ledge specimen” that consisted of a uniform layer of Sn that was covered by Cu on only half the sample. Whiskers are observed to grow in the Cu-free region of the sample, which is attributed to stress generated by the diffusion of Sn atoms along the network of columnar grain boundaries. The Sn diffusion is driven by the intermetallic growth, but the whisker density extends out much further than any measurable Cu concentration. Whiskers were also observed to grow in the Cu-coated region by punching through the overlayer, leaving a Cu-grain on the tip of the Sn whisker.

Emission Characteristics of Arrays of Diamondcoated Silicon Tips

ABSTRACTThe electron emission behavior of diamond-coated silicon whisker arrays was examined with a point-probe scanner and compared with the behavior of uncoated silicon whiskers as well as with diamond crystallites on a flat Si surface. Emission in all cases was inhomogeneous, and the emission site density was less than the whisker density. Both the diamond-coated and uncoated whiskers displayed a distribution of turn-on fields which peaked at around 10 V/µ, but the uncoated whiskers were observed to burn out if emission outputs exceeded 0.3 µA.