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Morphology and growth kinetics of straight and kinked Tin whiskers

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Michael, Joseph R.; Grant, Richard P.; McKenzie, Bonnie B.; Yelton, William G.

Time-lapse SEM studies of Sn whiskers were conducted to estimate growth kinetics and document whisker morphologies. For straight whiskers, growth rates of 3 to 4 microns per day were measured at room temperature. Two types of kinked whiskers were observed. For Type A kinks, the original growth segment spatial orientation remains unchanged, there are no other changes in morphology or diameter, and growth continues. For Type B kinks, the spatial orientation of the original segment changes and it appears that the whisker bends over. Whiskers with Type B kinks show changes in morphology and diameter at the base, indicating grain boundary motion in the film, which eliminates the conditions suitable for long-term whisker growth. To estimate the errors in the whisker growth measurements, a technique is presented to correct for SEM projection effects. With this technique, the actual growth angles and lengths of a large number of whiskers were collected. It was found that most whiskers grow at moderate or shallow angles with respect to the surface; few straight whiskers grow nearly normal to the surface. In addition, there is no simple correlation between growth angles and lengths for whiskers observed over an approximate 2-year period. © 2012 The Minerals, Metals & Materials Society and ASM International (outside the USA).

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TYPE Journal Article YEAR 2013
OSTIScopus

Copper ionic liquids: Tunable ligand and anion chemistries to control electrochemistry and deposition morphology

Journal of Electroanalytical Chemistry

Pratt, Harry D.; Ingersoll, David I.; Hudak, Nicholas H.; McKenzie, Bonnie B.

A multi-technique investigation was performed on three copper-based ionic liquids to elucidate the influence of coordinating ligands and charge-balancing anions on the electrochemical properties of the materials. Galvanostatic cycling of Cu(OHCH2CH2NH2)6(BF 4)2 (Cu1) in 1-butyl-3-methyl-imidazolium hexafluorophosphate gave partially reversible plating of copper that was consistent with cyclic voltammetry data (collected using an ionic liquid-based reference electrode verified with measurements of ferrocene, cobaltocene, and lithium). Scanning electron microscopy also showed pitting in the copper-coated surface of the electrode that was consistent with the stripping wave observed by cyclic voltammetry. Potentiostatic deposition in neat Cu1 showed significant dendrite formation. The substitution of the OHCH2CH 2NH2 ligands of Cu1 with stronger coordinating NH(CH 2CH2OH)2 in Cu(NH(CH2CH 2OH)2)6(BF4)2 (Cu2) resulted in the complete suppression of both copper stripping and dendrite formation. Substitution of the BF4- anions of Cu2 with CF3SO3- in Cu(NH(CH2CH2OH)2)6(CF 3SO3)2 (Cu3) shifted the copper deposition 0.1 V more negative and produced slightly larger spherical particles (1.5 μm versus 5 μm). The results suggested that while the anion composition influenced particle size, and the metal-ligand bond strength helped control particle morphology, both factors affected the electrochemical properties including the plating and stripping of copper. © 2013 Elsevier B.V. All rights reserved.

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TYPE Journal Article YEAR 2013
DOIOSTIScopus
Results 76–100 of 156
Results 76–100 of 156