Theory of Tin Whisker Growth: “The End Game”

Abstract

Previous theories of the tin whisker growth proposing various dislocation mechanisms have been largely disproved. This paper presents a new and different theory for the mechanism of tin whisker growth. The theory addresses the fundamental requirements for Sn to diffuse to the base of the whisker grain and proposes a mechanism for whisker initiation and growth. Part of this is a theoretical proposal as to what makes the whisker grain different. The role of oxidation in whisker growth is also briefly addressed. Using this theory, attempts are made to illustrate how different whisker shapes are created. Finally, a proposed potential solution to tin whisker growth is presented, assuming that this theory is correct.

Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

“…[12][13][14][15] Many mechanistic models for whisker growth, generally asserting that whiskering is a stress-relaxation process and relying on a self-sustaining source of continuous feed material at the whisker root, have been proposed; 5,[12][13][14][15][16][17][18][19] however, there is still no single universally accepted mechanism which completely explains whisker growth. Much of the debate on the mechanism arises from the lack of understanding of the mechanistic dependence of whiskering on the microstructure and the crystallographic texture of Sn.…”

Micro- and Nanostructure of Zn Whiskers and Their Coating

“…The presence of a long-range mechanism is coherent with results in the literature and has been accepted for a while by the community. 17,18 EBSD experiments performed on the sample show several differences between the grains at the root of the whisker and the grains into the Zn coating:…”

“…Starting from the fact that the Zn coatings prone to whiskers are composed of columnar grains under compressive stress, Smetana 17 and Vianco and Rejent 19 both suggested a model of whisker formation and growth based on recrystallization. This experimental work unambiguously demonstrates that, as suggested in both models, recrystallization plays a role in the whisker formation.…”

“…However, none of these models explains all the observations. In his model, Smetana 17 explains how whisker formation relaxes the stress of the system. The first step is the formation of oblique grain boundaries during recrystallization of the coating.…”

Investigation of Whisker Growth from Alkaline Non-cyanide Zinc Electrodeposits

“…10,11 Etienne et al correlated the recrystallisation of zinc grains with whisker growth, reporting that grains near the root of whiskers were recrystallised, 12,13 which is consistent with tin whisker growth mechanisms based on recrystallisation. [14][15][16] A more thorough overview of zinc whisker-related research can be found in a recent review paper. 17 In comparison with tin whisker research, comparatively few papers have been published in relation to zinc whisker growth, and some of the results are contradictory, such as those relating to the influence of thermal treatments on whisker growth.…”