An investigation of tin whisker growth over a 32-year period

Abstract

Purpose: This paper presents the results of a 32 year old laboratory study of whisker growth from tin electrodeposits that was originally undertaken to gain an increased understanding of the phenomenon of tin whisker growth.Design/methodology/approach: Whisker growth was evaluated using electroplated C-rings (both stressed and un-stressed) that were stored throughout in a desiccator at room temperature. Analysis has recently been undertaken to evaluate whisker growth and intermetallic growth after 32 years storage. SEM analysis has been performed to investigate whisker length and, using polished cross-sections, the morphology, thickness and type of intermetallic formation. Findings:Normal tin plated deposits on brass and steel with a copper barrier layer nucleated whiskers within 5 months and in each case these grew to lengths between 1 and 4.5 mm. For normal tin electroplated onto brass, a one or two month nucleation period was needed before whiskers developed. They reached a maximum length of about 1.5 mm after 6 months and little or no further growth occurred during the subsequent 32 years. Very few whiskers grew on the tin-plated steel samples and no intermetallic formation was observed.None of the fused tin-platings nucleated whiskers during the 32 year period. Practical implications:Knowledge about vintage whiskers is important in order that we can take steps to increase the resiliency of our space missions. Similarly, such knowledge is important to engineers engaged on products reaching their nominal end-of-life, but where for reasons of economy, these products cannot be replaced Originality/value: This study represents a unique insight into whisker growth and intermetallic formation over an extremely long time period.

Extraordinary Nanocrystalline Pb Whisker Growth from Bi-Mg-Pb Pools in Aluminum Alloy 6026 Moderated through Oriented Attachment

“…The serrations are considerably thin, in the range of 50–80 nm in width (see insert of Figure 5 a), which correspond to individual single crystal growth segments that interchange in orientation. The origin of the segmentation is either from the slight shifting of individual slip planes [ 50 , 51 ] and nano-twinning [ 52 ] due to pipe diffusion caused by the stacking fault energy [ 19 ] or segmentation caused by repeatedly breaking and reforming of the surrounding oxide layer at the whisker base [ 3 ]. The growth of whiskers has been also seen to change throughout the growth process.…”

Revealing the Pb Whisker Growth Mechanism from Al-Alloy Surface and Morphological Dependency on Material Stress and Growth Environment

“…However, whisker formation is not homogeneous nor simultaneous. Whiskers tend to grow from the same material from minutes to months or even years [ 31 ], making a prediction of their growth through various models elusive. Furthermore, the varying incubation time for whiskers at different positions from the same samples have erupted many contradictions to established theories and proposals for additional theories that intend to explain stochastic growth [ 8 , 32 , 33 , 34 , 35 , 36 , 37 ].…”

The stochastic growth of metal whiskers

“…A whisker may stop growing for a while, then start growing again." 26,27 MW growth randomly interrupted for years 28 and days 29,30 was observed; Fig. 1 presents a compilation.…”

“…FIG.1: Compilation of published data on the intermittent MW growth for different capping, environmental and stress conditions (unspecified here): (a) different capping,29 (b) different environments,30 (c) various substrates and stresses 28. Several domains showing a decrease of MW length in graph (c) are artifacts related to the problems with identification of the maximum length whisker 31.…”