Evidence of 3D strain gradients associated with tin whisker growth

Hektor, Johan; Marijon, Jean-Baptiste; Ristinmaa, Matti; Hall, Stephen; Hallberg, Håkan; Iyengar, Srinivasan; Micha, Jean‐Sébastien; Robach, Odile; Grennerat, Fanny; Castelnau, Olivier

doi:10.1016/j.scriptamat.2017.09.030

Cited by 22 publications

(12 citation statements)

References 28 publications

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“…It is evident that the coating has a columnar grain structure (one grain throughout the thickness). A similar arrangement was found by Hektor et al [20]. This type of microstructure is typical for lead-free solders and plays an important role in the formation of whiskers by allowing for fast grain boundary diffusion towards the whisker root [29,30,31,32].…”

Section: Resultssupporting

confidence: 69%

“…The largest IMC grain before the heat treatment was located just below the whisker. The presence of large IMC particles below the whisker has previously been reported [20,32,38]. This suggests that large IMC grains can act as preferred nucleation sites for tin whiskers.…”

Section: Resultssupporting

confidence: 54%

“…The bulk sample was prepared by coating a high-purity copper substrate with approximately 7 μm of tin using electron beam evaporation. Electron beam evaporation of tin has been shown to produce a columnar grain structure [20], similar to the grain structure obtained by the more industrially relevant method of electroplating [23]. Coatings deposited using electron beam evaporation are also free of organic contaminants which can influence the stress field and the whisker growth kinetics; in electroplated coatings, these contaminants originate from additives in the electrolyte.…”

Section: Methodsmentioning

confidence: 96%

“…One limitation of these full-field techniques is that variations of the strain field within the mapped grains are not easily measured. Reconstruction of 3D strain maps with a spatial resolution limited by the size of the beam can be achieved using Differential Aperture X-ray Microscopy (DAXM), which uses a polychromatic X-ray beam to probe only the deviatoric part of the strain tensor [19,20]. To remedy these limitations, Hayashi et al developed a version of 3DXRD that uses a focussed monochromatic X-ray beam that is scanned across the sample [21,22].…”

Section: Introductionmentioning

confidence: 99%

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Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment

et al. 2019

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The 3D microstructure around a tin whisker, and its evolution during heat treatment were studied using scanning 3DXRD. The shape of each grain in the sample was reconstructed using a filtered-back-projection algorithm. The local lattice parameters and grain orientations could then be refined, using forward modelling of the diffraction data, with a spatial resolution of 250 nm. It was found that the tin coating had a texture where grains were oriented such that their c-axes were predominantly parallel to the sample surface. Grains with other orientations were consumed by grain growth during the heat treatment. Most of the grain boundaries were found to have misorientations larger than 15∘, and many coincidence site lattice (CSL) or other types of low-energy grain boundaries were identified. None of the grains with CSL grain boundaries were consumed by grain growth. During the heat treatment, growth of preexisting Cu6Sn5 occurred; these grains were indexed as a hexagonal η phase, which is usually documented to be stable only at temperatures exceeding 186 ∘normalC. This indicates that the η phase can exist in a metastable state for long periods. The tin coating was found to be under compressive hydrostatic stress, with a negative gradient in hydrostatic stress extending outwards from the root of the whisker. Negative stress gradients are generally believed to play an essential role in providing the driving force for diffusion of material to the whisker root.

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Section: Resultssupporting

confidence: 69%

Section: Resultssupporting

confidence: 54%

Section: Methodsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment

et al. 2019

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“…An understanding of the stress distribution within the tin coating, particularly in the vicinity of whiskers, would be advantageous to elucidate the influence of the oxide coatings on stress generation and relaxation mechanisms within the coating. Synchrotron radiation X-ray studies have been used previously to investigate the development and distribution of compressive stresses within tin coatings [14,18,[37][38][39][40].…”

Section: Summary Of the Effect Of Oxide Coatings On Whisker Growthmentioning

confidence: 99%

The effect of different post-electroplating surface modification treatments on tin whisker growth

Haspel

Ashworth

Wilcox

et al. 2019

Transactions of the IMF

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There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the 'cracked oxide theory' was proposed by Tu in 1994. The current study has investigated the effect of both a molybdate conversion coating and a tungstate conversion coating on tin whisker growth from Sn-Cu electrodeposits on Cu, and compared it with that from an electrochemically-formed oxide produced from a potassium bicarbonate-potassium carbonate electrolyte. X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of both immersion time and applied potential on the thickness and composition of the oxide film. The XPS studies show that the oxide film formed using either of the conversion coating baths is significantly thicker than that produced from the potassium bicarbonate-potassium carbonate bath.Initial observations suggest that both the tungstate-based conversion coatings and the molybdate-based conversion coatings significantly reduce whisker growth by over 80 % for all conversion coating systems compared with a native air-formed oxide and provide improved mitigation compared with the electrochemically formed oxides previously investigated.

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Method for inhibiting Sn whisker growth on Ti2SnC

Zhang

Tang

et al. 2022

J Mater Sci

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Evidence of 3D strain gradients associated with tin whisker growth

Cited by 22 publications

References 28 publications

Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment

Scanning 3DXRD Measurement of Grain Growth, Stress, and Formation of Cu6Sn5 around a Tin Whisker during Heat Treatment

The effect of different post-electroplating surface modification treatments on tin whisker growth

Method for inhibiting Sn whisker growth on Ti2SnC

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