Spontaneous Growth of Whiskers on Tin Coatings: 20 Years of Observation

Britton, S. C.

doi:10.1080/00202967.1974.11870313

Cited by 94 publications

(35 citation statements)

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“…[7][8][9][10] The particular case of the formation of whiskers from the Sn surface when it is electroplated on copper has been of significant interest to the microelectronics industry. 2,[11][12][13][14][15] Such Sn whiskers are usually a couple of micrometers in diameter but can grow to several millimeters in length over time while an electronic component is in service. These whiskers can bridge the gaps between closely spaced interconnects and can create short circuits, leading to system failure.…”

Section: Introductionmentioning

confidence: 99%

“…The formation of single-crystal whiskers on the surface of metals such as Sn, Zn, Cd, and Al has been studied over the past six decades, [1][2][3][4][5][6] and in the 1950s, significant effort was expended in understanding the mechanism of whisker growth. [7][8][9][10] The particular case of the formation of whiskers from the Sn surface when it is electroplated on copper has been of significant interest to the microelectronics industry.…”

Section: Introductionmentioning

confidence: 99%

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Plastic deformation processes in Cu/Sn bimetallic films

et al. 2008

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Although the driving force for the growth of Sn whiskers from the surface of Sn coatings on copper is thought to be internally generated stress due to the formation of Cu 6 Sn 5 at the Cu/Sn interface, little is known about the nature of this internal stress and how it cracks the surface Sn oxide (an important precursor to whisker formation). Arguments based on elasticity alone do not appear to be sufficient and suggest an important role for plastic deformation. Direct observations, made by transmission electron microscopy of cross-sectioned bimetallic Cu/Sn thin-film specimens, confirm plastic deformation of the Sn grains due to the formation of Cu 6 Sn 5 . Dislocation motion and pile-up at the surface Sn oxide, rotation associated with subgrain boundary formation, interaction of the subgrain boundaries with the Sn surface, and diffusional processes are various mechanisms that can produce stress at the Sn surface and crack the Sn oxide.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plastic deformation processes in Cu/Sn bimetallic films

et al. 2008

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“…The first evidence that thermal treatment could be used as a tin whisker mitigation method was reported by Glazunova in 1962 [32], who suggested that samples treated at 100℃ for more than 6 hours or at 150℃ for more than 2 hours were much less prone to develop whiskers. Britton [33] in his 1974 paper proposed that thermal treatment at 200℃ for 1 hour completely prevented whisker growth on tin-electroplated copper for a period of 5 years. In 1975, Sabbagh and McQueen [34] reported a negative influence of thermal treatment on tin whisker mitigation.…”

Section: Zinc Whisker Researchmentioning

confidence: 99%

Zinc whisker growth from electroplated finishes – a review

Ashworth

Wilcox

2015

Transactions of the IMF

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Electroplated zinc finishes have been associated with the electronics industry for many years as a result of their excellent corrosion resistance and relatively low cost. They are normally applied onto ferrous products to provide corrosion protection in a range of different environments. However, the formation of spontaneously grown whiskers on zinc electroplated components, which are capable of resulting in electrical shorting or other damaging effects, can be highly problematic for the reliability of long life electrical and electronic equipment. The growth of zinc whiskers has been identified as the cause of some electrical and electronic failures in telecommunications and aerospace based applications, with consequences ranging from mild inconvenience to complete system failures.Investigators have been striving to address the problems induced by whisker growth since the 1940s. However, most research effort has been focused on tin whiskers; especially following European Union environmental legislation that restricted the use of lead (Pb), which when alloyed with tin (3 -10% by weight) provided effective tin whisker mitigation. Compared with tin whisker research, much less attention has been paid to zinc whiskers. A number of mechanisms to explain zinc whisker growth have been proposed, but none of them are widely accepted and some are in conflict with each other. The aim of this paper is to review the available literature in regard to zinc whiskers; to discuss the reported growth mechanisms, to evaluate the effect of deposition parameters and to explore potential mitigation methods. This paper presents a chronologically ordered review of zinc whisker related studies from 1946 to 2013. Some important early research, which investigated whisker growth in tin and cadmium, as well as zinc, has also been included.

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“…In general, intermetallic compounds within the Sn deposits, internal stresses, and crystal coherency between the deposited Sn film and substrate are known to be key causes of whisker formation [2][3][4][5] and these continue to be investigated. 6) Heat treatments have been explored for inhibiting whisker formation. However, the mechanisms of heat treatments for inhibiting whisker formation are still unknown.…”

Section: Introductionmentioning

confidence: 99%

Effects of Microstructure of Deposited Sn Films and Orientation Index of Cu Foils on Sn Whisker Formation Using Substitutionally-Deposited Sn Films

et al. 2009

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The effects of the orientation indexes of Cu foils, used as a copper pattern for flexible printed circuits (FPC), and the grain size of substitutionally-deposited crystalline Sn films on Sn whisker formation were investigated. In particular, the relationship between the grain size of substitutionally-deposited Sn films and the structure of intermetallic compound deposits formed at the interface between the substitutionallydeposited Sn films and Cu foils, as a function of aging was examined. Two types of Cu foils were used as substrates in this study. One had granular-shaped grains 0:5$1:0 mm in size while other had pillar-shaped grains about 5.0 mm in size. We called the former ''with the gelatin additive'' and the latter ''with the Cl À ion additive'' since we used gelatin and Cl À ions for the fabrication of Cu foils. In addition, single crystal Cu (100), (110), (111) samples were also used as substrates. Two types of the Sn deposition bath were used in this study, a hydrofluoroboric acid bath and an organic acid bath. The structures of the deposited Sn films and Cu foils were investigated using TEM and SEM. The number of whiskers formed on the Sn-deposited film increased with aging. The number of whiskers formed on the substitutionally-deposited Sn films using the hydrofluoroboric acid bath was larger than that formed using the organic acid bath. The number of whiskers formed on the deposited Sn films on the Cu single crystal (111) was larger than that formed on the deposited Sn films on the other single crystals. The mechanism of inhibiting whisker formation by heat treatment was also investigated. No whiskers were seen on the substitutionally-deposited Sn films with heat treatment. Analysis of TEM selected-area diffraction patterns obtained from the sample subjected to heat treatment indicated the presence of Cu 6 Sn 5 and Cu 3 Sn intermetallic compound deposits near the interface between the deposited Sn films and the Cu foils. The results suggest that the microstructures of the substrates strongly affect the Sn whisker formation on substitutionally-deposited Sn films.

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Spontaneous Growth of Whiskers on Tin Coatings: 20 Years of Observation

Cited by 94 publications

References 3 publications

Plastic deformation processes in Cu/Sn bimetallic films

Plastic deformation processes in Cu/Sn bimetallic films

Zinc whisker growth from electroplated finishes – a review

Effects of Microstructure of Deposited Sn Films and Orientation Index of Cu Foils on Sn Whisker Formation Using Substitutionally-Deposited Sn Films

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