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Mechanical Properties of Metals and Alloys
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
The growth of tin whiskers is an annoying problem in electronics. Tin has been used as a solder joint material. Over time, whiskers are observed to grow from the tin surface that can result in short-circuiting of the electronics, thus creating reliability problems. This is especially serious for electronics used in unmanned space vehicles such as satellites, in which repair cannot be done easily. Researchers speculated the cause to be some sort of creep phenomenon, given that tin has a low melting temperature. Oxygen appears to play an important role. Oxidation of tin to form tin oxide involves a volume expansion, thus creating compressive stress that drives the formation of tin whiskers. We may consider this phenomenon to be oxidation-induced creep. Whisker growth can therefore be suppressed or eliminated by the removal of oxygen from the environment.
Temperature Dependence of Microelectronic Package Failure Mechanisms
Published in Pradeep Lall, Michael G. Pecht, Edward B. Hakim, Influence of Tempemture on Microelectronics and System Reliability, 2020
Pradeep Lall, Michael G. Pecht, Edward B. Hakim
Increasing the thickness of the coating reduces the stress, decreasing the chance of whisker growth. Tin coatings of thicknesses exceeding 0.0004" (10 micrometers) prevent the growth of whiskers [NASA, 1992]. To obtain stress-free coating, the method of applying the tin coat should preferably be hot dipping. If electroplating is used, the tin coat should be reflowed to relieve the residual plating stress. Using 2 to 3% lead in conjunction with tin also protects against whisker formation [NASA, 1992, Knott, 1992]. This is a contamination-actuated mechanism and has no temperature dependence.
Predictive and Analytical Tools in Design
Published in Ali J Jamnia, Khaled Atua, Executing Design for Reliability within the Product Life Cycle, 2019
The growth of whiskers is related to the materials and processes used to plate and solder the components on the printed circuit board (PCB) as well as the environment to which the equipment is subjected. It does not depend on the components used, and a variety of components such as diodes, transistors, integrated circuits, microcircuit leads, and even PCBs have been affected. Many metals have been known to whisker, and as such, designers and engineers should be mindful to avoid components plated with materials as well as processes that would facilitate whisker formation.
The effect of different post-electroplating surface modification treatments on tin whisker growth
Published in Transactions of the IMF, 2019
D. M. Haspel, M. A. Ashworth, G. D. Wilcox, X. Bao, R. J. Mortimer
A tin whisker is commonly a filamentary growth of pure tin, which will generally grow from thin tin electroplate, and can grow up to lengths of a few millimetres, though more commonly they will grow up to a few 100 microns.1 Tin whiskers can cause major reliability problems in high value, long-life electronics, such as rocket guidance systems and aerospace systems, mainly due to them growing from one surface and coming into contact with another, adjacent, surface resulting in a short circuit and subsequent electronic failure.2 Electronics can also fail if whiskers are broken off and subsequently land across adjacent terminals. If the current in the circuit is high enough, the whisker can volatilise into a conductive metal gas, which could result in the creation of a metal vapour arc.3 The metal vapour arc reaction can generate sufficiently high temperatures to melt metals and incinerate polymers.