Tin whiskers: pure tin, single crystal, spontaneously grown from compressively stressed regions
• Growth driven by residual compressive stresses, localized stress relief.
• Most prevalent in thin nearly pure tin thin layers subject to residual and thermal expansion mismatch stresses.
• Effective mitigation methods are generally limited to reducing residual stresses
o Electroless plating
o Annealing
• Concern is greatest for long life fail safe devices.
o Military
o Space – vaporized metal gas from a short can cripple space vehicles

Knowledge of tin whiskers, spontaneously grown pure tin single crystal filaments, has been around for decades, but they’ve have recently garnered attention due to the elimination of lead in electronic assemblies. Growth is driven by residual compressive stresses in thin, high tin composition coatings, but the exact growth mechanism is unknown. Whiskers can potentially cause short circuits in electronic assemblies when thin tin coatings are present. As devices shrink interconnect pitch becomes finer, increasing the potential for whiskers to cause shorts.