Tin whiskers: a case study

Pure electroplated tin is susceptible to the growth of fibrous whiskers that can produce short circuits and, under some conditions, vacuum metal arcs capable of sustaining hundreds of amps. Typical whiskers are 3-4 mu m in diameter and approach 2 mm in length; they are strong enough to penetrate one layer of conformal coating. The physical and electrical properties of tin whiskers and the reasons for their growth are discussed. A methodology to disposition to use of tin in existing spacecraft hardware is presented. It permits the use of tin when growth conditions are strongly adverse or when the tin-plated components are conformally coated. In cases where whisker growth is considered possible and problematic, removal and replacement, or careful cleaning and conformal coating is required.