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58 SMT007 MAGAZINE I JUNE 2025 attention in recent years, they are not a recent phenomenon. In the early 20th century, during the vacuum tube era, high-purity tin solder used in early radio equipment led to the formation of these unintended growths, which frequently caused short circuits. is historical context underscores the importance of understanding their formation mechanisms, associated risks, and potential solutions in modern electronics. Historically, people addressed tin whiskers by adding lead (Pb) to solder alloys used for component leads, pads, and circuit boards with hot air solder leveled (HASL) finishes. Research indicates that even tin-lead (Sn-Pb) surfaces can develop tin whiskers under cer- tain conditions, but they tend to be shorter and less harmful than those on lead-free surfaces. Because of the classification of lead as a haz- ardous substance and the introduction of strict regulations, this method is now primarily used in specific industries such as the military, aero- space, and medical sectors. Mechanisms of Growth Tin whisker growth is influenced by a com- bination of plating conditions and environ- mental factors, including thin tin plating, residual stress during the tin plat- ing process, and insuffi- cient intermetallic com- pound formation. When plating tin onto copper, copper-tin intermetal- lic compounds—specifi- cally Cu6Sn5 or Cu3Sn— form at the interface between the tin and the base metal. in tin plat- ing is more susceptible to whisker growth because of the greater compres- sive stress it develops compared to thicker plat- ing. is can distort the tin structure, creating the conditions for whis- kers to form and grow. Environmental fac- tors also play a crucial role in whisker develop- ment. Temperature fluc- tuations and high humid- ity can induce mechan- ical stress and promote electrochemical reac- tions that drive whis- ker formation. In addi- tion, compressive stress Figure 2: Tin whiskers can reach lengths of 0.025 inches (0.635 mm) on 100% bright tin-plated connector leads stored under typical conditions within just four months.