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8 SMT Magazine • May 2015 In my lecture, Tin Whiskers—All You Should Know, an audience member expressed the de- sire to know more about the theory behind tin whiskers and requested that I "spend more time" discussing it. This five-part series, The Theory Behind Tin Whisker Phenomena, serves as a response to that request. Indeed, physical phenomena occur as a re- sult of scientific principles. For tin whiskering, there are reasons and mechanisms behind its occurrence. Thermodynamics shows us that in the ab- sence of external energy input, nature sponta- neously directs to a state of lower energy and stress/strain in a material or a system and the energy tends to be released by making changes over time. Should the fact that whiskers spon- taneously grow out of the surface of the tin coating be associated with the change in energy state (stress/strain) in the coating in the direc- tion that lowers its energy state? Basic mecha- nisms readily release stress/strain without grow- ing whiskers out of the surface. So why do they? Is there a fundamental distinction between the crystal growth within the lattice and the growth out of surface, which protrude like whiskers? Additionally, in order to grow whiskers, there must be a supply of the material (tin atoms). Where and how does the supply come from? And what does it take to allow the supply to move through along a passable path at a rate that is fast enough in a finite time frame? by Jennie Hwang H-TECHnologiES group SmT PROSPECTS & PERSPECTIVES The Theory Behind Tin Whisker Phenomena, Part 1 ColuMn

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