Three-dimensional problems of the theory of elasticity

The phenomenon of tin pest has been known for hundreds of years. Tin is one of the most common materials used in electronic products and systems. It is found in solders, as a surface finish for printed circuit boards, and as plating for connectors. Tin pest is the formation of tin in the phase of α‑tin, which particularly happens in pure tin that transforms from white β‑tin to gray α‑tin at temperatures below 13.2 °C. In this phase, tin is a structurally weak and readily crumbly powder that is not acceptable in electronic systems that must be reliable at low temperatures. Understanding how tin pest occurs is important for evaluating electronic reliability. Although most electrical devices are not exposed to low temperatures for a long period, for many industries, such as automotive (Snow-Cats), telecommunications base stations (cell phone towers), military (weapons systems), space (satellites), and outdoor recreation, the electronics must be reliable at all temperatures.This paper presents a comprehensive review of the tin pest phenomenon research and focuses on new experimental data regarding the formation of tin pest effects. The data presented and analyzed here enable manufacturers to make the right decisions when choosing a tin-based alloy for low-temperature applications. Suggestions on how this information affects the lead-free industry and recommendations for future work to clarify and evaluate the occurrence of tin pest for electronic circuits are presented. Common arguments about the risks of using tin, especially whether tin alloys are acceptable for low-temperature applications and whether lead-free solders should be exempt from regulations, are also discussed. The common assumptions are: (1) lead-free alloys can be safely used in low-temperature applications if solder paste joining technology is used, and (2) joints from solder paste benefit from both the presence of flux residues and tin oxide particles, which combined make the allotropic transformation extremely unlikely. Based on the data discussed in this review, an appendix summarizes the tin-pest-retarding effects on lead-free alloying metals.