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This Bulletin provides a brief description of tin whisker formation and describes various methods recommended by government and industry to reduce the risk of tin whisker-induced failures in electronic hardware. It is not a mandate nor does it contain any requirements. A tin whisker is a single crystal that emerges from tin-finished surfaces. Tin whiskers can pose a serious reliability risk to electronic assemblies that have pure tin finish. The general risks fall into several categories: [1, 2, 3, 8, 16] Short Circuits: The whisker can create a short circuit, either by 1) growing from an area at one potential to an area at another or 2) breaking free and later bridging these areas. In some cases, these shorts may be permanent and cause catastrophic system failures. A transient short may result if the available current exceeds the fusing current of the whisker, and the whisker can fuse open.

This document is intended for use as technical guidance by Aerospace system suppliers, e.g., Aerospace system Original Equipment Manufacturers (OEMs) and Aerospace system maintenance facilities, in developing and implementing designs and processes to assure the continued performance, quality, reliability, safety, airworthiness, configuration control, affordability, maintainability, and supportability of high performance aerospace systems (subsequently referred to as AHP) both during and after the transition to Pb-Free electronics. This document is intended for application to aerospace products; however, it may also be applied, at the discretion of the user, to other products with similar characteristics, e.g., low-volume, rugged use environments, high reliability, long lifetime, and reparability. If other industries wish to use this document, they may substitute the name of their industry for the word “Aerospace” in this document.

This Standard establishes processes for documenting the mitigating steps taken to reduce the harmful effects of Pb-free tin finishes in electronic systems. This Standard is applicable to Aerospace, Defense, and High Performance (ADHP) electronic applications which procure equipment that may contain Pb-free tin finishes.