Raytheon Integrated Defense Systems

The author published an application-specific tin whisker risk assessment algorithm in 2003, and issued an updated version in 2004. This algorithm is currently being used by a variety of high reliability manufacturers to manage the risks posed by tin whisker induced failures. Other similar methods have been developed elsewhere and are also being used. During the past year experimental data has become available on the performance of conformal coating for containing tin whiskers. Additionally, data and a model have been published concerning the distribution of tin whisker lengths. This paper outlines the incorporation of this new understanding into improved risk assessment methodologies. A model is presented that can be used to quantify the mitigation provided by imperfect conformal coating. Differences in the results predicted by the current and proposed improved methodologies, and their implications are discussed. Background Manufacturers of high reliability electronics must manage the risks associated with tin whiskers, while continuing to meet other important customer-driven requirements such as performance, cost, and delivery schedule. Standardized approaches for managing these trades are in use in the industry and have been embodied in the new standard GEIA-STD-0005-2, which is currently out for balloting. A documented process for performing detailed risk assessments is required for compliance to the standard, and also to satisfy the concerns of the customer base. A risk assessment algorithm tool has been developed to provide a standardized method for performing application-specific tin whisker risk assessments. The details of the latest revision of this tool (Revision B) have been described previousl