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Characterization of Metallic Whiskers in Lead-Free Solders
University of Kentucky Ecological solutions for replacing toxic lead-based solders in the electronics industry are sought worldwide for applications in biomedical, space, and warfare technologies. Unfortunately, a host of problems exist with lead-free solders, the most notable being metallic whisker growth. Metallic whiskers, which form under normal service conditions, typically cause short circuit failures due to the growth of whiskers across electrical leads – failures that lead to unpredictability, unreliability, economic losses, and potential loss of life. With advances in the miniaturization of electronics, the whisker growth phenomenon promises to be a significant problem to solve in order to succeed in the manufacture of nanoelectronics. Understanding whisker growth is a critical problem for global and Kentucky industries that need to achieve prime reliance in the next generation of lead-free solders. To date, there are many hypotheses, but no widely accepted mechanisms, for whisker formation and growth. The lack of understanding concerning whiskers is partly due to the fact that whisker growth has not yet been extensively studied under service conditions. The underlying theme of this project is the discovery of materials science based knowledge that will aid in whisker abatement strategies in future lead-free based solders, and in the controlled growth of whiskers for use as electrical leads in nanoelectronics. This project has three specific aims: 1) gain fundamental microstructure-based understanding of the nucleation and growth mechanisms of metallic whiskers in lead-free solders under approximated service conditions (e.g. mechanical stress and electric current); 2) quantify and model the kinetics of whisker growth; 3) help to build a future workforce vital to the US technology industry by training graduate students in microelectromechanics of materials with experimental and numerical simulation skills essential for the characterization and design of electronic materials. The results will help researchers at the University of Kentucky seek federal funding to establish a strong research team specializing in the area of advanced manufacture of electronic materials.
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