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SRNL

Image courtesy NASA Electronic Parts and Packaging Program 1406203734

Researchers at the Savannah River National Laboratory (SRNL) have identified a treatment method that slows or prevents the formation of whiskers in lead-free solder. The problem was discovered by Bell Laboratories in the late 1940s and was resolved by adding lead to the tin solder. Due to the Reduction of Hazardous Substance Initiative, which restricts lead in various types of electronic equipment, the solder and plating industry has moved to lead-free products. Spontaneous growth of tin whiskers takes place (as shown here in this NASA image) and, as these extend in length, contact with neighboring electronic components causes device failure as in F-15 radar and Galaxy IV and VII satellites. This continues to be of concern in communications and weapons systems, and potential failure will become more prevalent with the miniaturization of electronic components and increased Pb-free solders usage. Typical mitigation is achieved by the application of conformal coatings; however, the extra coating material causes heavier weight and may be breached over time by the tin whiskers. Researchers have found that gamma irradiation used for a short period changes the metallic crystal growth mechanism and the shape of the whiskers without changing the solder chemistry.

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