Long Term Monitoring and Failure Detection of Tin Whiskers Bridging Adjacent Leads on SOIC Components
Authors: Owen Thomas, Chris Hunt, Martin Wickham and Kate Clayton Company: National Physical Laboratory Date Published: 9/27/2015
Abstract: A measurement system was designed and constructed to measure the continuity between adjacent leads of SOIC components every 15 minutes. In phase 1, the sample build and test methodology were developed. The components were made with a daisy-chained, encapsulated lead frame deliberately tin plated such as to increase the rate of whiskering before being bent, cropped, assembled to a circuit board and finally put on test phase 2. The failure criteria for a tin whisker short was a resistance of less than 100 kilo-ohms between adjacent leads of the SOIC. The development of whiskers on unmitigated samples was investigated. In most cases the whisker shorts became open again and showed a lot of intermittency with repeated shorting. After 6 months, 75% of failed components were again open circuit. This illustrates the importance of event detection or continuous measurement over spot checks.