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Estimating the Probability of Electrical Short Circuits from Tin WhiskersTo comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish .
Document ID
20110004885
Acquisition Source
Kennedy Space Center
Document Type
Conference Paper
Authors
Courey, Karim J. (NASA Johnson Space Center Houston, TX, United States)
Asfour, Shihab S. (Miami Univ. FL, United States)
Onar, Arzu (Saint Jude Children's Research Hospital United States)
Bayliss, Jon A. (NASA Kennedy Space Center Cocoa Beach, FL, United States)
Ludwig, Larry L. (NASA Kennedy Space Center Cocoa Beach, FL, United States)
Wright, Maria C. (NASA Kennedy Space Center Cocoa Beach, FL, United States)
Date Acquired
August 25, 2013
Publication Date
May 10, 2010
Subject Category
Electronics And Electrical Engineering
Report/Patent Number
KSC-2010-079
Meeting Information
Meeting: 2010 Aircraft Airworthiness and Sustainment Conference (AA and S)
Location: Austin, TX
Country: United States
Start Date: May 10, 2010
End Date: May 13, 2010
Distribution Limits
Public
Copyright
Public Use Permitted.

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