Metal Whiskers: Failure Modes & Mitigation Strategies - NEPP - NASA

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• A Brief History of Metal Whiskers Outline • System Failure Modes Caused by Metal Whiskers • A Few Mitigation Strategies to Reduce Harm From Metal Whiskers December 5, 2007 Metal Whiskers: Failure Modes and Mitigation Strategies Zinc Whiskers on Hot Dip Galvanized Steel Pipe • NO WHISKER GROWTH THEORY TO BE DISCUSSED!!! Cover Photo: Tin whiskers on Tin-Plated Beryllium Copper PCB Card Rails 2
What are Tin or Zinc or Cadmium Whiskers? • Hair-like structures made of a single grain, or only a few grains, that sometimes erupt from a metal. Coatings of Tin, Zinc and Cadmium are especially able to develop whiskers; but, whiskers have been seen on Gold, Silver, Lead, and other metals too • Growth occurs over time by accretion of metal ions at the base NOT the tip • LENGTH: Log-normally distributed Rarely up to 10 mm or more (Typically ~1mm or less) • THICKNESS: Range 0.006 to >10 um (Typical ~ 1 um) • Fundamental theories for growth mechanism DO NOT enable prediction of the time-dependence of whisker density, whisker lengths or thicknesses – To be useful a theory should identify what we must control to make confident predictions – Such a theory has remained elusive December 5, 2007 Metal Whiskers: Failure Modes and Mitigation Strategies Tin Whiskers on Tin-Plated Ceramic Chip Capacitor 3
Page 1: Metal Whiskers: Failure Modes and M
Page 5 and 6: Whisker Resistant Metal Coatings
Page 7 and 8: 1960’s Vintage Transistor Guess W
Page 9 and 10: “There is a name for those who su
Page 11 and 12: Metal Whisker Melting Current -- Pt
Page 13 and 14: Sustained Metal Vapor Arcing • Ga
Page 15 and 16: My Whisker “Stress Relaxation The
Page 17 and 18: Three Whisker Mitigation Strategies
Page 19 and 20: NASA Goddard Whisker Mitigation Stu
Page 21 and 22: Uralane 5750 - 2 Mils Thick 9-Years
Page 23 and 24: 2 Mils Uralane = Very Effective Whi
Page 25 and 26: Whiskers Lift and Peel Conformal Co
Page 27 and 28: Thank Goodness for Euler Buckling a
Page 29 and 30: Effects of Conformal Coating -- 2
Page 31 and 32: Contact Information Jay Brusse Pero
Page 33 and 34: Tin Whiskers Forming “Circus Tent
Page 35 and 36: A Few Recent Whisker Experiences
Page 37 and 38: • Basic Equipment: - Binocular Mi
Page 39 and 40: Field Technicians and Failure Analy
Page 41 and 42: "The Five Stages of Metal Whisker G
Page 43: An Example of “Melting” a Tin W

Metal Whiskers: Failure Modes & Mitigation Strategies - NEPP - NASA

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