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

Will Whiskers Buckle Before
Puncturing a Distant Coated Surface?
• The displacement of the conformal coat due to a whisker pushing
against the coating is:
D
( ) ⎟ 2
3
3
⎛ 1 −ν
⎞⎛
F ⎛ ⎞ ⎛ ⎞⎛
⎞
B ⎞ π
2 E W d
= ⎜
⎟
⎟⎜
⎟ ≈ ⎜
⎟ 1 −ν
⎜ ⎟ ⎜ 2
⎝ E ⎠⎝
d ⎠ ⎝ 32 ⎠ ⎝ E coat ⎠⎝
L ⎠
coat
Where
D = Displacement of conformal coat
ν = Poisson’s ratio
E coat = Young’s Modulus of coating
E W = Young’s Modulus of Whisker
d = “Diameter” of whisker
L = Length of whisker
F B = Euler Buckling Strength
of the whisker
December 5, 2007 Metal Whiskers:
Failure Modes and Mitigation Strategies
F B
Conductor
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