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

Circuit to Measure Resistance of a Metal Whisker
• Use of a simple “Ohmmeter” to measure the resistance of a metal
whisker is NOT preferred
– Ohmmeter may supply V out < V breakdown for the insulating films (oxides,
moisture) that form on a metal whisker
– Ohmmeter may supply V out > V melt causing the whisker to melt before
resistance can be measured
• Instead, a variable power supply and a ballast resistor should be used
to overcome the above complications
– Adjust V out > V breakdown of insulating films on whisker
– When V out > V breakdown, R B quickly drops V whisker < V melt
Circuit to measure Rw V −IRB
RW
=
I
Choose R B such that
V whisker < 80% V melt
December 5, 2007 Metal Whiskers:
Failure Modes and Mitigation Strategies
+
-
V
A
R B ~ 100 kohms
I
R W
36