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TIN WHISKERS: URBAN MYTH?
3

TIN WHISKERS: URBAN MYTH?

TIN WHISKERS: URBAN MYTH?

(OP)
Hello,
A colleague yesterday regaled me with stories of "tin whiskers" (presumably strands of tin escaping) occurring in a vacuum when the wrong stainless is used. But he couldn't remember which stainless is the "wrong" one. I have never heard of this.
1. Is there any truth to the "tin whiskers" story?
2. If so, with what stainless does this occur?

Thanks,
'ziner

Peace Through Superior Fire-Power!

RE: TIN WHISKERS: URBAN MYTH?

This has lead to failure of electronics in some environments.  Yes it can happen.  It would not have anything to do with SS, only tin based materials.

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RE: TIN WHISKERS: URBAN MYTH?

There was a show tonight on the History Channel that discussed  various Engineering Disasters. There was quite a discussion specifically about Tin Whiskers and the failures of electronic equipment. There was quite a few of SEM pictures of the whiskers.  There is a lot of work being done at the University of Maryland.

RE: TIN WHISKERS: URBAN MYTH?

Nothing to do with stainless steel.
Vacuum isn't necessary, either.

Tin whiskers nucleate & grow from the surface of ~pure tin electroplating. Alloying can prevent, but unfortunately, lead was one of the most effective whisker inhibitors.
Some whiskers from the NASA Goddard Center:



Besides the afore-mentioned sites, the electronics industry has published some useful documents on mitigating the problem:
Current Tin Whiskers Theory and Mitigation Practices Guideline - JP002 (March 2006):
http://www.jedec.org/DOWNLOAD/search/JP002.pdf

iNEMI Recommendations on Lead-Free Finishes for Components Used in High-Reliability Products Version 4 (12-1-06) http://thor.inemi.org/webdownload/projects/ese/tin_whiskers/Pb-Free_Finishes_v4.pdf

An article "Tackling tin whisker test" gives conditions for accelerating possible whisker growth from samples:
http://www.tmworld.com/article/CA6251552.html

NIST has also done some work as part of their lead-free solders program:
"The Formation of Whiskers on Electroplated Tin Containing Copper" http://www.metallurgy.nist.gov/reports/NIST_Whisker_PRICM4.pdf

Although a common belief that tin whiskers never form from galvanizing (hot dipped zinc coating on steel), cases have been found:
"The Driving Force Behind Whisker Growth"
http://www.metalfinishing.com/editors_choice/articles/051108_Lahtinen.htm

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