Graham,

I've not seen any mathematical expressions that give the maximum possible 
length of a Tin whisker. Myself, I've seen whiskers covering the distance 
across the whole diameter of a radar waveguide! Ku band. In this case the 
whiskers were not one single but lots of them. We thought that the 
electromagnetic wave that passed would blow these tiny things, but they 
didn't change. We had to move them away with pressurized air. As to the 
question, Tin whiskers can be at least 20 mm long.

Inge


----- Original Message ----- 
From: "Graham Collins" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, June 12, 2008 12:12 PM
Subject: [TN] Tin Whiskers - how long? Size matters!


Good day TechNet
A tin whisker question.

If (hypothetically, as this thankfully hasn't been built yet) a pure tin 
finish part is used, what sort of length whisker could happen?

What we are looking at is this: a part we want to use is only available with 
a pure tin finish on copper.  Matte tin, not bright.  So if we use it, and a 
tin whisker grows, how long might it grow?  If the part is (for example) 
10mm away from adjacent parts, and a realistic maximum whisker length is 
less than that, it obviously mitigates (YES, but does not entirely remove) 
the risk.

The only value I've seen is in a Dave Hillman/Doug Pauls presentation from 
Apex 05, wherein it is stated that they "can be 9.5mm long".  Dave /  Doug, 
any comment on this?  Can you cite a source?  Does matte vs bright tin make 
a difference?

regards,

Graham Collins
Halifax Production Engineering
(902) 873-2000 ext. 6215


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to 
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to 
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
for additional information, or contact Keach Sasamori at [log in to unmask] or 
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------