That may be so, but there is a Jedec document standard for doing whisker
testing.  It was revised and re-released in May of this year.  That
document is what the whisker testing is based on.
It uses the most common triggers that they believe cause whiskers.
Temperature cycling and humidity.

Our products are built to Class 2.  They need to be reliable - they are
not throwaway electronics (is there such a thing anymore, with WEEE?),
but probably the most stress they'll see from their environment may be
the shipping air travel, and probably some ongoing vibration fan noise
during use.  There are also screws and washers or other metalwork
sometimes in contact with the PCB, when mounting a heatsink, or chassis
frame to the assembly.

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: 23-Nov-05 9:16 AM
To: [log in to unmask]
Subject: Re: [LF] Tin Whisker testing on assemblies

Genny,

I find this interesting because from my readings both here on the LF
List serve and in the various trade magazines most organizations are
unclear what the exact cause is or how they can best generate
"controlled failures" on command.  Tin Whiskers are real, but being able
to generate them at will seems allusive.

Am I off base here?

Phil 

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Wednesday, November 23, 2005 9:57 AM
To: [log in to unmask]
Subject: [LF] Tin Whisker testing on assemblies

The components we've been sourcing all say that they've been thru tin
whisker testing.  
Is there any value or reason to doing additional testing at the finished
assembly level that uses those components, as well?  
Are lots of companies doing this?

Just for information purposes, I investigated the cost of tin whisker
testing on one assembly, and I was told we should test three samples,
the test would take 18wks +, and cost $14-17K.  

They recommended we test components or coupons, instead.  Since the
components have already been tested by the manufacturers, the only
reason I can see for doing that is if we didn't trust the manufacturer,
or wanted independent validation.

Are there conditions on an assembly, though, that might not exist at the
component level that make it important to retest?

This is a huge investment.  Just trying to figure out whether it is
worth it.

Genny

-------------------------------------------------------------------------------Leadfee Mail List provided as a service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop/(start) delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL/(MAIL)
Search previous postings 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
-------------------------------------------------------------------------------