Hi Sherif! As Mike F. mentioned, silver oxide is as nearly as conductive as
metallic silver. However. silver finishes will for silver sulfide films
when exposed to sulfur sources which significantly increases their contact
resistance. You may be able to penetrate the sulfide film with increased
pressures or different probe tip geometries. I would recommend you also
investigate what potential sulfur sources the pwas were exposed too - I
have documented the formation of silver sulfide films on immersion silver
pwbs in our manufacturing operations (using SERA testing) but not within a
two week timeframe. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





Sherif Refaat <[log in to unmask]>@ipc.org> on 01/08/2003 09:35:21 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
       to Sherif Refaat <[log in to unmask]>

Sent by:    TechNet <[log in to unmask]>


To:    [log in to unmask]
cc:

Subject:    [TN] Immersion Silver oxidation



Hi Technetters,

I've got a situation here where boards coated with Immersion Silver were
partly assembled before the Holidays and the assembly was completed this
week.  So, the boards were left in the factory, uncontrolled environment,
for over two  weeks. The circuitry on the side that was assembled first
exhibits oxidation.  The oxidations does not allow the In-Circuit test
probes to have good contact  with the test pads, hence causing lots of
false opens.

Any recommendations regarding how to remove Immersion Silver oxidation
from assembled boards? The Immersion Silver Chemistry supplier is located
overseas and because of the time difference I can not get an immediate
answer. I  heard about a more pointy test probes that may be able to
penetrate the  oxidation but the factory does not accept this solution.

Can any one help?

Thanks in advance.

Sherif,




---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------