Jim,

We have utilized immersion silver as a PWB surface finish on a large
quantity of boards for the past few years. Our experience has been excellent
and it is now the preferred finish at some of our manufacturing locations.
George Wenger of our research center and I submitted a paper which he
presented that detailed our qualification and experience (up to that point)
at the September 1999 IPC Surface Finish Forum. Since then we have qualified
several PWB shops for this use and have qualified another chemistry vendor's
process. We have found if stored properly, the finish retains excellent
solderability for over a year. It handles multiple thermal excursions well
and has superior hole fill characteristics compared to OSP's. We did see a
few start-up issues with our initial board vendor, but since then things
have gone smoothly. To date, I have seen two  relatively minor assembly
issues. The first is that the surface will darken if exposed to sulfur. The
solderability remains good, but cosmetically it was very noticeable. This
became evident at one location when after the first side surface mount
operation, boards were placed onto an ESD mat that had a high sulfur
content. Switching to a new type of mat resolved this issue. The second
issue is pin contact at ICT. If you are not wave soldering or if you
selectively wave solder, then some of the test pins may contact silver
coated pads. If your test fixtures are set up to handle OSP coated boards I
would expect no issues, but if they have only tested to solder previously,
there might be a need to either change probe types or optimize the fixture.
As far as cost is concerned I would expect it to be between the cost of an
OSP coated board and that of a HASL finish. If you would like further
information please contact me.

Thanks,
Robert Furrow
SMT Process Engineer
Lucent Technologies
978-960-3224    [log in to unmask]

> -----Original Message-----
> From: Jim McMurry [SMTP:[log in to unmask]]
> Sent: Monday, November 06, 2000 9:05 AM
> To:   [log in to unmask]
> Subject:      [TN] IMMERSION SILVER SURFACE FINISH
>
> Jim McMurry@PATAPSCO
> 11/06/2000 09:05 AM
>
> I am interested in hereing from anyone who may be using or may have used
> immersion silver finish on production or prototype pcb's.  I would like to
> know
> the good and bad sides of this finish.  If there are any information
> resources
> available on the subject.  Are there any cost comparisons?
>
> Thank you all for your time and response.
>
> --------------------------------------------------------------------------
> -------
> Technet Mail List provided as a free 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 Technet
> Search previous postings at: www.ipc.org > On-Line Resources & Databases >
> E-mail 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
> --------------------------------------------------------------------------
> -------

---------------------------------------------------------------------------------
Technet Mail List provided as a free 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 Technet
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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
---------------------------------------------------------------------------------