Carl -

Immersion silver is our finish of choice for most of our PCBs - both leaded
and lead free. There is one known reliability issue referred to as "copper
creep." In customer environments with high sulfur along with humidity and
air flow, you can get catastrophic failures. This usually affects vias or
other areas where there is no solder over the silver. Both Dell and HP have
published on the topic and we have confirmed failures due to the problem as
well. We have been working with the immersion silver finish suppliers on
potential improvements.

Industries like tire manufacture, water treatment, paper processing etc.
are likely candidates for problems.

You can do a quick google search on the topic. If you cannot locate the
papers, you can contact me for more details.

Cheryl Tulkoff
Senior Reliability Engineer
Phone:(512) 683-8586
Fax: (512) 683-8520
National Instruments
11500 N. Mopac Expressway
Building C
Austin, TX 78759-3504




                                                                           
             Carl VanWormer                                                
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             08/10/2007 04:07                                      Subject 
             PM                        [TN] Silver PCB finish and          
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              Carl VanWormer                                               
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For non-BGA, surface mount boards, we have always ordered HASL boards.  In
our progress towards ROHS compliance, management has changed the default
specification to ENIG.  Our board house has HASL, ENIG, and Silver as
options, with Silver at about the same price as HASL and ENIG with a
significant premium (along with a 2 to 3 days added to the processing
time).  When I asked management why we couldn't use Silver, I was told that
there are significant problems with the Silver processed boards (with no
real explanation).

My question to the Group:  Is there any good reason to avoid Silver as a
surface finish on my consumer and industrial boards?

Your scary stories are welcomed . . .

Thanks,
Carl





Carl Van Wormer
Cipher Systems
1800 NW 169th Place, Suite B-100
Beaverton, OR  97006
Phone (503)-617-7447 extension 20




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