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April 2002

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From:
Bev Christian <[log in to unmask]>
Date:
Wed, 17 Apr 2002 15:23:18 -0400
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"TechNet E-Mail Forum." <[log in to unmask]>, Bev Christian <[log in to unmask]>
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Ditto to what George said.  And outside of suppliers with vested interests,
you aren't going to find anyone with more knowledge on this than George.

regards,
Bev Christian
Research in Motion

-----Original Message-----
From: Wenger, George M. [mailto:[log in to unmask]]
Sent: April 17, 2002 1:01 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion Silver


I think the obvious answer is that the other 97% of the rest of the world
are waiting for someone to sign on the dotted line that there is nothing
wrong with immersion silver, its reliable and and we'll never have trouble
with it.  The 3% who are using it have done their homework and aren't
relying on someone else telling them it is okay.  They have found out that
immersion silver works at lest as well as other surface finished, is much
flatter than HASL, isn't susceptable to "Black Pad", is as reliable as
solder joints made to HASL or OSP boards, and the problems one can have with
imemrsion silver can be handled.

Regards,
George

George M. Wenger (908)-546-4531 [log in to unmask]
Distinguished Member Technical Staff
Celiant Corporation, FMA Lab, 40 Technology Drive, NJ 07059



-----Original Message-----
From: Jack C. Olson [mailto:[log in to unmask]]
Sent: Wednesday, April 17, 2002 11:22 AM
To: [log in to unmask]
Subject: Re: [TN] Immersion Silver


Hmmm,

Well, at some point in EVERY new technology it was used by less
than 3% of the world, eh? Guess I'm just a trailblazer....

naw, just kiddin ya.
I subscribed to a magazine called Circuitree, and the last issue
came bundled with another publication called "The Board Authority"
which has some very well written (and well researched!) articles
on alternate finishes. I can't see any downside to using silver
in our applications, and I've looked all through the archives for
Technet, DesignerCouncil and PCDlist forums, still no show-stoppers,
so we tried it for the first time on our last design. Yes, HASL and
NiGold do work fine, but maybe we can get the same functionality
for cheaper, and do our fab vendor a favor in the process, since
they seem to prefer it (less steps? more reliable? not sure) maybe
the fab guys can answer that one....

Jack





"WEEKES, MICHAEL    HS-SNS" <[log in to unmask]>
17Apr2002 09:16 AM


To:   "'TechNet E-Mail Forum.'" <[log in to unmask]>
      "'Jack C. Olson'" <[log in to unmask]>
cc:

Subject:  RE: [TN] Immersion Silver
Retain Until: 05/17/2002 Retention Category: G90 - Information and Reports
Caterpillar Confidential:  Green


There must be some reason why less than 3% of the world has moved toward
immersion silver.  Why doesn't HASL or NiGold work for your application?

Mike

-----Original Message-----
From: Jack C. Olson [mailto:[log in to unmask]]
Sent: Wednesday, April 17, 2002 7:39 AM
To: [log in to unmask]
Subject: Re: [TN] Immersion Silver


The PCD magazine list went down before I could get an
answer to this question, does anyone have experience
with silver and contact switches?

==============================================

Most sources say a silver surface will not be solderable
after a month or so unprotected. (Even in a baggie it will
be okay a year later?)
Anyway, you say it is good for switches, which would solve
some of our hard gold plating problems.

But I would think the "unsolderability" of the aged silver
surface (unprotected in the unit and tarnished?) would
affect the reliability of the switches, wouldn't it?

Jack






Rob Mongey <[log in to unmask]>@freelists.org
4Apr2002 06:08 AM

Please respond to [log in to unmask]

Sent by:  [log in to unmask]



To:   [log in to unmask]
cc:

Subject:  [pcdlist] Re: Immersion Silver
Retain Until: 05/04/2002 Retention Category: G90 - Information and Reports
Caterpillar Confidential:  Green



Hi all,
     Good to see Immersion Silver is starting to take off. We've been using
it
in here for about two years, and it is now our prefered board finish (We
get silver finish unless we specify differently.) More common useage will
mean that maybe more Far Eastern shops will start supplying it.

     We started to use Silver because it is so adaptable to what we need
our
PCB surface finish to do, namely:

1. Good solderability. (Silver excels at this, ask any vendor).
2. Flatness for fine pitch SMT. (Silver is as flat, if not flatter than
Gold)
3. Mechanical strength for carbon pill switch contacts / Elastomer
contacts. ( Flash Gold is weak, and hard Gold gives SMT solderability
problems)
4. Stability for compression power contacts. (We have power contacts on our
PCBs that mate to battery contacts via a spring compression. We found that
the nickel under gold can cause problems with electrochemical migration
toward our battery contact.)

Immersion silver is the most suitable choice that can do all four. I'd use
gold as an alternative, but we'd have to compromise our designs somewhat.

We specify our Silver finish as 0.1 Microns Min to 0.2 Microns Max, over
bare copper. Anyone else do it differently? Or do we trust our board shops?
:)

                                                      Regards,
                                                           Rob Mongey.
                                                         CAD Technician.

     Robert Mongey <[log in to unmask]>  Tel    : +353 (0)91 774300
     Bio Medical Research                Direct : +353 (0)91 774338
     BMR House,                    Fax    : +353 (0)91 774302
     Parkmore Business Park West,        Mobile : +353 (0)87 2485262
     Galway
     Rep of Ireland.

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