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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 11 Aug 2015 11:03:35 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (154 lines)
I was referring primarily to Pb-free solders, but from what I know and from what we've done, the same applies to Pb-Sn- based ones.

Regards

Vladimir
‎
Sent from my BlackBerry 10 smartphone on the Rogers network.
  Original Message  
From: Mike Fenner
Sent: Tuesday, August 11, 2015 10:05
To: [log in to unmask]
Reply To: [log in to unmask]
Subject: Re: [TN] immersion silver

Hmm

Wouldn't it be as well to remember those discussions were about Sn/Pb
systems not Pb free? This was in the days when "solder" was assumed to mean
Sn/Pb. The effects of silver in high tin lead free alloys is rather
different

I was never quite sure the observations fitted well with Sn62 which at one
time was around 50% of Sn/Pb pastes with not a lot of evidence for either
Sn62 or Sn63 alloy. Or rather there was a lot of evidence for one alloy or
the other depending on what the reporter's company was actually using. 
I assumed the Ag "contamination" problems reported from the Ag finish were
due to non uniform dispersal into the Solder in the specific case being
investigated. I never met these problems more generally.


Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Tuesday, August 11, 2015 2:15 PM
To: [log in to unmask]
Subject: Re: [TN] immersion silver

Thank you Dave :-). I also had a long discussion with Warner about that case
he always referred to but had never seen any specifics. Do you have anything
to shear just to feed my curiosity?


Thank you 

Vladimir

Sent from my BlackBerry 10 smartphone on the Rogers network.
From: David Hillman
Sent: Tuesday, August 11, 2015 08:28
To: TechNet E-Mail Forum; Vladimir Igoshev
Subject: Re: [TN] immersion silver


Hi team - well, as usual the truth actually lies in the middle of the
technical discussion. Supporting Vlad's point, solder is fairly robust to
silver in terms of degrading integrity influences so in most of our
soldering situations its not an issue. Supporting Werner's point, he did
have a specific case where silver embrittlement of the solder joint was the
root cause of a series of solder joint failures. Werner and I had long
discussions on that case as it was very interesting despite being somewhat
of an odd case. So the final answer is silver can be an issue but it takes
some specific metallurgical conditions. The immersion silver surface
finished used today on printed circuit boards will not contribute to the
degradation of solder joint integrity.

Dave

On Tue, Aug 11, 2015 at 7:02 AM, Vladimir Igoshev
<[log in to unmask]> wrote:
Hi Guy,

With all due respect to Warner memory, silver IS NOT like gold and DOES NOT
cause embrittlement.

Therefore, from the reliability point of view it wouldn't matter what
thickness of IAg was on a board, as long as we ONLY talking about the amount
of Ag which would and up in the joints after re-flow.

Regards,

 Vladimir

Sent from my BlackBerry 10 smartphone on the Rogers network.
  Original Message  
From: Guy Ramsey
Sent: Tuesday, August 11, 2015 07:37
To: [log in to unmask]
Reply To: [log in to unmask]
Subject: Re: [TN] immersion silver

If Werner were alive he would be reminding us that silver, like gold, is a
contaminate in tin solder.
Early finishes, prior to 2005 or so, weren't good for multiple reflows. Some
presumed it was too thin.
I believe the problem was the durability of the organic additives that
retard oxidation of the silver.
Not perfect, but it is my preferred surface finish, but not too thick.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Kelly
Sent: Monday, August 10, 2015 3:47 PM
To: [log in to unmask]
Subject: [TN] immersion silver

Hi All,
Why would someone choose thick immersion silver over thin? Are these
different chemistries? Regards Steve Kelly


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