Hi Vlad - due to confidentiality issues, Werner was not able to discuss all
of the case but the situation was a castellated component configuration
which used silver instead of gold for the castellation finish which
resulted in a solder joint that contained a significant amount of silver.
The Ag-Sn intermetallics were so bad that the solder joint integrity was
compromised. Clearly a silver embrittlement issue but not a case we
normally find in the industry.

Dave

On Tue, Aug 11, 2015 at 8:00 AM, <[log in to unmask]> wrote:

> 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
>>
>>
>> Phone(O) (416) 750-8433
>> Phone (C) (416) 577-8433
>>
>> If the recipient to whom this e-mail is sent has an NDA with PFC Flexible
>> Circuits Limited this e-mail is considered confidential and is subject to
>> any NDA agreements between the respective parties.
>>
>> See PFC on "How its' Made" in Canada on July 7th at 8 p.m. on the
>> Discovery
>> Channel
>>
>>
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