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February 2013

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From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 8 Feb 2013 11:47:17 -0600
Content-Type:
text/plain
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Hi Inge - I would not recommend using an eraser - you may remove the 
silver sulfide but you end up leaving eraser debris in and on the surface 
which can cause solder joint integrity problems. Erasers are meant to fix 
word problems not contamination problems.

Dave



From:   Inge Hernefjord <[log in to unmask]>
To:     <[log in to unmask]>
Date:   02/08/2013 11:05 AM
Subject:        Re: [TN] Silver Sulfide & Plasma
Sent by:        TechNet <[log in to unmask]>



It came to my mind what we use to do if the tarnish isn't too thick and we
talk about just few boards: we used an old times electric eraser! Fast,
cheap, good result.

Inge

On 7 February 2013 20:36, Inge Hernefjord <[log in to unmask]> wrote:

> Seņor Burke es muy inteligente !
>
>
> On 7 February 2013 17:26, John Burke 
<[log in to unmask]>wrote:
>
>> If it is very bad why not run it back through a local board shop 
through
>> acid etch and re-coat after all it is an immersion process.....
>>
>> Just a thought.
>>
>> John
>> John Burke
>>
>> General Manager/COO
>>
>> Zollner Electronics Inc
>> Plant Milpitas
>> 575 Cottonwood Drive
>> Milpitas, CA 95035
>> Phone:          + 1 408 434 5442
>> Fax:            + 1 408 434 5401
>> Mobile:         + 1 408 628 2433
>> E-mail:         [log in to unmask]
>> Internet:  www.zollner-electronics.com
>>
>>
>>
>> From:   Gerald Bogert <[log in to unmask]>
>> To:     <[log in to unmask]>
>> Date:   02/07/2013 05:07 AM
>> Subject:        Re: [TN] Silver Sulfide & Plasma
>> Sent by:        TechNet <[log in to unmask]>
>>
>>
>>
>> ----- Original Message -----
>> From: Stadem, Richard D. [mailto:[log in to unmask]]
>> Sent: Wednesday, February 06, 2013 08:53 AM
>> To: [log in to unmask] <[log in to unmask]>
>> Subject: Re: [TN] Silver Sulfide & Plasma
>>
>> Hi, Rich
>> If you have mildly tarnished IAg-finished PWBs, I recommend you print
>> paste on part of one of the PWBs or a complete solder sample coupon and
>> send it through the reflow as a solderability test. They will usually
>> solder out to the edges of the pads just fine. You can then wick off 
any
>> solder and still use it as a production PWB.
>>
>> Wayne is correct. Plasma will take the finish right off.
>>
>> If there are solderability issues, go back to the PWB vendor. There are
>> processes where they can strip off the IAg finish and re-plate the IAg,
>> and I have done this two or three times with no issues. If the PWB
>> supplier does not have this capability, there are others who can do 
this
>> for you, even if they did not fabricate the PWBs in the first place.
>> Typically the PWB supplier outsources this type of plating, and they 
can
>> tell you who can re-plate it for you.
>> I have used IAg PWBs that sat around in a warehouse for 5 years in a
>> previous life, completely exposed to the elements, and had turned a 
darker
>> shade of pale, so to speak. But they soldered up with a better DPMO 
than
>> the ones less than 6 months old!
>> dean
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
>> Sent: Tuesday, February 05, 2013 5:31 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Silver Sulfide & Plasma
>>
>> Hi Rich-
>>
>> Mildly oxidized ImAg usually solders fine, even if it doesn't look 
good.
>> So try a bit.  If you really need to do something, then I don't think a
>> plasma will help.  There is only a very tiny amount of silver on the
>> surface, so if you remove the ugly stuff, you'll most likely expose a
>> bunch of copper.
>>
>> So IF anything is needed, then the common approach is to REDUCE the 
silver
>> oxides and sulfides back to elemental silver.  This is done the same 
way
>> as advertised frequently on late night TV (only they use snake oil and 
do
>> voodoo dances):
>>
>> Heat some water up to 70C and add 1TBS/quart of baking soda.  Dissolve 
the
>> baking soda.  Then take some new shiny aluminum foil and crumple it up,
>> then iron it back out.  Put this in the hot water bath with the circuit
>> board.  It doesn't have to actually make contact with the circuit 
board,
>> and you really don't need a whole lot of aluminum foil.  Within about 2
>> minutes, the freshly exposed aluminum will pull the oxygen and sulfur 
away
>> from the silver and you will be back close to the original finish.
>>
>> Rinse THOROUGHLY in DI water, then dry the board in an oven until it is
>> completely baked out.
>>
>> Wayne Thayer
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
>> Sent: Tuesday, February 05, 2013 5:54 PM
>> To: [log in to unmask]
>> Subject: [TN] Silver Sulfide & Plasma
>>
>> Any of you ever have luck cleaning silver sulphide off of a PCB enough 
to
>> make it solderable with NC flux, by using plasma?
>>
>> If so , can you please provide me with the gas mix you used?
>>
>> Thanks
>>
>> Rich  Kraszewski
>> PLEXUS
>>
>>
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