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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