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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