So, instead of kicking the dog, we can blame the onions? Works for  
me....

Graham Naisbitt

On 26 Aug 2008, at 18:06, Whittaker, Dewey (EHCOE) wrote:

> So it's not good in a cryogenic environment?
> Dewey
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas O. Pauls
> Sent: Tuesday, August 26, 2008 8:43 AM
> To: [log in to unmask]
> Subject: [TN]
>
> It is also not good to use if you are processing Vidalia onions.  A
> presentation I was at earlier this year on industrial controllers  
> talked
>
> about corrosion on electronics in an onion processing plant in  
> Georgia.
> As
> it turns out, Vidalia onions are high in sulfur.
>
> Doug Pauls
>
>
>
>
> "Stadem, Richard D." <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 08/26/2008 10:07 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> "Stadem, Richard D." <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN]
>
>
>
>
>
>
> Thats one for all of us to keep in the files. Thanks Mark!
>
> I know that IAg is not a good choice for things like control boards  
> for
> washers and dryers and dishwashers (the laundry and dish soaps contain
> large amounts of sulfides), heating furnaces or heating units, under
> hood automotive applications, heavy industrial controls, devices  
> mounted
> in coastal salt spray areas, car wash controls, near swimming pools or
> other areas with any chlorine concentration.
>
> Typical use of IAg is in office products, telecommunications, medical
> devices, consumer electronics, computers, etc.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D.
> (Mark)
> Sent: Tuesday, August 26, 2008 9:37 AM
> To: [log in to unmask]
> Subject: [TN]
>
> Any environment that contains sulfur, like hydrogen sulfide or sulfur
> dioxide should preclude the use of IAg.  The sulfur will react with  
> the
> silver and "grow" sulfides which can be electrically conductive
> resulting is shorts between vias.  This can occur even when the
> concentrations are within OSHA limits for human exposure.
> Silver sulfides can be semiconductors or conductors depending on the
> chemical composition.  They are black in color instead of silver, any
> exposed silver will be affected.
>
> Mark Woolley
> Failure Analyst
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of James Verrette
> Sent: Tuesday, August 26, 2008 8:25 AM
> To: [log in to unmask]
> Subject: [TN]
>
> What characteristics of the end use environment would cause IAg to not
> be an appropriate finish and why?
>
> Jim Verrette
> Senior Electrical Engineer
>
> ------------------------------
>
> Date: Mon, 25 Aug 2008 08:24:35 -0500
>
> From: "Stadem, Richard D." <[log in to unmask]>
>
> Subject: Re: ENIG White paper
>
> Dave,
>
> You write as if you are not at all familiar with IAg, which is totally
>
> understandable. However, IAg has been around in full production mode  
> for
>
> many years now, and is rapidly becoming the most-used finish in the
>
> market. Do not confuse it with immersion tin finish, which has  
> little or
>
> no shelf life.
>
> IAg-finished circuit boards have a recommended shelf or storage life  
> of
>
> about 1 year. However, if packaged properly in a hermetically sealed  
> bag
>
> with silver saver paper liners, and stored away from sulfates, it is
>
> possible to use boards up to 5 years old or even longer with no issues
>
> whatsoever. All you need to do is call out the packaging on the
>
> fabrication drawing per IPC 4553.
>
> I have soldered IAg boards that sat around exposed to the elements for
>
> more than 4 years in previous lives, and they soldered up just fine,  
> no
>
> change in the DPMO.
>
> Some of the bare boards we use here at GD are 34" by 40", 48 layers,
>
> 1/2" thick, cost is about $48,000 each. Their finish is IAg. =20
>
> I have had a lot of experience with IAg over the past 10 years or so,
>
> having seen at least 150,000 IAg boards assembled and soldered with
>
> every type of component you can think of, and I have never experienced
>
> any issues with them. I have experienced many, many issues with ENIG,
>
> however, and that is the finish that would keep me up at night waiting
>
> for the bomb to go off. There are many reliability issues associated
>
> with ENIG such as black pad, brittle nickel, etc., etc, but just think
>
> about the fact that you are soldering to nickel, which has a  
> dissolution
>
> rate about 50 times slower than copper.
>
> Should you ever have a solderability issue with IAg, you can have the
>
> fabricator rework the finish. If you have an issue with ENIG, the only
>
> thing you can do is rework your scrap account.
>
> However, you need to take the end-use environment into consideration
>
> when you select a circuit board finish. ENIG (unfortunately) may be  
> your
>
> best choice. I would fully qualify just one assembly at a time, and I
>
> would fully qualify it. For Space use, I would not suggest IAg.
>
> -----Original Message-----
>
>
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