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February 2006

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Subject:
From:
R Sedlak <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, R Sedlak <[log in to unmask]>
Date:
Mon, 20 Feb 2006 13:46:04 -0800
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Joseph:

Just because it seems a good idea, I thought I might give some discussion and background on this subject.

The "Sodium Chloride" concept was chosen as perhaps the worst possible scenario.  The Sodium Chloride is measured by the conductivity of warm stagnant wash water, and virtually any soluble salt will increase the conductivity, and thus register as "Sodium Chloride".   In fact, it is highly unlikely that these values are in fact Sodium Chloride, principally because real Sodium Chloride is so soluble, and thus readily rinsed in process rinses, from surfaces.

What the test is probably measuring are heavy metal salts, and particularly, (perhaps this is now, or going to be, history) they were/are likely Lead salts.  This is because many/most Lead salts are particularly slow to dissolve, and thus do not rinse readily, but will dissolve and stand up to be measured, in the "Sodium Chloride" test.

Chloride is a strong corrosion accelerator, and one of the worst things to have on an electrical device, but most of the moieties measured as Sodium Chloride are not nearly as dangerous.

FYI..

Rudy Sedlak
RD Chemical Company

"Joseph H. Smith" <[log in to unmask]> wrote: Fellow technetters,

I realize that there is an expected specification levels for the NaCl contamination of PCB's.  Pardon me if I may be asking a dumb question, but does plated metal such as housings and the like be under the same specification limits for NaCl?   Are there guidelines or documentation within the industry which state this value?  These are metals that may come in close proximity to the PCB but necessarily mounted on the PCB.

Andrew Kettlewell
Sr Process Engineer
Sypris Electronics
Tampa, Fl
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