Suzanne

Salt fog / spray testing for conformal coatings - good question.

To my knowledge the only extant standards that quote such testing are:

IEC 61086 - 2 - 1995
British Defence Standard Def-Std 59/47 Issue 4

I believe that these specifications continue to use the original test as
defined in MIL-STD-202E dated 16 April 1973 superceded by MIL-STD-202F dated
1 April 1980 and then MIL-STD-810E Method 509.3 dated July 1989. All of
these now cancelled without replacement.

In all cases, as I can see, this involves a salt fog test that shall be
conducted AFTER all other climatic tests in a suitable environmental
chamber.

A salt solution shall be prepared using sodium chloride containing on the
dry basis not more than 0.1% of sodium iodide and not more than 0.5% of
total impurities. This shall be added at not more than 5% by weight: 5 +/-1
of salt to 95% deionised water.

This salt solution shall be added to the chamber via atomisation nozzles at
12 to 18 psi  2 to 3 mils diameter at a rate of 3 quarts (2.8 litres) per 10
ft3 (0.28M3) of chamber volume per 24 hours.

The testing shall be done over a minimum of 48 hours followed by a 48 hour
drying period or they can be cycled over 24 hour periods (wet and dry).

The measurement of SIR shall be >1E08

You might note that all coatings types AR - UR - SR - ER - XY pass this
testing.

I do not know who wrote the original MIL-STD-202E in 1972 / 73 (maybe one of
you Techies knows this?)  but it seems to have been plagiarised ever since.

As to the question of the coating thickness - this will be as determined by
the vendor.

Finally, and anticipating the question, the difference between Salt Fog,
Salt Mist and Salt Spray testing is the concentration of the salt solution.

If anyone wants copies of these documents I have them, but you will have to
load me with beer (takes a long time!) at the next IPC meeting - in
Minneapolis.

I hope this helps.

> Does anyone have literature or real life testing on the performance of
> paralyne under a salt fog test?  What thickness was required to pass salt
> fog testing?  Was the cca directly exposed or was it inside a box/device?
>
> Suzanne Nachbor
> Supplier Quality Engineer/Commodity Lead
> Phone:  763-957-3923
> Fax:  763-792-2486
> e-mail:  [log in to unmask]

--
Regards Graham Naisbitt

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Cell: 079 6858 2121
Office: +44 (0)1252 813706

Concoat Limited - Engineering Reliability in Electronics

Web: www.concoat.co.uk  and  www.concoatsystems.com

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