In a message dated 12/03/1999 5:40:37 PM US Eastern Standard Time,
[log in to unmask] writes:

> So it sounds like these organic materials are fungus nutrients and,
>  depending on your application environment, may need to treated with
>  fungicide. Since this is a special requirement, it will need to specified
on
>  the procurement documentation.

Time for a little history.  When I was at Naval Avionics, I got some good
historical perspectives from my boss, who had been there for 30 years.  In
the 1960s and 70s, many of the rubber materials and other electronics grade
materials had fillers and other components which DID support biological
growth.  Things were fine in the US, but when the materials encountered the
hot and humid jungle conditions of southeast asia, the fungus ate the
electronics.  Literally.  The military then made the specification that all
electronics grade materials must be non-nutrient in nature, or in other
words, fungus and other biological agents could not eat it.  The problem with
the reversion of coatings (e.g. two-part coatings reverting to the individual
components under humid conditions) also arose during this time frame.

The requirement that military grade electronics have materials that are
non-nutrient in nature propagated through all of the military specs to this
day, although it is largely unnecessary.  Virtually all laminates, solder
masks and coatings are non-nutrient in nature.  I suppose it is still in the
specs to prevent suppliers from going back to the really cheap materials.

If the goal is to have materials that fungus won't eat, the non-nutrient
clause covers it.  If, on the other hand, your circuit assemblies are in a
fungus-rich environment, and you want all surfaces to be treated so as to
kill fungus whenever possible, then I can see needing a fungicide.  A topical
fungicide might work better, providing it does not cause other failure
mechanisms.

Doug Pauls

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