Inge,
Attached are 2 reports that should give you a better idea of the
hazards you are facing.
The first is titled "Avionics Systems, Reliability, and Harsh
Environments" June of 2001
The second is titled "Static Intercept and Corrosion Intercept" by
Lucent Technologies.
You have serious issues!
David A. Douthit
Manager
LoCan
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On Nov 26, 2007, at 7:11 AM, Hernefjord Ingemar wrote:
> Hóla hombres,
> I've went through a 144 page report on US army vehicles in the
> sandy and dusty Iraq. Finest particles cross any filters and land
> on the PWBs. Weight% of Fluorides, Chlorides, Nitrates, Bromides,
> Nitrates and Sulfates vary a lot, depending on if you are in
> Basra, Kirkuk or other spots. So, we read typical Chloride from
> 1ppm to 35,000 ppm. The red dust+humidiy makes a vehicle of any
> sort a wreck on less than a few years. Now, anyone dust professor
> at TN? What will aggressive dust do to Acrylic coating and what
> level of Fluorides, Chlorides etc is dangerous? 1,000 ppm? 10,000
> ppm? or what? The fat report is good at describing the hard life
> for mil electronics, but not a word about what levels are doing
> harm. Anyone? Ugh?
> /Inge
>
> -----Original Message-----
> From: Hernefjord Ingemar
> Sent: den 22 november 2007 09:37
> To: 'TechNet E-Mail Forum'; 'Gumpert, Ben'
> Subject: RE: [TN] Conformal Coating Breakdown
>
> If the rework is extensive, don't you just strip off the coating
> and put on new coating after the rework is done?
> Inge
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gumpert, Ben
> Sent: den 14 november 2007 13:01
> To: [log in to unmask]
> Subject: [TN] Conformal Coating Breakdown
>
>
> Anyone have some information on what happens to conformal coatings
> as you heat them up, what temperature do they start to deteriorate?
> (Specifically acrylics and urethanes)
>
> What I'm really getting at is that I have some boards that need hot
> air rework, but they have been coated. There are moisture sensitive
> components on the board, so I would like to bake the boards prior
> to rework. I would prefer to make the bake as short as possible,
> but that puts the temperature (125°C) at the top of the temperature
> range for these coating materials. (In fact, some boards that I
> have baked have gotten a brown tint to the coating).
>
> Will I do any damage to the conformal coating by baking at this
> temperature? If not, what temperature would cause damage?
>
> Thanks,
> Ben Gumpert
>
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