I'll send them from my office tomorrow, if not David already has done it.
After reading David's stuff, I begin to doubt the benefit with acrylic
coating. At least the one we use. If he is right, halides, chlorides and
like will find its way through the coating in a very short time. I
recommended Parylene C for MIL boards years ago, but the acrylic spokesmen
won. Still, acrylic conformal coating is said to be excellent as protection
against humidity, but I think that is without large contents of said salts.
/Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Victor G. Hernandez
Skickat: den 27 november 2007 14:55
Till: [log in to unmask]
Ämne: Re: [TN] Conformal Coating Breakdown and Iraqi dust
Inge and David,
I failed to save the reports before deleting the string mail. Can
you please share the reports once again?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Tuesday, November 27, 2007 4:03 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating Breakdown and Iraqi dust
David,
Thanks for reports. I also have your book.
Now, in one of the reports (page 17)there is a test on Polyethylene and
Intercept(TM). It says, that it takes 7 days for a 1 ppm Chloride
environment to breakdown Polyethylene, while it takes 35 years for the
Intercept. In both cases the film thickness is 2 mils. This has two
sides, one surprising and one frightening:
1. Is Intercept really that superior?
2. If Polyethylene is out after only 7 days, then what about acrylic
coatings, e.g. Humiseal 1B31? Will Chloride ions penetrate after only a
number of days, rather than years?
Furthermore, on page 17, 1 ppm Chloride is named 'normal environment'.
Who said that?
The dust from Iraq has up to 0.4 weight% of Sulphur or Chlorine (EDS).
If 1 ppm of Chloride penetrates 2 mils of Polyethylene in 7 days, then
0.4% of Chlorine(Chloride)sounds to me like catastrophic!
What's the expert's opinion? I suppose there is no such experts in this
forum, but you may at least have an idea.
/Inge
-----Original Message-----
From: David Douthit [mailto:[log in to unmask]]
Sent: den 26 november 2007 19:05
To: TechNet E-Mail Forum; Hernefjord Ingemar
Subject: Re: [TN] Conformal Coating Breakdown and Iraqi dust
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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