...planning on sharing it? :-)
Rigo
Sr. Quality Assurance Engineer
Workmanship Standards, Code 300
NASA, Goddard Space Flight Center
Greenbelt, MD 20771
Phone. (301) 286-6129
Fax. (301) 286-6576
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Tuesday, February 14, 2012 4:50 PM
To: [log in to unmask]
Subject: Re: [TN] Conf Coating in Cold and Clammy
Thank you all for your responses, especially all the off line clam comments.
I was not really looking for responses on how to produce a cold and clammy environment. That I can do. What I was looking for are case studies of functional hardware being tested at cold and clammy conditions where this test mode produced failures. Dock Brown sent me an excellent one (thanks Dock). That is more what I was looking for.
Doug Pauls
From: Chris Mahanna <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/13/2012 03:26 PM
Subject: Re: [TN] Conf Coating in Cold and Clammy
Sent by: TechNet <[log in to unmask]>
Very interesting...
Here's what I would try:
Prove you can stabilize 10C/85 RH chamber (this might not be easy) Bond a thermoelectric chiller to the back of a comb pattern Bond a thermistor to the surface near the comb pattern (by the guard
maybe?)
Coat and cure.
Using the thermistor as the feedback control for the chiller, cyclically drive the comb surface to ~7.5C (allowing light condensation), then let it warm and the condensate evaporate (or absorb) to complete the cycle.
I'd guess that with reasonable airflow you could get several cycles an hour.
Not the kind of thing you can scale up to dozens of samples, but 10 might be doable in a single chamber.
Chris
Chris Mahanna
Robisan Lab
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: 2012/02/10 4:42 PM
To: [log in to unmask]
Subject: [TN] Conf Coating in Cold and Clammy
Good afternoon all,
Recognizing that asking a question of this group late on a Friday afternoon is questionable judgement on my part, I will give it a shot anyway.
I am in the midst of the most perplexing material investigation of my life. Provided I do not get shot, hung or tarred/feathered, I will have some neat stuff to publish in the next few years. I have a general question on testing coatings, other than what you might do in aerospace.
Most temperature-humidity tests done on conformal coating are of the cyclical variety, 25C to 65C, 90% RH for a week. This one is found in
MIL-I-46058 and IPC-CC-830 and is used for material qualification. Nothing unusual there.
There are cyclical temperature-humidity test that are done as part of product qualification, such as DO-160E or MIL-STD-883. But these are also of the cyclical variety and 25C to 65C is common there as well. Nothing unusual there.
How would one simulate a coated assembly, stored in a cold and clammy environment (40-50F, 85-100% RH with probable dew points each day) for months at a time, then powered up?
Are there any tests done in your industry that tests a coatings resistance to a prolonged cold and clammy conditions? Ideally with some form of acceleration factor? I know that the automotive industry has something called a "damp heat" kind of test, but have no experience with that.
I know I can program my humidity chamber for an environment, but don't really have time to let it sit 3-6 months. It has been suggested that I jump in my time machine and go back 6 months and I would be done by now, but my flux capacitor went through our Kyzen cleaning process and has no flux left. I blame Hillman.
So, any thoughts would be appreciated.
Doug Pauls
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