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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 10 Mar 2004 05:45:44 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (257 lines)
Graham,

For the record, acrylic coatings have been in use in the aerospace industry,
on flight systems of all types and locations, for over 30 years now. We have
even seen circuits running with water as they pass the dew point, no failure
recorded.

I take exception to that!
I have personally documented over 100 failures due to moisture in
aircraft systems!!

David A. Douthit
Manager
LoCan LLC

Graham Naisbitt wrote:

>Folks
>
>For the record, acrylic coatings have been in use in the aerospace industry,
>on flight systems of all types and locations, for over 30 years now. We have
>even seen circuits running with water as they pass the dew point, no failure
>recorded.
>
>Their chemical resistance is excellent (MIL Spec term) but they do have
>selective solvent resistance including moisture (remember that water is a
>solvent) but can easily be removed using most chlorinated or fluorinated
>solvents.
>
>Urethanes will provide better solvent resistance hence they are more
>difficult to rework / repair.
>
>I was once asked: "does you coating survive exposure to "Skydrol", an
>aviation hydraulic fluid that should NEVER be drunk!!! (Worse than Mountain
>Dew I am told!)
>
>I asked why, and was informed that it was: "in case the circuit gets sprayed
>by this stuff whilst in flight."
>
>My reaction: "This is a circuit in the cockpit of the aircraft, and you are
>worried about the effects of a hydraulic leak of Skydrol spraying onto a
>circuit in a sealed housing - why? There ain't no pilot still in there...."
>
>"Er, good point. Hadn't really thought that one through...."
>
>They used an acrylic!
>
>--
>Regards Graham Naisbitt
>
>[log in to unmask]
>
>Cell: 079 6858 2121
>Office: +44 (0)1252 813706
>
>Concoat Limited - Engineering Reliability in Electronics
>
>NEW Additional Web address: www.conformalcoating.com
>
>www.concoat.co.uk     www.concoatsystems.com
>
>
>
>
>>Hans, All,
>>
>>We use both AR and UR in different applications on Class 3. It really
>>depends on your end use and fitness for use, and in particular the unit or
>>requirement specification you are trying to meet. AR is easier to rework
>>etc, bit that also means it can be less effective when it comes to
>>protection... tougher coating = generally harder to remove.
>>
>>If you have a requirement to protect against aircraft fluids etc, then AR
>>will be a poorer choice. If you want to use it in a telephone box, AR will
>>do a great job. AR does however have better moisture properties than UR.
>>None of course are truly hermetic, but they will do well in a
>>condensation/evaporation scenario.
>>
>>AR may be good for rework (if/when it is needed), but it also needs to be
>>good for service, which may be decades.
>>
>>Clive ff.
>>
>>
>>
>>-----Original Message-----
>>From: Hinners Hans M Civ WRALC/LUGE [mailto:[log in to unmask]]
>>Sent: 09 March 2004 15:00
>>To: [log in to unmask]
>>Subject: Re: [TN] Pros and Cons on Type UR vice Type AR Conformal
>>Coating
>>
>>
>>             *** WARNING ***
>>
>>This mail has originated outside your organization,
>>either from an external partner or the Global Internet.
>>   Keep this in mind if you answer this message.
>>
>>I've approved switching from UR to AR at the request of the repair line. The
>>assemblies are IPC-A-610 Class 3, on aircraft,crew accessible cargo area.
>>
>>Hans
>>
>>~~~~~~~~~~~~~~~
>>Hans M Hinners
>>AC-130 Systems Engineer
>>
>>WR-ALC/LUGE
>>Special Operations Forces / Combat Search & Rescue
>>System Program Office
>>226 Cochran St
>>Robins AFB, GA 31098
>>DSN Prefix: 468
>>Com: (478) 926 - 5847
>>Fax: (478) 926 - 4911
>>mailto:[log in to unmask]
>>
>>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
>>Sent: Tuesday, March 09, 2004 8:15 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Pros and Cons on Type UR vice Type AR Conformal Coating
>>
>>      One thing to know is that AR can be coated to patch UR but not the
>>other way around. Patching AR with UR creates a mix that takes too long to
>>dry, stays soft. So to switch from UR to AR is recommended.
>>      Regards,
>>      Ramon
>>
>>
>>
>>>-----Original Message-----
>>>From: - Bogert [SMTP:[log in to unmask]]
>>>Sent: Monday, March 08, 2004 4:55 PM
>>>To:   [log in to unmask]
>>>Subject:      [TN] Pros and Cons on Type UR vice Type AR Conformal Coating
>>>
>>>As a Class 3 customer we are considering mandating transition from
>>>Type UR
>>>
>>>
>>to Type AR conformal coating, to make it easier to replace failed
>>components.  Are there any Class 3 users of Type AR coating?  What is track
>>record for using Type AR?  Are there any compatibility issues with certain
>>types of solder masks?  Any input you have would help.  Another advantage
>>with AR would be for returned equipment.  The OEM could remove all the
>>coating from an assembly using alcohol, then perform
>>
>>
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>>>
>>for additional information, or contact Keach Sasamori at [log in to unmask] or
>>847-509-9700 ext.5315
>>
>>
>>>-----------------------------------------------------
>>>bed-of-nails testing to quickly identify failed components.
>>>
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