David
I know and respect what you are saying, but if it were all as you describe,
we would have aircraft falling out of the sky on such a regular basis that
nothing would fly today.
As to Graham - well I haven't tasted them all, so I would be spoilt for
choice, and whilst I made up my mind - Scotch and soda!
--
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
> David
> Were the 100+ failures due to a failure of the conformal coating
> material, or are they attributable to another issue - contamination
> under the coating, poor application, bad design? The best coating in
> the world is only a band-aid on a poorly designed or built product.
>
> And on a less serious note, to the other Graham: OK, one should not
> drink Skydrol, but what aviation hydraulic fluids would you normally
> imbibe??? I'm sticking with the G&T.
>
> regards,
>
> Graham Collins
> Process Engineer,
> Northrop Grumman Canada Corporation
> Halifax
> (902) 873-2000 ext 6215
>
>>>> [log in to unmask] 03/10/04 08:45AM >>>
> 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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