1. Melting/evaporation of "Ar"
4. Apparent permeation of "SR" by chemical contaminants,
5. Delamination of "UR" coatings
Dave:
From the above, it is apparent that none of the coating is
100% all the time.
Regards,
Ramon
> -----Original Message-----
> From: David Douthit [SMTP:[log in to unmask]]
> Sent: Wednesday, March 10, 2004 2:02 PM
> To: [log in to unmask]
> Subject: Re: [TN] Pros and Cons on Type UR vice Type AR Conformal
Coating
>
>
>
>
>
> Graham,
>
> I did encounter certain cases of application/coverage issues but the
> vast majority were
> (>75%) were due to degradation/failure of the coating to maintain
> effective barriers.
> The issue I have is that these problems generally occur after the
> "warranty" period has expired.
> There are no readily available test methods or equipment capable of
> determining the effectiveness
> of coatings after they have been in the field for extended periods.
>
> Most problems were due to :
>
> 1. Melting/evaporation of Ar with low Tg (15 degrees C) when exposed to
> internal forced air cooling.
>
> 2. Permeation of AR coatings by foreign material (dust and particles)
> when Tg was exceeded
>
> 3. Cold flowing of AR into places it was not suppose to be when Tg was
> exceeded.
>
> 4. Apparent permeation of SR by chemical contaminants, causing color
> changes and increase sensitivity
> to moisture.
>
> 5. Delamination of UR coatings from circuit traces when exposed to
> several years of
> temperature cycling combined with high moisture/condensation
conditions
> (this resulted in corrosion of the circuitry).
>
>
> Do coatings degrade/wear out? YES!
> How long does this process take? It depends on the operational
> environment, type of coating,
> application
> process, and circuitry design.
>
> Is there any methodology which can predict or verify optimal coating
> performance for extended periods? Not currently.
>
> I have written a paper about this titled "Avionics Systems, Reliability,
> and Harsh Environments".
> It was presented May 9th, 2001 in Washington D.C. at the 57th annual
> American Helicopter Society
> Meeting.
>
> You may also get a copy of the following paper "Are Lead-free Assemblies
> Especially Endangered by Climatic Safety?" presented by Zestron at this
> years APEX meeting. They have covered many of the same issue I did.
>
> David A. Douthit
> Manager
> LoCan LLC
>
>
> Collins Graham wrote:
>
> >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
> >>>
> >>>
> >>>
> >>>
> >>>>---------------------------------------------------
> >>>>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >>>>
> >>>>
> >To
> >
> >
> >>>>unsubscribe, send a message to [log in to unmask] with following text
> >>>>
> >>>>
> >in
> >
> >
> >>>>the BODY (NOT the subject field): SIGNOFF Technet To temporarily
> >>>>
> >>>>
> >halt
> >
> >
> >>>>or (re-start) delivery of Technet send e-mail to
> >>>>
> >>>>
> >>>>
> >>>>
> >>>[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >>>
> >>>
> >>>
> >>>
> >>>>To receive ONE mailing per day of all the posts: send e-mail to
> >>>>
> >>>>
> >>>>
> >>>>
> >>>[log in to unmask]: SET Technet Digest
> >>>
> >>>
> >>>
> >>>
> >>>>Search the archives of previous posts at:
> >>>>http://listserv.ipc.org/archives Please visit IPC web site
> >>>>http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> >>>>
> >>>>
> >>>>
> >>>>
> >>>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.
> >>>>
> >>>>
> >>>>
> >>>>
> >>>---------------------------------------------------
> >>>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >>>
> >>>
> >To
> >
> >
> >>>unsubscribe, send a message to [log in to unmask] with following text
> >>>
> >>>
> >in the
> >
> >
> >>>BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
> >>>(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
> >>>
> >>>
> >Technet
> >
> >
> >>>NOMAIL or (MAIL) To receive ONE mailing per day of all the posts:
> >>>
> >>>
> >send
> >
> >
> >>>e-mail to [log in to unmask]: SET Technet Digest Search the archives
> >>>
> >>>
> >of
> >
> >
> >>>previous posts at: http://listserv.ipc.org/archives Please visit IPC
> >>>
> >>>
> >web
> >
> >
> >>>site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
> >>>information, or contact Keach Sasamori at [log in to unmask] or
> >>>
> >>>
> >847-509-9700
> >
> >
> >>>ext.5315
> >>>-----------------------------------------------------
> >>>
> >>>---------------------------------------------------
> >>>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >>>To unsubscribe, send a message to [log in to unmask] with following
> >>>
> >>>
> >text in
> >
> >
> >>>the BODY (NOT the subject field): SIGNOFF Technet
> >>>To temporarily halt or (re-start) delivery of Technet send e-mail to
> >>>[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >>>To receive ONE mailing per day of all the posts: send e-mail to>
> >>>[log in to unmask]: SET Technet Digest
> >>>Search the archives of previous posts at:
> >>>
> >>>
> >http://listserv.ipc.org/archives
> >
> >
> >>>Please visit IPC web site
> >>>
> >>>
> >http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> >
> >
> >>>for additional information, or contact Keach Sasamori at
> >>>
> >>>
> >[log in to unmask] or
> >
> >
> >>>847-509-9700 ext.5315
> >>>-----------------------------------------------------
> >>>
> >>>********************************************************************
> >>>This email and any attachments are confidential to the intended
> >>>recipient and may also be privileged. If you are not the intended
> >>>recipient please delete it from your system and notify the sender.
> >>>You should not copy it or use it for any purpose nor disclose or
> >>>distribute its contents to any other person.
> >>>********************************************************************
> >>>
> >>>---------------------------------------------------
> >>>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >>>To unsubscribe, send a message to [log in to unmask] with following
> >>>
> >>>
> >text in
> >
> >
> >>>the BODY (NOT the subject field): SIGNOFF Technet
> >>>To temporarily halt or (re-start) delivery of Technet send e-mail to
> >>>[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >>>To receive ONE mailing per day of all the posts: send e-mail to
> >>>[log in to unmask]: SET Technet Digest
> >>>Search the archives of previous posts at:
> >>>
> >>>
> >http://listserv.ipc.org/archives
> >
> >
> >>>Please visit IPC web site
> >>>
> >>>
> >http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
> >
> >
> >>>additional information, or contact Keach Sasamori at [log in to unmask]
> >>>
> >>>
> >or
> >
> >
> >>>847-509-9700 ext.5315
> >>>-----------------------------------------------------
> >>>
> >>>
> >>>
> >>>
> >>>
> >>---------------------------------------------------
> >>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >>To unsubscribe, send a message to [log in to unmask] with following text
> >>
> >>
> >in
> >
> >
> >>the BODY (NOT the subject field): SIGNOFF Technet
> >>To temporarily halt or (re-start) delivery of Technet send e-mail to
> >>
> >>
> >[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >
> >
> >>To receive ONE mailing per day of all the posts: send e-mail to
> >>
> >>
> >[log in to unmask]: SET Technet Digest
> >
> >
> >>Search the archives of previous posts at:
> >>
> >>
> >http://listserv.ipc.org/archives
> >
> >
> >>Please visit IPC web site
> >>
> >>
> >http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
> >information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> >ext.5315
> >
> >
> >>-----------------------------------------------------
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> >---------------------------------------------------
> >Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >To unsubscribe, send a message to [log in to unmask] with following text
> >in
> >the BODY (NOT the subject field): SIGNOFF Technet
> >To temporarily halt or (re-start) delivery of Technet send e-mail to
> >[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >To receive ONE mailing per day of all the posts: send e-mail to
> >[log in to unmask]: SET Technet Digest
> >Search the archives of previous posts at:
> >http://listserv.ipc.org/archives
> >Please visit IPC web site
> >http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
> >information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> >ext.5315
> >-----------------------------------------------------
> >
> >---------------------------------------------------
> >Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> >To unsubscribe, send a message to [log in to unmask] with following text in
> >the BODY (NOT the subject field): SIGNOFF Technet>
> >To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
> >To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
> >Search the archives of previous posts at:
http://listserv.ipc.org/archives
> >Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information,
or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
> >-----------------------------------------------------
> >
> >
> >
> >
>
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
> -----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
