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. 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>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 -----------------------------------------------------