[time-nuts] Conformal Coating

Tom Knox actast at hotmail.com
Tue May 15 02:02:01 UTC 2012


That sounds like what we use in the AeroSpace industry. I remember the UV dye. 
Thanks

Thomas Knox



> Date: Mon, 14 May 2012 21:13:55 -0400
> From: sam.reaves at gmail.com
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Conformal Coating
> 
> For conformal coating I recommend Humiseal Acrylic 1B73 in aerosol. You can
> also get it in brush form. I believe that Chemtronics used to offer acrylic
> coating as well, maybe even re-packaging the Humiseal product. I don't know
> if there is a source for small quantities of Humiseal but it is a fine
> product.
> 
> I have also used Krylon clear acrylic that you can get at Wall-Mart in a
> pinch. The acrylic coatings I have found are better for HiZ circuits that
> have requirements for low-leakage. Consult the can for solvents and make
> sure that what you are coating are compatible with Toluene, Ketones,
> Acetone, etc. be careful around connectors as the coating will wick into
> connectors as the 1B73 is a fairly low viscosity. You can also get Humiseal
> formulations 1B38 and 1B66 which are also Acrylics but are brush on and
> require a one gallon minimum purchase. The shipping cost for a gallon is
> almost as much as the product due to the requirement that it be shipped as
> a hazardous material (flameable). The acrylics can be dissolved with MEK or
> any of the solvents I have listed above. You can remove a small amount with
> a Q-Tip.
> 
> The Humiseal product also has a UV indicator in it that glows blue under a
> black light so you can check coverage.
> 
> I have tested Humiseal Acrylic on probably 1000+ PCB's and it has yet to
> fail me. It is also easy to rework and re-coat after repairs.
> 
> You can also get polyurethane coatings but I do not recommend them since
> they are more difficult you use, not as easy to remove
> and have better performance for HiZ and RF circuits.
> 
> Good luck and let us know how you make out.
> 
> Sam
> W3OHM
> 
> http://www.hmcelectronics.com/product/Chemtronics/CTAR12
> 
> 
> 
> 
> On Mon, May 14, 2012 at 7:31 PM, <time-nuts-request at febo.com> wrote:
> 
> > Send time-nuts mailing list submissions to
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> > than "Re: Contents of time-nuts digest..."
> >
> >
> > Today's Topics:
> >
> >   1. Re: Why are 1PPS signals so skinny? (Jim Hickstein)
> >   2. Re: Why are 1PPS signals so skinny? (Azelio Boriani)
> >   3. Re: wwvb weak on east coast especially when the pre-amps
> >      under wa... (Michael Blazer)
> >   4. Re: wwvb weak on east coast especially when the pre-amps
> >      under wa... (Azelio Boriani)
> >   5. Re: Why are 1PPS signals so skinny? (Michael Blazer)
> >   6. Re: Why are 1PPS signals so skinny? (Bob Camp)
> >   7. Re: wwvb weak on east coast especially when thepre-amps   under
> >      wa... (Alan Melia)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Mon, 14 May 2012 18:18:20 -0500
> > From: Jim Hickstein <jxh at jxh.com>
> > To: time-nuts at febo.com
> > Subject: Re: [time-nuts] Why are 1PPS signals so skinny?
> > Message-ID: <4FB192BC.4060801 at jxh.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > On 2012/05/14 18:02, time-nuts-request at febo.com wrote:
> > > https://assist.daps.dla.mil/quicksearch/  is the search site for
> > military standards.
> >
> > Hmm.  Doesn't find MIL-TGDBP-41.  I got this from my (now late) great
> > uncle, Bob
> > Sedgwick -- who was to hydraulics what I am to computers, only he has a
> > number
> > of patents.
> >
> > Some smart-aleck at Wright Field, as it then was, put this on a drawing,
> > and it
> > went without comment for quite a while until someone tried to look it up.
> >  This
> > escalated to a bird colonel, who then tracked down the miscreant.
> >
> > It stands for Make It Like The G-D Blueprint For Once.
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Tue, 15 May 2012 01:21:26 +0200
> > From: Azelio Boriani <azelio.boriani at screen.it>
> > To: Discussion of precise time and frequency measurement
> >        <time-nuts at febo.com>
> > Subject: Re: [time-nuts] Why are 1PPS signals so skinny?
> > Message-ID:
> >        <CAL8XPmOc8cLJ3aGBcqJsJB=FbW5XTQ-_FY54R9edDUDUX+ADTg at mail.gmail.com
> > >
> > Content-Type: text/plain; charset=ISO-8859-1
> >
> > Maybe the correct number is MIL-STD-188-115?
> >
> > On Tue, May 15, 2012 at 1:18 AM, Jim Hickstein <jxh at jxh.com> wrote:
> >
> > > On 2012/05/14 18:02, time-nuts-request at febo.com wrote:
> > >
> > >> https://assist.daps.dla.mil/quicksearch/  is the search site for
> > >> military standards.
> > >>
> > >
> > > Hmm.  Doesn't find MIL-TGDBP-41.  I got this from my (now late) great
> > > uncle, Bob Sedgwick -- who was to hydraulics what I am to computers, only
> > > he has a number of patents.
> > >
> > > Some smart-aleck at Wright Field, as it then was, put this on a drawing,
> > > and it went without comment for quite a while until someone tried to look
> > > it up.  This escalated to a bird colonel, who then tracked down the
> > > miscreant.
> > >
> > > It stands for Make It Like The G-D Blueprint For Once.
> > >
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> >
> >
> > ------------------------------
> >
> > Message: 3
> > Date: Mon, 14 May 2012 18:23:31 -0500
> > From: Michael Blazer <mblazer at satx.rr.com>
> > To: time-nuts at febo.com
> > Subject: Re: [time-nuts] wwvb weak on east coast especially when the
> >        pre-amps under wa...
> > Message-ID: <4FB193F3.6000503 at satx.rr.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > Here's comparison for various type of conformal coating:
> > http://mgchemicals.com/downloads/appguide/appguide0404.pdf.<
> > https://assist.daps.dla.mil/quicksearch/>
> >
> > I think there is a type that is 'serviceable' and removable with alcohol.
> >
> > Mike
> >
> > On 5/14/2012 6:01 PM, GandalfG8 at aol.com wrote:
> > > The other option of course is to pressurise the box with dry air to
> > ensure
> > > a positive pressure differential, such that the net flow is always
> > outwards
> > > at  all points, but it's probably easier just to provide a drain hole:-)
> > >
> > > However, whilst a drain hole will prevent the build up of a lake inside
> > the
> > >   enclosure it still doesn't prevent condensation forming on circuit
> > boards,
> > > and  powered circuit boards and condensation don't really go well
> >  together.
> > >
> > > As per earlier comments, it's quite difficult to keep any externally
> > > mounted enclosure totally moisture free, so it's much easier to accept
> > the
> > > inevitable and allow for it.
> > >
> > > In a past life I designed quite a few circuit boards that  were required
> > to
> > > be fitted in externally mounted vented enclosures, so not  a great deal
> > of
> > > pressurisation there then:-), and I usually specified that  both sides
> > > should be sprayed with a plastic coating following final test.
> > >
> > > I can't remember now exactly what this stuff was called, but it  was
> > > readily available in the UK from both RS and Farnell as an aerosol
> > plastic  spray
> > > that provided a good barrier but was a bit more flexible than the  usual
> > MOD
> > > spec conformal coatings.
> > > It melted easily under a soldering iron, albeit with a foul  pong:-), so
> > > reworking was no problem, and resisted moisture remarkably  well.....
> > >
> > > problem solved:-)
> > >
> > > Nigel
> > > GM8PZR
> > >
> > >
> > >
> > >
> > >
> > > In a message dated 14/05/2012 23:10:30 GMT Daylight Time,
> > > arnold.tibus at gmx.de writes:
> > >
> > > The only  solutions I think:
> > > Apply air pressure tight boxes having a breathing hole  an the bottom,
> > > mount the
> > > box that no rain and water can penetrate from  the top or sides. If the
> > > hole is big enough,
> > > eg. 2mm, no pressure  difference is possible and no pumping effect will
> > > occur.
> > > (If the hole is  too wide, small animals may penetrate).
> > > Or,
> > > when using a pressure tight  box, it must be stiff and sealed to
> > > withstand under all
> > > temperature  conditions more then 1 bar/ 100 kPa. Do not forget that  all
> > > feed
> > > throughs must be of real hermetic type, normal coaxial  connectors are
> > > not tight!
> > > Don't route cables directly in, because no  cable braid or mesh is  vapor
> > > tight.
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> > >
> >
> >
> > ------------------------------
> >
> > Message: 4
> > Date: Tue, 15 May 2012 01:25:54 +0200
> > From: Azelio Boriani <azelio.boriani at screen.it>
> > To: Discussion of precise time and frequency measurement
> >        <time-nuts at febo.com>
> > Subject: Re: [time-nuts] wwvb weak on east coast especially when the
> >        pre-amps under wa...
> > Message-ID:
> >        <CAL8XPmPCB-DWCpoT0NmfP+TdpdRcK-XjXxVJWyTJA+RQmux9dg at mail.gmail.com
> > >
> > Content-Type: text/plain; charset=ISO-8859-1
> >
> > We use the Plastik70 from Kontakt chemie
> >
> > On Tue, May 15, 2012 at 1:23 AM, Michael Blazer <mblazer at satx.rr.com>
> > wrote:
> >
> > > Here's comparison for various type of conformal coating:
> > > http://mgchemicals.com/downloads/appguide/appguide0404.pdf.<
> > > https://assist.daps.dla.mil/quicksearch/>
> > >
> > > I think there is a type that is 'serviceable' and removable with alcohol.
> > >
> > > Mike
> > >
> > >
> > > On 5/14/2012 6:01 PM, GandalfG8 at aol.com wrote:
> > >
> > >> The other option of course is to pressurise the box with dry air to
> > ensure
> > >> a positive pressure differential, such that the net flow is always
> > >> outwards
> > >> at  all points, but it's probably easier just to provide a drain hole:-)
> > >>
> > >> However, whilst a drain hole will prevent the build up of a lake inside
> > >> the
> > >>  enclosure it still doesn't prevent condensation forming on circuit
> > >> boards,
> > >> and  powered circuit boards and condensation don't really go well
> > >>  together.
> > >>
> > >> As per earlier comments, it's quite difficult to keep any externally
> > >> mounted enclosure totally moisture free, so it's much easier to accept
> > the
> > >> inevitable and allow for it.
> > >>
> > >> In a past life I designed quite a few circuit boards that  were required
> > >> to
> > >> be fitted in externally mounted vented enclosures, so not  a great deal
> > of
> > >> pressurisation there then:-), and I usually specified that  both sides
> > >> should be sprayed with a plastic coating following final test.
> > >>
> > >> I can't remember now exactly what this stuff was called, but it  was
> > >> readily available in the UK from both RS and Farnell as an aerosol
> > >> plastic  spray
> > >> that provided a good barrier but was a bit more flexible than the  usual
> > >> MOD
> > >> spec conformal coatings.
> > >> It melted easily under a soldering iron, albeit with a foul  pong:-), so
> > >> reworking was no problem, and resisted moisture remarkably  well.....
> > >>
> > >> problem solved:-)
> > >>
> > >> Nigel
> > >> GM8PZR
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> In a message dated 14/05/2012 23:10:30 GMT Daylight Time,
> > >> arnold.tibus at gmx.de writes:
> > >>
> > >> The only  solutions I think:
> > >> Apply air pressure tight boxes having a breathing hole  an the bottom,
> > >> mount the
> > >> box that no rain and water can penetrate from  the top or sides. If the
> > >> hole is big enough,
> > >> eg. 2mm, no pressure  difference is possible and no pumping effect will
> > >> occur.
> > >> (If the hole is  too wide, small animals may penetrate).
> > >> Or,
> > >> when using a pressure tight  box, it must be stiff and sealed to
> > >> withstand under all
> > >> temperature  conditions more then 1 bar/ 100 kPa. Do not forget that
> >  all
> > >> feed
> > >> throughs must be of real hermetic type, normal coaxial  connectors are
> > >> not tight!
> > >> Don't route cables directly in, because no  cable braid or mesh is
> >  vapor
> > >> tight.
> > >> _______________________________________________
> > >> time-nuts mailing list -- time-nuts at febo.com
> > >> To unsubscribe, go to
> > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > >> and follow the instructions there.
> > >>
> > >>
> > >>  _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> >
> >
> > ------------------------------
> >
> > Message: 5
> > Date: Mon, 14 May 2012 18:26:58 -0500
> > From: Michael Blazer <mblazer at satx.rr.com>
> > To: time-nuts at febo.com
> > Subject: Re: [time-nuts] Why are 1PPS signals so skinny?
> > Message-ID: <4FB194C2.6090401 at satx.rr.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > I haven't heard that one before.  I try to slip in the TLAR check in all
> > the test procedures I write.  When 'they' ask, I look at it and say:
> > "That Looks About Right".
> > Mike
> >
> > On 5/14/2012 6:18 PM, Jim Hickstein wrote:
> > > On 2012/05/14 18:02, time-nuts-request at febo.com wrote:
> > >> https://assist.daps.dla.mil/quicksearch/  is the search site for
> > >> military standards.
> > >
> > > Hmm.  Doesn't find MIL-TGDBP-41.  I got this from my (now late) great
> > > uncle, Bob Sedgwick -- who was to hydraulics what I am to computers,
> > > only he has a number of patents.
> > >
> > > Some smart-aleck at Wright Field, as it then was, put this on a
> > > drawing, and it went without comment for quite a while until someone
> > > tried to look it up.  This escalated to a bird colonel, who then
> > > tracked down the miscreant.
> > >
> > > It stands for Make It Like The G-D Blueprint For Once.
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> > >
> >
> >
> >
> > ------------------------------
> >
> > Message: 6
> > Date: Mon, 14 May 2012 19:30:49 -0400
> > From: Bob Camp <lists at rtty.us>
> > To: Discussion of precise time and frequency measurement
> >        <time-nuts at febo.com>
> > Subject: Re: [time-nuts] Why are 1PPS signals so skinny?
> > Message-ID: <0CE3BEF7-A1BA-4CE1-8A74-3364B2A80302 at rtty.us>
> > Content-Type: text/plain; charset=iso-8859-1
> >
> > Hi
> >
> > I would bet that the basic electrical definition of the "skinny" PPS dates
> > at least to the mid 50's if not earlier.
> >
> > Bob
> >
> > On May 14, 2012, at 3:20 PM, Magnus Danielson wrote:
> >
> > > Mark, Azelio and Bj?rn,
> > >
> > > On 05/14/2012 06:33 PM, bg at lysator.liu.se wrote:
> > >> Mark&  Azelio,
> > >>
> > >> Or even 10V into 50ohm, 20us... See figure 3-4 in ICD-GPS-060.
> > >>
> > >>     http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf
> > >>
> > >> More modern 3-5.5V into 50ohm, 20us.
> > >>
> > http://contracting.tacom.army.mil/majorsys/jab/DAGR%20Interface%20Specification.pdf
> > >>
> > >> Above are two standards demanding short skinny 1PPS pulses. Are there
> > any
> > >> other standards with distinct shape requirements on 1PPS pulses?
> > >
> > > You need to look at MIL STD 188/155 which if I recall things was
> > initially formed in the 60thies.
> > >
> > > An AccuBeat presentation actually says that the PPS was originally
> > defined in it.
> > >
> > > The MIL STD 188/155 is actually a 10 V peak level, so it was much hotter
> > than we are used to know. It specified 5 MHz as base frequency, or power of
> > 2 multiples (10, 20, 40 MHz... ).
> > >
> > > It was later reformulated in the PTTI spec, which ICD GPS 060 is a
> > derivate. The 50 ns rise and 1 us fall slopes comes from that spec.
> > >
> > > I was not able to find MIL STD 188-155 on the net right now, but I have
> > been able to download it before, so if someone is a more lucky it should
> > surface. I should have my download somewhere.
> > >
> > > Cheers,
> > > Magnus
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 7
> > Date: Tue, 15 May 2012 00:32:11 +0100
> > From: "Alan Melia" <alan.melia at btinternet.com>
> > To: "Discussion of precise time and frequency measurement"
> >        <time-nuts at febo.com>
> > Subject: Re: [time-nuts] wwvb weak on east coast especially when
> >        thepre-amps     under wa...
> > Message-ID: <012501cd3229$cb66eae0$4001a8c0 at lark>
> > Content-Type: text/plain;       charset="iso-8859-1"
> >
> > Well almost Nigel, if you look at molecule mean velocities they are always
> > able to diffuse down a concentration gradient (i.e from wet into dry)
> > despite a small reverse presure gradient. It just takes longer under those
> > conditions :-))....which is often "enough"
> >
> > Alan G3NYK
> > ----- Original Message -----
> > From: <GandalfG8 at aol.com>
> > To: <time-nuts at febo.com>
> > Sent: Tuesday, May 15, 2012 12:01 AM
> > Subject: Re: [time-nuts] wwvb weak on east coast especially when
> > thepre-amps
> > under wa...
> >
> >
> > > The other option of course is to pressurise the box with dry air to
> > ensure
> > > a positive pressure differential, such that the net flow is always
> > outwards
> > > at  all points, but it's probably easier just to provide a drain hole:-)
> > >
> > > However, whilst a drain hole will prevent the build up of a lake inside
> > the
> > >  enclosure it still doesn't prevent condensation forming on circuit
> > boards,
> > > and  powered circuit boards and condensation don't really go well
> > together.
> > >
> > > As per earlier comments, it's quite difficult to keep any externally
> > > mounted enclosure totally moisture free, so it's much easier to accept
> > the
> > > inevitable and allow for it.
> > >
> > > In a past life I designed quite a few circuit boards that  were required
> > to
> > > be fitted in externally mounted vented enclosures, so not  a great deal
> > of
> > > pressurisation there then:-), and I usually specified that  both sides
> > > should be sprayed with a plastic coating following final test.
> > >
> > > I can't remember now exactly what this stuff was called, but it  was
> > > readily available in the UK from both RS and Farnell as an aerosol
> > plastic
> > spray
> > > that provided a good barrier but was a bit more flexible than the  usual
> > MOD
> > > spec conformal coatings.
> > > It melted easily under a soldering iron, albeit with a foul  pong:-), so
> > > reworking was no problem, and resisted moisture remarkably  well.....
> > >
> > > problem solved:-)
> > >
> > > Nigel
> > > GM8PZR
> > >
> > >
> > >
> > >
> > >
> > > In a message dated 14/05/2012 23:10:30 GMT Daylight Time,
> > > arnold.tibus at gmx.de writes:
> > >
> > > The only  solutions I think:
> > > Apply air pressure tight boxes having a breathing hole  an the bottom,
> > > mount the
> > > box that no rain and water can penetrate from  the top or sides. If the
> > > hole is big enough,
> > > eg. 2mm, no pressure  difference is possible and no pumping effect will
> > > occur.
> > > (If the hole is  too wide, small animals may penetrate).
> > > Or,
> > > when using a pressure tight  box, it must be stiff and sealed to
> > > withstand under all
> > > temperature  conditions more then 1 bar/ 100 kPa. Do not forget that  all
> > > feed
> > > throughs must be of real hermetic type, normal coaxial  connectors are
> > > not tight!
> > > Don't route cables directly in, because no  cable braid or mesh is  vapor
> > > tight.
> > > _______________________________________________
> > > time-nuts mailing list -- time-nuts at febo.com
> > > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> >
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > time-nuts mailing list
> > time-nuts at febo.com
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >
> > End of time-nuts Digest, Vol 94, Issue 89
> > *****************************************
> >
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
 		 	   		  


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