[time-nuts] Conformal Coating
Sam Reaves
sam.reaves at gmail.com
Tue May 15 01:13:55 UTC 2012
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:
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> 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
> *****************************************
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