[time-nuts] Conformal Coating

Tue May 15 02:51:47 UTC 2012

The Humiseal and Chemtronics Acrylic both meet the Mil Spec 'AR' rating. 
(I've had to track down this document trail.)  I believe the MG 
Chemicals also meets the same spec.  The MG and Chemtronics are readily 
available at most local electronic stores, Newark, Mouser and other 
distributors.

Mike

On 5/14/2012 8:13 PM, Sam Reaves wrote:
> 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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