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---Does anyone use epoxy to cover circuit boards once they are in the box? If
so, can you recommend some brand names that I may be able to order online or
buy at a store?
What is your purpose for such a process?Does anyone use epoxy to cover circuit boards once they are in the box? If
so, can you recommend some brand names that I may be able to order online or
buy at a store?
TIA,
Joe
For assemblies that are meant to be serviceable, one would want toDoes anyone use epoxy to cover circuit boards once they are in the box? If
so, can you recommend some brand names that I may be able to order online or
buy at a store?
Hi John,On Mon, 29 Mar 2004 15:55:33 GMT, "Joe"
nuisancewildlife@nospamearthlink.net> wrote:
Does anyone use epoxy to cover circuit boards once they are in the box?
If
so, can you recommend some brand names that I may be able to order online
or
buy at a store?
---
Depending on what your goal is for potting the circuitry, epoxy may be
a very bad choice because of its exotherm and because of its
dimensional instability as it cures. What are you trying to
accomplish?
--
John Fields
Hi John,Joe wrote:
Does anyone use epoxy to cover circuit boards once they are in the box?
If
so, can you recommend some brand names that I may be able to order
online or
buy at a store?
TIA,
Joe
What is your purpose for such a process?
--
John Popelish
Thank you for the info, Dark Matter, my circuits would not need to beOn Mon, 29 Mar 2004 15:55:33 GMT, "Joe"
nuisancewildlife@nospamearthlink.net> Gave us:
Does anyone use epoxy to cover circuit boards once they are in the box?
If
so, can you recommend some brand names that I may be able to order online
or
buy at a store?
For assemblies that are meant to be serviceable, one would want to
use a varnish humidity barrier such as Dolph's ac-51 or ac-43.
If no future servicing is expected, one can use epoxy, but one must
remeber that such materials shrink when curing, and PCB assemblies
will fracture parts or suffer other damage if the epoxy cross
sectional thickness is too high.
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
There are also thermally conduct versions for conduction cooled
brick designs.
Since the mediums are so expensive, the industry generally only
fully encapsulates for either security (dongle, etc) or environmental
(HV in a vacuum, humidity, etc) type reasons.
It isn't a cheap route. The varnish is the cheapest way to go.
Bake the PCB out before any assembly, and again if aqueous cleaning is
used, right before application of the humidity barrier.
BTW, such materials, and vented type electrolytic caps don't work
well together. You must assemble the boards without the caps before
the last bake and clean cycle, then carefully attach the caps, hand
cleaning each solder joint. The shellac, can seal the vent, and
vacuum impregnation is not the greatest idea.
PC Boards are hygroscopic. Good luck deciding. Dow Corning, and
General Electric are two makers of potting compounds, though they do
not sell directly, you must find a polymers dealer.
Speaking of RTV, how about plain old silicone sealer,There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
For low voltage applications, sure, it would be fine. But leave oneOn Mon, 29 Mar 2004 13:09:55 -0800, DarkMatter
DarkMatter@thebarattheendoftheuniverse.org> wrote:
snip
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
Speaking of RTV, how about plain old silicone sealer,
from GE or others?
Thank you John, sounds like just what I was looking forOn Mon, 29 Mar 2004 21:17:02 GMT, "Joe"
nuisancewildlife@nospamearthlink.net> wrote:
I am trying to protect a circuit board once it is in the enclosure (black
box) from things like vibration, shock, and especially moisture. I use
all
my devices outdoors and the extremes of temperature and sunlight,
sometimes
I can see the condensation on the inside of the box.
I thought something to weatherproof and totally encapsulate the board
would
be helpful.
---
There are many encapsulant manufacturers, among them Master Bond and
Emerson and Cuming. I've used E&C wencapsulants in the past and was
well satisfied with them. Here's a link:
http://www.emersoncuming.com/YourSolution/index.jsp?id=1&c=167
--
John Fields
Thanks for all the links, John, it will take me awhile to sort thru them,Joe wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:40684970.62E22427@rica.net...
Joe wrote:
Does anyone use epoxy to cover circuit boards once they are in the
box?
If
so, can you recommend some brand names that I may be able to order
online or
buy at a store?
TIA,
Joe
What is your purpose for such a process?
--
John Popelish
Hi John,
I am trying to protect a circuit board once it is in the enclosure
(black
box) from things like vibration, shock, and especially moisture. I use
all
my devices outdoors and the extremes of temperature and sunlight,
sometimes
I can see the condensation on the inside of the box.
I thought something to weatherproof and totally encapsulate the board
would
be helpful. I remember a (very) long time ago, I worked at a local lab
where
we made large capacitors for NASA. There was a potting compound we used,
it
was brown in color and had to be mixed with a curing agent, then placed
in a
vaccuum chamber to pull all the air bubbles out. Then we would pour it
over
the circuit and let it harden. Something like that.
Joe
If you want to pour epoxy in the box you might use something like
this, though there is some risk that it will distort as it hardens and
damage some of the components. Curing it slowly (starting with it
cool) helps.
http://www.abra-electronics.com/catalog/chemicals/gc16.html
You can find key words to search out similar things like this:
http://www.crosslinktech.com/epoxies.htm
http://www.transene.com/epoxies_potting.html
http://www.magnapoxy.com/magencap.htm
http://www.emersoncuming.com/YourSolution/properties.jsp?appId=65&geoId=0
I have used this product from that last vendor, and it has the
advantage of being almost indestructible. It is pretty highly filled
with inert mineral fillers, so it seldom overheats or shrinks. When
it hardens, it is basically a rock.
http://www.emersoncuming.com/YourSolution/ProductDetails.jsp?i=77
You can also dip the board in melted paraffin wax, first, to keep the
potting epoxy from actually bonding on to the parts or board. But it
will melt in the sun. The professionals often dip the board in
silicone resin to give it an elastic coat before potting.
--
John Popelish
Hi Bob,On Mon, 29 Mar 2004 13:09:55 -0800, DarkMatter
DarkMatter@thebarattheendoftheuniverse.org> wrote:
snip
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
Speaking of RTV, how about plain old silicone sealer,
from GE or others? It's fairly cheap, conforms well,
waterproof, and doesn't have thermal expansion problems
like epoxies. It doesn't flow on as well as the expensive
conformal coatings, so it will be a little messy to apply.
Maybe squirt it into the enclosure and force the lid on,
then wipe up whatever is squeezed out?
Just a thought...
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
compounds are very thin and runny when first mixed up, and are firm"Bob Masta" <NoSpam@daqarta.com> wrote in message
news:40697376.1589701@news.itd.umich.edu...
On Mon, 29 Mar 2004 13:09:55 -0800, DarkMatter
DarkMatter@thebarattheendoftheuniverse.org> wrote:
snip
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
Speaking of RTV, how about plain old silicone sealer,
from GE or others? It's fairly cheap, conforms well,
waterproof, and doesn't have thermal expansion problems
like epoxies. It doesn't flow on as well as the expensive
conformal coatings, so it will be a little messy to apply.
Maybe squirt it into the enclosure and force the lid on,
then wipe up whatever is squeezed out?
Just a thought...
Hi Bob,
good suggestion, I think. Do you mean like the silicone caulking they sell
at home depot? It comes in a tube for use in a caulking gun for outdoor use
around windows and door frames. I have used it for caulking windows and
stuff, and it does dry flexible. Is that what you are referring to?
The real problem is the fact that it doesn't move well. RTV potting
The stuff I am thinking of is called "silicone sealant" and is not"Bob Masta" <NoSpam@daqarta.com> wrote in message
news:40697376.1589701@news.itd.umich.edu...
On Mon, 29 Mar 2004 13:09:55 -0800, DarkMatter
DarkMatter@thebarattheendoftheuniverse.org> wrote:
snip
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
Speaking of RTV, how about plain old silicone sealer,
from GE or others? It's fairly cheap, conforms well,
waterproof, and doesn't have thermal expansion problems
like epoxies. It doesn't flow on as well as the expensive
conformal coatings, so it will be a little messy to apply.
Maybe squirt it into the enclosure and force the lid on,
then wipe up whatever is squeezed out?
Just a thought...
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Hi Bob,
good suggestion, I think. Do you mean like the silicone caulking they sell
at home depot? It comes in a tube for use in a caulking gun for outdoor use
around windows and door frames. I have used it for caulking windows and
stuff, and it does dry flexible. Is that what you are referring to?
Joe
Talking specifically about "Araldite" does that shrink and apply stress toOn Mon, 29 Mar 2004 15:55:33 GMT, "Joe"
nuisancewildlife@nospamearthlink.net> Gave us:
Does anyone use epoxy to cover circuit boards once they are in the box?
If
so, can you recommend some brand names that I may be able to order online
or
buy at a store?
For assemblies that are meant to be serviceable, one would want to
use a varnish humidity barrier such as Dolph's ac-51 or ac-43.
If no future servicing is expected, one can use epoxy, but one must
remeber that such materials shrink when curing, and PCB assemblies
will fracture parts or suffer other damage if the epoxy cross
sectional thickness is too high.
There are soft compounds we refer to as encapsulants that can be
use. Many different formulations exist, such as RTV, and
"PolyUrethane" types. None are cheap. Even a small pint sample will
likely cost you up to a hundred bucks.
There are also thermally conduct versions for conduction cooled
brick designs.
Since the mediums are so expensive, the industry generally only
fully encapsulates for either security (dongle, etc) or environmental
(HV in a vacuum, humidity, etc) type reasons.
It isn't a cheap route. The varnish is the cheapest way to go.
Bake the PCB out before any assembly, and again if aqueous cleaning is
used, right before application of the humidity barrier.
BTW, such materials, and vented type electrolytic caps don't work
well together. You must assemble the boards without the caps before
the last bake and clean cycle, then carefully attach the caps, hand
cleaning each solder joint. The shellac, can seal the vent, and
vacuum impregnation is not the greatest idea.
PC Boards are hygroscopic. Good luck deciding. Dow Corning, and
General Electric are two makers of potting compounds, though they do
not sell directly, you must find a polymers dealer.
Don't know from experience on circuit boards, but I recall thatTalking specifically about "Araldite" does that shrink and apply stress to
components ??
From observation it certainly will flow into voids at moderate temps of say
40c.