Good coating for condensation protection?

[Bill Stock]

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of filling
the enclosure with silicone caulk, but I imagine some spray coating might be
better?

 

[Rich Webb]

On Wed, 29 Dec 2004 15:20:58 -0500, "Bill Stock" <Me7@Privacy.net>
wrote:

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of filling
the enclosure with silicone caulk, but I imagine some spray coating might be
better?

With my deep experience with silicone caulk (including leaky showers ;-)
I'd say that the problem with silicone is that it doesn't "wet" many
surfaces. If there's any motion or vibration, I'd be afraid that it
would develop a small gap at the surface interface and draw up water via
a capillary effect. I'd go with marine epoxy, myself.

One-off project or 100K/month commerial or ...?

--
Rich Webb Norfolk, VA

 

[R.Lewis]

"Bill Stock" <Me7@Privacy.net> wrote in message
news:HuGdnTvDrbM7jE7cRVn-3w@rogers.com...

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of filling
the enclosure with silicone caulk, but I imagine some spray coating might
be
better?

How about using some conformal coating\lacquer made specifically for the
type of task you describe?
>

 

[John Larkin]

On Wed, 29 Dec 2004 15:20:58 -0500, "Bill Stock" <Me7@Privacy.net>
wrote:

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of filling
the enclosure with silicone caulk, but I imagine some spray coating might be
better?

Most air-dry silicone caulk has acetic acid, which is bad news for
electronics.

Epoxy is good, or an acrylic casting compound. Use slow-set epoxy...
the fast stuff gets hot as it cures. The resin they use to fiberglass
boats is good and cheap. Mold-making (2-part) silicone is excellent.

For conformal coating, ordinary polyurethane varnish is pretty good.

John

 

[Watson A.Name - \"Watt Su]

"Bill Stock" <Me7@Privacy.net> wrote in message
news:HuGdnTvDrbM7jE7cRVn-3w@rogers.com...

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of
filling
the enclosure with silicone caulk, but I imagine some spray coating
might be
better?

In my experience, it takes many,. many coats of spray to make a decent
thick coating on a PCB, and each coat has to dry, making it take a long
time. It's better to dip coat the part.

 

[Rich Webb]

On Wed, 29 Dec 2004 19:40:13 -0800, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

"Bill Stock" <Me7@Privacy.net> wrote in message
news:HuGdnTvDrbM7jE7cRVn-3w@rogers.com...
I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of
filling
the enclosure with silicone caulk, but I imagine some spray coating
might be
better?

In my experience, it takes many,. many coats of spray to make a decent
thick coating on a PCB, and each coat has to dry, making it take a long
time. It's better to dip coat the part.

Is that still effective if surface mount parts are used instead of dips?

<ducks head, runs for cover>

--
Rich Webb Norfolk, VA

 

[Nicholas O. Lindan]

"Bill Stock" <Me7@Privacy.net> wrote

I've got a temperature sensor circuit which is subject to severe
condensation. What's a good protective coating? I was thinking of filling
the enclosure with silicone caulk, but I imagine some spray coating might be
better?

Is it possible to have just the sensor in the condensing atmosphere?

If not, then you will need a small 'Hoffman Enclosure' with a NEMA (I
forget the #) rating.

If you use epoxy you may want to use marine epoxy, that's the stuff
they make boat hulls out of, available at boat shops. Also called
'West Epoxy'.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/