Need Help Sourcing/Selecting Potting Compound for Electronics

[loadhawg]

I have a very specific one-off project. It's a small clear plastic
cylinder closed at one end, 5cm (2") diameter and 2cm (.75") deep. I'm
placing the electronic components/battery in it and need to 'fill up'
the rest to the top with what I believe is called a potting compound
(like an encapsulant?) and make it air/water tight.

More specifically it needs to cure or dry to still be 'soft' -
absolutely no firmer than household silicon caulk. But it needs to
pour in with thin water-like viscosity so that it fills up any air
pockets etc. Finally it is very desirable that it be clear - again
like a silicon caulk. I think I would prefer it to be silicon based
and out of simplicity a 1-part type.

I tried some GE silicon II caulk after heating it up - same thick
viscosity as at room temperature and it's a bit of a 'milky' color
too. I've googled around but all I've found are surprisingly expensive
compounds marketed to large scale production operations often in
fairly large quantities. All I need is a tube or 2 of something or
other to seal up my personal project.

Appreciate any recommendations or references... - thanks

 

[catguy]

I have a very specific one-off project. It's a small clear plastic
cylinder closed at one end, 5cm (2") diameter and 2cm (.75") deep. I'm
placing the electronic components/battery in it and need to 'fill up'
the rest to the top with what I believe is called a potting compound
(like an encapsulant?) and make it air/water tight.

More specifically it needs to cure or dry to still be 'soft' -
absolutely no firmer than household silicon caulk. But it needs to
pour in with thin water-like viscosity so that it fills up any air
pockets etc. Finally it is very desirable that it be clear - again
like a silicon caulk. I think I would prefer it to be silicon based
and out of simplicity a 1-part type.

I tried some GE silicon II caulk after heating it up - same thick
viscosity as at room temperature and it's a bit of a 'milky' color
too. I've googled around but all I've found are surprisingly expensive
compounds marketed to large scale production operations often in
fairly large quantities. All I need is a tube or 2 of something or
other to seal up my personal project.

Appreciate any recommendations or references... - thanks

How about this?.....Paul

http://www.usahardware.com/inet/shop/item/12250/icn/20-086694/dap_inc/00816.htm

 

[loadhawg]

Thanks I'll look into it more but DAP (A great brand) likely makes
this as a competitor to the GE Silicon II caulk I already tried
(though this is specifically clear but as it turns out the GE stuff I
had dries clear). Problem w/ the GE (and I suspect DAP) is that it
comes out much too THICK even after heating. I need something with
much lower easy flowing (closer to water?) viscosity to fill
airpockets before it cures.

Either the DAP or GE goop would be perfect once dried! (if I could get
them to fill in the air gaps)

Thanks again

 

[z]

Thanks I'll look into it more but DAP (A great brand) likely makes
this as a competitor to the GE Silicon II caulk I already tried
(though this is specifically clear but as it turns out the GE stuff I
had dries clear). Problem w/ the GE (and I suspect DAP) is that it
comes out much too THICK even after heating. I need something with
much lower easy flowing (closer to water?) viscosity to fill
airpockets before it cures.

Either the DAP or GE goop would be perfect once dried! (if I could get
them to fill in the air gaps)

Thanks again




- Show quoted text -

Way back when, whatever place I was buying this kind of stuff from had
two types of such; self-leveling and whatever they called the
notselfleveling one. Sounds like you're looking for self-leveling;
just like the name suggests, you pour it in wherever and it flows like
water before it sets. So it's out there, you just need to find it.

 

[TexNick]

Hysol makes an extensive line of industry standard products for
encapsulation and conformal coating.

Google "Hysol"

This link will give you a lot of info, I know it's a strange looking
link ... but it will narrow the list down ... they make hundreds of
products :

http://www.henkelna.com/cps/rde/xch...advanced|x=0|y=903|pageIndex=0|action=search|

Here is one of many online distributors for Hysol products :

http://www.ellsworth.com/Hysol.html

 

[TexNick]

As an afterthought, i offer a few points for consideration :

( 1 ) Encapsulating resins have different temperature coefficents than
many electronic components. The resins will expand and contract at a
different rate than the electronic components as the temperature
changes. This can sometimes cause components such as integrated
circuits (IC's) to crack or become damaged. One of many solutions to
this problem is to first coat the device ( circuit board &
components ) with "Latex Solder Mask". After the Latex dries pour the
"Encapsulating Resin" over the device. The Latex will act as a cushion
and isolate the circuitry from the ridged resin. The Latex also offers
a certain degree of mechanical shock resistance.

Google "Latex Solder Mask"

These guys sell both Resins and Latex :

http://www.marvac.com/SearchResult.aspx?CategoryID=909

( 2 ) Non-sealed adjustable and mechanical assemblies such
Potentiaometrs and Relays should be sealed to prevent the
"Encapsulating Resin" from entering those devices. The "Latex Solder
Mask" will solve this type of problem.

( 3 ) Power components such as "Power Transistors" can generate a lot
of heat. You may need to mount "heat generating components" on a heat
sink and allow the heat sink to protude outside of the "Encapsulating
Resin". If you use Latex, make sure none of the components will become
so hot as to char the Latex. Charred Latex could become "Electrically
Conductive".

!!! CAUTION CAUTION CAUTION !!!
If you decide to use "Latex Solder Mask", MAKE SURE THE LATEX IS NON-
CONDUCTIVE.
Most "Latex Solder Mask" is NON-CONDUCTIVE.
Pure "Liquid Latex" is NON-CONDUCTIVE.

Some Latex products ARE CONDUCTIVE though. These products have many
uses such as Anti-Static coatings.

Here is an example of "CONDUCTIVE LATEX" ( Don't use anything like
this stuff ) :
http://news.thomasnet.com/companystory/537953

MAKE SURE ALL OF THE ENCAPSULATION PRODUCTS ARE NON-CONDUCTIVE.

Hope this helps
Good Luck