Is epoxy non-conductive

[Hoagie_one]

I need to use a spot of epoxy on a circuit board and I want to make sure it's not gonna short anything out.

Thanks

[SirPeale]

Not as far as I know.  Companies use epoxy all the time to seal in chips so you can't get to them.

[SoundDoc]

Just make sure not to use the extra strength Black Graphite epoxy.....
It does conduct electricity. Not the best conductor, but it does. I used it once to try and repair a antenna support that had broken. Took me a while to figure out what it was.

Anyway, the standard clear epoxy is fine. I use it all the time as a potting compound for small circuits and devices I want to waterproof/shockproof.

SD

[MonitorGuru]

> "Just make sure not to use the extra strength Black Graphite epoxy....."

Isn't that the stuff that Bally/Midway used to seal out the pirates from the Pac-Man Plus and ShootTheBull daughter boards???

http://www.multigame.com/pacplus.html

[SoundDoc]

I know the stuff your talking about MonitorGuru, I usually see it potting eol terminators for networks, lots of automotive controllers they don't want you to get into etc...

The stuff that's used to pot circuits isn't conductive though, Its usually a specially pigmented epoxy, and has other special properties. I use it around work to seal and shock protect sensors and controllers that are going into hazardous enviroments.  For one, it isnt corrosive, and epoxy many times ends up being corrosive, and can eat the circuit your trying to protect.
It also mixes up initially a lot thinner than epoxy, more like warm honey, and flows around componenets better. Its also about 10x the cost of regular epoxy  

The Grapihte epoxy, or black Liquid Steel type epoxy that you can get at Home Depot IS however somewhat conductive.

I was working on a large ham radio tower, and found a cracked ceramic insulator on his antenna, I repaired it with graphite epoxy putty,(the only thing I had availiable) and when we put it back in service, we found about a decrease of about 50 watts in his output power. After checking everything, and not being able to figure out where it was going, I checked the insulator and found it warm. Replaced it, and the power was right back up.
I never thought that It may have been conductive, so I took some to work with me and "played" around with it on the hipot tester.
This is going back more than 8 years now, but on a typical piece of PCB, with standard trace spacing, it would normally easily pass a 5000kv test, but after curing some epoxy on the board, it started conducting right off the bat, and finally brokedown/arc'd at around 400v.

It may be fine for potting small circuit boards, but I'd never try and fix a cracked flyback connector with it....

SD

[Kremmit]

Posted by: SoundDoc  Posted on: Today at 01:30:18pm  

It may be fine for potting small circuit boards, but I'd never try and fix a cracked flyback connector with it....

I actually DID fix a cracked flyback with epoxy.  It was JB weld brand "JB Stik", which comes as a tube of ...umm.. modeling clay.  There's a core of lighter, grey "clay", inside an outer layer of darker black "clay", you just tear off a chunk, mash it up, and press it into the hole in your flyback or whatever.  I used it instead of a more liquid sealant because I didn't want any of it to drip inside the flyback itself.  The back of the package claims electrical resistance is 30,000 megohms.  It sure stopped the big, blinding arc of electric death that was pouring out of my flyback!  

[RandyT]

Something to watch out for:

Just because an adhesive isn't conductive today, doesn't necessarily mean that it won't be tomorrow.

I remember a whole batch of monitors from the "old days" that started arcing out after a few years because the glue they used in the manufacture of them changed in properties and actually became conductive.  

I'm hoping that got that kind of stuff under control by now, but it's something to think about.

RandyT

[ErikRuud]

Aside from the black graphite epoxy, you can also get a silver epoxy that is intended to be conductive.  It is obscenely exspensive and generally only available from electronics supply companies.

Depending on what you are trying to accomplish, you might be better off using a silicone adhesive.

[AlanS17]

two words:

"hot glue"

[SoundDoc]

RandyT:
That reminds me as well of a insulating insulator coating I read about a few years ago.
They were spray coating high voltage insulators with this insulating coating to prevent the connectors from rusting.
But the coating built up a higher static charge in the wind, attracting  more dust and dirt to to the insulator than normal, dropping its insulative ability, which started to cause arcing and premature failure of the insulators.... hehehe....

Kremmit:
Don't get me wrong, I use epoxy to fix just about everything, including electonic parts, I was just saying watch out for the black graphite epoxys. In this case, it would most likely not make a difference.
I was just getting at as with anything though, "Epoxy" is a general designation for a product, and there are dozens of manufacturers, and thousands of types. Its just important to ensure that the product you are using, is suited to the type of application its being used it, or it can cause even more problems.
I've never tried that "stik" epoxy for flyback repair though... I usually buy a new stick every couple of years, and watch it harden in my toolbox...

Relating back to the origional question...
Using just about any type of epoxy should be fine and cause no problems.
If it was a cracked circuit board your repairing, my prefered method of repair over epoxy woulf be thick CA glue, (crazy glue). It usually soaks well into the fiberglass boards, and allows you to still solder across a broken trace.


now look what I've started....

[Hoagie_one]

hmmm, hot glue

[MonitorGuru]

I wired up an Arkanoid harness to Jamma edge connector adapator (using an old Commodore VIC-20 cartridge as the card edge side) and I glazed the hotglue over all the mini wires I used to create the thing.  Works 2 1/2 years later without problems.

(The reason it was built that way was because I had an Arkanoid in a cabinet with the classic Taito wiring, and then wanted to be able to swap in an Arkanoid 2 DOH board without having to rewire the cabinet.... Not many times you build an adaptor to go backwards )

[SoundDoc]

Someones going to shoot me soon.....  

You just have to watch what your using hot glue on.....
My dad got this brilliant idea,
He took out his house soffets drilled them up, made custom drilled and measured boards, and eventually recessed all the christmas lights into the soffets so that all that you see from the gound, is christmas lights, evenly spaced around the house, no visable wires! and when their turned off, you cant even see them.
He would never have to take down christmas lights again!

the moral is:
Don't use Hotglue to hold the bulb sockets in place...

DOH!! In this case, EPOXY worked better (the second time around).  
http://www.sbszoo.com/projects/xmas.htm
I've got to get him to update the page with the epoxy info..

If you have to make wiring mods to circuit boards, or make after factory changes, nothing holds the wires you've soldered onto the bottom of the board in place as well as hot glue.

[Gameboy.au]

Also keep in mind that epoxy is also used as a heat conductive.

Many high end electronics (intrinsically safe mobile phones etc) use it so that parts of PCBs do not go above a certain temperature, and there is no chance of sparks or arcing (which is why intrinsically safe mobile phones are used in petrol and oil refineries)  

Just something to keep in mind, so make sure it doesn't go anywhere near heat sensitive parts, like wiring etc.