# Does thermal epoxy conduct electricity?



## Macaw (Feb 4, 2006)

I ordered a pair of the new K2 emitters from 4sevens. The data sheet for these LEDs indicate that the heat sink slug must be electrically isolated from the leads. Will thermal epoxy provide enough electrical insolation to prevent problems?

I planned to mod a LedBeam flashlight but I found continuity between the heatsink and the cathode side of the emitter. Do the luxeon III emitters allow for electrical contact between the slug and cathode side?:help:

Does Radio Shack sell non electrical conducting thermal epoxy?


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## gadget_lover (Feb 4, 2006)

It depends on which thermal epoxy. Arctic sells a version that isolates as well as one that conducts. I think the "silver" conducts and the alumina does not, but you'd better check their web site or wait for someone else to chime in.


Daniel


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## scott.cr (Feb 6, 2006)

A lot of the heatsink epoxies are deliberately electrically insulative. So if you find one that says it's electrically insulative, then you can feel safe that it's dielectric.

Some epoxies are meant for circuit repair and such and are designed to conduct electricity.... so like Daniel said just be careful to read before you buy.


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## nemul (Feb 6, 2006)

gadget_lover said:


> It depends on which thermal epoxy. Arctic sells a version that isolates as well as one that conducts. I think the "silver" conducts and the alumina does not, but you'd better check their web site or wait for someone else to chime in.
> 
> 
> Daniel



yep...

Arctic Alumina Adhesive is a pure electrical insulator, neither electrically conductive nor capacitive...

Arctic Silver 5 is made with 99.9% pure micronized silver and will conduct electricity...


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## Chop (Feb 6, 2006)

On the other hand, if the sink you are putting it on is anodized, it is a moot point. You won't need to worry about it since anodizing isn't conductive. Of course, you'll want something non conductive for potting the converter that you use.


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## Silviron (Mar 28, 2006)

I just rigged up a little test jig to measure the conductivity of Arctic Silver rather than relying on my memory of something that was a a casual observance from about a year and a half ago in the first place...







I mixed up some Arctic Silver Adhesive and spread it on a bit of plastic, and embedded a couple of stranded wires in it (one is about 22 ga, the other about 20 ga, just scraps I had handy).

Let it cure for about 5 hours.

The ends of the embedded wires are about 5 mm apart.

Tested it with three meters: one fairly expensive digital, a cheap digital and a medium priced analog meter.

Off the scale readings on all meters. (in other words not any reasonably measurable conductivity)

Tried measuring the resistance by poking the meter test probes directly into the Arctic Silver itself..... Resistance still off the meter no matter how close I get the probes.

Once, when the probes were about 1/4 mm apart I thought I got a reading of about 20 Megohms... But trying to duplicate the readings I discovered that I had a tiny bit of skin contact from a finger on each probe.

So... electricity traveling between a tiny patch of skin on each finger, up the arms, across the chest has less resistance than 1/4mm of Arctic Silver.

Maybe a lab quality ohmmeter or a highly sensitive galvanometer could measure it, but if my experiment is any indication, and my math is correct, we are talking more than a GigOhm of resistance per milimeter.

'Shorting' an unprotected 18650 LiIon through my little test jig , even for about two hours (so far) doesn't seem to heat anything up, and metering that, my most sensitive meter shows a fairly constant .0005 volt.... But with nothing but three feet of open air contacting the probes, that meter reads anywhere from +0.3 to -0.3 V.... So, I don't know what, if anything that .0005 V means, although directly shorting the probes together shows 0.0000 V.

I'll leave that LiIon 'shorted' through the test jig until something conclusive happens... and if something melts, explodes or anything otherwise interesting happens, I'll let you know. (Assuming I survive it   )

But in short the conductivity of Arctic Silver Adhesive is minimal... but possibly just enough to mess up a project if you get sloppy with it.

Here is what the MANUFACTURER  says about it:

*Negligible electrical conductivity: 
Arctic Silver Thermal Adhesive was formulated to conduct heat, not electricity.*_
NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause
problems if it bridged two close-proximity electrical paths._


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## HEY HEY ITS HENDO (Apr 2, 2006)

nemul said:


> Arctic Silver 5 is made with 99.9% pure micronized silver and will conduct electricity...


.........Hey nemul, you`ve raised a good question here, Arctic Silver 5 may well "include" silver, which is 99.9% pure, but Arctic Silver 5 does not contain 99.9% pure silver either by volume or weight, hmm !!




so the big question is, "how much silver does Arctic Silver 5 ACTUALLY contain"
.......... well i`ve checked out the website, and....

Quote, Arctic Silver 5 uses three unique shapes and sizes of pure silver particles

Quote,Arctic Silver 5 contains over 88% thermally Conductive filler by weight. In addition to micronized silver, 

....Nope, .... it dont say how much silver though!! ... (am i missing something?)


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## reefphilic (Apr 2, 2006)

One thing I couldn't understand is that the conductive epoxy that I've used contain silver particles and has a surprisingly good conductivity wherelse Artic Silver epoxy which also contain silver has such a low conductivity as observed by Silviron. :thinking:


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## Silviron (Apr 2, 2006)

I'm just guessing here; but there are some (moderately to pretty good) electrically conductive polymers... Maybe the actually electrically conductive epoxies use conductive polymers in combination with metal particles.


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## reefphilic (Apr 3, 2006)

Did some lab experiments on conductive polymer many years ago. Can't remember much but if I recall correctly. Conductive polymer has conductivities that is worst than the worst metallic conductors. 

The conductive epoxy that I've used has resistance of 0.1ohm when measured with the probes about 1-2cm apart. This is better than I've expected. Maybe conductive polymer technology has improved tremendously during these years.


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