Heatsink Paste vs Dielectric Grease

[Bob_Roller]

I installed a Dyna brown coil on the '84 LS yesterday, to replace the non-OEM coil that was installed on the bike .

When I placed the order with Motorrad Elektrik, I ordered a tube of 'heat-sink paste', but after looking at it closely, it is in reality dielectric grease .

I've used Dow Corning DC-4 dielectric grease on the "81 R65 ICU heat-sink, for about 25 years, with no ill results so far .

So are the two materials interchangeable ?

[MrRiden]

Different. Dielectric grease is meant to lubricate & seal while being non conductive [electrically]. Heat sink paste is meant to transfer heat and eliminate hot / cold spots. I have some here I think, left over from building a few PCs. I could run it over tomorrow or hit the local Radio Shack for a tube. They are really meant for different purposes.
rich
who uses both at werk

[Barry]

I agree with MrRiden the two things are intended for different purposes and you should probably use the right stuff if you can get it.

However that doesn't mean dielectric grease won't work.

Heat transfer paste is a big topic in the computer world (and a big money spinner). I'm reminded of the guy who tested the heat transfer coefficient of various cheap and expensive exotic compounds and found little difference in performance. He also tested Marmite and toothpaste and they worked just as well as the expensive stuff at least in the short term until they dried out. And that I think is the clue to why you have used dielectric grease with success. If it doesn't dry out and provided its only a thin film I wouldn't be suprised if it works just fine.

[Bob_Roller]

I was just a bit surprised to see that the product that I got was dielectric grease, when it was shown as heat sink paste .

I thought, this time I'm going to do it right !!!!

I'm going to send the owner of Motorrad Elektrik an email Monday, and see what his comment is on this subject .

I figured dielectric grease was a suitable substitute, as I've been using it since I moved to Phoenix 16 years ago, and if anyone should develop problems I should, for the extreme heat environment my R65 operates in .

[MrRiden]

No quarrel with what Barry said. If you wanted to experiment I'd bet even some copper foil from the hobby shop would make a good heat transfer substitute behind the icu.

[nhmaf]

Heatsink paste (the good stuff anyway) general has a high silicon (not silicone) content and is designed to conduct heat well and fill small voids/imperfections between (2) surfaces to facilitate heat transfer and surface area.    It is generally much more solid in particle content (hence it is called "paste" not "grease") and is not supposed to change its conductivity over time as it may dry out slightly.   Dielectric grease is designed to be very non-conductive (electrically speaking) which tends to make it less thermally conductive.  Its thermal conduction properties change more dramatically over time as it dries out, but it's primary purpose is to prevent corrosion to exposed electrical contacts, which it does well.

you've been basically lucky in that you've changed the dielectric grease often enough, or things haven't gotten hot enough where the differences made much difference.   In many applications, using the wrong material will definitely cause semiconductor junction temperatures to rise above the failure point, with subsequent (Expected) failure.

I highly recommend that you drop by a local computer store or radio shack (in the USofA anyway) and pick up a $2.50 tube of heatsink paste for the back of your ICU.

[montmil]

I'm in the "them's two different birds" camp. Dielectric Grease and Heat Sink Paste are not the same. On the other hand, I trust Rick Jones at Motoraad Elektrik 100 percent. So. . . perhaps they might serve the same purpose?

Just today, on Airheads, there's a lengthy forum conversation on just this topic along with other grease types and uses. Several Airheads "of note" state that dielectric grease works on the ICU and aluminum heat sink mating surfaces.

I'm sticking with the Radio Shack variety. I believe the consistency of the material plus the paste stays "workable" for an extended time; as in years.

"Sticking with"... paste... get it? Monte made a pun.

[Justin B.]

Rick might have shipped the wrong stuff...

[Bob_Roller]

I checked the Motorrad Elektrik website, and it is stated, that it is dielectric grease, and continues to say that it is used for the ICU to prevent overheating .

So I got it wrong !!!

But to further complicate this thread, I went to the Radio Shack website, and came up with four products, silicone heat sink paste, super thermal grease, silicone heat sink grease, and silver thermal compound .

So my best guess is, if you renew whatever you apply, say once a year, it will probably work in most cases .

[beemer]

Ive used Copper Grease,and it works well,you know, the stuff they use on car brake pads to remove heat,and stop the brakes sqealing.

[Justin B.]

The different compounds have different heat transfer characteristics.

[nhmaf]

I guess that I am wondering how people are qualifying the "it works well". statement(s).   Is it just because the ICU didn't fail/become faulty due to overheating?

[beemer]

I guess that I am wondering how people are qualifying the "it works well". statement(s).   Is it just because the ICU didn't fail/become faulty due to overheating?

Well let's just say"it does what it says on the tin"

[nhmaf]

I'll stick with heatsink paste for heatsink interfaces, and dielectric grease for battery terminals, etc.    I have test data on heatsink paste and other interface materials effectiveness on higher powered electronics which I've designed and I am comfortable with.   I think that if the ICU was trying to dissipate more than 30Watts per sq inch of interface area the differences in material properties would soon become much more obvious.

[Bob_Roller]

Went to Radio Shack today, and got heat sink paste, going to put it on the ICU heat sinks of both R65's this afternoon .