What is the difference between heat sink compound and themalgrease? 1

[farley99]

What is the difference between heat sink compound and themalgrease?

Is it better to use one or the other? Can both be used?

 

[Cluttermagnet]

The two terms are used pretty much interchangeably, so far as I have seen. That being said, there are a couple of different types. The more basic compound is a silicone-based gel that comes in a tube and is semi-transparent. It does help increase heat conduction between a heat source (IC) and a heat sink. The 'better' stuff also comes in a tube and is white in color. As I remember, they have added some zinc oxide to the basic silicone type that makes it even better at conducting heat across the tiny gaps you always have between any two 'flat' surfaces.

Use the compound by applying a thin, even coat to both mating surfaces. If you ever remove and then replace a heatsink from the same IC, it is a very good idea to clean off both surfaces and apply a fresh coat of the compound to each before remating them.

 

[red54]

Additionally, if it is the cpu you are putting this under, make sure that the compound doesn't overflow onto the pins of the ic. Had this happen on one and couldn't get it to run a full speed. Once it was cleaned it worked fine.

Time flies when you don't know what you're doing...

 

[dakota81]

A note, you want very little grease between the cpu & heatsink. Just a small dab of grease in the middle of the cpu is all you need, the pressure of the heatsink pushing onto the cpu will spread out the grease. Reasons are, first you don't want grease leaking off the cpu die, and secondly the grease is actually worse at transfering heat than a solid metal to metal contact; the grease is there to fill in the imperfections on the surfaces of the heatsink & cpu where it would otherwise be very small air pockets between the surfaces.

 

[Cluttermagnet]

As I mentioned before, both mating surfaces should be coated with a thin even coat of heatsink compound. With a thin coat, there would be no danger of any excess getting into the IC pins area. I would not rely on most heatsink mounting methods to cause a 'blob' of the material centered in the middle of the CPU to spread out and coat all surface areas uniformly. This has been especially true with my tube of Thermalloy Z9, which is the white, zinc oxide type. It comes out of the tube fairly thick. I have found it is best to start with a small blob in the middle of each surface (both CPU and heatsink) and by using a patting motion with the forefinger, gradually cause the material to spread out and uniformly cover the entire surface with a fairly thin film. I think it is very important to make sure to coat both mating surfaces. The thermal conductivity of any IC/CPU surface area not coated with the compound should be, by all rights, significantly lower, and this can only harm cooling overall. The key here is to keep the coating thin. Too thick might be as bad as none at all.