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Topic Title: Guide to Thermal Compound
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Created On: 06/04/2004 01:09 PM
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 06/04/2004 01:09 PM
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xamlit
Senior Member

Posts: 1206
Joined: 11/02/2003

Let me first start off by saying that this is not what to do:

http://home.comcast.net/~xamlit/errr.jpg' ">http://home.comcast.net/~xamlit/errr.jpg

One of the problems with transferring the heat between the processor and the heatsink has to do with the thermal interface. Neither the heatsink nor the processor has a completely smooth surface. This creates an air pocket between the heatsink and cpu and creates a very high thermal resistance. To alleviate this problem thermal compound was introduced. TC creates a conductable surface that fills in the imperfections in the metal between the cpu and heatsink creating a more efficient conductable interface leading to faster heat dissaption and lower cpu temps.

There are different types of thermal medians that are available on the market
including :

Thermal Tape - this is the most simplest type of thermal interface. It is very easy to use and dosen't require mounting bracks The down-side is that it is a very poor conductor.

Thermal Pad - this is found mostly on the heatsinks on retail cpu+fan packs. Thermal Pads does not adhere the heatsink to the cpu. It is in a solid state at first but as the cpu heats up it begins to melt and fills in the imperfections between the cpu and heatsink. Its pretty decent but definetly not the best.

Thermal Grease - the most common form of thermal grease is a simple metallic ceramic emulsified in synthetic oil or grease, typically silicone. Other forms can include materials such as micronized silver, boron nitride, aluminum and zinc oxides. The most common element that you will found in Thermal Grease is silver. Since it has a very low thermal resistance it is the ideal choice. This is the predominant choice of PC Builders. It is a non-messy alternative to other forms of compounds and allows re-application with out having to deal with any adhesion issues. It is viewed as the best thermal compound available.

Thermal Epoxy - very much like thermal grease except that it is mixed with an adhesion substance called resin. It is basicly has the same purpose of thermal tape but is presented in a different form.

Although the liquified form of thermal interface may be the choice of many PC Builders there are still risks involved. Some thermal compounds contain conductive material. If too much of that compound was applied to a cpu there is a possibility of it creating a unwanted circuit between the bridges on the cpu, thus causing damged to your processor. The picture posted above is a great example of that. If I were using a conductive form of thermal compound my processor would have been fryed /sad.gif' border='0' style='vertical-align:middle' alt='sad.gif' /> . But luckily I wasn't. /wink.gif' border='0' style='vertical-align:middle' alt='wink.gif' />

In terms of application of thermal grease there should only be a "rice size" amount on the die of your cpu. For the new Athlon 64 dies you should spread a zigzag amount of thermal compound across the die forming a Z with the compound. Too much or too little thermal interface material can lead to improper heat transfer... Either way your cpu temps are going to be rocketing through the roof!


It is important to also be aware of the fact that AMD only uses thermal pads on the retail heatsink and fans. Any other application of thermal interface material will render your warranty void!

Edit: For most of the new A64 cores they now cover the proper use of certain thermal compounds on their products like AS5. Be sure to confirm this for your own specific processor. I am not responsible for anything you do to over/under heat your processor. /excl.gif' border='0' style='vertical-align:middle' alt='excl.gif' /> So be careful! /excl.gif' border='0' style='vertical-align:middle' alt='excl.gif' />

I felt compelled to write this because as some of you might know in the forum I had many problems with thermal compound application. People here were very gracious enough to help me out. I wrote this because I thought everyone should know!
Any comments or suggestions? PM me.


Xamlit

Last Edited: Novemeber 14th, 05
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