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Old April 1, 2013, 02:42 PM
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Default Thermal basics : a.k.a. What thermal paste.....

This is a basic explanation of heat transfer , and how to make your cpu coolers etc. work more efficiently.I'll try to avoid the maths , but it's a complicated subject so bear with me.

This is a work in progress , as I think about it.

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Lesson #1 : The basic parts of a thermal system : The hot part and the cold part....Heat always goes from hot to cold.

The entire universe by it's very nature is constantly decaying into heat.Heat is abundant.

"Cold" is the absence of heat . You almost always require an input of energy to make "cold"....The 'net' energy always increases the 'heat' in the universe.

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(Yea , we are waaaaay past simple I know..)

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So back to cooling your CPU :

Lesson #2 : "Heat" is energy . Like any other energy source , it needs to be conducted.....Some pathways are better than others.

In the case of cooling a CPU , The heat moves from the CPU to the heatsink , and is conducted by the materials of both.(Ceramics and metals) .


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Old April 1, 2013, 02:46 PM
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Lesson #3 :

The most important part in a simple heat transfer like CPU to heatsink is the conduction path.Usually metal-to-metal.....Soooo , the important bit is "Surface area" .You want as much metal on metal contact as you can get.

There are a couple things that affect this ;

- 1 : Flatness.

- 2 : Smoothness.

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1:

Flatness means exactly that...Planar uniformity...."Flat" .....warped heatsinks are no good !! , on the same token , warped CPU's are bad too !

This is why 'lapping' works . "Lapping" is designed to make things flat....nowadays we can use milling machines to do the same , but the bottom line is this ;

If the CPU and heatsink are both truly flat , they will have more surface area for conduction.

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2:

"Smoothness" is basically the grit of sandpaper you used to make it 'flat'.

'Scraped flat' is a lot different than 'Optically flat'.....Once again we are just increasing the suface area.

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Old April 1, 2013, 02:46 PM
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Lesson #4

T.I.M. aka 'thermal interface material /gooop/thermal paste/etc'.....is the last .1 percent of the equation in the whole surface area thang.It's designed to fill the teeny scratches left from the "smoothening"


I assure you , optically flat/smooth heat paths need no tim.Skin oil would do it.

Thermal paste really isn't designed to fill large gaps.

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Lesson #5

Clamping pressure !!!

This is an often overlooked part of the equation . CPU clips are spring loaded for a reason.

Commercial semiconductors that require heatsinks are ususally done with a torque wrench....The 'compression' , once again increases surface area.

Always make sure things are clamped down , and even pressure is better than high pressure.

---


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Old April 1, 2013, 03:39 PM
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Lesson # 6 .

Interfaces.

Every time the heat has to move from one material to another (an 'interface' ), there are losses . In the case of CPU's , the heat goes from silicon to ceramic to metal......then you mount your heatsink.

This is why "De-lidding" / "IHS removal" works . You are eliminating 2 'interfaces'.

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Lesson # 7 ( ....and this is probably the important one !)

90% of the time , a basic off-the-shelf cooler will work ! No fuss , no bother !! Here's the thing : They have been over-engineered twice.

Unless you are trying for major OC's / etc.....You don't need anything else.Things like expensive heatsink compound are really a waste.

Unless that .01 percent matters to you of course.

That will be my last post.....the advanced stuff , for those who DO want that extra bit.

------

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Old April 2, 2013, 04:48 PM
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More stuff : (The advanced bits)

Materials/conductivity/etc

As I've said earlier , the "conduction path" for heat is the key , but some materials are better than others . A copper heatsink works faaaaaar better than an aluminum one . And a silver one would be better than copper.

Start here :

Thermal conductivity - Wikipedia, the free encyclopedia

It's at this point we're into custom engineering.

I'll throw up a bunch more links , and I would welcome critique from everyone !!

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Old April 2, 2013, 05:11 PM
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Quote:
Originally Posted by BrainEater View Post
Lesson #1 : The basic parts of a thermal system : The hot part and the cold part....Heat always goes from hot to cold.

The entire universe by it's very nature is constantly decaying into heat.Heat is abundant.

"Cold" is the absence of heat . You almost always require an input of energy to make "cold"....The 'net' energy always increases the 'heat' in the universe.
Just a minor niggle, but you have that backwards. The universe will eventually reach equilibrium and suffer what is known as heat death. So, entropy leads to a serious cold rather than an epic inferno.
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Old April 3, 2013, 03:59 PM
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Yep , you're right.....that's 'eventually' tho......right now the universe bleeds off as heat.

--

And more importantly , right now , all (mechanical ?.../ driven ? ) cooling on the planet earth is done with net gain on the 'heat side'.

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Old April 4, 2013, 04:46 PM
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I have been looking into delidding my 1090 but I'm prepared to replace it if things go south. Interested in trying? I still have to make sure my block will work without the lid tho... clearances etc.

cool post tho. cheers.
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Old April 5, 2013, 03:13 PM
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Thx bud !

I'm just trying to organize a decent set of links.

It's 'technically' a very complex subject , but it's not difficult when explained , that's my hope with this thread....

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Old October 23, 2013, 02:38 AM
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Quote:
Originally Posted by BrainEater View Post
A copper heatsink works faaaaaar better than an aluminum one . And a silver one would be better than copper.
Any reason why copper is used instead of silver on heat sinks? (material cost i guess)
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