Thermal Grease - vital or not?

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Mystery Man

New Member
I have just installed a new mothboard and CPU (an Intel dual core 2.2MHz).

There was no little tube of thermal grease supplied with the CPU, and no mention of it in the accompanying booklet, but the Motherboard manual says thermal grease should be used.

Is thermal grease absolutely necessary (the CPU won't be overclocked), or is it not vital with Intel chips (possibly because the accompanying fan has a pattern of metal contacts on it's base which connects with the CPU?)
 
Shane

Shane

Super Moderator
Staff member
if you got a Intel heatsink/fan with your processor then there should already be some Thermal paste on the bottom of teh heatsink.

and yes you do need it :)
 
M

Mystery Man

New Member
I don't think so, unless it's invisible! As I said, there is a kind of metal radial pattern, for want of a better description, on the base of the fan, which fits directly against the top of the CPU - thats the way the illustrations in the enclosed booklet show to connect it, with nothing to suggest thermal paste shuld be applied. The CPU is running at around 38 degrees Celsius, so I guess it is OK as it is.
 
F

funkysnair

VIP Member
tell us where you got it from and the exact model and some one might know if it comes with thermal paste as standard
 
J

jrm249

New Member
most retail processors do come with the paste on, i'd say you definitely need some.. as to which brand, doesn't make a whole heap of difference but people prefer to go with better grease if they are gonna OC.
 
O

oregon

Active Member
i'm pretty sure it won't hurt the cpu if you don't have thermal paste. you will just get temps much higher than you otherwise would, though probably still safe.
 
T

TrainTrackHack

VIP Member
^Umm...what??? You need at least SOME kind of thermal compound, be it a pad, paste or the pre-applied goo... otherwise, the HSF ain't gonna be much better than nothing.
 
Yeti

Yeti

VIP Member
Elimin8or said:
wanna know about how long your cpu will last with out thermal paste? like 10 seconds!!!!
Click to expand...

hackapelite said:
^Umm...what??? You need at least SOME kind of thermal compound, be it a pad, paste or the pre-applied goo... otherwise, the HSF ain't gonna be much better than nothing.
Click to expand...

Alright, though it isn't the smartest thing to do, running a computer without thermal paste won't fry the CPU under normal conditions.

A quick example - let's take a decent heat sink that has a temperature delta of 15C with a 60W load (i.e. if the ambient temperature is 25 C, the CPU is 40 C). That would mean that the heat sink has an overall resistance of 0.25 C/W. Now under a 100 KN/m2 contact pressure, copper has a contact resistance between 1E-4 and 10E-4 m2-C/W, and aluminum between 1.5E-4 and 5E-4 m2-C/W. For a square inch CPU (or more accurately its heat spreader) 100 KN/m2 translates to 14.5 pounds of force which is within the range of heat sink clamps. For a very conservative calculation we'll take 10E-4 C/W to be the contact resistance. The overall resistance then becomes 0.25 (for the heat sink) + (10E-4 m2-C/W)* 1 in2, which comes out to be 0.424 C/W. Using this as the new overall resistance the new temperature delta is 25.4 C. So if the computer was running at 40 C under 60W of load with a good heat sink setup, now it would run at 50.4 C - not the best, but far from critical. I should repeat, though, that I don't recommend running without thermal paste.
 
2048Megabytes

2048Megabytes

Active Member
Imsati posted this and I thought it was so good I copied it. Here's how a professional applies thermal paste to a processor:

As mentioned before, I have over clocked to begin with and I am overly-obsessed with certain things, thermal paste being one of them, oddly enough so I've stressed out about finding that 'perfect' application for a long time. First, take a good-quality thermal paste, such as Arctic Silver-5. Place a small amount on the processor and carefully spread it over the entire heat-shield (on the processor, not the actual heat sink).

The goal here is to make an even, thin layer, and the end result is no striations/lines. (You're done when you think you can barely see the heat-shield, but it might just be your eyes playing a trick - does that make sense?) My wife watched me spend 5 minutes one time making it perfect, so take your time with it. Now, re-seat the processor in the socket and lock it into place. Once it's in there, carefully put a BB-sized dab of additional thermal paste in the center of the processor. Gently place the heat sink over it and lock it into place very carefully. The pressure from it being locked will spread the BB-sized dab you placed evenly over the core of the central processing units heat-shield.

I let each method cure for a while and checked temperatures periodically. My Pentium D 940 Processor saw a 40 degrees Celsius Idle temperature. over the next 3-4 days it dropped to 34-37 degrees Celsius, and then maybe a week after that evened out to 31-32 degrees.
 
M

Mystery Man

New Member
I bought the CPU from Dabs.com - a brand new, still sealed Intel E2200 dual core processor... and the enclosed booklet, which used diagrams to show how to install it definitely makes no mention of thermal grease. The earlier poster who said that it was probably already on the bottom of the fan is probably right if it is so essential, but I am puzzled as to why direct metal to metal contact isn't just as good as with thermal grease - after all, metal conducts heat better than anything, surely?

As I said, the CPU is running at 39 degrees, so clearly doesn't seem to be having any overheating issues.

I will try to contact Intel directly, to see what they have to say on the subject.
 
M

Mystery Man

New Member
Just found this on Intel's web-site:

Thermal interface material (preapplied attached to the bottom of the heatsink) provides effective heat transfer from the processor to the fan heatsink.

Duh. Sorry for doubting you, Nevokanaza :)
 
T

TrainTrackHack

VIP Member
Yeti said:
A quick example - let's take a decent heat sink that has a temperature delta of 15C with a 60W load (i.e. if the ambient temperature is 25 C, the CPU is 40 C). That would mean that the heat sink has an overall resistance of 0.25 C/W. Now under a 100 KN/m2 contact pressure, copper has a contact resistance between 1E-4 and 10E-4 m2-C/W, and aluminum between 1.5E-4 and 5E-4 m2-C/W. For a square inch CPU (or more accurately its heat spreader) 100 KN/m2 translates to 14.5 pounds of force which is within the range of heat sink clamps. For a very conservative calculation we'll take 10E-4 C/W to be the contact resistance. The overall resistance then becomes 0.25 (for the heat sink) + (10E-4 m2-C/W)* 1 in2, which comes out to be 0.424 C/W. Using this as the new overall resistance the new temperature delta is 25.4 C. So if the computer was running at 40 C under 60W of load with a good heat sink setup, now it would run at 50.4 C - not the best, but far from critical. I should repeat, though, that I don't recommend running without thermal paste.
Click to expand...

Makes sense in theory, but you apparently forgot one critical factor - the heatsink never makes perfect contact with the CPU. The surface of the HSF or the CPU whatever (was it called shim? I'm referring to the metal piece on the die) is not perfectly even, it's full of microscopic scratches,holes, pits&whatnot. Even though in most cases these are invisible to the eye, these allow enough air (excellent insulator) between the heatsink and the CPU to - no matter how good contact they're making - effectively cripple all heat transfer.
 
Yeti

Yeti

VIP Member
hackapelite said:
Makes sense in theory, but you apparently forgot one critical factor - the heatsink never makes perfect contact with the CPU. The surface of the HSF or the CPU whatever (was it called shim? I'm referring to the metal piece on the die) is not perfectly even, it's full of microscopic scratches,holes, pits&whatnot. Even though in most cases these are invisible to the eye, these allow enough air (excellent insulator) between the heatsink and the CPU to - no matter how good contact they're making - effectively cripple all heat transfer.
Click to expand...
That's exactly what contact resistance is. What did you think I was calculating?

Vizy93 said:
i think my AMD manual thing mentioned that the cpu can fry itself in 10 seconds.
Click to expand...
Under what conditions?
 
T

TrainTrackHack

VIP Member
Yeti said:
That's exactly what contact resistance is. What did you think I was calculating?
Click to expand...

Oh well, I'm none too sure as to how to calculate this stuff, I thought you missed something. I read articles "contact resistance" and "thermal conductivity" on wikipedia, I think I'm clear (enough) on what you mean, though I doubt things work out this conveniently in real world. Not that I'd really care anyways, as long as you keep not recommending running without thermal paste, I'll be happy ;)
 
just a noob

just a noob

Well-Known Member
unless you can get a perfectly leveled heatsink and processor to make perfect contact, i would say you need it, but from what it sounds like you already have it, and your temperature isn't all that bad, my pentium 4 runs at around 45*C on load with thermalpaste, so your nowhere near the cpu frying itself
 
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