Originally posted by: movingincircles
noob here, never applied thermal paste
any souls want to point me to a 101 tutorial?
I don't know how far you've got with your problem... Just a few points:
Your stock heatsink probably had some acrylic phasechange heatinterface material on it. That's fine, but only good for one mounting. If you remount the heatsink, remains must be gently removed with the help of isopropyl alcohol. Oh, - and don't pull off the heatsink with lots of force! Twist it a very little, patiently, until it releases.
Temperatures into 70C with Prescotts seem almost "normal". But not desirable. However, I've surrendered to the view that you have to let them go up to ~66C. So set your shutoff higher than 60C. 60C shutoff is a bit unreasonable with a Prescott. This may solve your problem.
What can you do to get temperatures down? Copper! Normally, Aluminum is fine and on a low power CPU copper won't make much of a difference. But copper makes a good deal difference for a really hot CPU.
The nature of cpu cooling is like this:
CPU(temp4)--Paste.transport--
Heatsink.Base(temp3)--Heatsink.transport--
Heatsink.Fins(temp2)--transfer--
Cooling air(temp1).
A certain power output (energy/time) of heat has to be transported through this chain. If we consider the case of sustained CPU load for 40 minutes or more, the temperatures along this chain will have stabilized. So that the energy/time that is transfered to air, by temp2-temp1, is equal to the energy/time that is output by the CPU!
The energy transfer is driven by the difference between temp2 and temp1. So temp2 will increase until the difference is high enough to drive the transfer of the full power output. More power, requires a higher temperature difference to drive the transfer of more energy/time.
The very same then applies to the transport through the heatsink. Temp3 will rise until the temp3-temp2 difference is high enough to transport the energy. It's like you have water tube, and need to transport a certain volume of water through it per minute. You will need to increase the pressure at the input end until you get the sufficient flow. Here's where the copper comes in. Copper is a wider gauge tube. So it will require less pressure to accomplish the required flow.
Aluminum is a very good heat conductor. It's thermal conductivity is 238 W/mK.
But copper is much better. Coppers conductivity is 400 W/mK.
So with copper, we will have a lower temp3-temp2 difference driving the energy transport.
The same thing again then applies to the interphase paste layer, temp4-temp3.
The entire chain is fixed from the outside, temp1! We then desire the least *steep* temperature ladder possible, to arrive at a low CPU temperature, temp4.
The thing you can do about temp1 is sufficient airflow through the case.
The thing you can do about the temp2-temp1 step, is a more vigorous airflow, higher CPU-fan speed.
The thing you can do about step temp3-temp2 is copper and/or clever design, minimizing transport distance.
The thing you can do about step temp4-temp3 is to get the thermal paste layer right, which basically is as thin as possible.
Arctic Silver 5 is a fantastic paste in terms of thermal conductivity. However, it is not possible to get AS5 very, very thin. Which is why, with very smooth and flat surfaces on heatsink and CPU-heatspreader, white silicon paste is preferable. Personally I think it's easier to apply as well, but that might just be habit. You should be able to get silicon paste many times thinner than AS5, and AS5 is not good enough to make up for that. If you need to fill gaps however, AS5 is outstanding.
I have made a little spatula, cut from an old plastic membership card. It takes very little silicon paste, maybe 1/4 - 1/3 of a ricegrain. But I usually get too much, (ketchup) so I don't have a real check. I then carefully spread it on the CPU, very, very thin and as evenly as I can get it, with the spatula. It's somewhat delicate work. It should be thinner than you think it should be
🙂
Arctic Silver have instructions on their website, for applying AS5. I think you basically leave a glob on the cpu and squeeze it out with the heatsink, but you should check.
Copper has an additional advantage. It has fantastic thermal capacity, so it works like a 'reservoir' of cooling. With shorter durations of power output, temp3 will rise slowly and maybe never reach the sustained level. If the cpu temperature is a curve with tops and valleys, copper will smooth that curve, cutting off the tops.
Pitfalls:
Thermal pastes are usually quite toxic, straight through the skin! So don't touch the stuff! (If it weren't for the very special purposes, the stuff probably wouldn't be legal.)
Copper heatsinks are actually *too heavy*. You should avoid transporting your PC, and take great care not to subject it to any bumbs.
Zalman 7000 AlCu is a good compromise. It has copper through the center, where it's most critical, and achieves lower weight through use of Aluminum for the rest.
(Also, in my experience, good heatsink design, are those 'conventional' looking ones, that have a wide bottom copperbase that distributes and transports the heat to the bases of the aluminum fins.)
