How To Fit and Change a Heat Sink and Fan (HSF)
In an attempt to keep cool, Ian Waugh finds another use for cotton buds and Isopropyl Alcohol…
You will doubtless be aware that computer processors such as the CPU (Central Processing Unit) and GPU (Graphics Processing Unit) generate a lot of heat. As they work harder, they generate increasing amounts of heat. If they become too hot they can get damaged or performance can become unstable. Which is why it's important to keep them cool.
Most PCs use a combination of a heat sinks and fans (HSF) to cool the CPU and other parts of the computer system. Water cooling is becoming increasingly popular, particularly among overclockers, but it's not without its dangers and we aren't looking at it here.
Building a new PC gave us the opportunity to try a couple of cooling options for the AMD Phenom 9600 CPU - the Akasa Lo-Noise Cooler and Arctic Cooler's Freezer 64 Pro (opens in new window).
Installing a HSF should be a straightforward business but you need to take precautions so we'll run through the basics here.
Safety first
First of all, if you're messing around inside your PC, make sure it's switched off!
Secondly, you need to ground yourself to protect the PC's innards from the ravages of static electricity. You can ground yourself by keeping the mains plug in and touching the PC's chassis but many people prefer to pull out the plug and use an anti-static wrist strap such as Lindy's Anti Static Service Kit
If you're fitting the HSF before the motherboard has been installed in the case, your job will be easier but the principle is the same.
Many HSFs come with thermal compound already on the base but if it doesn't, you need to apply some. The compound forms a close join between the HSF and the CPU so the heat is evenly distributed and whisked away through the sink and fan. It's not a glue. The paste fills the small valleys and troughs on the surfaces of the CPU and HSF (at a microscopic level) so there is a gap-free connection between the two.
First, ensure that the CPU is clean and dust-free. You could even clean it with a little isopropyl alcohol (see below for details).
Apply only a small amount of thermal compound, about 1.5mm (some say the size of a screw head or one-and-a-half grains of rice).
Too much paste and the heat transfer will not be good as it acts as an insulator. Too little and there will not be a good contact and the CPU will get too hot. A little goes a long way, and the HSF clamps ensure the two components fit together very tightly.
If you're not sure about the quantity, you can clamp the two parts together and then release them and check how well the compound has spread.
Fitting the HSF
The actual fitting of the HSF varies from one CPU and socket to another. Some HSFs simply clip over the CPU while others may connect to a backing plate. As ever, you should read the instructions that come with the unit.
When fitting the HSF, make sure the fan is blowing the right way. This will usually be towards the rear of the case, assuming the rear fan is blowing air out of the PC. Some cases may be set up differently and expel air through the front so check.
The fan on some HSFs simply blow air away from the heat sink, effectively into the side of the case, so in this case, orientation is probably not an issue.
Removing a HSF
If you want to put a new HSF on a CPU, you need to remove the old HSF first. Undo the clamps or clips and gently twist the HSF left and right, just a little, to loosen the thermal compound and free it from the CPU as you lift it. Don't simply pull it upwards as you may damage the processor or board.
Next, you need to remove the old thermal compound from the CPU. Do this carefully with cotton buds, tissues, and isopropyl alcohol (sometimes called rubbing alcohol). Isopropyl alcohol evaporates quickly, leaving a clean, dry surface and is ideal for cleaning electrical components. It is very flammable, though, so take care with its use.
And that's basically it!
After booting your PC, check the CPU's temperature either in the BIOS or with a monitoring application such as HWMonitor www.cpuid.com/hwmonitor.php.
If the temperature seems abnormally high, the HSF may not be properly secured onto the CPU so switch off and check the clamps or clips.
It's also possible that you've used too much or too little thermal compound in which case you'll have to remove the HSF to fix it. You should be able to tell by looking at the distribution of the compound on both surfaces. It should be thin and evenly distributed on both.
Reseat the HSF, reboot and check the temperature again.
Finally, while it's generally okay to leave the side or front off the case while installing and checking components, you will usually get much better air flow if you close the case.
