With processors working at higher and higher clock speeds, a certain concern with thermal dissipation is necessary, because the higher the clock used, the higher the heat produced. To give you an idea, a 486DX2-66 dissipated something between 3 and 6 W, while a modern Pentium 4 processor with 3.8 GHz dissipates 115 W! In case you don’t adopt a thermal solution compatible with the specific model of processor you use in your system,
several problems can appear, such as random resets, freezes, reduction of processor lifespan, and it can even make the CPU burn, in extreme cases.
Several solutions were proposed in order to solve those problems, such as the elaboration of a new motherboard standard (the BTX standard was created to maximize air circulation inside the PC) and the launching of cases with ventilation ducts and liquid cooling systems.
But those solutions are still expensive and we are not always willing to pay for them. Those who work assembling and selling computers are aware of market problems and know how difficult it is to convince a client that the final cost of the computer got higher due to a better cooling system. In most times the client is not very interested in that and their only concern is the price.
But there’s a simple and cheap solution to be used with the right cooler for the specific model of processor installed, that can help reduce the problem of processor overheating: the use of thermal grease.
In this tutorial we’ll talk about the role of the thermal grease in the process of thermal dissipation, how to correctly use it and the most common mistakes made during thermal grease application.
What’s The Use of Thermal Grease?The device used to remove the processors heat is the cooler. Each processor requires a specific type of cooler. The use of an inefficient or wrongly dimensioned cooler can cause overheating problems.
But the cooler alone doesn’t solve the overheating problem. There’s another “bad guy” in the story: heat transfer between the processor and the cooler.
From the microscopical point of view, the physical contact between the processor and the cooler isn’t perfect. Imperfections that exist both on processor surface and cooler surface prevent the 100% perfect contact between them.
As both surfaces aren’t perfectly even, minuscule gaps of air are formed when putting them together. As air is a terrible heat conductor (its conductibility coefficient is 0.026 W/m°K), the heat will pass with more difficulty from the processor to the cooler, which can result in overheating.
Figure 1: Air gaps formed by the junction of processor and cooler.
To solve the problem and improve the heat transfer between the processor and the cooler, we should apply thermal grease between them in order to fill in the tiny gaps of air. By doing so, the heat transfer between the processor and the cooler is more easily made, since the thermal grease has higher conductibility coefficient than the air.
Figure 2: Gaps of air filled by thermal grease.
Thermal grease can be found in electronics parts stores and its use is indispensable. Besides, it’s a really cheap component.
On the next pages we will talk about how to correctly apply the thermal grease and also about the most common mistakes made when applying thermal grease.
The Thermal GreaseThe thermal grease is basically composed by silicone and zinc oxide, but there are more elaborate greases that can even contain ceramic and silver – noble materials that promise more efficiency in heat transmission.
Its price can range between P250 and P1,100, in the case of greases that have silver in their composition.
Thermal grease can be foundin many kinds of packages and usually come with the cooler. In Figure 3 you see some kinds of packages.
Figure 3: Many kinds of thermal greases.
There are also coolers which have some material applied from factory, it’s the case of coolers that come with the processor (“in-a-box”) or even some coolers sold alone found in the market.
In the case of coolers that come together with the processor and coolers of recognized brands, the quality of the material applied is usually good and both AMD and Intel recommend the use of those compounds.
Figure 4: Cooler in-a-box for Pentium 4 with thermal compound.
Figure 5: Cooler in-a-box for Athlon 64 with pre-applied grease.
Figure 6: Cooler in-a-box for AMD socket 462 processors with thermal compound.
All the compounds above are good quality ones and have better efficiency than regular thermal greases. If you bought a super thermal grease with silver, of course you should remove the original compound and apply the new grease instead.
But the use of those compounds “from the factory” has some inconveniences. The first one is that they can be used just once, i.e., if you remove the cooler for some reason, you’ll have to clean the old compound and apply the original one again – and it’s hard to be found – or apply thermal grease instead. Another very common problem is that the compound ends up sticking the heatsink to the processor, making cooler removal difficult.
In the case of Intel socket 478 and AMD sockets 754 or 939 processors it’s very common to pull the cooler and take out the processor fixed to the heatsink, something that ends up damaging the processor in most cases. The tip here is to use a hairdryer to heat the heatsink a little, in order to melt the thermal compound and then remove the heatsink with lateral movements. But don’t use the hairdryer too much.
There are also cheaper coolers hat come with a graphite square or thermal tape similar to gum, that are terrible heat conductors. In this case you should remove those compounds and apply thermal grease instead.
Figure 7: Cooler for Socket 7 with graphite compound you should remove.
Many people believe that the more thermal grease, the better. But a lot of grease turns out to be insulating, not to mention that grease in excess ends up dropping and reaching motherboard contacts. Remember that most greases don’t conduct electricity, but there are greases that take metal in their composition, which turn them into conductors, and this may cause short circuit and destroy your equipment.
We will show in details how to apply thermal grease on several kinds of processors.
In case the processor and/or cooler have thermal on them, you should remove it before applying a new thermal grease.
In Figure 8 you see the case of a Sempron processor that was originally mounted with a cooler that already had thermal compound.
Figure 8: Sempron processor with remains of thermal compound.
In this case you first have to clean the rests of thermal compound. Use a cotton swab with isopropyl alcohol (isopropanol). This kind of alcohol is purer (doesn’t contain water) and can be found at electronics equipments stores or drugstores.
Figure 9: Clean all the remains of thermal compound.
Figure 10: The processor is clean and ready to receive the thermal grease.
You can also clean the rests of thermal compound that remained on the heatsink. We used an utility knife to rub out the rests of the compound, being careful not to scratch the cooler base. To finish, use a piece of cloth with isopropyl alcohol (isopropanol) to remove the rests of thermal compound.
Figure 11: Cooler with rests of thermal compound.
Figure 12: With a utility knife, rub out the rests of compound.
Figure 13: Final cleaning.
Figure 14: Cooler ready to be installed.
With all remains of thermal compound removed, you can now apply the new thermal grease.
Socket 462 ProcessorsSocket 462 is used by Athlon, Athlon XP, Duron and Sempron socket 462 processors and its fixation is similar to that of older processors (Pentium, Pentium III, Celeron and AMD K6), therefore the next instructions also work for those old processors.
Using a cotton swab, put a small amount of thermal grease on the processor. Don’t put too much grease, because the excess can make the heat transfer worse instead of better.
Figure 15: Apply a small amount of grease on the processor.
Don’t worry about covering the whole area of the processor (pink part) because the cooler pressure itself will make it uniform.
Figure 16: Correct amount of thermal grease.
Next, carefully install the cooler over the processor. Notice that socket 462 has a side bigger than the other: the side next to the processor installation lever is larger than the opposite side. Coolers for socket 462 will also have a side bigger than the other. If you pay attention, one of the sides of the lock that fixes the cooler to the socket is longer than the other. Therefore the longer side should be facing the larger side of the socket (the side of the lever), while the shorter side should be facing the smaller side of the socket.
A common mistake when installing coolers on socket 462 processors is installing the cooler “inverted”, i.e., rotating 180ยบ in relation to its correct position.
In some PC cases it may be necessary to remove the motherboard in order to install everything with no problems.
Figure 17: Put in position and fix one side.
Then, using a screwdriver, fix the cooler. Use the screwdriver as a lever to fix the cooler clip to the socket. Don’t make excessive pressure on the cooler to avoid damages to the processor. Be careful not to let the screwdriver slip and hit the motherboard.
Figure 18: Finishing the cooler fixation.
After fixing the cooler, connect the fan power plug.
Figure 19: Cooler correctly installed.
Socket 754 and 939 Processors
Sockets 754 and 939 are used by Sempron socket 754, Athlon 64, Athlon 64 FX and Athlon 64 X2 processors.
First make sure both surfaces – of processor and cooler - are clean and free from impurities, as we show in Figure 20.
Figure 20: Processor ready to receive the thermal grease.
Using a small spatula (which can be made out by cutting a piece of the hard transparent plastic from the processor box), apply some thermal grease on the center of the processor. Don’t worry about covering the whole processor area because the cooler pressure will make it uniform. See Figures 21 and 22.
Figure 21: Applying the thermal grease.
Figure 22: Correct amount of thermal grease. The arrows indicate where you should fix the cooler.
Socket 754 and 939 Processors (Cont'd)
After applying the thermal grease, you should obviously install the cooler. The process is relatively simple and doesn’t require the use of tools. Just fix the cooler and close its rotative lock, as we show in the pictures below.
Figure 23: Position and fix one side.
Figure 24: Fix the other side and close the lock.
Figure 25: Pull the lock to the end.
Figure 26: Cooler locked.
After installing the cooler over the processor, install the cooler power plug to the motherboard.
Figure 27: Connect the fan wire.
That’s it, the thermal grease is correctly applied and your cooler is installed.
Socket 478 Processors
Socket 478 is used by the older Pentium 4 and Celeron socket 478 models. The process of applying thermal grease to those processors is similar to the process of socket 754 and 939 processors.
First make sure the processor surface is completely clean and free from dirt and remains of thermal grease form past applications, see Figure 28.
Figure 28: Checking if the processor surface is clean.
Using a small spatula (which can be made out by cutting a piece of the hard transparent plastic from the processor box), apply some thermal grease on the center of the processor. Don’t worry about covering the whole processor area because the cooler pressure will make it uniform. See Figures 29 and 30.
Figure 29: Applying the thermal grease.
Figure 30: Thermal grease correctly applied.
The next step is to install the cooler over the processor, of course.
Socket 478 Processors (Cont.)
To install the cooler, just place it over the processor and press it for the thermal grease to spread correctly.
Figure 31: Installing the cooler.
Next, move the cooler lever back and forth. This will move the four cooler hooks in such a way to make them connect to the four supports on the motherboard. See Figures 32 and 33.
Figure 32: Moving the cooler lever.
Figure 33: Move the cooler lever to the end.
Then, install the fan power plug to the motherboard and that’s it, the thermal grease will be applied and the cooler installed.
Figure 34: Installing the fan plug.
Socket 775 Processors
Socket 775 is used by Pentium 4, Pentium D and Celeron D processors. The way of fixation is very different from other types of processors. In socket 775 the pins are on the motherboard and not on the processor, that’s why the motherboard officially supports only twenty installation and removal operations. After that, there’s no guarantee that the board will work properly. So, don’t unnecessarily remove your socket 775 processor from the motherboard!
First make sure both surfaces – of processor and cooler - are clean and free from impurities and that the processor is well installed.
Figure 35: Processor ready to receive the thermal grease.
Using a small spatula (which can be made out by cutting a piece of the hard transparent plastic from the processor box), apply some thermal grease on the center of the processor. Don’t worry about covering the whole processor area because the cooler pressure will make it uniform.
Figure 36: Applying the thermal grease.
Next, install the processor cooler, as we’ll show on the next page.
Socket 775 Processors (Cont.)
The cooler must be aligned to the four holes located on the motherboard.
Figure 37: Installing the cooler.
After putting the cooler over the processor, you should “close” all the cooler locks by using a screwdriver. Observe Figure 38 to know the correct position. The arrow must face the outer side and the notch of the white part must touch the black support.
Figure 38: Lock in the correct position.
You should press the locks two-by-two, diagonally.
Figure 39: Locking the cooler on one side.
Figure 40: Locking the cooler on the other side.
It’s very important to check if the cooler really is well fixed and if all the locks are in the correct position.
Figure 41: Cooler correctly installed.
Most Common Mistakes
Every day in our labs we see many different mistakes regarding cooler installation and use of thermal grease.
The most common is using too much thermal grease. Excess of thermal grease spoils the correct heat dissipation, besides the possibility of drop to the outside and putting the system in danger.
Processors that have exposed components, such as the Athlon XP, can be subject to short circuits if the thermal grease closes the contact of its bridges or of the exposed components, such as capacitors and resistors.
In the processor in Figure 42, besides the excess of thermal grease, someone stuck a warranty seal right on top of the processor rubber pads that support the cooler. The thickness of that seal increases the pressure on top of the processor, and this pressure can break it.
Figure 42: Duron with too much thermal grease and seal covering the rubber pads.
Another very common mistake are the warranty seals placed on the contact part between the heatsink and the processor. Don’t accept processors with seals covering it. If you have a processor with a seal on its top, remove it right away.
The processor in Figure 43 is a poor 200 MHz Pentium MMX. Besides the seal covering practically the whole contact area between the processor and the heatsink, it was also using the cooler in Figure 7, that uses graphite as heat conductor.
Figure 43: Seal covering practically all the processor.
Other problems that we frequently see are broken processors – mainly Athlon XP and Sempron socket 462 processors – due to mistakes during cooler installation (putting the cooler at the wrong position or using too much strength when fixing the cooler) and people that substitute the thermal grease to toothpaste, liquid silicone, olive oil, glue, etc. Believe us, it happens!
Figure 44: Socket 462 cooler installed in the wrong position.
Figure 45: Processor damaged due to bad cooler mounting.
SOURCE:
http://www.hardwaresecrets.com/article/274/12
