Basic Air Cooling Guide

**Jester** · May 8th, 2010

Aftermarket CPU cooling solutions are often skipped, since both Intel and AMD include their own heat sink. While it is true that the stock heat sink will do for stock CPU clocks, many of us have the urge to overclock, especially if your CPU is bottlenecking your graphics solution. Aftermarket CPU heat sinks can be purchased for a low price, and they're much better than the standard cooling solutions.

There are many choices when it comes to third party CPU cooling solution. You have a variety of brand names such as Arctic Cooling, Cooler Master, Prolimatech, Thermalright, Thermaltake, Zalman, and much more. Many CPU coolers differ in construction and functionality. So here I will go over the basics and help you choose a good product.

What Should I Look for in a CPU Heat Sink?

A good construction is a must. CPU heat sinks are comprised of several key components.

Base - The base of the heat sink is placed directly onto the CPU, absorbs the heat from the CPU, and the heat is then carried away by heat pipes. The base is usually made of copper, since copper isn't very expensive and it conducts heat exceptionally well. Silver conducts heat even better, but you won't find a heat sink that has a silver base.

You want a base to be as flat as possible, so that it can make the best contact with the CPU. You don't want the base to have a rough surface, it will harm performance. A flat, smooth, and shiny surface is what you want.

Many heat sinks are starting to use HDT technology. HDT stands for "heat-pipe direct touch". With this design, there is no solid base. The base is actually just the heat pipes of the cooler, but flattened around the base. The heat pipes function as the base. This design is used to cut costs. With HDT technology, the base is never as flat as a normal base, and HDT coolers tend to have a rough base.

Many enthusiasts lap their heat sink and CPU. Lapping is the flattening and smoothening of the surface, using various types of sand paper and smoothing it down. However, this can go wrong and it voids your warranty. Good lapping jobs offer good performance. I've never done this myself.

Example of a good base on a stock heat sink (Thermalright Venemous-X).

Heat Pipes - Heat pipes carry the heat away from the base. They are usually made out of copper so that the heat can be transferred quickly. Aftermarket CPU heat sinks in a tower form factor tend to have between 3 and 6 heat pipes, but of course there are exceptions. The diameter of heat pipes are usually 6mm, but again there are exceptions.

The more heat pipes the better. More heat pipes means more heat can be transferred.

You want heat pipes to be somewhat exposed, so that cool air can cool off the heat pipes. But more importantly, you want the heat pipes to make contact with the fins quickly. Copper can absorb heat very well, but fins are what dissipate heat. You don't want heat trapped in your heat pipes.

On some coolers such as the Prolimatech Megahalems, the heat pipes form a straight line. This is not desirable as they are not exposed to much air from the fan(s), so heat dissipation is slower. This also utilizes a very small amount of fin space. On other coolers, the heat pipes form two lines. This is better than the previous method as more fin space is utilized and the heat pipes have greater exposure. However Cooler Master has debuted a new heat pipe arrangement on their V6 and V6 GT coolers. The heat pipes form a V shape which allows each heat pipe to be exposed to air from the fans, resulting in better heat dissipation than the previous method. This also allows more fin space to be utilized.

Here is such a heat pipe design, the cooler shown is the Cooler Master V6 GT.

Fins - Well, I just told you what fins are made for. They're meant to dissipate the heat from the CPU. Fins are almost always constructed out of aluminum, since it is lightweight, cheap, and lasts long. While copper absorbs and transfers heat better, it is more costly and heavier. Fans are mounted to the fins, so that the heat is blown off the fins and out of the case.

There are two generic fin designs. The first is a widely spaced design. Heat sinks with widely spaced fins have less fins, but more space between them. This design is used so that the cooler can function well with low CFM (quiet) fans. With more space between the fins, it is easier for air to pass through.

The other fin type is a dense fin design. Heat sinks with dense fins have more fins, therefore less space between them. This way it is harder for air to pass through, so louder and more powerful fans are necessary. The advantage to this design is that the increased amount of fins means more heat can be dissipated. I prefer this design since I don't care for noise, I care for best cooling. This design is only really necessary for CPUs that have four or more cores. A heat sink of this design will allow more overclocking headroom.

A higher fin surface area results in greater heat dissipation. Heat sink manufacturers increase the fin surface area in several different ways. One way is adding more fins, and the positives and negatives of doing so is discussed above. Another way is increasing the density of the fins, making them more thick. The positives to this are that thicker fins can hold more heat, but this also makes it harder for air to pass through the heat sink body, once again making higher pressure and CFM fans more necessary, which brings on additional noise. Several cooler manufacturers such as Thermalright and recently Cooler Master have found away to increase fin surface area in a much more efficient way. This way has no drawbacks. They angle the fins slightly, which increases the surface area of the total fin space but does not restrict airflow or increase size. Thermalright used this design for a long time - look back at the Ultra 120 and Ultra 120 EXTREME heat sinks. The design carried over to their Venomous-X heat sink and their Cogage Arrow, which is an updated IFX-14. Cooler Master uses this design on their V6 and V6 GT coolers.

So you want a CPU cooler that has a copper base, copper heat pipes, and a fin design which fits your needs. That's not all. You want a heat sink that has good soldering, therefore increased rigidity and durability. You don't want your nice new heat sink falling apart, do you?

Many heat sinks have nickel plating all over the heat sink. This is done to preserve the copper and aluminum, so that the cooler will last longer. The downside is increased cost.

Widely spaced fin design. Cooler shown is the Noctua NH-U12P.

Dense fin design. Cooler shown is the Thermalright IFX-14.

A typical 120mm heat sink with a widely spaced fin design has around 48 fins. A typical 120mm heat sink with a dense fin design has about 56 fins.

Don't overlook the mounting system of a CPU cooler. Not only does a mounting system make installation simpler or more difficult, but the pressure that a mounting system provides affects performance as well. A high pressure mounting system offers the best performance.

What About Thermal Paste?

Thermal paste, also known as TIM (thermal interface management) is a necessity for air cooling, water cooling, and even extreme cooling. You see, when a heat sink (or water block) is mounted to a component, there will always be space between the component and the base of the heat sink. The space is of course filled with air. Air doesn't transfer heat well at all, so you need something to fill the gap between the heat sink and the component. That's where TIM fits in.

Thermal paste fills in the gap between the base and the component. So thermal paste must conduct heat well. A more thin paste is preferred for flat surfaces, since it is easier to apply. For more rough surfaces you will need something a little bit thicker to fill in all of the spaces. You don't want a paste that is electrically conductive (duh, I don't know of any such TIM anyway) or electrically capacitive (has the ability to hold an electric charge).

Thermal pastes require a curing time - a break in period before they perform well. Many pastes require a long period of time to perform well (up to 200 hours). Others have no curing time and perform well immediately.

There are many different thermal pastes to choose from. The basic types of thermal pastes are covered here.

Here are the popular and best choices, and my opinion on them (after reading reviews, and after personal experience for some of them).

Arctic Cooling MX-2 - Aluminum oxide based, not electrically capacitive, thin so easy to apply, no curing time required.
Arctic Cooling MX-3 - Aluminum oxide based, not electrically capacitive, slightly thicker than MX-2, no curing time required. Performs slightly better than MX-2.
Arctic Silver 5 - Polysynthetic silver based, electrically capacitive, moderate viscosity, 200 hour curing time required.
Arctic Silver Ceramique - Zinc oxide based, not electrically capacitive, thick so more difficult to apply, 25 hour curing time required.
Cooler Master ThermalFusion 400 - Aluminum oxide based, not electrically capacitive, moderate to thick viscosity, no curing time required.
IC Diamond 7 Carat - Carbon and aluminum oxide based, not electrically capacitive, thick so more difficult to apply, no curing time required.
IC Diamond 24 Carat - Carbon and aluminum oxide based, not electrically capacitive, thick so more difficult to apply, no curing time required.
OCZ Freeze - Aluminum Oxide based, not electrically capacitive, thin so easy to apply, no curing time required.
Shin-Etsu MicroSi G751 - Aluminum oxide based, not electrically capacitive, moderate viscosity, no curing time required.

The difference between the above pastes in terms of performance is small, no more than a few degrees. I have tested Arctic Silver 5, Arctic Cooling MX-2, and OCZ Freeze. OCZ Freeze was the best performer, followed by AC MX-2. I will be trying AC MX-3 next.

You can compensate for thick pastes. Close the syringe or tube, and put it in a hot cup of water (not boiled, just hot). Let it sit for a little while and it should be thinner.

Here is a review of 80 thermal pastes, all of the above pastes were tested except for AC MX-3 since it is the newest.

http://benchmarkreviews.com/index.ph...=150&Itemid=62

How to Clean Off Thermal Paste and Prepare a Surface for Thermal Paste

Before applying thermal paste, you want the heat sink (or water block) and the component cleaned off, looking brand new. You don't want to clean off the parts using paper towels or anything too rough. What you want to use are cotton swabs, q-tips, and perhaps tooth picks to clean off remainders in tight spots.

To clean off TIM, you want to use high percentage alcohol or ArctiClean. High percentage alcohol works far better than lower percentage, and ArctiClean is a great product by Arctic Silver. It works better than alcohol, and it can clean off a surface and prepare it. If you use alcohol, you want to let the surfaces dry before application.

ArctiClean is rather cheap too, but more expensive than alcohol. LINK

The application of thermal paste depends on the type of heat sink and surfaces used. For a standard heat sink (no HDT), the best method is to put a small rice-grain sized drop of TIM onto the CPU, not the heat sink. Then put the heat sink directly on top of the CPU. It will spread it out best by itself.

For HDT coolers, the best method is to put a rice-grain sized drop in between the heat pipes, and then put it onto the CPU.

It spreads out looking like this.

For GPUs, the best way to apply TIM is to put paste onto the GPU (not the heat sink), and spread the paste over the GPU in a rather thin layer.

Good Brand Names

Here are brand names that have good CPU heat sinks for a good price.

Cooler Master - They're higher end heat sinks are solid but lacking in performance (they have a concave base and odd design). Great lower budget options.
Noctua - Good choices, but overpriced. Great mounting systems, flat bases, great construction.
Prolimatech - New company. They're three options are among the best. Great mounting systems, flat bases, great construction.
Scythe - Great lower budget options.
Thermalright - Great options for those with a high budget. Their heat sinks tend to have a rather rough base and mediocre mounting system.
Xigmatek - Good lower budget options.

List of Heat Sinks

$30 and below

My #1 recommendation is the Cooler Master Hyper 212 Plus. It is compatible with socket LGA 1366, LGA 1156, LGA 775, AM3, AM2+, and AM2. It has four HDT heat pipes, made out of copper, and a dense aluminum fin design. It comes with a fan. Great deal.

http://www.newegg.com/Product/Produc...-065-_-Product

$31-$40

The Scythe Mugen 2 is perhaps the best choice. It has a normal nickel plated copper base, 5 copper heat pipes, a dense fin design, and it's huge. It comes with a fan.

http://www.heatsinkfactory.com/scyth...scmg-2100.html

$41-$50

One choice is the Xigmatek Dark Knight. While it lacks heat pipes (it only has three direct touch copper heat pipes), it has a dense fin design and comes with a decent white LED fan. The Scythe Mugen 2 is be a better choice. Not recommended.

http://www.newegg.com/Product/Produc...TEK-_-35233029

A better choice in this price range is the Titan Fenrir. This large heat sink features an HDT base with four copper heat pipes. It utilizes a dense fin design and is packaged with a 120mm x 25mm fan. Performs surprisingly well, even better than the Scythe Mugen 2. Highly recommended, one of the best price to performance heat sinks out there. It performs nearly as well as the more expensive heat sinks. The only downside is the lack of a nickel plating.

http://www.heatsinkfactory.com/titan...tc-nk85tz.html

The best choice by far in this price range is the Cooler Master V6. This large heat sink features a flat copper base, six 6mm copper heat pipes in a V pattern which exposes each heat pipe to cool air and utilizes more of the fin space. It features 55 aluminum fins and is packaged with a 120mm x 25mm fluid dynamic bearing fan. Best performing heat sink so far, it is actually comparable to the Noctua NH-D14 at heavier loads and better than the Prolimatech Megahalems and Thermalright Venomous-X for heavy loads, despite its $49.99 price tag. Since it has a very dense fin design, high CFM and high pressure fans are necessary. The heat sink has a 5 degree tilt increasing the surface area without increasing size, thus maximizing cooling performance and minimizing air resistance. It comes with a fan shroud but they will not work with 120mm x 38mm fans, so you'll need to find your own way to use them.

Cooler Master V6 and V6 GT Landing Page

$51-$60

You have quite a few choices in this price range. One of which is the Cooler Master V8. I do not recommend this heat sink. While it is durable, has a decent mounting system, offers decent performance, and comes with a fan, the performance is beat by the Xigmatek Dark Knight and Scythe Mugen 2, both of which are much cheaper. This is due to the odd heat pipe design on the V8. It takes some time for some of the heat pipes to make contact with the fins.

http://www.sundialmicro.com/cooler_m...2075_1471.html

You can buy a Thermalright ULTRA-120 EXTREME (TRUE) for this price. This heat sink has a nickel plated copper base that isn't very flat. The mounting system isn't very good either. Six nickel plated copper heat pipes bring the heat to a large amount of nickel plated aluminum fins. Great construction, great performance. It was the best heat sink for quite some time. Does not come with a fan, and newegg has the black one for $60.

http://www.newegg.com/Product/Produc...-022-_-Product

The best choice in this price range is the Prolimatech Megahalems. Again, it does not come with a fan, but the pros heavily outweigh the con. It has a flat nickel plated copper base, six nickel plated copper heat pipes, a large amount of nickel plated aluminum fins, and a perfect mounting system. Performs slightly better than the TRUE and most other heat sinks. Revision B is compatible with LGA 1366, LGA 1156, and LGA 775.

http://www.heatsinkfactory.com/proli...pu-cooler.html

$61 and above

The Noctua NH-U12P had some popularity, but it really is not worth the price. It has a widely spaced fin design (less fins), and only four nickel plated copper heat pipes. This means it can't transfer or dissipate as much heat as the competition. The base is flat and the mounting system is great though. It comes with one or two high end, quiet 120mm fans which it performs well with. But if you like to overclock, and you have a hot quad core (or more) processor, there are better choices.

http://www.newegg.com/Product/Produc...tua-_-35608014

One of the worst choices you can make is buying the Cooler Master V10. This oversized, overpriced heat sink performs slightly better than the V8 due to a better heat pipe and fin design. Just like the V8, it has a nickel plated copper concave base, nickel plated copper heat pipes (10 instead of 8), nickel plated aluminum fins, and good soldering. But it can't outperform a TRUE, Megahalems, and other cheaper heat sinks. It covers the RAM with a horizontal set of fins and comes with two of the same fans that the V8 comes with. The price is simply ridiculous.

http://www.newegg.com/Product/Produc...20master%20v10

The Noctua NH-D14 is an interesting heat sink. It uses a double vertical fin design. Much like the NH-U12P, it features a flat nickel plated copper base, nickel plated copper heat pipes, and nickel plated aluminum fins. It features a widely spaced fin design like the NH-D14, but this is not a downside to this heat sink since it has two sets of fins. There are 48 fins on each side, 96 total. This means it can dissipate much more heat than standard coolers, while remaining more quiet.

This heat sink has 6 heat pipes compared to 4 on the NH-U12P, and it supports three fans. It can transfer and dissipate large amounts of heat, but even without fans it will cover several RAM slots. The middle cannot mount a 120mm x 38mm fan. It is compatible with 140mm fans. It features rubberized shock absorbers to lower fan noise.

http://www.newegg.com/Product/Produc...tua-_-35608018

You can get a Prolimatech MegaShadow in this price range. It's just a black Megahalems, but it was limited edition.

http://www.crazypc.com/products/mega-shadow-508603.html

A good choice is the Prolimatech Armageddon. This heat sink is tall and slim. This design is very innovative. They didn't cut down on the number of fins, and the taller design allows for the use of 140mm fans (which I don't recommend anyway, more on this later). The advantages of the tall and slim design are that the heat pipes are exposed to more cool air, and you don't have to worry about hitting your RAM heat sinks when using 120mm x 38mm fans.

The Armageddon features six nickel plated copper heat pipes, a flat nickel plated copper base, a great mounting system, and a dense nickel plated aluminum fin design. Highly recommended.

http://www.frozencpu.com/products/10...em_.html#blank

Thermalright made a comeback with the Venemous-X. This heat sink is better than the TRUE and on par with the Megahalems/MegaShadow/Armageddon. The size is about the same as the Megahalems/MegaShadow, the base is more flat than their previous coolers but still not very smooth. Mounting system isn't as pleasant as Prolimatech. Because of these downsides, I can't quite recommend it seeing as how it costs more than the Megahalems.

http://www.crazypc.com/products/venomous-x-509765.html

Lets not forget the Cogage Arrow. It has a nickel plated copper base which again is not very smooth, and the mounting system isn't very good. On the other hand, it has four nickel plated copper heat pipes that measure 8mm (opposed to the normal 6mm). It has 110 fins - 55 on each side with an angled tilt thus increasing the surface area. It can be fitted with three fans, whether they're 120mm x 25mm, 120mm x 38mm, 140mm x 25mm or 140mm x 38mm. The Noctua NH-D14 can't hold a 38mm thick fan in the middle but this one can. Lap it and you have the best heat sink by far... if you can fit it.

http://www.crazypc.com/products/coga...ow-509890.html

The Cooler Master V6 GT is one of the best CPU coolers out there. At $69.99 it is roughly the same price as the Prolimatech Megahalems and Thermalright Venomous-X, but the V6 GT can perform better at higher loads and it comes with two 120mm x 25mm fluid dynamic bearing fans. It is an attractive option with its unique looks, including black fan shrouds and an LED strip which can be toggled between red, blue and purple. It has a flat electroplated copper base, six electroplated 6mm heat pipes and 55 aluminum fins in a very dense pattern. The heat pipes are in a V array which expose each one to cool air and utilizes more of the fin space. This heat sink has a 5 degree tilt which increases the surface area without increasing the size of the cooler, thus maximizing cooling performance and also minimizes air resistance. This performs on par with the Noctua NH-D14 at higher loads despite its smaller size. A must have.

Cooler Master V6 GT Landing Page

We arrive at the final and best CPU cooler. Best as in the best performing cooler. And the champion here is the Thermalright Silver Arrow. It is just a Cogage Arrow but with a much more smooth base, like the Venomous-X, as well as a much better mounting system with adjustable pressure like the Venomous-X. Even in stock configuration this cooler is the best, and I was a bit shocked myself since the two PWM fans it comes with (each one is 160mm x 140mm x 28mm) are only rated for a max of 1300 RPM/73 CFM/21 DBA which is even better than the NF-P14 fans.

Thermalright Silver Arrow Product Page

What are Good Fans for CPU Heat Sinks?

For heat sinks and water cooling, you want high end fans that have a high static pressure, good CFM rating (cubic feet per minute), and some people want low noise, therefore fans with a low DBA rating is recommended for such people. You should know about the different types of bearings used on fans.

Sleeve bearing fans use two surfaces lubricated with oil or grease as a friction contact. Sleeve bearings are less durable as the contact surfaces can become rough and/or the lubricant dry up, eventually leading to failure. Sleeve bearings may be more likely to fail at higher temperatures, and may perform poorly when mounted in any orientation other than vertical. The lifespan of a sleeve bearing fan may be around 40,000 hours at 40 °C. Fans that use sleeve bearings are generally cheaper than fans that use ball bearings, and are quieter at lower speeds early in their life, but can grow considerably noisier as they age.
Rifle bearing fans are similar to sleeve bearing, but are quieter and have almost as much lifespan as ball bearings. The bearing has a spiral groove in it that pumps fluid from a reservoir. This allows them to be safely mounted horizontally (unlike sleeve bearings), since the fluid being pumped lubricates the top of the shaft. The pumping also ensures sufficient lubricant on the shaft, reducing noise, and increasing lifespan.
Ball bearing fans use ball bearings. Though generally more expensive, ball bearing fans do not suffer the same orientation limitations as sleeve bearing fans, are more durable especially at higher temperatures, and quieter than sleeve bearing fans at higher rotation speeds. The lifespan of a ball bearing fan may be around 63,000 hours at 40 °C. Some fans use one ball bearing, some use two and some use one ball and one sleeve. The latter is cheaper and less effective.
Fluid dynamic bearing fans have the advantages of near-silent operation and higher life expectancy than even ball bearing fans, due to the lack of contact with the shaft, bearing and thrust plate. However, these fans tend to be the most expensive.
Magnetic bearing fans, in which the fan is repelled from the bearing by magnetism. Stabilizes the rotor axis. Noctua's Self-Stabilizing Oil Pressure Bearing (SSO Bearing) is a fluid dynamic bearing with a magnet.

Low-Noise Fans

These fans are recommended for heat sinks that have widely spaced fins.

Noctua NF-P12 - Very high end 120mm x 25mm fan, hence the price. Features a high quality SSO bearing (fluid dynamic + magnetic - decreased noise, increased lifespan) and can perform up to 1300 RPM/54.36 CFM/19.8 DBA. Features rubber sound dampeners and a unique fan blade design that lowers noise. LINK

Noctua NF-P14 - Very high end 140mm x 25mm fan. Limited compatibility. Same SSO bearings and design as the NF-P12, save the rounded frame. Performs up to 1200 RPM/64.96 CFM/19.6 DBA. LINK

Scythe S-Flex - There is a large variety of Scythe S-Flex fans. The differences are the rotation speed, therefore the CFM and noise values are different as well. These 120mm x 25mm fans use a fluid dynamic bearing and are very high end. LINK

Scythe GentleTyphoon - There are a few GentleTyphoon 120mm x 25mm fans. The differences are the rotation speed, therefore the CFM and noise values are different as well. These fans use ball bearings and offer very good static pressure, better than all of the other 120mm x 25mm fans in this category. Therefore these are the best fans in this category for cooling heat sinks and radiators. They also run rather quiet considering their speeds. LINK

Thermalright FDB - There are four Thermalright FDB fans. The differences are the rotation speed, therefore the CFM and noise values are different as well. These 120mm x 25mm fans are identical to the Scythe S-Flex fans, however the rotation speeds are a bit different. LINK

High Airflow Fans

These fans are recommended for CPU heat sinks that have a dense fin design. While some of the previous fans had good airflow, these are better but much noisier. The following fans measure 120mm x 38mm, so make sure you have either low profile RAM sticks and proper space for these wide fans.

A single 120mm x 38mm fan will outperform pretty much any dual 120mm x 25mm or 140mm x 25mm fan setup. This is due to the much higher static pressure, and these fans tend to spin fast, increasing the CFM and noise values drastically.

Delta - Delta has a large variety of 120mm x 38mm fans, all of which are very high quality (ball bearings), and feature unrivaled airflow. The obvious downside is noise level considering the speeds at which they spin. LINK
Panaflo - Panaflo has good 120mm x 38mm fans that aren't incredibly noisy and have a very good construction. They use hydro wave bearings which are very quiet and the lifespan is very long. LINK

So there you have it. You have a good amount of options for heat sinks, fans, and thermal paste. I personally recommend the Scythe Mugen 2 if you're on a very low budget. If you can afford up to $50, the best choice is the Cooler Master V6. At high loads it beats the Prolimatech Megahalems/Armageddon and Thermalright Venomous-X which cost more and do not come with a fan unlike the V6. The V6 actually performs on par with the Noctua NH-D14 at high loads. If you can afford up to $70, go for the Cooler Master V6 GT.. A few more bucks will get you the best air cooler out there, the Thermalright Silver Arrow.