- CPU cooling acronyms
- Types of CPU Coolers
- Benefits and Types of CPU air coolers
- Benefits and Types of CPU Liquid Coolers
- Stuff to check before purchasing CPU coolers
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Integrated heatspreader. The top silver cap area on the processor is called IHS. The CPU core is under the IHS. Heatspreaders pulls the heat from the processor core, therefore spreading the heat evenly for the CPU cooler to do its job. IHS is a flat plate made of copper.
Usually, CPU manufacturers solder the IHS against the CPU for the best contact. In some cases, CPU manufacturers use other methods when soldering is not possible for many reasons. For example, Intel used thermal paste instead of the usual soldering method for certain desktop processor architecture types. It’s Haswell and Haswell-refresh ‘Devil’s Canyon’ desktop CPUs are the best examples of such processors. Many enthusiasts remove the IHS of such CPUs using certain methods (which voids the warranty on the CPU) to change the pre-applied thermal paste with a better one. Doing this method on a processor with a soldered IHS will destroy the core, making it unusable. The process of removing the IHS from the processor is called delidding.
The soldered method is the most common method to keep the IHS in contact with the core, and considered as the best way to maximize heat transfer.
Thermal Interface Material is required to help to dissipate heat from the IHS of the processor to the CPU cooler’s heatbase. Since CPU coolers remove heat via conduction, both surfaces need to be very smooth. For the naked eye, it may seem that the processor and the heatbase are smooth even with CPU coolers with the best heat base finish. But under the microscope, there will be many surface imperfections and abrasions. It’s not possible for manufacturers of processors and CPU coolers to make these surfaces smooth on that level.
Hence, a thermal paste is required to seal off that gap and provide better heat dissipation. A thermal paste is a TIM, and it helps to bridge these imperfections for optimal contact by filling the gaps in the middle. What separates between different thermal paste choice is the ability of effectively transfer heat from the processor’s IHS to the heatsink. This is called thermal conductivity. The paste with good thermal conductivity, the better.
Along with the conductivity, the application’s lifespan and long-term reliability is also important. With many SKUs and number of cores enabled in a series of processors, it is vital to choose te best one for the processor that you are purchasing. Low-quality thermal paste with no long term reliability will lead to overheating and maybe even damage both the surface. The application’s lifespan lets you use the system without
There are two types of thermal pastes, the ones that are electrically conductive, and the ones that are not. Non-electric conductive thermal pastes have been around for a long time. The reason is self-explanatory- no fear of the thermal paste being electrically conductive. It is best to check if the thermal paste you are buying is non-conductive.
Thermal pads, thermal adhesives, fillers, gels and the thermal paste (also referred to as thermal compounds or thermal grease). Thermal paste is commonly applied for CPU. There are many types of thermal paste but these are the ones that are usually around:
On most count, thermal paste manufacturers have their own proprietary mixture in thermal pastes, but they are all based on 5 types. There could be few more types, but these are the ones that are usually around:
This paste is used more as a filler rather than providing the best thermal contact. These are very cheap and isn’t really widely used in today range as many options are out there which provides the best thermal conductivity for modern processors.
These types usually contain aluminum or silver particles to provide good thermal efficiency. The main drawback is that these are electrically conductive. If the user applies too much of this thermal paste which eventually spreads due to heat and pressure between the IHS of the processor and the heat base, eventually it would pour out of the CPU, potentiallly leading to short-circuit. This was widely used until non conductive variants were widely available.
Metal based thermal pastes have a curing time. It means that these types take a certain time of usage to achieve a maximum potential of optimally transferring heat. ‘Artic Silver 5’ thermal paste is a very well-known (and still used by some people at the time of writing) metal-based thermal paste. The manufacturer says the following:
During the CPU’s initial use, the compound thins out to enhance the filling of the microscopic valleys and ensure the best physical contact between the heatsink and the CPU core. Then the compound thickens slightly over the next 50 to 200 hours of use to its final consistency designed for long-term stability.
Ceramic-based is probably the first non-conductivity type thermal paste. These are usually not considered as the best performing thermal paste type, but is well known to have a very long lifespan, making it ideal for long-term maintenance.
Carbon-based is the most commonly available variants with the best of both worlds- non-conductive to electricity and a better heat transfer paste, depending on the quality of the thermal paste make. Though its not recommended to over apply thermal pastes, it provides that peace of mind that accidental spills will not short circuit the system.
Technically, diamond-based is a variant of carbon-based.Manufacturers of such thermal paste used very tiny particles of diamond mixed with the grease. Diamond-based thermal paste usefulness is debatable, mostly considering there are other carbon-based thermal pastes which have a higher quality. These cost more than carbon-based thermal pastes and the lifespan of the paste per application varies depending on the processor and the workload. But there has been a case where users observed a certain diamond-based thermal paste causing physical damage on the CPU cooler, the processor’s IHS and even the GPU core, hence voiding warranty. It could be a very bad batch with the improper mixture, but then it could also be due to tiny particles of diamonds causing surface damages.
Ceramic, carbon and diamond-based thermal pastes also have an advantage of not having any curing time.
In any case, cleaning the thermal paste due to accidental spills will require a good amount of time, patience and the right tools for the job. It is, therefore, best to apply what will be required, roughly assuming the application. I prefer the pea method with solid flat heatbase as the pressure and heat will spread the paste on its own. The longevity of such thermal paste depends more on the quality and heat spread across the surface of the IHS.
Most thermal pastes are provided in a syringe which is best as it helps to apply the thermal paste directly. Some provide the grease in a tub while some provide it in a small packing, usually bundled with certain low-cost CPU coolers. Some CPU cooling manufacturers provide a pre-applied option spread evenly across the CPU cooler’s heatbase. Both surfaces need to be cleaned properly before applying any paste. Applying a fresh coat over older thermal paste may affect cooling or even make it electrically conductive. Safe practice is the best, and its best to clean the older application before applying a new one.
The passive component of the CPU cooler with fans is called heatsink. Passive cooling units, such as the ones found on motherboards, graphic cards and many other components are also called as heatsink.
A heat pipe helps to transfer heat from the base of the CPU cooler towards the heat fins, which is then cooled down by a fan. A heat pipe’s outer casing is made of either aluminum or copper (usually copper- with or without nickel plating). The heatpipe contains fluid inside an inner enclosed pipe. Manufacturers fill the a part of the heatpipe with a fluid. When the heatsink dissipates heat from the processor, the heatpipe that has a contact on the cooler’s base heats the fluid, eventually causing it to evaporate, but the vapour stays within the sealed pipe.
Once the gas reaches towards the other end of the heatpipe, the fan cools the external part of the heatpipe, which eventually cools the vapour within, therefore turning it into a liquid state. The heat pipe’s effectiveness largely depends on the filling, size and the amount of time it takes to cool down the vapour as quick as possible which leads to quick heat exchange. Ther number of heatpipes, thickness and height plays a role, depending on the overall design of the CPU cooler.
The ability to withstand and dissipate heat depends a lot on the thermal conductivity of the fluid inside the heatpipe.
The base of the heatsink that gets into the contact of the IHS is called heat base. The base is usually either made of copper or aluminum. Just like heatpipes, they are either with or without nickel plating to avoid oxidation. Along with aluminum fins, it provides that shiny aesthetics that people love.
There are two types of heat base- the standard flat and the direct heatpipe. The flat surface is explanatory as one can see from the image below. The direct heatpipe has direct contact with the CPU. In such cases, the copper exposed pipes have a made to be flat to have proper contact with the CPU coolers. Some manufacturers claim that this can provide better heat dissipation. Many users believe that this is nothing more than a cost-cutting method. Depending on the quality of workmanship, direct heatpipes may or may not be good. A badly made direct heatpipe based CPU cooler would require more thermal paste. There’s a chance of slightly more uneven contact, and even have a certain amount of thermal paste being collected between the heatpipes. On a personal note, I prefer flat base, especially with a polished finish because this way minor imperfections are usually lesser.
Heat fins play an important role to dissipate heat. The fin arrangement, spacing between the fins, a number of fins, placement, shape, size equally plays an important role to dissipate heat. Usually, these are aluminum. In many low-profile, passive and even low-cost CPU coolers, manufacturers use a heat fin-only CPU cooler with a fan mounting on the top. Intel stock CPU cooler- again- is a good example.
Passive heatsinks are usually based on heat fins in contact with a flat surface of the sink. I feel that passive cooling used on the motherboards are more for aesthetic purposes and less providing for passive cooling. As long as the temperatures are kept within the temperature rating of components and sub-components, its all good.