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A motherboard heatsink is a cooling device used on certain chips found on system boards. The main chip or computer processing unit (CPU) requires a heatsink, and chipsets also use heatsinks. The size and design of these devices varies, as do materials and method of attachment.
When a computer is in use, electrical activity within the CPU and chipset generates considerable heat, which if not dissipated, will damage or even melt the chips, making them inoperable. A motherboard heatsink is secured to the top of a chip, providing an efficient path for heat to escape, first into the heatsink, then from the heatsink into the environment.
A motherboard heatsink is typically made of aluminum alloys or of copper. Aluminum alloys are good thermal conductors, and also have the advantages of being both lightweight and inexpensive. Copper is triple the weight and several times more expensive, but has twice the thermal conductivity of aluminum for even better heat dissipation. (Price-prohibitive diamond has the highest level of thermal conductivity, beating copper by a factor of five.)
In addition to materials, physical design also plays a major part in how well the device dissipates heat. Heatsinks feature rows of fins or pins extending up from the base. These fins or pins provide maximum surface area to dissipate heat while still allowing airflow between the rows to carry that heat away. This cools the surfaces, creating a dynamic path for continued dissipation.
An active heatsink comes with a small fan attached to the top of the fin or pin area, used to cool the surface. A passive heatsink lacks a fan, but is usually designed with a larger surface area. Some passive heatsinks are quite tall, and clearance can be an issue. The advantage of a passive model, however, is lack of noise.
Since the motherboard heatsink is responsible for keeping the chip cool, the chip face and base of the heatsink must be pressed together squarely and very tightly. This is accomplished through a locking mechanism that varies according to design. The heatsink might come with z-clip retainers, a clip-on spring-loaded mechanism, or a swing-down plastic arm to lock the heatsink down on to the CPU or chipset. Some types of attachment methods require the motherboard to have holes or a plastic retaining frame in place.
While the retaining method will press the chip surface against the base of the heatsink, there will still be minute voids between the two surfaces due to irregularities, imperfections and the roughness of the surfaces. Trapped air introduces resistance or gaps in the thermal path, which hampers cooling. To address this, a motherboard heatsink is always used in conjunction with a thermal compound that sits between the two surfaces, filling these gaps. Thermal tape is the least expensive type of compound, but is generally considered the least efficient. Thermal pads and tubed compounds made of various materials from silver to micronized diamonds are more popular among enthusiasts and still quite affordable.
Some chip manufacturers recommend particular types of compounds and heatsinks to use with their CPUs. CPUs that are packaged for retail sale typically come with a heatsink and thermal compound. In some cases, the CPU warranty is voided if the chip is used with a different heatsink or compound.
Heatsinks and compounds are readily available from computer and electronics outlets. Prior to purchasing a motherboard heatsink, be sure the attaching mechanism and footprint are compatible with your motherboard and computer case. Refer to the chip manufacturer for recommendations and warranty information.
@Soulfox -- That is all too true when it comes to computer towers, but things are a bit different in the mobile computing world. Laptop computers, tablets and smartphones are powered by CPUs that must run on low power to be useful at all (battery drain is a real concern for those devices).
You often have a small fan buzzing away inside of laptops, but it is very quiet compared to what goes on inside desktops. There is no fan inside of tablets and smartphones as the power consumption is kept extremely low in those and a typical heatsink will do just fine.
Here's the point of all this. It used to be that computer CPUs generated so little
heat that very small heatsinks were more than enough to do the job. CPUs got more sophisticated and heatsinks had to be augmented by fans. Perhaps we are getting to a point where we can go back to small heatsinks being enough to deal with heat generated by a CPU.
@Soulfox -- If you do need silence, there are some alternatives to a big old fan on top of a heatsink. Water cooling system are expensive but those work pretty well. Also, if you have the cash, a diamond encrusted heat sink can get rid of heat in a hurry.
But, as the article mentioned, the diamond option is a pricey one. And that is exactly why you have heat sinks topped with fans. Those are cost effective and should be fine for most people who don't give a hoot about a little bit of noise coming from a computer case.
Good luck finding a passive heatsink installed in any modern computer these days. The faster a CPU is, the more heat it generates and the better the heat dissipation needs to be. That means you will probably have a fan mounted on top of that heatsink and you will have to deal with some noise.
Don't let that get you down so much, though. You can either deal with a little noise or melt your CPU.