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What is a Heat Sink, and How Does it Work?

by Christopher Trick, on May 16, 2022 2:39:02 PM

What is a heat sink?

A computer's CPU (central processing unit) is often prone to overheating because some of its components overheat, posing risks to the entire computer's functionality. 

In this blog, you'll learn how heat sinks help protect your computer's CPU from overheating, ensuring maximum efficiency and the protection of critical parts and components.

What is a heat sink?

A heat sink is a piece of metal that sits on top of a computer chip such as a CPU and draws power away from components by letting it rise through a series of fins. 

By themselves, heat sinks are passive, meaning they have no moving parts. In most cases, however, the heatsink is combined with a fan that blows the hot air away or a liquid cooling solution that carries the heat halfway through the pipes. 

What is the purpose of a heat sink?

A CPU is prone to overheating because some of its components product heat. Without the heatsink, the heat generated by the components stay in your CPU, which will burn or fry it. 

Because most components are made of electronic chips, they absorb heat easily. If they receive too much heat, they become damaged and, therefore, useless, posing a risk to the functionality of high-performance computers

Having a heat sink is critical because it helps your CPU cool even if you use it for a long period of time. It is designed to absorb the heat coming from your CPU then disperse the heat away from its components. The dissipation of heat is possible because a heat sink has fins, which gives more surface area during a heat transfer. 

A heat sink needs to make strong contact with the source of heat in order to maximize cooling. Heat sinks use a thermal conductor to move the heat into fins, which have larger surface areas and thus disperse heat throughout the computer. 

How does a heat sink work?

A heat sink works by moving heat away from a critical component. This is done in four basic steps: 

  1. The source generates heat: This source may be any system that creates heat and requires the removal of said heat to function accordingly, such as mechanical, electrical, chemical, nuclear, solar, and friction. 
  2. Heat transfers away from the source: In direct heat sink-contact applications, heat moves into the heat sink and away from the source via natural conduction. The heat sink material's thermal conductivity directly impacts this process. That is why high thermal conductivity materials such as copper and aluminum are extremely common in the construction of heat sinks. 
  3. Heat distributes throughout the heat sinks: Heat will naturally travel through the heat sink via natural conduction moving across the thermal gradient from a high-temperature to a low-temperature environment. This ultimately means that the heat sink's thermal profile will not be consistent. As a result, heat sinks will often be hotter towards the source and cooler towards the sink's extremities. 
  4. Heat moves away from the heat sink: This process relies on the heat sink's temperature gradient and its working fluid--most commonly air or a non-electrically-conductive liquid.
    1. The working fluid passes across the surface of the warm heat sink and utilizes thermal diffusion and convection to remove heat away from the surface and into the surrounding environment.
    2. This stage relies on, yet again, a temperature gradient to remove heat from the heat sink. Therefore, if the surrounding temperature is not cooler than the heat sink, no convection and subsequent heat removal will occur.
    3. This stage is also where the total surface area of the heat sink becomes most advantageous. A large surface area provides an increased area for thermal diffusion and convection to occur. 

      Heat sink in action

Source: researchgate.net . A heat sinks moves heat away from a critical component. This is done in four basic steps: the source generating heat, transferring heat away from the source, heat distributing through the heat sink, and heat moving away from the heat sink.

What are the types of heat sinks?

There are three types of heat sinks: passive, active, and hybrid. 

Passive heat sinks

Passive heat sinks rely on natural convection, meaning the buoyancy of hot air alone causes the airflow generated across the heat sink system. The benefit of these types of heat sinks is that they do not require secondary power or control systems to remove heat from the system. However, passive heat sinks are less effective at transferring heat from a system than active heat sinks.

Passive Heat Sink

Source: easytechjunkie.com. Passive heat sinks rely on natural convection, meaning the buoyancy of hot air alone causes the airflow generated across the heat sink system. 

Active heat sinks

Active heat sinks utilize forced air to increase fluid flow across the hot area. Forced air is most commonly generated by a fan, blower, or even movement of the entire object.

An example of a fan producing forced air across a heat sink is the fan in your personal computer turning on after your computer gets warm. The fan forces air across the heat sink, which allows more unheated air to move across the heat sink surface, thus increasing the total thermal gradient across the heat sink system and allowing more heat to exit the overall system. 

Active Heat Sink

Source: amazeinvent.com. Active heat sinks use forced air to increase fluid flow across the hot area.

Hybrid heat sinks

Hybrid heat sinks combine some aspects of passive and active heat sinks. These configurations are less common, and they often rely on control systems to cool the system based on temperature requirements. 

When the system operates at cooler levels, the forced air source is inactive, only cooling the system passively. Once the source reaches higher temperatures, the active cooling mechanism engages to increase the cooling capacity of the system. 

Hybrid Heat Sinks

Source: impact-innovations.com. Hybrid heat sinks combine some aspects of passive and active heat sinks.

What is heat sink compound?

Heat sink compound--also known as thermal grease, thermal compound, CPU grease, heat paste, heat sink paste, and thermal interface material--is a stick paste that is used as an interface between CPU heat sinks and heat sources. 

Heat sink compound is used to fill gaps between the CPU or other heat generating components and the mechanical heat sink. The mechanical heat sink is placed over the CPU. Heat is drawn from the CPU though the mechanical heat sinks to its fins, where a fan blows air through to dissipate the excess heat.

Heat Sink CompoundSource: techspray.com. Heat sink compound is a stick paste that is used as an interface between CPU heat sinks and heat sources.

Final thoughts

Heat sinks play a critical part in dispersing heat away from a CPU and avoiding overheating, guarding the physical surfaces of critical parts and components. 

With an overheated CPU, a computer's functionality is compromised, impeding performance when and where it matters most. 

At Trenton, our boards are equipped with custom and standard heat sinks and blower fans from Dynatron to reduce the heat on the components and system holistically. 

Our engineers spend countless hours configuring a solution with the best cooling setup to extract heat and route it out of the chassis for optimal performance across all environments. 

We also perform thermal chamber testing on our parts and components in-house to ensure our systems meet the stringent standards and requirements of our military customers. 

This is why a high-quality heat sink is important, whether in active, passive, or hybrid form, as it protects the central component of a computer's infrastructure, ensuring maximum efficiency at all times.

Topics:High-performance computersheat sinkCPU

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