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

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 moves heat away from a component in four basic steps: 

1. The source generates heat: This source is any system that creates heat and requires it to be removed to function. 
2. Heat transfers away from the source: Heat moves into the heat sink and away from the source via natural conduction, which is directly impacted by the heat sink material's thermal conductivity. This is made possible due to high-thermal conductivity materials such as copper and aluminum in the heat sink. 
3. Heat distributes throughout the heat sinks: Heat naturally travels throughout the heat sink via natural conduction, moving across the thermal gradient from a high-temperature to a low-temperature environment. This means that heat sinks will usually 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, using thermal diffusion and convection to move heat away from the surface and into the surrounding environment.
   2. This relies on a temperature gradient, so no convection and subsequent heat removal will occur if the surrounding temperature is not cooler than the heat sink. 
   3. The total surface area of the heat sink becomes beneficial, as a large surface area provides an increased area for thermal diffusion and convection to occur. 
      

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 ability of hot air to float causes the airflow generated across the heat sink, and they do not require secondary power or control systems to remove heat. But passive heat sinks are not as effective at removing heat from a system as active heat sinks.

Active heat sinks

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

This is like 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. This increases the total thermal gradient across the heat sink, allowing more heat to exit.  

Hybrid heat sinks

Hybrid heat sinks combine characteristics of both passive and active heat sinks. These configurations are less common, often using 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 sink. 

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.

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.

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