Overview: This article explores the role of heat sinks in the thermal management of electronic devices to enhance device longevity, detailing their operating principles, types (active and passive), and factors influencing their efficiency. 

Heat dissipation and thermal failure are the primary types of failure in various equipment, including computer chips, lithium-ion batteries, gas turbines, and spacecraft. These are significant barriers to their growth. 

Why does the electronic component heat up?

The primary reason for heat generation in electronic components is the electrical resistance encountered by the flow of electric current. Every electronic device consists of finite numbers of resistors, and these resistors dissipate the power in the form of heat. 

Additionally, heat dissipation is a critical aspect of electronic design in processors, graphic cards, RAM modules, and high-performance devices, consisting of millions and millions of tiny transistors. The primary reason for transistor heat generation is the power dissipated at the collector-base junction during operation.

In each electrical component, the power that is dissipated across the equivalent resistance is converted into heat, which in turn elevates the temperature of the device. Elevated temperatures can shorten the device's lifespan and damage the electrical component. It is important to maintain the device's temperature within an acceptable range. Heat sinks are essential components of modern electronics, as they are responsible for thermal management and the optimal performance of various devices.

Heat Sink

Heat sinks are passive heat exchangers designed to dissipate heat generated by electronic components to the surroundings, preventing overheating and potential damage.

Operating Principle

The principle behind heat sink operation is based on the fundamental laws of thermodynamics, Fourier's law of heat. Fourier’s law of heat describes that heat moves from higher temperature areas to lower temperatures within a material whenever a temperature gradient exists in an electronic component. Heat transfer happens in three ways:

Conduction 

It is the process through which heat transfers from the component to the heat sink base. Even microscopic-level air gaps between the device and the heat sink result in ineffective heat transmission. To optimize this heat transmission, it is crucial to create an intact contact. Heat sink compounds minimize the air gap, thereby eliminating this issue.

Convection

It is the process by which heat is transferred from the heat sink to the surrounding air, water, or oil. The increased surface area of the fins or pins increases the heat sinks' efficiency. There are two types of convection: forced and natural. Forced convection is the term used to describe the phenomenon in which an external force causes convection. Natural convection is the term used to describe a flow that is induced by a temperature gradient and density difference.

Radiation 

It is a fundamental process of thermal energy transmission. Unlike conduction and convection, radiation does not require a medium for heat transfer, allowing it to occur even in a vacuum. Fig. 1 depicts the overview of the heat transfer principle, heat sink types, and applications.

Fig. 1 Overview of the heat transfer principle, heat sink types, and applications. Source: MDPI

Factors that Influence the Operation of Heat Sinks

Various factors influence the working of heat sinks, which includes:

Increased surface area

The surface area of the heat sink should be at least 10 to 20 times greater than the surface area of the electric component, which improves cooling performance.

Fins density and Fin spacing

Fin configuration is vital in determining airflow and dissipation efficiency. It is vital to design the fin parameters under specific conditions to optimize the cooling performance and reduce the temperature of the base surface, including the optimal fin stem height, fin branch length, branching angle, and shift distance. The increased number of fins proportionally increases the surface area for heat dissipation.

Material composition 

Aluminum, copper, or composite are the commonly used materials in the construction of heat sinks. Aluminum is lighter and affordable, with up to 205W/mK thermal conductivity. Copper has a thermal conductivity of up to 400 W/mK but is heavier and expensive. Certain composite alloys with specific properties are employed as heat sinks. The common methods employed in manufacturing heat sinks are extrusion, CNC machining, die casting, bonded fin., etc.

Thermal resistance

The thermal resistance of a heat sink is a vital parameter that quantifies its ability to dissipate heat from a component to the surrounding environment. It is typically measured in degrees Celsius per watt (°C/W) and represents the temperature rise per one watt of power. The thermal resistance of any heat sink should be as low as possible.

Airflow

It is one of the vital factors that influence the working of heat sinks. Airflow helps in transferring the heat away from the component and heatsink. For this purpose, a fan can be mounted on the heatsink, which is called forced cooling.

Types of Heat Sinks

Heat sinks can be classified as active or passive based on the convection process.

Passive heat sink

Heat dissipation is completely based on natural convection and radiation, with no moving mechanical parts. Natural convection heat dissipation is a common passive thermal management method for cooling electronic elements, and it does not require external power sources. Instead, the fluid moves through the heat sinks based on the unequal fluid density brought on by gravity or buoyant force. Fig. 2 shows 96CN-02500-A-200, which is an example of a natural convection heat sink.

Fig. 2 96CN-02500-A-200 natural convection heatsinks Source: oemsecrets

Active heat sink

The most effective method of removing heat is forced convection, achieved through a fan or compressor. The active heat sink requires less space than the passive heat sink to achieve the same level of heat transfer. However, it necessitates periodic maintenance due to the presence of moving elements. Fig. 3 shows CF1-1250-0515-1250BA, which is an example of a fan-cooled heat sink.

Fig. 3 CF1-1250-0515-1250BA fan-cooled heatsinks Source: oemsecrets

A Heat Sink to Consider

ATS-61270R-C1-R0

ATS-61270R-C1-R0, as shown in Fig. 4, is one of the most effective heat sink designs manufactured by ATS (Advanced Thermal Solutions), with high-performance fanSINK and maxiGRIP attachment. It provides superior thermal performance and has a 20% lower junction temperature and a 40% reduction in thermal resistance compared to straight fin and pin fin. This heat sink is part of ATS's high-performance line, which is designed to maximize surface area for more effective convection cooling.

Fig. 4 ATS-61270R-C1-R0 Source: oemsecrets

To conclude, heat sinks are essential components in modern electronics, providing thermal management to ensure the reliable operation and longevity of devices. Ongoing research and development in materials science and manufacturing techniques promise to deliver even more efficient and effective heat sink solutions.

Summarizing the Key Points

  • Heat sinks are essential for dissipating heat generated by electronic components, preventing overheating, and ensuring optimal performance and longevity of devices in various applications.
  • The effectiveness of heat sinks relies on factors such as increased surface area, fin density, material composition, and thermal resistance.
  • Active heat sinks utilize forced convection through fans for enhanced cooling, while passive heat sinks rely on natural convection, making them simpler but potentially less effective in high-demand scenarios.

Reference

Li, J., & Yang, L. (2023). Recent development of heat sink and related design methods. Energies, 16(20), 7133. https://doi.org/10.3390/en16207133

Li, Y., Roux, S., Castelain, C., Fan, Y., & Luo, L. (2023). Design and Optimization of Heat Sinks for the Liquid Cooling of Electronics with Multiple Heat Sources: A Literature Review. Energies, 16(22), 7468. https://doi.org/10.3390/en16227468

ALL ABOUT ELECTRONICS. (2019, March 30). What is a Heat Sink? Why are Heat Sinks used in Electronics? How Does Heat Sink Work? Heat Sink Explained [Video]. YouTube.
https://www.youtube.com/watch?v=LA6H_rGoJsI

oemsecrets-ATS-61270R-C1-R0 by Advanced Thermal Solutions