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What Is a Heat Sink and How Does It Work?

Overheating is problematic for your devices; that’s why heat removal is vital to control the temperature of electronic devices or similar heat sources.

Heat sinks are used in electronic devices to sink heat energy into the environment and to cool your devices. But what exactly is a heat sink, and how does it work?

How Heat Is Produced in Electronic Devices & Systems

In the modern era, we are surrounded by electronic systems and gadgets. From a microprocessor chip to a base transceiver station (BTS) for mobile communication systems, electronic products need electrical power to operate.

While some of that power is used for operating the device, the rest of it is dissipated (depending on the efficiency of the device), mostly in the form of heat.

However, due to the miniaturization of devices, electronic devices can’t accumulate heat and need to sink this heat energy into the environment. For this purpose, heat sinks are often used.

What Is a Heat Sink?

how a heat sink works

A heat sink is a part applied to a hot electronic device to absorb its heat through conduction and then throw this energy to the ambient environment through convection and radiation. A common structure of a heat sink is as shown below:

Electronic devices are designed in such a way that a minimal interface and thermally conductive materials are utilized to connect a heat-generating source and heat sink so that heat cannot accumulate inside the device. Heat sinks are designed in a way to provide a low thermal resistive path to devices for heat removal.

Heat Sink Mechanism

Heat sinks are made of thermally conductive materials, most commonly Aluminum (thermal conductivity: 237 W/m K). Aluminum is a low-cost metal compared to other thermally conductive materials like silver and gold.

The heat from a relatively small electronic casing is absorbed by a flat metal plate through conduction. Conduction is often facilitated by applying a thermal paste between the electronic device’s outer casing and the heat sink. This ensures proper physical contact with high thermally conductive paste.

thermal paste
Image credit: Hafizan Mohamad Noor/flickr

The heat from a relatively smaller electronic casing is meant to spread on the larger heat sink surface through conduction.

However, heat energy suffers a spreading heat resistance when a smaller surface area of the heat source comes in physical contact with a bigger surface area of the heat sink. That’s why it’s important to control spreading resistance by choosing the suitable contact thickness of the base plate of the heat sink.

structure of heat sink

A heat sink with minimal spreading resistance ensures that heat is almost evenly distributed on the base plate and fins. Thus, the surface area of the heat sink is efficiently utilized. However, calculating spreading resistance is outside the scope of this article.

On the other side of the heat sink base plate, many metallic fins are used to provide increased surface area for the thermal convection of heat. Fins are not placed too close together as this can hinder the ability of fluid, i.e., the air, in most cases, to flow freely between the fins for dissipating heat.

Natural vs. Forced Cooling

Evenly spread heat at the heat sink base utilizes the entire surface area provided by fins to throw heat into ambient air using either natural convection or forced air convection.

Natural convection is a process in which ambient air carries away the heat energy from heat sink fins using the natural flow of fluid, i.e., not applying pressure through an external source. In this process, the flow or speed of fluid molecules is slow.

cooling fans for PC

In the forced convection method for heat exchange, a blower or fan is used to increase the speed of fluid flow through the surface on the fins of the heat sink. Either a DC or a PWM fan can be used.

The increased airflow results in more heat carried away from the heat sink. Usually, forced convection is used in cases where a lot of heat power is required to be removed, or a smaller heat sink is mandated in a design.

Along with convection, heat radiation from the heat sink is also quite helpful in removing heat from the heat sink. Usually, heat sinks are colored black, increasing their thermal radiation capability.

Heat Sinks Keep Your Devices Cool and Running

A heat sink is an essential gadget for the reliable operation of an electronic device. Without them, our advanced smartphones, high-powered computers, and even LED lights won’t function as intended due to overheating.

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