What are heat sinks?

By AJ Born | June 18, 2024

What are heat sinks?

Meet the Connector: Heat sinks

Heat sinks provide thermal management in electronic or mechanical devices for components that can’t sufficiently dissipate heat to moderate temperature. For example, they are used to cool central processing units (CPUs) and graphics processing units (GPUs) in computers, with power transistors and other high-power semiconductor devices, and for optoelectronics such as lasers and LEDs. Heat sinks protect critical components from damage or performance loss by drawing heat away.

Heat sinks vary in design and capabilities depending on the device’s configuration. In general, they move the heat from the high-temperature component via a low-temperature fluid medium (air or liquid coolant). They are designed for maximum surface area in contact with the cooling medium. Heat moves through the heat sink to the medium because of natural conduction, which occurs when the ambient temperature is cooler than the heat sink. The fluid passes over the surface of the heat sink and moves the heat from the surface to the environment, using thermal diffusion and convection. A larger surface area increases this ability.

Passive, active, and hybrid

Passive heat sinks work by natural convection. The buoyant hot air generates airflow across the system. The advantage of a passive heat sink system is that it does not require secondary power or a control system to function.

Active heat sinks are more effective at reducing heat than passive systems. They use forced air generated by a fan, a blower, or movement of the device itself, to increase fluid flow across the hot area. One example is the fan in a computer that turns on when the computer gets warm. The fan forces unheated air across the heat sink surface allowing more heat to exit the system overall.

Hybrid heat sinks combine some aspects of passive and active heat sinks. Temperature requirements determine how the system operates. When temperatures are cooler, the system relies on passive cooling. When the temperature reaches a certain level, forced air (active cooling) kicks on to raise the heat sink system’s cooling capacity.

Materials

The heat sink’s thermal conductivity depends on its material. Heat sink materials absorb heat energy and transfer it to the environment for efficient cooling. They require high heat capacity and thermal conductivity. Aluminum and copper are typically used because of their high conductivity.

Aluminum alloys 6060, 6061, and 6063 are commonly used for heat sinks due to their thermal conductivity values. The values depend on the temper of the alloy. Tempering is a heat treatment technique to increase the alloys toughness by decreasing hardness.

Copper also has twice the thermal conductivity as aluminum and is resistant to corrosion and biofouling. It is also antimicrobial. However, copper is three times denser than aluminum, more expensive, and less ductile.

Design Notes

Construction: Heat sinks are designed with fins to encourage the free flow of air. Fins are flat plates with heat flowing in one end and dissipated into fluid as it travels to the other end. The fins must be vertically aligned and optimally spaced to maximize air flow and efficient heat transfer. One-piece aluminum heat sinks can be made by extrusion, casting, skiving, or milling. One-piece copper heat sinks can be made by skiving or milling. Sheet-metal fins can be soldered onto a rectangular copper body.

Material specifications: Copper or aluminum alloy

Markets and Applications

Automotive, Consumer Electronics, Datacom & Telecom, Industrial, Medical, Military and Aerospace, Transportation

Electronics including computers (CPUs & GPUs), vehicles (electric vehicle controllers), battery packs, telecommunications.

Suppliers

Avnet, DigiKey Electronics, Heilind Electronics, Mouser Electronics, RS, and TE Connectivity

Like this article? Check out our other Meet the Connector and Networking articles, our Materials Market Page, and our 2024 Article Archives

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AJ Born
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