Active vs passive cooling: Thermal management of electronic devices

In both examples, engineers created innovative tools to manage the thermal energy created by these heat-generating systems. We'll cover the basics of electronics cooling and review modern thermal management systems that we often take for granted.

Why do electronics get hot?

Surprisingly, the reason both the hard-working computer and the lightbulb get hot―and why any electronic device gets hot―is due to electrical resistance. Electrical resistance occurs when electrons move through a material as a result of a charge imbalance. The movement of these electrons through a material creates friction between the moving electrons and the (usually) crystalline structure of the material. This large amount of friction results in an excess of heat and often requires secondary cooling methods.

In modern electronics, the highest thermal energy producing components are LEDs and processing units (such as GPUs, CPUs, and TPUs), which are made using semiconductor materials. You can also find high thermal energy in voltage changing devices such as:

•  Resistors


•  Transformers


•  Converters


•  Inverters

CPU heat generation―and the systems that help control these chips' temperatures―is what causes the fan cooling system of a laptop to initiate and run during operation.

Passive cooling in electronics

Fundamentally, we can divide electronics cooling techniques into two categories: passive cooling and active cooling.

•  Passive cooling utilizes natural conduction, convection, and radiation to cool a component.


•  Active cooling requires the use of energy specifically dedicated to cooling the component.

One modern example of these two cooling categories of cooling is in heat sink and heat spreader design, both of which utilize fundamental heat transfer principles.

For example, the NVIDIA Jetson Nano comes assembled with a heat sink attached to the development board, right out of the box. This fanned-fin heat sink will sufficiently dissipate the energy away from the GPU and allow the development board to run correctly. Note the large black heat sink on the NVIDIA Jetson Nano image below.

Heat sinks are one of the most simple and common thermal management accessories. These components effectively move thermal energy away from a heat source, throughout a thermally conductive material, and into the ambient environment. Most heat sink applications are passive, utilizing natural heat transfer fundamentals.

Active cooling in electronics

In the image above, note that the heat sink's top horizontal plane features four through-holes. If the heat sink needs additional thermal cooling capability, you can use these four holes to mount a cooling fan. Adding a properly sized fan to this heat sink will force air across the component and allow for greater thermal transfer. Think of it like cooling down a hot cup of tea by blowing on it.

However, since the fan requires power, this thermal management system now becomes an active cooling system. You'll see active cooling technology at work in devices that create large amounts of thermal energy, such as:

•  Computers


•  Gaming devices


•  Televisions


•  Automobiles


•  Nearly all advanced computer applications

Learn more about thermal management options for mobile devices.

Other common electronics cooling solutions

Other common forms of thermal management in modern electronics include heat pipes and vapor chambers. You can find these thermal management components in personal computers, tablets, and other computing-intensive devices where space is limited and heat-generation is significant.

Heat pipes and vapor chambers utilize a sealed evaporation and condensation cycle, which requires no secondary energy and is considered a passive cooling technology. For more information, be sure to learn more about the fundamentals of heat pipe design.

In the image below, you can see a series of six heat pipes that move energy away from a CPU heat spreader to a horizontal-finned heat sink.

Lastly, thermal grease is extremely common in both active and passive cooling designs.

Thermal grease technology acts as a thermal interface between solid heat transfer accessories. Its most common application is between an IC's heat spreader and the heat sink that is cooling the chip. In the image below, you can see thermal grease is applied directly onto a chip package. Next, a heat sink or vapor chamber will be placed on top of the grease.

Advanced electronics cooling technology

There are various other novel and advanced forms of electronics cooling as well, most of which you'll find less frequently in common electronics. These include:

•  Liquid cooling devices, which pump chilled liquid through specialized CPU-mounted heat spreaders.


•  Liquid solutions, such as 3M's Novec™ Engineered Fluids, that are designed for full computer assemblies to be submerged in.

These fluids are not electrically conductive, but they have excellent heat transfer capabilities and are only used in extreme computing applications.

To shop thermal management accessories, Arrow.com has all of the resources you need for nearly any electronics design. You can also learn more about the ordering parameters and design for heat pipes or heat sinks to help you design these thermal management devices into your products today.

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