THERMAL MANAGEMENT OPTIONS IN CONSUMER ELECTRONICS
A Summary of Common Ways to Cool Electronic Devices
By: Nick Farrah, Product Line Director
Electronic components are an increasingly important and complex part of the devices we use every day. Numerous electronic and electrical components such as processors, batteries, lights and more all generate heat – and are found in everything from your toaster to your watch. The industry demands innovative cooling solutions to meet these challenges. Various materials and concepts with specific advantages and disadvantages are used to dissipate the heat loss. It’s important to understand the different cooling methods in order to optimize performance in your application.
Larger products, such as PC towers, can use active cooling concepts like fans. These are often not an option for smaller devices because they take up space, cause noise and require additional energy. Instead, passive methods of heat dissipation such as conduction, convection or heat transfer through thermal radiation are often used.
Conduction cooling is the transferal of heat from a hotter part to a cooler part by direct contact. To accomplish this, chip carriers can be made of ceramic, plastic or glass. With printed circuit boards, the electronic components are mounted on a board made of polymers and glass-epoxy materials. The usage of heat frames and thermal conduction modules provide a way to move the flow of heat from the circuit board to the heat sink.
Convection cooling is the transferal of heat to ambient air or liquids. Using a fan to blow air over the parts is an example of forced convection cooling. In passive cooling, a cavity might be filled with gas to promote transfer of heat. Liquid cooling is far more effective because liquids have much higher thermal conductivity rates than gases. Unfortunately, using liquid is also more likely to cause problems due to the increased chance of leakage, corrosion and condensation. Liquid also adds extra weight.
With thermal radiation heat transfers, there is no substance between the hot and cold materials. The operation of electronics produces thermal radiation, which is transported via electromagnetic waves away from the heated object. Other factors are still important, such as the temperature and texture of the component and the objects around it. The temperature difference between the circuit and surrounding material should be high. This is the least common method of cooling used in electronics.
One significant component in electronic devices is a heat sink. Heat sinks are specially shaped parts made of a good heat conductor, such as aluminum, with a large surface area. Heat transfer takes place via thermal radiation. To optimize thermal radiation, heat sinks are often painted black. The advantage of heat sinks is that they are cheap and easy to use. However, the more heat they must dissipate, the larger they need to be, which adds bulk to the device. What's more, heat dissipation takes place in the immediate vicinity of the component. And for very compact devices with little space, this is a problem.
Another way to dissipate heat is the use of a heat spreader. A heat spreader is a thin sheet of a good heat conductor such as copper or aluminum, which is placed directly on the item from which heat is to be dissipated. The sheet metal has the task of distributing the heat produced on the component over as large an area as possible. This makes it easier to transfer it to a heat sink mounted on the heat spreader.
In every cooling format, the material used has a significant impact on how effectively it cools, and therefore how well it performs. Thermal management materials include ceramics, glass, metals, alloys, metal matrix composites (MMCs), laminates and even plastics, for some applications. Metals such as silver, gold, aluminum and copper are good thermal conductors. However, when a combination of thermal conductivity and strength is desired, more advanced alloys should be considered. In addition, using structural materials endowed with superior thermal conductivity can help accomplish two objectives with one tool.
Copper is widely used in electronics and combining it with trace amounts of other metals can significantly enhance the properties of the base metal. Adding beryllium, for example, creates a material with high strength and hardness that is resistant to wear and corrosion, non-magnetic, and has excellent thermal and electrical conductivity. However, copper is heavy.
With weight being a significant concern, aluminum might be used to mitigate heat, but may not provide the structural support or CTE match needed for all applications. It can be useful to find an alloy that provides additional benefits that aren’t available with the base material alone. Our AyontEX™ alloy combines aluminum with silicon so it can manage heat and provide critical strength while matching copper’s coefficient of thermal expansion and maintaining the weight savings of aluminum.
These types of solutions will continue to be extremely important as electronic devices grow in complexity and availability. Increasingly powerful processors, displays, 5G components and batteries generate high heat losses, which must be dissipated in ingenious ways to maintain performance. Understanding the options for thermal management can lead to unique solutions for even the most challenging application.