Thermal management solutions play a crucial role in controlling the temperature of electronic devices and components. These devices generate a lot of waste heat, particularly in small enclosures and restricted areas, which undermine their efficiency.
By Potshangbam July
During the electronics manufacturing process, varying levels of heat are generated, posing a great threat to critical and sensitive components. When these components are overheated, they react in risky ways, even to the point of shutting down the system, apart from the deterioration in performance and premature aging of critical components. Thermal management systems are needed to protect the reliability and safety of these components, and prevent a complete breakdown. These systems ensure sensitive electronic parts continue functioning over the long term, by ensuring the temperature does not exceed or fall below defined limits. When the temperature soars, it has been proven that the life span of the components is affected by more than 50 per cent. Therefore, the demand for thermal management solutions and systems is high for applications like medical, consumer, automotive and power electronics, as well as in the military, to deliver the expected performance level during their lifetime.
Why thermal management?
Devices are shrinking, and need smaller and smaller components to fit into them. When these small components perform at high levels, the heat stress is high, which can make some of them behave in unreliable ways that can disrupt the performance of the device. This trend of the radical miniaturisation of electronics poses a critical challenge for smooth operation, as it makes components prone to overheating. This is where thermal management and thermal analysis comes into play.
Besides, thermal management effectively regulates temperature fluctuations in critical components, and resists the formation of condensates. When the thermal conditions are not monitored properly, it creates electrical resistance, limiting the performance of chips and other microelectronic components. This also leads to power leakage within a device. One should be aware that the rate of heat loss shoots up when the temperature of the components increases. Exposure to such heat can lead to health problems and other issues like skin reactions, rashes, burns, brain related issues, etc. Therefore, thermal management is very important. It enables thermal analysis, and mitigates thermal excess early in the process. In this way, thermal management systems can significantly increase the life expectancy and safety of electronic devices. Also, by reducing the heat stress, one can improve productivity and reduce mishaps in the workplace. In thermal management systems, there are three mechanisms that are used to transfer heat—conduction, convection (natural and forced), and radiation.
What fuels the demand for thermal management?
As per a report by ReportLinker, the global thermal management market is expected to grow from US$ 11.1 billion in 2019 to US$ 16.2 billion by 2024, at a CAGR of 8 per cent. Technological advances are fuelling the thermal management market, leading to the development of synthetic cooling systems and interface materials, cool chips for thermal management in electronic devices, and the greater use of natural refrigerants.
With growing environment concerns, there are stricter heat emission regulations that mandate the use of thermal management systems. With electronic devices becoming more complex and small, a lot of power is being dissipated from devices. To minimise this, air-cooling solutions are employed to reduce excess heat. However, air-cooling solutions are not very effective and may not be able to counteract the heat released from the devices. So, liquid cooling is used to deal with this shortcoming.
There is a growing awareness of the advantages offered by liquid cooling, which increases the consumption of thermal management solutions and, hence, drives the demand for these systems in the market. On the flip side, exorbitant price points and design complexity can slow down the demand for these systems.
However, overall, there is a surge in demand for thermal management solutions and systems from various industries, including automotive, electronics, defence, aerospace, telecommunications, chemicals, healthcare, etc.
Here are a few of the applications of thermal management systems.
Consumer electronics: Thermal management solutions are largely integrated in several consumer electronics products, such as personal computers, laptops, tablets, smartphones, gaming devices, etc. The thermal management for consumer electronics requires chip cooling, which protects components such as processors and transistors from overheating. The thermal management procedure for consumer electronics is said to be one of the most challenging in the technology space. With the increased use of microprocessors, from a 486 Intel chip to a multi-core processor, the rate of power consumption also increases, which leads to greater heat release. This has given rise to greater demand for thermal management systems in consumer electronics.
Automobiles: When it comes to automobiles, heat is generated from engine components, brakes, battery packs and lighting. To improve fuel efficiency, the engines have been downsized, which increases heat release. Moreover, dashboard displays, air conditioners, navigation systems, audio systems, etc, consume a lot of battery power. Excessive use of batteries generates heat, which needs to be dissipated. This has led to the adoption of thermal solutions that feature heat spreading and heat dissipating technologies.
Power electronics: IGBTs and other power electronic devices unleash a massive amount of heat from a small enclosure. Thermal management is crucial for power electronics systems to cool down the accumulated heat load from devices with a high voltage.
Aerospace: Thermal management is critical in the demanding environment of aircraft. Thermal management systems help in reducing weight and enhancing the reliability of the components. The lightweight carbon thermal-management systems, the CNT thermal interface, fuel cells and spray cooling are some of the innovations that are meeting the tough requirements of aero standards.
Medical: The requirement for thermal management solutions is high in the medical field, particularly for cooling electronics. The solutions include ensuring the temperature of an external device is within the prescribed norms for patient contacting surfaces, cryogenic cooling for surgery applications, etc.
Jade Bridges, technical manager of Electrolube, shares her insights and tips on effective thermal management.
Factors to consider when choosing thermal management materials
There are so many factors to consider when choosing thermal management materials, that it’s important to do your calculations, consider the equipment’s operational and environmental conditions and only then experiment. Underestimating these aspects could compromise the reliability of an electronic assembly and shorten its life expectancy.
Why is less often more when it comes to the application of thermal management
Thermal management products are designed to remove air from between a heat conducting component or device and its heat-sink. This could be a standard heatsink, or it could be the device’s housing; so thermal management products are designed to offer both protection and heat dissipation. As such, the air gaps could be very small (in the case of thermal interface applications) or up to a few millimetres in the case of a gap between component and casing. In all cases, air is the worst conductor of heat and the heat-sink or casing will be the best heat conductor. In order to ensure the most efficient heat transfer, all air must be displaced without adding extra thermal management material to widen the gaps further; therefore, we need to keep the quantity of thermal management material to the minimum.
Why doesn’t a thicker layer of thermal paste enhance its performance?
The thermal management product is designed to be flexible and should, to some degree, conform to the contours of the interface in a way that a solid metal material could not. However, a solid metal heat-sink will have a much higher bulk thermal conductivity than a thermal management material, such as a paste or phase change product, for example. Therefore, if you apply too much of the thermal management material, you are not only displacing air, you are also increasing the bond line thickness between the heat generating component and the heat-sink. By pushing the heat-sink further away from the component and putting a less thermally conductive material at the interface, the overall thermal resistance will increase, consequently reducing the efficiency of heat transfer.
What are the potential issues to be faced by not employing the correct thermal management practices?
If the temperature of a device or component is not controlled, it could lead to inconsistent performance, reduced efficiency or ultimately, even failure. The actual results will depend on each individual design’s requirements; hence the need to correctly assess which type of thermal management is most suited to your application.
How do I know if my thermal management process is a success?
You will know your thermal management process has been successful when you see improved efficiency of heat transfer, reduced thermal resistance and a lower temperature around the heat generating component or device. Effectively, the chosen thermal dissipation media will operate within the temperature limits defined for the device, whilst maintaining performance during changing conditions.
Efficient thermal management is an essential part of both current and future electronics design, particularly given the ongoing trend for product miniaturisation coupled with higher powered devices.
It can be overwhelming, with so many different types of thermal interface materials (TIM) at your disposal, to determine the correct one for your application, but by careful consideration and identifying the correct test regimes, it is possible to differentiate between products and select the most suitable material for your application.
What are the latest advances in thermal management technology and how are they different from traditional pastes and greases?
Phase change materials (PCMs), once heated above their phase change temperature, become highly thixotropic liquids that perform as well as – and sometimes even better than – a traditional thermal grease. Moreover, their low phase change temperature ensures low thermal resistance over a wide temperature range, safeguarding minimal bond line thickness with improved stability and pump-out resistance.
The application methods of PCMs for high volume production mean that most can be used in existing production processes with minimal, if any, changes, whilst also allowing for easy rework, offering many of the same benefits of traditional thermal pastes. As they offer greater longterm stability compared to thermal greases, they are better suited to thermally challenging applications where product life expectancy and reliability may be critical; such asautomotive electronics or remotely located wind power inverters, for example. Traditional thermal pastes/greases will continue to be a popular choice, although for some applications, especially those requiring greater long-term stability, a phase change material is likely to win over the crowd.