FEATURE EMC & THERMAL MANAGEMENT Against the elements James Fordham, RS Componentslooks at thermal management challenges in an IoT connected world
there may not be a lot of free space for fans, or enough power to run them. But modern fans offer functions that can alleviate some of these issues. For instance, Sanyo Denki’s 9RF range of fans can deliver airflow in both directions, reducing the space required for thermal management. The fans also feature PWM speed control to allow the design to save energy through efficient usage and reduce noise. In some cases, it will not be possible
he Internet of Things (IoT) is on course to have a faster uptake than any previous technology introduction. From almost zero at this start of this decade, research by BCG has estimated that there will be market spend of up to US$267 billion on IoT technologies, products and services by its end. Half of this predicted spend is expected to be primarily in manufacturing, utilities, transportation and logistics. Products for these applications will
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have to operate in some very hostile environments. Electronics systems are vulnerable to heat, cold, electrical noise and airborne particles. Heat can reduce the effectiveness and lifetimes of components, moisture and particulates can cause short circuits, and cold can affect the operation and the usable lifetime of equipment. It is important to either protect sensitive electronics components from the environment, or find ways to accurately estimate how these systems will perform in them. Environmental issues are not the only
problem that IoT equipment faces. Many systems for IoT will be situated in remote areas, or in places that are difficult to access for regular maintenance. This means that they often won’t be able to be connected to the mains supply, relying on batteries or being powered from energy harvested from the environment. The simplest solution is to use a case or
enclosure to protect the electronics inside. Cases can protect equipment from moisture and dust, but there can still be an issue from both heat and cold. Sealed
18 MARCH 2018 | ELECTRONICS
cases can trap the heat from components, which in turn can lead to hotspots forming, especially in areas near the top of the case. Traditionally, fans and heatsinks have been used to manage heat, and both can be used in IoT applications, although large heatsinks may be problematic due to space requirements. A thermal interface can ensure that the heat from components is transferred efficiently to the heatsink, which in turn can reduce the size of the heatsink required. Often, the thermal interface used is grease or paste, but more recently, specialised materials have been developed to provide a better thermal connection between the component and heatsink. These materials do not degrade over time in the same way grease will.
NEW THERMAL MANAGEMENT MATERIAL Panasonic’s new Soft-PGS material is a good example of this type of thermal interface material. Soft-PGS is a 200µm thick graphite sheet that can be compressed by 40%. The material guarantees thermal stability up to 400°C with thermal conductivity up to 400W/mK for the X-Y direction and 30W/mK in the Z direction. The material has also found another use that is particularly handy for IoT devices - as a thermally conductive layer that can be applied inside cases to prevent hotspots. Forced air-cooling, in the form of fans, has also been used extensively for thermal management. In IoT systems,
Figure 1:
It is important to protect sensitive electronics components from the environment, or find ways to accurately estimate how these systems will perform in them
to rely solely on cooling techniques, and action should be taken to try to negate thermal effects, or to plan for a shortened product lifetime. Fortunately, the effects of heat on electronics components are already well understood. Burn-in testing is already used for the accelerated testing of components. From this testing, we can tell how components will react under different ambient temperatures. For example, a fan running at 40°C ambient temperature may last 70,000 hours, while the same fan running at 60°C might only last 40,000 hours. Many IoT systems will be situated outdoors, or in inhospitable places such as industrial freezers. Cold can also affect the operation of electronics systems, especially by reducing battery capacity, making LCD screens less responsive, and producing condensation, which can short-circuit components. For systems operating in these conditions, a heater may be required to keep the system operating as normal. Stego makes a compact family of heaters especially for this scenario. The Stego range includes convection and panel heaters, as well as fan heaters to distribute the heat evenly. Stego also offers heaters that are designed to work in explosive environments with the new CREx family. The IoT offers huge opportunities to those that can provide the right products at the right time. These opportunities also bring challenges - mainly environmental. Electronics systems for challenging environments are possible, but it takes careful planning over the design cycle to ensure the maximum performance and lifetime.
RS Components
www.rs-online.com/designspark/ keeping-cool-in-the-world-of-iot
/ ELECTRONICS
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