Five Common Misconceptions about Thermal Design

Chris Aldham, Product Manager 6SigmaET/6sigmaet.info

Small, powerful, compact devices have always been at the heart of the electronics industry. But, with the constant demand for shrinking devices comes increased power densities and a lot more heat being generated in ever-decreasing spaces. The smaller the devices get, the more heat-conscious engineers need to be.

However, for too many design engineers, thermal issues are considered a low priority - primarily because thermal design is seen as a complex challenge, and a hassle they could do without. But this ignores the major headaches caused by poor thermal design – usually resulting in costly late stage thermal fixes.

If designers are to avoid these late stage pitfalls there are a number of common misconceptions about thermal design that need to be overcome. Here are my top five:

1. It’s all about keeping things cool Thermal design is actually all about ensuring that the device is kept at a constant temperature in order to run efficiently and effectively. So, while many engineers look to reduce the overall temperature of their products to avoid them overheating, some engineers might actually look to heat their products up to cater to the environments that they find themselves in, particularly those outdoor applications in cold climates.

2. Thermal design is not a priority and needs to be performed by mechanical engineers after electronics engineers have finished their design Even though mechanical engineers have a strong knowledge of physics and thermal dynamics, their thermal design capabilities and know-how might need some work. Most engineers understand the role of temperature and can figure out if something is getting too hot, but more often than not, this is discovered too late in the process, often resulting in costly thermal fixes. This is because 40% of design engineers consider thermal design a “low priority” when developing their devices. For many, their top priorities include ensuring product reliability, complying with regulations and innovating new features. But the irony of this is that accurate thermal design allows you to achieve all of these things. If engineers considered thermal issues in the very early stages of their designs, they would be able to stop products from overheating and designers can ensure that their designs remain reliable and can also help to comply with strict safety regulations. On top of this, by cutting down on power consumption and space (e.g. designing out unnecessary fans), thermal design can free up opportunities for new components and innovations within an end product or design.

3. Everything can be fixed with a fan or a heat-sink… Two of the most common go-to solutions for an overheating component is to simply “stick an extra fan here” or put a heat sink on top. However, as solutions go, adding a fan can actually be counter-intuitive because designers are just piling more components into an already over packed casing, which adds to the overall cost of materials, but also increases the energy consumption of the device. In the case of using a heat-sink, the reality is that they are in fact ‘heat moving devices’ rather than tools specifically aimed at absorbing heat. Even though the heat-sink may cool the component it is sitting on, it won’t just absorb the heat as it will also distribute the heat into the air around the heat sink. Despite many thinking that these are simple quick fixes to an overheated device, the reality is that if the layout and airflow of the device has not been designed for forced cooling, then adding a fan or a heatsink may not actually deliver the necessary cooling for the components and create new unseen problems…

4. Thermal simulations are complex and can only be conducted by the experts As the process of thermal design has evolved, so too have the tools required to conduct and perform accurate thermal simulations. Back in the day, design engineers needed to develop models and simulation scenarios themselves. But now, much of this work can be imported through CAD and is automated within the software. Gone are the days where engineers needed to invest in heavy-duty hardware to conduct simple simulations that need to be processed on a local machine. Today’s engineers benefit from the ability to export designs and simulations to cloud-based servers for maximum solving speeds. With these improved user interfaces of modern simulation suites, engineers no longer need to have an extensive knowledge of thermal design in order to manage the heat flow of their designs.

5. Thermal simulation tools are all the same Technically, all thermal simulation software uses a very similar approach, with many of the tools available on today’s market remaining unchanged over the last twenty years. The thinking behind this is that if the physical laws and equations related to heat flow haven’t changed, then why is there a need for the software to change. This premise has resulted in a number of packages that are decades old that do not provide the intuitive interfaces and levels of automation that design engineers today expect. Instead of treating thermal simulation as a set-in-stone process, engineers should take this opportunity shop around and experience difference tools before deciding which one is best suited to their project, device or working style.

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