Heat-quilibrium or the importance of balancing EMC with thermal engineering. By Tom Gregory.

Across almost every industry, the last decade has seen a significant rise in the number of electronic, electrical and communication systems. From the 53.6m metric tonnes of e-waste mentioned at COP26, to our collective inability to get our hands on a PS5, the tsunami of electronics that we live with has been a focal point in the news agenda this year.

It’s difficult to bring that waste down in such an intensely competitive marketplace, given the sheer volume of electronics we use day-to-day. Devices are always being re-imagined as faster, smaller and more digitally connected, with iteration after iteration attempting to marry performance with convenience.

That means more products being made obsolete, and thereby more wastage – which means we need to temper that focus with the production of longer-lasting products that consumers are satisfied with for longer.

This whirlwind of interconnected pressures is the driving force for engineers to find new and effective ways to ensure that their components remain compatible with one another. The size, shape and sophistication of individual components, or entire devices, need to be continually improved in order to achieve these goals

Invariably, this demands a rigorous approach to product design. Attempting to break new ground carries inherent risk, but any electro-magnetic interferences to components can cause a wide range of issues. From a minor audio glitch to a failure of mission critical systems such as aircraft controls, automotive safety systems, or medical devices, safety is paramount.

EMI obstacles

Electromagnetic interferences (EMI) is one of the most common obstacles to navigate here – academics have referred to it as “one of the biggest challenges in the production of any electronic device." Whenever the composition of a device changes, it needs to be re-examined.

Simply put, EMI is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. Without control of these disturbances, the device can be rendered entirely unfit for real-world deployment.

When deciding how best to deal with EMI, it’s key to remember that it is always more efficient and less expensive to deal with interference early — the further down the design chain you are, the more difficult and expensive it can be to mitigate EMI problems.

That means catching EMI in the design process – and nipping it in the bud.

Shields up

When it comes to tackling EMI, electronic designers will seek to incorporate electromagnetic compatibility (EMC) in their designs. EMC makes sure that electronic devices don’t emit excessive electromagnetic emissions and does not interfere with other electronics equipment.

Without correct certification for EMC, most markets will prohibit sales and there are repercussions for using non-compliant products in many industries too. In electronics design, beyond fundamental board layouts, the most common way of ensuring that components work correctly when in close proximity is shielding.

Shielding works by enclosing a component in conductive materials, including copper, steel, copper alloy 770 and aluminium. The metallic screening absorbs the electromagnetic interference, protecting the components enclosed from interference and stopping the device from interfering with other devices.  It’s analogous to a Faraday cage.

Heating up

However, these shielding components introduce some tricky thermal implications. By limiting airflow over components and trapping heat where it’s generated, any device is going to run much hotter, which will have a detrimental impact on both performance and longevity.

As such, EMC demands further and thorough consideration of how to transfer heat away from components, without compromising the shielding or adding further sources of electromagnetic interference.

There are tactics that can be used here. Holes are one pragmatic approach: by adding holes in shielding cans that are much smaller than the wavelength of the highest frequency for which shielding is required, heat can be allowed to escape without compromising the shield. Another approach is to create an effective conduction path: shielding cans made from high conductivity materials, effectively operating as heat spreaders to dissipate heat to the outer case.

Regardless of the most effective approach, engineers need to consider their shielding elements and thermal layouts together, as early on in the design process as possible. So how do they go about it?

Speeding up

Engineers of every stripe need to be able to simulate their designs before investing in the production of costly physical prototypes. Not only is the former much less expensive, but it also mitigates the risk of supply chain delays, both in terms of design speed and the potential cost of opportunity.

When it comes to balancing both thermal management and EMC shielding, the use of thermal simulation software provides the best opportunity to run these investigations. The capacity to trial different layouts and designs to determine the best balance between heat flow and shielding, without any physical investment, is an extremely powerful tool in an engineer’s arsenal.

Using electronics CFD software which is quick and accurate, engineers can test multiple designs, shapes and material thicknesses to figure out what works best for their devices.

For example, using simulation it’s possible to test the difference between a solid EMC shield, a shield with vents for heat flow, or gridded shield with multiple holes for ventilation.

Alternatively, adopting a fan to force-cool part of a design may work thermally and be very cost effective, but could also introduce localised electrical noise and a pathway through which EMI can pass.

Levelling up

Thermal control and protection from EMI are two fundamental qualities of quality electronics components. But with EMC shielding having the potential to limit or negatively impact thermal management across designs, engineers need to seriously consider how they balance these two needs, and which they should prioritise.

When attempting the right thermal and EMC design balance, it’s important to select the appropriate tools. Thermal simulation software capable of modelling a variety of materials, designs and concepts is the most likely to empower the engineer, giving them the opportunity to accelerate their designs at low cost.

It also affords them a chance to experiment, with a variety of models for other thermal solutions including fans, heatsinks and thermal interface material (TIM). Where a tightly enclosed shielding is required, these all provide viable options for board-level thermal management.

 Ultimately each industry sector comes with unique design challenges. In the case of aerospace and defence, for example, engineers may also need to ensure that their designs still operate at a variety of altitudes. In others – automotive and healthcare – engineers must ensure that products function properly in a varied electromagnetic (EM) environment, while still fulfilling the related and growing number of EMC standards and regulations.

These industries will have unique trends within them too, as engineers get to grips with thermal simulation. Future Facilities research found that almost two thirds (60%) of those working on automotive designs, for example, felt that their platform prevented them from properly optimising user safety. Choosing the right tools for the job is paramount.

When that is done, engineers are able to assess all of the factors within their field and explore the optimum solution to EMI challenges in a versatile and cost-effective environment.

Author details: Tom Gregory, 6SigmaET Product Manager, Future Facilities