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Design007-Sept2020

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54 DESIGN007 MAGAZINE I SEPTEMBER 2020 Automotive lighting was next in line to ben- efit from the technology. It started in the cabin with courtesy lights, then indicators. Even- tually, it came to the headlights when LEDs became powerful enough to drive the main beams on vehicles. That was a big game- changer. You can integrate the whole thing as a single unit. That became a massive area of development for IMS materials because it pro- vided another important advantage: reliabil- ity. You don't care so much if the lighting in your living room fails; you can simply replace it with another one. In the car, though, it's a big deal! The reliability benefit also opened up a host of other application opportunities, particularly in the automotive sector. The market literally came to IMS materials. In the last decade or so, there has been a massive change from con- ventional vehicles with internal combustion engines to cars with electronic systems. We now have electronic drive systems. There are a lot of applications in the car where electronics are now used in pretty high-power applications: there are DC converters, onboard charges, inverters for traction, electronic power sys- tems, high-power ECUs, and in-brake energy regeneration systems. There are big advantages. One is cost because the thermal management system is integrated into the board. The second benefit is that the weight can be kept down. Aluminum is light compared to a lot of other solutions that were being used in the past. Overall, IMS evolved from a simple, domestic, low-cost application to something that is high-end. It has been used in many other areas as well. Thermal management is required wherever there's high power. And what was possibly a niche product before may still be niche in some areas, but there are a lot of high-value niches, and they give a lot of value to the designer. They could design their thermal management around the circuit in the same package, which is sepa- rate from mechanical design. That is how we've come to where we are with systems today. Shaughnessy: If you have a designer work- ing on this board they know is going to have thermal problems, what sort of characteristics should they look for when they're comparing thermal materials? Morgan: The first thing to work out is how much heat you have to move. When you look at the equations for how heat moves and thermody- namics, you find the most important thing is the differential of temperature from the thing that's hot to the thing that's cold. You have to find a solution to maximize that. We think a lot about emissivity. When you look at the back of the aluminum, how much heat does that emit? How much heat does that radiate out? We have a coating that we can provide on the back of the materials called ER1, which gets you pretty close to black-body radiation on the back of the radiator. The number ranges between zero and one. One is perfect, and zero is completely not emitting. With it, we can achieve from around 0.05 for straight aluminum to around 0.85. The other thing you have to think about is the heat transmission through the substrates as well. There's a number for that. We call this thermal conductivity, which is measured in watts per meter Kelvin. Typical FR-4 laminate might be around 0.4–0.5. The first generation of the IMS materials was in the range of one Alun Morgan

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