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32 DESIGN007 MAGAZINE I APRIL 2021 uct is most likely going to be the most impor- tant factor. It may be competing against many other similar devices on the market and there- fore must be both reliable and high performing but with an emphasis towards the latter. For a safety-critical device, you absolutely need reli- ability. It may not be "all singing and dancing" but as long as it does the job it is intended to do without failure, it will be acceptable. ere is usually a trade-off with the properties of any design but remember, by considering thermal management from the start, it should be pos- sible to achieve highly in both areas. Is there a drive for higher and higher levels of thermal conductivity? Yes, you could say that there is a drive for increased levels of thermal conductivity. How- ever, if you were to investigate each response in detail, thermal conductivity may not actually be the desirable factor engineers are looking for. In all applications, everyone is striving for improved performance and greater efficiency. Simply increasing the level of thermal conduc- tivity alone may not offer you these improve- ments. When specifying the thermal conductivity required, it should be based on the end appli- cation conditions and requirements. It should also consider the design of the unit/substrate and the application method of the thermal management compound. If the product is not applied correctly—for instance, if air voids are present—then the product cannot offer the full level of thermal dissipation it is capable of. In general, when you increase the thermal conductivity you must adjust the amount or type of fillers used in the thermal management material and that could impact the viscosity of the product, which in turn affects the over- all performance of the product in the end use application. is change may also impact other properties, such as electrical conductivity/ insulation, the material's behaviour in changing temperature conditions, etc. erefore, while most will say that with electronics becoming more powerful and being used in more chal- lenging environments (and so higher thermal conductivities are needed), each application should be reviewed holistically to make sure that you achieve the best performance from the thermal management material, not just rely on the thermal conductivity value alone. Heat generation rises in line with miniaturi- sation and the desire for higher performing components—what are the solutions? Look at the design of the unit/PCB; are there any ways in which heat could be dis- tributed more effectively? For example, if all heat-generating components are now in one area and close together, could they be relo- cated? is sounds simple to do but in prac- tice it is not always possible. Other ways to effectively dissipate the heat away from certain areas is to ensure you have the best thermal interface material for your application. at means checking the thermal resistance at the interface, or more simply, checking the tem- perature of components or areas of the board. When you have this starting information, you can look at ways to improve heat dissipation by adjusting the thermal interface material used, for example. is could be moving to a product with higher thermal conductivity, however, make sure it can still be applied correctly to enable it to perform as expected. As well as looking at the interface materials used, you could also look into the gaps around the board. Are there any areas where hot air It may not be "all singing and dancing" but as long as it does the job it is intended to do without failure, it will be acceptable.

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