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84 DESIGN007 MAGAZINE I JUNE 2022 a non-bonding, non-curing product should be used. If thermal protection is localised to one component, a curing product is the better choice as it will avoid migration of the mate- rial to neighbouring components. However, if that component or area is sensitive to changes in coefficient of expansion, it must be ensured that the cured product used does not cause any negative impact over the application temper- ature range. With consideration of the appli- cation requirements in unison, the optimum thermal management product can be defined, achieving increased performance and reliabil- ity of the design. ere's a lot to consider for successful ther- mal management. Getting it wrong could com- promise the reliability of an electronic assem- bly and shorten its life expectancy or even prove critical. It's strongly advised to do your calculations; consider the application require- ments as well as operational and environmental conditions, and test, test, test. Experimenting with the product in the actual design is the only way to truly understand the performance that can be achieved and conclude with the correct selection of thermal management products. First and foremost, seek some expert advice, discuss your application, and identify the most suitable products for review. DESIGN007 Jade Bridges is global technical support manager at Electrol- ube. To read past columns from Electrolube, click here. Down- load your free copy of Electrol- ube's book, The Printed Circuit Assembler's Guide to… Confor- mal Coatings for Harsh Environments, and watch the micro webinar series "Coatings Uncoated!" 4. Know your dimensions Understanding the dimensions of your appli- cation is critical to the selection of appropri- ate thermal management materials. A thermal interface is the space between a component and its heat sink, and the thermally conduc- tive media used in this space are referred to as thermal interface materials. is space is usually very small, i.e., on the micron scale. A gap filling application, on the other hand, is more to do with the distance between a com- ponent and the metal housing that encloses an electronics assembly and is usually measured in millimetres. For example, a thermally con- ductive material is placed to help minimise the chances of hot spots within the unit itself while the casing is used as the heat sink. e difference between a few microns and a few millimetres could be critical to the per- formance of the thermal medium chosen. For example, if you place a TIM in a gap filling application, it is likely to be unstable in a thicker layer; with vibration or following a period of temperature cycling, it could easily be dis- placed. And if a gap filling material is used in a thermal interface application, it will be very difficult to achieve a thin, even film, creating a higher thermal resistance at the interface and consequently reduced heat transfer efficiency. 5. Tips for material selection As discussed, for an interface material, the bond line thickness needs to be as thin as pos- sible to minimise thermal resistance. For a gap filling material, the dimensions of the gap need to be considered and environmental factors evaluated to decide whether a curing or non- curing product would be best in terms of the stability of the material under the application conditions as well as considering the possible effect on physical stresses within the unit. In all cases, the operating temperature range and environmental conditions of the applica- tion need to be reviewed. If very high tempera- tures are expected, a silicone may be required, and if the assembly is subject to rework, then There's a lot to consider for successful thermal management.