Francois-Saint-Cyr, A., Marovic, B., and He, W., "Tackling the Thermal Design Challenges of Smaller, Lighter, and More Efficient Avionics Systems," SAE Technical Paper 2013-01-2165, 2013, doi:10.4271/2013-01-2165.
Electronic systems play a key role in the high reliability and safety of modern aircrafts. Components have become smaller and faster leading to an increase in power density and making thermal management a more vital part of the overall design. This paper will demonstrate how thermal transient testing combined with computational fluid dynamics (CFD) can help balance these design constraints and ensure that critical devices will work safely within their prescribed temperature limits.The first part of the paper will focus on the thermal characterization of a component using a continuous measurement method known as the static method per JEDEC51-1 standard. This data provides an insight of the overall component thermal performance and it can also be translated to structure function which helps with detecting potential internal thermal bottlenecks, such as a die attach material. This non-destructive technique can also be used to assess the performance of aging components and highlight any material degradation.The second part of the paper will illustrate how a 1D thermal compact model can be generated from the thermal characterization and how it can be inserted into a thermal simulation of an avionics system. Adding such a model to a computational fluid dynamics analysis allows calculating an accurate junction and case temperature for the component without having to discreetly represent the geometrical part of the chip such as the die or the solder balls.