Thermal Materials and Testing: Key Solutions for Mil/Aerospace Electronics Systems
Thermal Materials Developments,Thermal Materials Testing, and Thermal Systems:Key Solutions for Mil/Aerospace Electronics Systems
Tutorial by CMSE 21 Conference
Instructor:Dave Saums, DS&A LLC,
Electronic design at the system level consists of integration of an array of different individual semiconductor and electrical components. Integration of disparate component types for vehicle electrification includes IGBT power semiconductors, ICs, RF devices, discrete power semiconductors, capacitors, battery cells, and subassemblies such as DC-DC converters. Many of these component types, while highly efficient, also dissipate some amount of heat. Managing heat dissipation becomes the responsibility of mechanical engineers responsible for the system enclosure, internal mechanical and thermal design, and balancing many competing factors – while also meeting overall system design requirements.A major failure mechanism for electronic systems is inadequate heat dissipation, both from individual components and at the system level. Heat is the single largest cause of failure, with vibration and dust and other environmental factors as examples of other causes.
Thermal interface materials (TIMs) provide a critical intermediary between processors, power transistors, IGBT power modules, battery cells and cold plates, and other components that generate heat and heat sinks and mechanical components – to allow transfer and spreading of a given heat load to larger metallic surfaces and ultimately to the ambient air. Thermal materials, broadly defined, can include materials that act as heat spreaders (i.e., moving heat in-plane) and as interface materials (i.e., through-plane, through a stack of materials from point source to ultimate heat sink). Substrate materials provide another critical piece in the overall system design, and these include polymeric- and ceramic-based solutions. Developments in this area continue to push cost and performance levels, to meet new system design requirements.
Testing of thermal materials (including heat spreaders and thermal interface materials, as well as substrate materials) is a continuing area for improvement in methodologies and equipment, as well as understanding of data output. Primary test methodologies will be discussed, indicating the purposes for which each test methodology is intended, as well as interpretation of data. Thermal management systems include air cooling and several types of liquid cooling technologies. Liquid cooling technologies include heat pipes and loop heat pipes, single-phase pumped liquid systems, and two-phase liquid cooling systems, with water/glycol, commercial dielectric fluids, or low-cost refrigerants as coolants. Categorizing and evaluating this range of thermal management technologies is increasingly important as a key component of vehicle electrification, and as the industry moves towards higher temperature operation of power semiconductors (silicon, GaN, and SiC). This tutorial presentation will provide insight across this range of different technologies and will include examples of system implications.