Electronic Design

When Heat Is On, Thermal Characterization Keeps Things Cool

All designers are aware, or should be, that excess heat accelerates the failure of electronic systems. Not only that, but it is the most common direct cause of failure of both ICs and LEDs. According to the U.S. Air Force, temperature-related failures account for 55% of the premature demises of defense-related systems.

Thermal management of systems goes up and down the food chain, from component design to subsystems to system-level design. Thermal analysis needs to be carried out at all three levels if there is to be a solid foundation for end-system reliability on the thermal front. Analysis of thermal issues, though, is not without its challenges.

For one thing, suppliers of IC packages and LEDs must provide accurate thermal data for their products. Most only supply bulk heat dissipation in watts. For another, analysis must include accurate characterization of component heat paths and barriers to heat dissipation. Someone has to create thermal models of components to include in system thermal analysis, and these models require expertise in such matters. They’re also difficult to verify.

Mentor Graphics has been taking a higher-profile approach to this problem since the establishment of its Mechanical Analysis Division. Now, that group has delivered the industry’s first integrated component-to-system thermal characterization and analysis methodology.

The methodology combines the T3Ster thermal transient tester for semiconductor packages and LEDs with Mentor’s FloTHERM thermal simulation and analysis tool. Between the hardware and software, designers now can create accurate thermal simulation models. Moreover, the combination complies with the JEDEC JESD51-14 measurement methodology standard for the junction-to-case thermal resistance of power semiconductor devices.

On the front end of the methodology is the T3Ster transient tester, used to determine the thermal characteristics of devices. Suppliers of components, IC packages, and LEDs use this measurement hardware to create exhaustive thermal profiles of devices. Subsystem and system-level integrators also use it. The T3Ster test methodology ensures higher accuracy and repeatability compared to classical steady-state measurements based on older standards.

Models created with the data generated by the T3Ster tester are inputs to FloTHERM thermal simulations. Mentor’s FloTHERM product allows engineers to implement virtual prototypes using advanced computational fluid dynamics (CFD) techniques to simulate airflow, temperature, and heat transfer in electronic systems.

The combination enables manufacturers to optimize their LED and IC package designs for effective heat dissipation. After building a device prototype, they can characterize the device from a thermal perspective and build accurate models for use in FloTHERM thermal software simulations at both the subsystem and full system levels. Systems integrators then can further verify their heat management solutions with physical measurements using the T3Ster hardware.

With this methodology, IC package designers, suppliers, and system developers can perform fully automated, measurement-based modeling of power semiconductor packages. The JESD51-14-compliant measurements taken by the T3Ster hardware are automatically converted into compact thermal models for FloTHERM simulations.

Similarly, CFD models of IC packages can be compared to T3Ster measurements. Once validated, those CFD models are used to generate DELPHI compact models for FloTHERM and system-level thermal analysis (see the figure). Or, the validated 3D thermal model itself can be used directly in FloTHERM simulations as well.

With the addition of Mentor’s TERALED hardware for thermal and radiometric characterization of high-power LEDs, the T3Ster/FloTherm combination becomes a solution for measurement and automatic modeling of these devices.

Mentor Graphics
www.mentor.com/mechanical

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