Mentor Graphics talks about its new CFD analysis software and heat flow congestion in chip design

(October 25, 2010) — Mentor Graphics Corporation (NASDAQ: MENT) has announced its next-generation FloTHERM 3D computational fluid dynamics (CFD) software for electronics cooling applications. Called FloTHERM 9, the software provides bottleneck (Bn) and shortcut (Sc) fields so that engineers can identify where heat flow congestion occurs in the electronic design and why. It also identifies thermal shortcuts to resolve the design problem. Erich Bürgel, GM, Mechanical Analysis Division at Mentor Graphics, describes the process in a podcast interview.

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Together, the Bn (Figure 1) and the Sc (Figure 2) fields elevate the use of simulation from an observation tool that identifies heat management problems, to a thermal design problem-solving tool that suggests potential solutions to the designer. The Bn field shows where in a design the heat path is being congested as it attempts to flow from high junction temperature points to ambient. Design changes to these bottlenecks can help solve the heat flow problem. The Sc field highlights possible solutions where the addition of a simple element to the design will provide a new effective heat flow path to further cool the system. The end result is faster and more efficient resolution of heat management problems, Bürgel told ElectroIQ.



Figure 1a. No bottlenecks exist in a metal bar conducting heat along it.

Figure 1b. Addition of a plastic low thermal conductivity insert will raise the temperature ‘upstream’ of it. Its bottleneck affect is clearly visible as the red (high Bn number) region.



Figure 1c. Reducing the width of the bar has the same temperature raising affects as the plastic insert.
Again, the Bn number highlights the bottleneck area.

Figure 1d. The Bn number is formulated as the dot product of the temperature gradient and heat flux vectors at any one point.

Two additional enhancements have been made in the new FloTHERM v.9 product: XML model and geometry data importing to enable FloTHERM integration into existing data flows, and a direct interface to the Mentor Graphics Expedition PCB design platform. The direct interface enables users to import native Expedition PCB data, and delete or edit additional objects (heatsinks, thermal vias, board cutouts, EM cans) for more accurate thermal model design development.



Figure 2a. The Sc number shows where best to introduce a new thermal shortcut path. Figure 2b. In this case adding a thermal bridge at that location allows the heat to shortcut to the colder copper and reduce the overall temperature rise in the system.

Commenting on the new product, “The value of FloTHERM 9 is in the time and the cost it saved us when developing an IC for a new generation of Energy Star-compliant mobile phone chargers,” stated Nigel Heather, VP, Engineering at CamSemi. “The baseline simulation using the bottleneck feature quickly highlighted a potential thermal issue, and further iterations confirmed our solution.” He added that, to achieve the same result by building prototype boards, would have taken a long time and drawn resources away from other critical work.

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