What? Christmas is over and you’re still not a thermal analysis expert?

By voporta

Fear not! Thermal design is no longer reserved for specialists alone. The benefits of adding thermal simulation to your PCB design flow are substantial – fewer schedule delays, increased reliability, and lower product costs – so it would be a shame to limit them to engineers who have specialized knowledge of thermal analysis and CFD (computational fluid dynamics).

PADS FloTHERM XT, with its CAD-centric user interface, is easy to use and affordable, enabling all engineers to consider thermal design throughout the design process, from concept through design exploration and optimization, to final verification.

Tips for Executing Thermal Design in the PCB Design Flow

The trick is to start thermal analysis early in the design process, as early feedback will guide later design. You can learn a lot using simple representations of the housing, board, and components prior to committing to layout.

Have fun and experiment! With PADS FloTHERM XT you can quickly validate or eliminate changes as you go. For example, not all package styles perform equally so why not investigate thermally relevant IC junction temperatures for different package styles prior to package selection?

You can also investigate how component placement impacts airflow. Large components can shield smaller components from cooling air. If the air behind the larger component gets caught, the components in that area get hot. A good tip is to place rectangular components parallel to the primary flow direction.

In later stages of the design process, after exploring component selection and placement, export the routed board to PADS FloTHERM XT with full stackup information to account for copper coverage of signal, power, and ground planes, and dielectric layers containing vias and interconnects. This will allow heat to be spread more accurately as it travels through all the layers.

To predict junction temperatures and confirm that ICs will operate well below maximum operating temperatures, you can update the models of thermally relevant ICs with higher-level models, such as two-resistor or DELPHI CTMs (compact thermal models), or with model representations that include full internal construction geometry, materials, die size etc.

The CAD capability of PADS FloTHERM XT allows you to create or import a complex geometrical representation of the housing that is identical to the actual physical part. To account for heat conduction from the components to the PCB to the enclosure, mount the PCB to a detailed model of the enclosure. Then the model of the device to be produced is ready for further exploration and optimization.

So, if Santa has come and gone and there is still no CAD-friendly thermal analysis software under your tree, head on over to our Downloads page and try it yourself for free. No sleigh required.

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This article first appeared on the Siemens Digital Industries Software blog at