FROM EDN EUROPE: Upfront analysis spots thermal problems in pc-board placements
By Graham Prophet -- EDN, May 13, 2004
With many designs operating at higher power densities and required to operate in tightly packaged enclosures, thermal design can become critical to the success of a pc-board design. However, you may be used to thinking of thermal design as a remedy applied relatively late in the design cycle. A software package from thermal-analysis-tool vendor Flomerics aims to change that belief. Flo/PCB allows you to make and evaluate a component placement at the conceptual-design stage, based on thermal considerations (Picture).
Beginning with a functional block diagram of your circuit, which is separate from your mainstream pc-board design-tool flow, you can quickly generate a layout, place it in the thermal environment that the board will occupy, and get a "quick-look" analysis that will tell you whether the board has major thermal problems. The strength of Flo/PCB is that any of the engineers involved in the board design, whether electronic or mechanical, can use it without the level of knowledge needed to use the full Flotherm analysis tool.
However, behind its simple sequential pushbutton-style interface, Flo/PCB is still performing full computational fluid-dynamic analysis. From the block diagram, you either assign or fetch power dissipations from library elements, and you can carry out a simple drag-and-drop trial placement. You can apply a library of standard environments or adapt them if you know a lot about the final environment. Flo/PCB then solves the board's thermal performance, giving you sorted and filtered information. For example, you might choose to see only those components that are overtemperature, and in order of severity. You can do a partial analysis; if you know the overall power dissipation of the board but have placed only a few of the components, the package will "smear" the rest of the power across the board, again allowing a quick-look facility.
Flomerics acknowledges that thermal-design considerations will not dominate your board-layout process. But signal integrity, for example, will often follow intuitively from the functional block diagram in initial placement. Flo/PCB interfaces via IDF format to hand the pc-board design back to the mainstream tool flow for further work and to Flotherm for detailed thermal analysis.
The Flo/PCB level of analysis will be sufficient for few teams designing with Flo-therm, says Flomerics managing director Mike Reynell. However, Flo/PCB provides fast analysis early in the cycle that could save you a later board revision. And with Flo/PCB retailing for $7900/seat/year, Reynell expects multiple installations to act as satellites to each full Flotherm installation.
Flomerics, +44 208 487 3000, www.flomerics.com.
