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Two years ago I entered into a collaboration with Dr. Johannes Adam, from Leimen Germany. Johannes has written a software simulation tool called Thermal Risk Management (TRM). We used it to look at the thermal characteristics of PCB traces under a variety of conditions, and it is hard for me to contain my excitement and enthusiasm for what it does and what we learned about traces using it. Our collaboration resulted in the publication of numerous articles and a book. In this article, I’ll talk about some of the capabilities of TRM that really caught my attention. (Note: TRM has much more power than I will have space to discuss in this article. See the technical note at the end of the article for more on this.)
TRM allows us to model a PCB trace and predict its thermal properties. So the first thing we did was model a variety of traces and compare the results with the data in IPC-2152. The data fit very well, giving us confidence that the process was valid. But if the software could fit a single trace in isolation, then it could also predict the temperature of a trace under a variety of other conditions that board designers more typically face, such as changes in length, the proximity of adjacent traces, and the presence of planes. For example, Figure 1 illustrates the thermal patterns around a trace with and without a plane directly under the trace. The presence of a plane clearly lowers the trace temperature and widens the area of the board where the thermal profile spreads.
But TRM also allows us to view things in many other dimensions. For example, Figure 2 shows the thermal profile of a cross-sectional view of the board underneath the trace. The thermal profile underneath the trace through the board without the plane extends all the way to the far side, but the thermal profile of the board with the plane changes dramatically at the plane. I know of no other way to look at this profile other than with a computer simulation.
To read this entire article, which appeared in the February 2017 issue of The PCB Design Magazine, click here.