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PCBD-Feb2017

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12 The PCB Design Magazine • February 2017 by Douglas G. Brooks, PhD Two years ago I entered into a collaboration with Dr. Johannes Adam, from Leimen Germa- ny. Johannes has written a software simulation tool called Thermal Risk Management (TRM). We used it to look at the thermal characteris- tics 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 [1] . 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 pre- dict 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 [2] . 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 pre- dict 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 with- out a plane directly under the trace. The pres- ence of a plane clearly lowers the trace tempera- ture and widens the area of the board where the thermal profile spreads. EXCITING NEW TECHNOLOGY: Thermal Risk Management FEATURE Figure 1: Thermal profile of a trace with and without an underlying plane.

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