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48 DESIGN007 MAGAZINE I SEPTEMBER 2020 In this column, I will focus on answering five questions about thermal management at the design and PCB levels. These questions were sent to me from one of the owners at Monsoon Solutions, where I now work. Jeff Reinhold, EE and designer, asked: 1. When I get a datasheet that calls out some area of copper for heat dissipation, how do I translate that requirement to fit my board that may or may not have the specified area available? 2. How much heat does a via dissipate, and how does size and fill change that? 3. Does moving heat to internal layers help at all or even work? 4. How do I identify potential thermal issues? 5. How do I translate a heat dissipation requirement, in whatever form it is given, into parameters I can use to design a solution? Some of the questions I can answer from my "previous life" in PCB fabrication, but for oth- ers, I asked my co-workers for their comments. 5 Questions About Improving Thermal Management Question #1 Regarding the first question, Kevin Carrington, a design engineer at Monsoon, said: Thermal management is all about deltas. Heat only moves along a gradient, so if heat isn't actively being removed, then it's simply spread, which means your delta-T is dimin- ished. Spreading over a long enough time achieves steady-state, so understanding a use scenario is often important. Putting more cop- per in the circuit board would have zero impact on thermal management if the board is at a steady-state condition. The physical size of parts is very important when considering heat dissipation. A great example is the power SO-8 package that many discrete FETs come in nowadays and have largely replaced the DPAK components. Parts in those packages are often rated very simi- larly for operating parameters, but the DPAK is far superior when it comes to getting heat out because of the size of the thermal tab. The Bare (Board) Truth Feature Column by Mark Thompson, CID+, MONSOON SOLUTIONS

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