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Johannes Adam is the creator of a simulation tool called Thermal Risk Management (TRM) used to help PCB designers and design engineers predict hot spots on the board before during layout. He and Douglas Brooks, founder of UltraCAD Design, have used the tool to produce several technical articles and a book on the subject. In this interview, they tackle the biggest misconceptions they see from designers and engineers who deal with thermal management issues.
Andy Shaughnessy: Doug, talk a little bit about your work with thermal and how you got involved with Johannes.
Douglas Brooks: I became involved in thermal issues on PCB design when I wrote an article for a magazine in ‘96 and compared some results from the then IPC traces, which went back to the MBS traces. I saw data in another article that was different by about 40%. Then, IPC-2152 was published, and that was about 25% lower temperature than previous NBS data that went back to the 1950s primarily because they were using more current boards and also they were doing a more careful study. But it still raises a question of how come there was such a big difference between the article data and the IPC data. I began to theorize that the difference had to do with the difference in measurement technique. IPC used a technique that, in effect, measured the average temperature of a trace, and the article data measured the peak temperature in the center of the trace.
I was looking around for a way to verify that, and I saw a thermal image of a trace that I traced back to Johannes in about 2016. I contacted Johannes, and we started a conversation. He sent me a copy of his software. He was very patient while I started coming down the learning curve of that software, and we entered into a collaboration that went from trying to look at the differences in data to things like how hot is this via? Can you measure the resistivity of a trace? What happens when you bring up a parallel trace? Can you get into the fusing questions? This ballooned over the years into what became the book that we published back in 2018. Then, there were some other ancillary articles that reflected various chapters in that book.
Johannes has been a great help to me. I’m now retired, which allows me time to do some of these things. Artech House is going to publish an updated version of our book in the first quarter of 2023.
Shaughnessy: Johannes, give us a quick background. You are a rocket scientist, correct? You’re one of the few that I know.
Johannes Adam: I’m not a rocket scientist, but I am an astrophysicist (laughs). And by the way, conduction-cooled boards in vacuum can also be simulated. I've been involved in programming since my undergraduate studies or even in high school, starting with punch cards. Doug actually contacted me in November of 2014 when I was giving an electronics cooling seminar in Hannover. At that time, I had been working in the field of trace heating and temperature prediction since more or less 2001. I knew Doug's work, but I was too shy to contact him. The interest in trace heating came from questions from users of FloTHERM at Bosch, who I was supporting as a support engineer at that time. They asked about the temperature of the trace, and I had to say, “I can calculate the ventilation of your device, but an amp is not an input value.” I started looking at these IPC design rules and literature.
It was not until much later that I had the idea of writing my own software that focuses on the PCB, traces, layer structure, pads, and drilled holes to calculate the temperature of the traces and components if the amps or the watts are given. This began in 2009, when I started my developments. Now, we have a very good third-generation TRM software tool, and the users are happy because it is easy to use, and neutral design data can be read and parameterized, but you are still free to add additional technological ideas and play with them. We have already made a small step toward electrodynamics in which it is possible to calculate the self-inductance and mutual inductance of nets.
To read this entire interview, which appeared in the September 2020 issue of Design007 Magazine, click here.