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28 DESIGN007 MAGAZINE I NOVEMBER 2022 ADAM RESEARCH Most of are aware that when we pass an elec- trical current through a trace (conductor), the trace will heat up. is temperature increase is caused by the I 2 R power loss dissipated in the resistance of the trace. e resistance of a copper trace is mostly determined by its geometry (cross-sectional area), and there are lots of studies trying to look at the relationship between the current down a trace (of known size) and the resulting temperature of the trace 1 . But the situation is much more complicated than this. ere are physical properties that exist that result in helping to cool the trace. ese properties are usually a combination of conduction of the heat away from the trace Electronics vs. Physics: Why Vias Don't Get Hot through the material, convection of the heat away from the trace through the air, and radia- tion of the heat away from the trace. A stable temperature is reached when the I 2 R heating equals the cooling—i.e., when the electronic and physical properties are balanced 2 . We have spent several (enjoyable) years collab- orating on these effects. Douglas is an electrical engineer and understands electronics. Johannes is a thermodynamics physicist, and understands heat transfer. Between us we learned a lot about the thermal characteristics of vias. Vias Don't Get Very Hot Traces heat because of the current through their resistance, resulting in I 2 R power losses. Feature Article by Douglas Brooks, PhD and Johannes Adam, PhD