Douglas Brooks

In this article, Douglas Brooks and Johannes Adam illustrate how the thermal impacts of heated traces and pads are not limited to the board layer on which they exist; read on to see how they are reflected on every board layer above and below them.

What happens when you apply current to a trace? How long until disaster ensues? Douglas Brooks and Johannes Adam melted some boards, turned traces into flames, and applied some equations to shed some light on these questions.

It turns out that dielectrics, in fact, cool traces more efficiently than does convection + radiation, and therefore internal traces are relatively cooler. In this article, Brooks & Adam examine the question: Is there a predictable relationship between the external temperature of a trace and the internal temperature of the same trace carrying the same current?

Current density can be an interesting concept. Graphics based on current density can be fascinating. But from a practical standpoint, current density is irrelevant. It is a consequence of other things, not a determinant of them. What follows will explain why.

The inescapable conclusion from the analysis presented here is that the conventional wisdom has been wrong! The current does not determine the temperature of the via. Find out what does.

The ability to analyze and predict the current/temperature effects of isolated traces is helpful, but the actual temperature of a trace may be different because of uncertainties in the actual trace thickness or board material thermal conductivity coefficient. This article traces the effort to see what PCB board parameters have the most impact in determining trace temperatures, followed by a look at related PCB design considerations. Read on to learn more.