Design007 Magazine


Issue link:

Contents of this Issue


Page 19 of 129

20 DESIGN007 MAGAZINE I SEPTEMBER 2020 for a one-dimensional adiabatic heat transport through (e.g., a thin heat conducting sheet), but it cannot describe the heat spreading in the board (not even in a homogeneous plate). Therefore, it is obvious that there is no pana- cea for temperature prediction. Simulation: A Better Way to Predict Temps A numerical analysis can cover both the big picture and the details for better prediction. What makes a PCB a complex geometry is the sequence of copper layers and prepregs, the stackup, the pattern of the copper tracks in the layers, the artwork or layout, and the place- ment of the components. Let's look at a few examples. These calculations were performed with Thermal Risk Management (TRM) soft- ware, which was developed by my company ADAM Research and can be used by the users of all ECAD systems by importing standard files (e.g., Gerber, drill files, netlists, text and Excel files). There are even export and import wizards for Altium Designer. It is even possible to use TRM with no layout data at all, for example, for preliminary place- ment studies or technological studies. The board will be calculated in three dimensions, even if desired as transient and with or with- out electrical sources (see the article by Doug Brooks in this issue). That will take between one and a few minutes. Much attention is paid to the user interface to have as much as pos- sible in view at once, both in the input and in the results. It is truly easy to use and a teach- ing and learning tool for the EE (Figure 1). Examples In the first three examples, the value of the power dissipation is always 1 watt for the pur- pose of comparison, the PCB is always in "still air" (i.e., free convection), and the ambient temperature is always 20°C. Using the calcu- lated component temperature, a thermal resis- tance "case-ambient" R th,C-A = (T case – T amb ) /1W can be read off directly. The fact that this value differs from board to board shows that also R th,C-A values in datasheets are not suitable for individual temperature predictions. 1. Arduino The two-layer Arduino board is a standard Eagle [4] software installation. Solder mask and silkscreen do not need to be imported into the thermal model and are used here for illustrative reasons only. We only charge the central com- ponent IC3. Around the component, there is Figure 1: The TRM user interface. Figure 2: View of the TRM model of the two-layer Arduino board with solder mask and drilled holes. In the vertical direction, the geometry has been expanded by a factor of 10. The size is 100 mm x 53 mm. The components are hidden.

Articles in this issue

Archives of this issue

view archives of Design007 Magazine - Design007-Sept2020