As fiXtress analyses are performed before PCB layout is done, and real thermal data is not known, this module estimates the board temperature increase due to self-heating, and takes this information to be used during Component Derating Analysis and MTBF prediction.

The module takes into account the exact power dissipation of each component, and estimates the average temperature rise above the coldplate temperature (dT).

An example is presented in the following table:

The PCB coldplate temperature is 71ÖC, dT is 6.4ÖC, generating components temperature of 77.4ÖC.
The tool adds for each component the internal component heat, e.g. Tj=83.4ÖC for U3.

Mini Thermal Analysis

The following picture demonstrates the temperature map from a thermal 3D simulation.
We can see that the results are similar.
We conclude that the Mini thermal analysis serves as a best practice to assess the PCB temperature before PCB layout and component placement.

Why early thermal analysis is important?

Early thermal analysis is the basis for other analyses such as component derating and MTBF, allowing to detect over stressed components before placement.

With the information provided by the Mini-Thermal tool users can, before layout, place hot components in a cooler area and define the proper cooling method and the amount of airflow.

This helps to develop a more realistic and effective cooling system, and to prevent overdesign or overstress.

In this stage design changes are easy and cheap.

Engineers normally use the Mini-Thermal analysis, and after placement, conduct a thermal 3D simulation.

Customers are reporting an accuracy of +/- 3% between the BQR Mini-Thermal analysis and the 3D simulation.