7.2. Example 2: Find Available Thermal Margin for Cooling Solution
The module’s thermal solution includes a 50mm x 50mm x 25mm heat sink, no air flow and the device is on a 10-layer board.
From the table in the Variables Affecting the Heat Flow Path topic, we see that the percentage heat transfer to the heat sink is 55%.
To input the cooling solution ΨCA value into the PTC Thermal tab, you perform the following calculation:

In the PTC thermal tab, choose the calculation mode as Find available thermal margin for cooling solution.
Input the ΨCA of 11°C/W and the ambient temperature, T, of 50°C.

This results in a thermal margin of 14.46°C.
This example illustrates that the available cooling solution is adequate for the system and device power. The cooling solution can be redesigned to a smaller/less effective one, if required.