PocketPD HW1.3 introduces significant changes in thermal design. In the previous version, the magnets did not attach to the PCB and served only as a mounting mechanism. HW1.3 connects the magnets directly to the back of the PCB using thermal adhesive tape, allowing heat transfer when mounted to a ferromagnetic surface. With a large external thermal mass, PocketPD was able to maintain its internal surface temperature below 70 °C. This is all done through passive cooling. You can check out the detailed test results here.

Note that, even without the heatsink, PocketPD still can maintain an internal temperature below 80° C at 5 A max load without active cooling.