You cool things (without TEC) by giving a surface that accepts heat well (either high specific heat capacity, or thermal conductivity), and expanding its effective surface area, while also increasing mass.
Then you ask your marketting folks how to make this feature something to charge more for, and you get stack cooling.
Inq pic
Heat goes from ICs to the normal PCB to the "stack cool" plate, where they can go to air. Given that most of the time there is no cooling at all on these things, you really don't need a lot to make a difference.