Thermal Via conductivity in Flotherm
 

I am Using Flotherm for simulation of power supplies. I want to use thermal via in PCB to cool D2PAK and other diodes. Please let me know how we calcilate thermal conductivity to key in in Flotherm. Do we use Orthotropic conductivity or normal conductivity. What value generally we key in. I know it will depend on Pitch also. Please anyone clarify the method of calculation.

Are you using the FloEDA window to define the vias?

No, I am still using Flotherm 7.1. So to create thermal via, i just use cuboid and apply all the concerned property.:)

I'd strongly advise you upgrade to 8.1 and use the new FloEDA window that has advanced PCB import and creation capabilities, including the specification of an area of vias (in terms of number+pitch or %coverage). Kx=Ky and Kz are automatically calculated.

If you want to do it manually then it's a question of considering thermal resistances in parallel to calculate an area Kz (FR4 // Cu // PlatingMaterial), Kx and Ky are going to be near FR4 value. If I explain it in any more detail maybe you wouldn't upgrade ;)