I have a mpcb from top to down:

heat source

copper track

0,1mm dielectric polymer (0,2W/mk)

1,5 mm thickness aluminum

the manufacturer says is an equivalent to 2W/mk but  I don't think is a realistic Simulation.

How usually you simulate the MPCB? do you consider every layer ?

the Interface resistance of the polymer is easy to simulate with the relative function, but I cannot put two interface thermal resistance one on top other for the copper track.

How usually you do it?