O.K. it's done!
For easy of comparison I HAVE EXAGGERATED THE TIM LAYER IN THE CALCULATIONS!!! It’s now 0.25 mm instead of 0.025 mm
Contour plot:
- Just for illustrating the isolines from the CPU/die to the cooling medium in a 2-D slice (scale = 10 x 10 mm)
- Don't mind the concentration scale in the contour plot, I haven't calibrated the calculation on a temperature scale here.
x-y plot:
- All three TIM compound have the same results (within 0,1 oC) and plot as one line
So, what you can see in the x-y plot (which is temperature corrected) is that the TIM compound doesn't matter (I’ve tried goop, AS3 and pure copper conductivity), it's the heat flux across the solid/solid boundary that's limiting. I've also done a calculation without TIM layer (direct HS to copper block contact); this improves the delta T with ~10% (-1.1 oC for the CPU/die).
So, my hypothesis right now is that:
1) the exact compound composition doesn’t matter that much
2) ensuring a perfect contact between solid interfaces is the most important aspect of a good TIM
3) even in a perfect fit situation TIM adds ~10% to the deltaT (+1.1 oC on a total of +14 oC)
I’ll try to evaluate the thickness of the TIM layer on the slope later on.
[EDIT] I've applied a fairly low load: 60 watt
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