Cold-plate Spreading Resistance revisited.
1) Think*
Bill is 90% right indicating h~2w/c.However this should be expressed as h~868w/m2*c for
calculation purposes.
The difference is mostly academic :
Have included the Total Resistance of the Coldplate.
This is obtained via:
Coldplate Resistance(c/w)= Total Resistance(Waterloo) - Contact Resistance
Contact Resistance= 1/(Area x h) , where h is expressed in w/m2*c.
The effect on Die Temperatue :
Kryotherm is used.
Rc is the Coldplate Resistance + 0.0833c/w( TIM resistance for a 11x11mm layer)
* Think I am
wrong in equating h to the heatsink's Thermal Conductance(w/m2*c).
The Film Coefficient(h) is the Thermal
Conductance of the Coldplate's cold surface. This is taken as the [Reciprocal of the sum of Resistances] x Area.
Resistance(to ambient)= PeltierC/W + Heatsink(C/W to ambient) +TIMs(C/W)
Resistance(to ambient) is minimum when Heatsink(C/W to ambient)=0 and TIMs(C/W)=0.
The Film Coefficient(h) is maximum when Resistance(to ambient) is minimum
The Film Coefficient(h) will always be less than the inherent h~868w/m2*c Thermal Conductance of the Peltier.
Kryotherm suggests that
PeltierC/W ~ 0.5(actually 0.420) and hence the Maximum Film Coefficient(h) ~ 868w/m2*c (actually 1033w/m2*c) :
