A very useful method of formulating the Total Thermal Resistance of ordinary mesa structure of DDR IMPATT diode oscillators are presented in this paper. Calculation of Total Thermal Resistance of the device along with other components associated with it, maintaining acceptable accuracy is very much important to determine the thermal performance of the oscillator during continuous wave steady state operation. A lumped analytical model of heat transfer in ordinary mesa structure of DDR IMPATT diode on semi-infinite heat sink is developed, from which the entire thermal resistance formulation is done. Calculations of Total thermal resistances associated with different DDR IMPATT diodes with different base materials operating at 94 GHz (W-Band) are included in this paper using the author’s developed formulation for both type-IIA diamond and copper semi-infinite heat sinks separately. Heat Sinks are designed using both type-IIA diamond and copper for all those diodes to operate near 500 K (which is well below the burn-out temperatures of all those base materials) for CW steady state operation. Mathematical expression of temperature inside the heat sink as a function of radius and thickness is developed and using this expression the temperature profiles inside the heat sinks are investigated thoroughly. Results are provided in the form of necessary plots and tables. This formulation will be very useful tool to design Heat sinks for practical IMPATT oscillators
