Numerical analysis and IR scan test for thermal resistance of GaAs MMIC in a communications satellite

Thermal resistance of a 3 GHz power amplifier MMIC has been calculated with finite element (FE) analyses. Through comparative FE analyses it has been found that a carrier for infrared (IR) scan test should have high thermal conductivity if it is for measuring thermal resistance of an MMIC only. IR scan results showed that the FE analysis provided temperature distribution quite close to the real and, also, that IR scans could not measure the maximum channel temperature because of not enough resolution. Consequently it has been proved that the FE method can provide more realistic thermal resistance of an MMIC than IR scan test when the gate length is smaller than IR scanner's resolution as well as when the gate is screened by an airbridge.