Thermal deformation model of the submodule of the X-band output power amplifier

The results of 3D modeling in the Comsol Multiphysics software environment and calculation of temperature and thermal deformation fields of GaAs crystals of monolithic integrated circuits (MIS) of microwave amplifiers as part of the submodule of the X-band output power amplifier (VUM) and their contact connections with the substrate in pulse modes of operation with different duty cycles are presented. It is shown that the maximum temperature and thermomechanical stresses in the MIS crystal in the dynamic mode of operation significantly exceed the calculated values for the stationary mode and strongly depend on the pulse duty cycle of the power dissipated by the MIS. Thermomechanical stresses take the maximum value in some narrow region near the boundary of the adhesive connection of the MIS crystal with the mounting plate; this maximum value strongly depends on the temperature coefficient of expansion (TCR) of the adhesive and takes the lowest value when the TCR of the adhesive is equal to the TCR of the GaAs crystal.