THERMAL-ANALYSIS OF GAAS POWER MONOLITHIC MICROWAVE ICS MOUNTED WITH EPOXY ATTACHMENT

The effect of chip-mounting attachment on the thermal resistance of Ga As power field effect transistor (FET) modules has been experimentally investigated, The thermal resistance was evaluated for different GaAs chip thickness of 150 and 250 mu m through an electrical method utili zing temperature dependence of Schottky-barrier in the GaAs metal semi conductor FET's (MESFET's). The thermal resistance of low-cost epoxy-m ounted GaAs chips, suitable for uniplanar monolithic microwave IC's (M MIC's), was found not to increase even up to a chip thickness of 250 m u m, while that of AuSn-mounted GaAs chips increased as was convention ally expected, Numerical simulation has also been presented for the si milar case of GaAs power MMIC's. The result of simulation suggests tha t lower thermal conductivity of attachment material, such as epoxy att achment, leads to larger optimum chip thickness that minimizes the tot al thermal resistance.