Advanced collector-up (C-up) heterojunction bipolar transistors (HBTs) with the thermal-via configuration (TVC) have been analyzed using a genetic algorithm (GA). Novel packaging structures are presented and evaluated in detail. With careful optimization, the thermal performance can be maximized by improving the thermal resistance over 40%, and the conventional TVC can be further reduced by 35%. The proposed approach is demonstrated on the multifinger InGaP/GaAs C-up HBT, which is attractive as the active component in power amplifiers. A comparison of measured, finite-element-calculated, and GA-extracted results has been made. Consequently, it is shown that the remarkable thermal management can be achieved with a miniature heat-dissipation design, and the thermally stable InGaP/GaAs C-up HBT should be feasible for implementation in intelligent wireless communication systems.