The goal of this work is to present a pulsed-voltage measurement scheme which allows separation of impact-ionization and self-heating effects in the lead-up to device breakdown in high-speed SiGe HBTs, and demonstrate that it enables probing of the dynamic behavior of the operative breakdown mechanisms. By leveraging pulsed-mode measurements, we show an interesting time-dependence of the dominant operative breakdown mechanism. Investigation of the time-dependence of breakdown will facilitate a better understanding of the dynamics of the RF safe operating area (RF-SOA) of SiGe HBTs, which is critical for extracting maximum performance in SiGe for highspeed circuits.