The integrated design flow that links simulation, layout, and electromagnetic (EM) analysis is the foundation for modern RF/microwave integrated circuit (IC) design. The inclusion of thermal simulation in this flow is now possible with modern thermal solvers linked into RF/microwave integrated design tools. Silicon germanium (SiGe) heterojunction bipolar transistor (HBT) power amplifier (PA) design is used as an example where such a flow is most beneficial due to numerous issues such as array sizing and thermal runaway. An electrothermal flow is discussed relative to some overall metrics for design flows and that incorporates the availability of an integrated thermal solver into the earliest parts of, and potentially throughout, the entire design flow. The result is a flow that potentially reduces iterations during the design process and boosts design performance by freeing up margin.