Abstract:
Although GaAs transistors are broadly used in numerous fields of telecommunication because of their highfrequency capability, the low thermal conductivity of the substrate compared to silicon is critical for many power applications. Especially the unavoidable temperature differences within the gate during pulse operation lead to a time-dependent nonlinear transistor behavior. The degree of this phenomenon strongly depends on thermal boundary conditions like the heat transfer coefficient between die and base plate and other thermal parameters related to assembling techniques. In this paper we demonstrate how a thermal design of a power transistor assembly can be optimized with mutually dependent electrical and thermal properties. We applied a simulation tool (TRESCOM II) developed at our institute especially for the thermal analysis of electronic components and assemblies. The heat transfer coefficient was established by comparing experimentally determined and calculated temperature differences. Uncertainties and limitations of reverse modeling is also discussed.