Heat Conduction in Microwave Devices With Orthotropic and Temperature-Dependent Thermal Conductivity

This paper deals with steady-state heat conduction in integrated circuits due to surface heating. Temperature-dependent and orthotropic thermal conductivities are assumed, and an exact formula is obtained for the temperature field in the integrated circuit due to arbitrary surface flux loading. These general results are then specialized to specific forms of surface flux representative of multifingered FETs of arbitrary gate length, gatewidth, and pitch. Numerical results are presented for a representative transistor on a gallium-arsenide substrate and comparisons are made, where possible, to existing approximate solutions, as well as to finite-element results. The examples are chosen to highlight the effects of orthotropy and temperature dependence of thermal conductivity on the junction temperature of devices on integrated circuits