Vishay Barry offers three substrate options on which to build RF power resistors, including beryllium-oxide, aluminum-nitride, and alumina. Beryllium-oxide has the best thermal conductivity of the three with 270 W/m-K and offers the best RF performance due to the low dielectric constant of 6.7. Aluminum-nitride offers the next best thermal conductivity of 170 W/m-K and dielectric constant of 8.8. Alumina, the most economical option, offers good thermal conductivity of 25 W/m-K and a dielectric constant of 9.8, still suitable for high-frequency applications. The choice of substrate is determined by the design parameters, such as size, applied power, and desired frequency response. The substrates can be cut into almost any size and thickness to fit a variety of power levels and customer design requirements.