Thermal rating characteristics of UHF power capacitors

The demands of miniaturization and high reliability of capacitors are interrelated with the characteristic physical parameters of its dielectric, electrode, and termination material constituents. The same parameters determine the thermal design and rating of a capacitor. Equally important, the circuit designer requires well-defined component data on power rating, heat dissipation, temperature, voltage, and current ratings. For the correct choice of components the supply of comprehensive information is expected from the capacitor manufacturer. While the evaluation of components in their real-life mounting and thermal conditions of system environment is beyond the scope of manufacturers´ inspection, valuable information may be gained from the dielectric loss-frequency characteristics of the capacitors. Thermal ratings for both thick- and thin-film dielectric single-and multi-layer capacitors were evaluated using ESR-frequency characteristics and calculated conditions of thermal equilibrium. The methods of evaluation and its results are shown for a number of types of multilayer porcelain capacitors