The complex permittivity of aluminum nitride substrates

A facility for the accurate measurement of the complex permittivity of nonmetallized substrates over waveguide bandwidths has been developed. It has been used to measure the permittivities of aluminum nitride substrate materials manufactured by several different companies. The permittivity values have been found to be significantly different. The measured loss tangents may be acceptable for some applications where a heat-sinking substrate is required. The differences between the loss tangents of the materials manufactured by the different companies indicate that the production process has a significant effect on the loss of the material. The loss tangent of aluminum nitride substrate materials might therefore be reduced by further improvement of the production process.<>