The electrolytic copper powder oxidized in air at various temperatures is tested to understand the effect of oxidation on the dielectric properties at the microwave frequency for the use in the high frequency semiconductor equipments. The X-ray diffraction for these oxidized copper powders is performed to identify the different oxide phases and its crystal structures. The morphology of the oxidized and pure copper particles has been observed using the scanning electron microscopy. The EDX analysis has been carried out to determine the oxide phases. The different oxide phases present in the oxidized samples are confirmed from Raman spectra analysis. The dielectric properties of these powdered samples are evaluated using the transmission coefficient data measured by the vector network analyzer in the X-band of microwave frequency range. The dielectric constant and the effective conductivity (dielectric loss) are increased with the increase in powder density of pure as well as oxidized copper powders. However, the real part of the complex permittivity and the effective conductivity (dielectric loss) are getting reduced with increasing the volume fraction of oxide phases. The prepared dendrite shaped oxidized electrolytic copper is the unique candidate in the preparation of composite which is used as a heatradiating board of the semiconductor equipment, an electrostatic adsorption device, and a dielectric board of the electrostatic adsorption device. (C) 2015 Elsevier B.V. All rights reserved.