Silver diffusion and mechanism of CaO-MgO-SiO2 glass ceramics in millimeter-wave properties

Abstract

Glass ceramics have demonstrated excellent millimeter-wave dielectric properties for low-temperature-co-fired-ceramic (LTCC) devices applied in the 5G communication. This study highlights silver (Ag)-diffusion mechanism and millimeter-wave dielectric properties of CaO-MgO-SiO2 glass ceramics co-fired with Ag electrode near nucleation temperatures. Ag diffusion and elemental inter-diffusion occur during the endothermic-exothermic process near nucleation temperatures (~820 °C), where Ag diffused into the glass-ceramic matrix and resided around the diopside-phase grain boundaries while other metal elements (Zn, Mg, and Al) diffused into the Ag layer. Oxygen ions can flee from the glass-ceramic network above glass transition temperature during the endothermic process and react with the Ag ions to form the Ag-O bonds. The low dielectric dissipation in the millimeter-wave range remains after Ag diffused into the matrix. However, conductivity of Ag-electrode layer decreases at a GHz frequency due to the inter-diffusion elements with lower electric conductivities.