present invention relates to a Cd-free and Pb-free glass composition comprising, based in mol %, 1-10% MO where M is selected from Ba, Sr, Ca and mixtures thereof, 5-30% MgO, 0.3-5% CuO, 0-2.5% P₂O₅, 0-2.5% ZrO₂, 24-45% ZnO, 2-10% Al₂O₃, 35-50% SiO₂ and 0.1-3% A₂O where A is selected from the group of alkali elements and mixtures thereof wherein the glass composition is useful in thick paste dielectric materials which are compatible with AlN substrates.