The 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% P.sub.2O.sub.5, 0 2.5% ZrO.sub.2, 24 45% ZnO, 2 10% Al.sub.2O.sub.3, 35 50% SiO.sub.2 and 0.1 3% A.sub.2O 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.