A glass-ceramic is provided having a thermal expansion coefficient in a range of 3-6 ppm/.degree. C., a dielectric constant that is less than 5 and a Quality factor Q of at least 400. The glass-ceramic consists essentially of SiO.sub.2 in a range of 45-58 wt %, Al.sub.2O.sub.3 in a range of 10-18 wt % and MgO in a range of 10-25 wt %. A method of making the glass-ceramic is also provided. Further, an electronic package is also provided, including a base member and a glass-ceramic substrate bonded to the base member.