Hermetic glass-metal compression seal

In a hermetically sealed lead-in structure for an electronic device comprising a glass-metal compression seal which includes a steel outer member having an opening therethrough, a unitary glassy sealing member positioned in the opening in the steel outer member and hermetically sealed to the steel, and a metallic conductor passing through the glassy sealing member and hermetically sealed thereto, wherein the steel outer member is composed of a steel having an average linear coefficient of thermal expansion (30.degree.-300.degree. C.) in the range of about 120-130 .times. 10.sup.-7 /.degree. C. and the metallic conductor is composed of cobalt-nickel-iron alloy having an average linear coefficient of thermal expansion (30.degree.-400.degree. C.) of about 46-52 .times. 10.sup.-7 /.degree. C., the improvement wherein the glassy sealing member is composed of a material selected from the group consisting of:

• (a) a glass having an average linear coefficient of thermal expansion (0.degree.-300.degree. C.) of about 88.5 .times. 10.sup.-7 /.degree. C. and a composition consisting essentially, in parts by weight, of about 63 parts SiO.sub.2, 2.6 parts Al.sub.2 O.sub.3, 14 parts SrO, 5.8 parts Na.sub.2 O, 8.9 parts K.sub.2 O and 3.0 parts B.sub.2 O.sub.3, and
• (b) a mixture having an average linear coefficient of thermal expansion (0.degree.-300.degree. C.) of about 84 .times. 10.sup.-7 /.degree. C. and a composition consisting essentially of 6 parts zircon and 100 parts glass by weight, the glass consisting essentially, in parts by weight, of about 66 parts SiO.sub.2, 12 parts BaO, 2.7 parts Al.sub.2 O.sub.3, 2.0 parts B.sub.2 O.sub.3, 6.7 parts Na.sub.2 O, 6.6 parts K.sub.2 O, 2.0 parts ZrO.sub.2, 0.7 parts Li.sub.2 O and 1.6 parts F.