Glass Sealing Rod (Fe54-Ni29-Co17)

Glass Sealing Alloy Rod (Fe54/Ni29/Co17) is an iron-nickel-cobalt alloy equivalent to ASTM F-15 Kovar®, engineered to a coefficient of thermal expansion of 4.81 × 10⁻⁶ K⁻¹ — closely matched to borosilicate and hard glass compositions — enabling the formation of hermetic glass-to-metal seals that remain leak-tight through repeated thermal cycling without generating destructive interfacial stresses. With a melting point of 1450 °C, density of 8.36–8.5 g/cm³, and tensile strength of 510–520 MPa in the annealed condition, it provides the mechanical robustness needed for feedthroughs, connector pins, and structural elements within hermetically sealed assemblies. A Curie temperature of 435 °C means it remains magnetically soft at and above room temperature, a consideration for components in magnetically sensitive systems. Pre-oxidation of the alloy surface to form an adherent iron oxide interlayer is the established mechanism by which a strong, wetting bond to the glass is achieved during the sealing process. Typical applications include vacuum tube and lamp seals, hermetic feedthroughs in electronic and medical device packages, analytical instrument housings, glass-to-metal interfaces in optoelectronic components, and solar thermal receiver tube seals where long-term vacuum integrity is critical.