Glass-to-metal (GtM) and glass/ceramic-to-metal (GCtM) seals are used to produce hermetic joints in high reliability electrical feedthrough applications. The seals between the insulating glass or glass-ceramic and the connector body (shell) and those between the glass or GC and the electrical contact pins must remain hermetic even under severe thermal cycling and high pressure conditions. Because GtM sealing is performed at high temperatures, the metals being joined can undergo significant metallurgical changes that could affect the properties and performance of the assemblies. The microstructure development at the GtM or GCtM interface will be discussed as well as metallurgical changes taking place within the metallic members of the assemblies. Specific areas of research include 1) Pre-oxidation and GtM sealing of austenitic stainless steels to alkali barium silicate glass, 2) Alloy depletion and phase transformations near the stainless steel surface due to pre-oxidation and GtM sealing, and 3) Phase transformations in precious metal electrical contact pins during GCtM sealing. All of these aspects of GtM sealing presented unique challenges which were addressed by a full suite of materials characterization techniques.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.