feedthrough

Definition

(Noun) A connector made by fusing a glass bead to a tubular ferrule and a concentric conductor wire. Ferrule and wire are typically low-expansion alloys such as Kovar, Alloy 42 or Alloy 48. The glass bead is expansion-matched to the alloy used so that temperature cycling will not break the chemical bond between the metal alloy and the glass. Good feedthroughs (FTs) are hermetic, i.e. helium leak-free.