Glass to Metal Seal Small Diameter Tubing

The typical process utilizing tubing in glass to metal seal applications is as follows: First, tubular products made out of these alloys are typically fabricated to specifications via drawing, cutting and reductive machining. Second, electrical conductors or fiberoptic leads are inserted through the center of the tube, and then glass fills in the gaps between the wires or leads and the inside diameter of the tube. Finally, the metal tube portion can be bonded via a variety of means to a metal housing for use in the end product, such as sensors, batteries, reactors, semiconductors and medical devices.

Once the glass cures, a hermetic seal is created---sealing one side of the assembly from any atmospheric intrusion from moisture or gases on the other side. This barrier also enables connectors to pass through vacuum tight portions of an assembly or machine.. Since the glass both bonds well to these tube alloys and expands at a very similar rate as the metal itself, changes in temperature do not compromise the hermetic seal between the glass and the metal tube even as the operating environment rises or falls. These glass to metal tube seals are robust and have long operating lives because glass does not age or degrade whereas organic materials are prone to breakdown in relation to both time and environmental exposure.

Sealing applications rely on glass to metal seal alloys like Nickel 52 (952) or Sealvar (Kovar(R)) to ensure the hermetic barrier remains intact regardless of environmental extremes around the seal.

• Sealvar / Kovar ® has similar a similar coefficient of expansion to hard borosilicate glasses and can be welded, drawn and formed to size in a manner to permit consistent expansion and contraction under various thermal conditions. Applications include assemblies with microwave tubes and select ceramics.
• Alloy 52 has a similar coefficient of expansion to soft glass, and can be welded, drawn and formed to size to allow consistent expansion and contraction as application temperatures change, making it particularly suitable for lighting and sensor applications for nickel alloy 52 small diameter tubing.