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Glass To Metal Seals

IP.com Disclosure Number: IPCOM000098437D
Original Publication Date: 1960-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Handen, C: AUTHOR

Abstract

Glass to metal hermetic insulating seals are widely employed to support lead wires which protrude from headers in various electrical devices such as transistors. The failure of one seal permits moisture to enter the device and impair its electrical characteristics. An important cause of seal failure may be attributed to the progressive minute cracks which develop in the glass during handling from stresses occurring at the glass to metal interface of the lead wires. Once such cracks begin, they may continue to propagate until failure of the seal occurs.

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Glass To Metal Seals

Glass to metal hermetic insulating seals are widely employed to support lead wires which protrude from headers in various electrical devices such as transistors. The failure of one seal permits moisture to enter the device and impair its electrical characteristics. An important cause of seal failure may be attributed to the progressive minute cracks which develop in the glass during handling from stresses occurring at the glass to metal interface of the lead wires. Once such cracks begin, they may continue to propagate until failure of the seal occurs.

An improved seal is made by creating a boundary or interface beyond which glass cracks cannot progress. Several discrete layers of glass which are separated from each other by ceramic spacers are employed. A metal header 10 includes a pair of bores 11 which support a pair of leads 12 by compression type seals. Glass washers 13 separated by ceramic spacers 14 support the leads 12 in the bores 11. The metal header 10 may have a coefficient of thermal expansion which is much less than that of the glass washers 13. Various techniques for making compression type seals may be employed to anchor the leads and the glass washers in the bores. The ceramic spacers 14 isolate adjacent glass washers 13 so that if stresses create a crack in one glass washer, the ceramic spacers greatly reduce the likelihood of its propagation to the next washer.

The described crack inhibiting technique is also applicable to...