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Firing of Glass Substrates Above Their Annealing Point

IP.com Disclosure Number: IPCOM000079890D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Tummala, RR: AUTHOR [+2]

Abstract

A glass substrate 1 begins to flow, bond and conform to the underlying ceramic substrate 2, whenever they are heated above their annealing point. The bonding between ceramic and glass substrates causes the glass plate 1 to camber, due to mismatch in thermal expansion between the glass substrate and the ceramic plate. It is difficult to select ceramic plates that are compatible with glass substrates. This method eliminates cambering of glass plates by eliminating bonding between glass and ceramic plates.

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Firing of Glass Substrates Above Their Annealing Point

A glass substrate 1 begins to flow, bond and conform to the underlying ceramic substrate 2, whenever they are heated above their annealing point. The bonding between ceramic and glass substrates causes the glass plate 1 to camber, due to mismatch in thermal expansion between the glass substrate and the ceramic plate. It is difficult to select ceramic plates that are compatible with glass substrates. This method eliminates cambering of glass plates by eliminating bonding between glass and ceramic plates.

The ceramic plate 2 is prepared first by polishing to about a 0.1 mil flatness. This plate is then coated with a bed of extremely fine particle powder material 3. The glass plate 1 is then placed on the powder bed of inorganic material 3 and fired at temperatures which cause the overlying dielectric 4 to flow. Warping is eliminated under these conditions, because the temperature gradient of the plate is eliminated.

Soda-lime-silica substrates, for example, can be fired flat at temperatures of 620 degrees C (70 degrees C above their annealing point) by depositing a layer of at least 0.5 mil of <1 mu alumina powder particles. The powder material neither sticks to the glass nor to the ceramic and eliminates warping.

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