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Low Distortion Dielectric Overcoat Glasses

IP.com Disclosure Number: IPCOM000082152D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Brownlow, JM: AUTHOR

Abstract

The warp of plate glass (Na(2)O = 16%) under the action of molten dielectric glass occurs above 596 degrees C. Distortion of this type makes otherwise acceptable dielectric glasses, unusable.

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Low Distortion Dielectric Overcoat Glasses

The warp of plate glass (Na(2)O = 16%) under the action of molten dielectric glass occurs above 596 degrees C. Distortion of this type makes otherwise acceptable dielectric glasses, unusable.

The warping of the plate glass is thought to be caused by sodium preferential transport from the plate glass into the dielectric glass, during flowout of the latter. Typically, dielectric glasses contain no alkali. It has been found that warping of the plate glass can be avoided by adding from 2% to 3% Na(2)O to the dielectric glasses, while adjusting the silica and alumina such that other desirable properties prevalent in these glasses are retained. Desirable properties of the dielectric glasses are:
1) Easy removal of bubbles during flowout (610 degrees-620

degrees C).
2) High rigidity at temperatures (490 degrees-500 degrees C)

during subsequent thermal cycling.
3) High moisture resistance and
4) A reasonably close thermal expansion match between the

dielectric glass and the plate glass.

Exemplary of glass compositions to achieve these results are found within the following compositional ranges: % by

Weight.

PbO 55.0-56.0

SiO(2) 15.9-14.5

Al(2)O(3) 4.7- 3.9

B(2)O(3) 14.7-15.9

MgO 2.6- 2.7

Ca(O) 3.8- 3.9

Na(2)O 3.0- 1.8.

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