Diffusion-barrier materials for thick-film piezoresistors and sensors formed therewith
First Claim
1. A sensing structure comprising a substrate, at least one electrical-insulating layer on the substrate, an interface layer on the electrical-insulating layer, and a thick-film piezoresistor on the interface layer, the interface layer having a composition comprising particulate alumina and particulate zinc oxide closely divided and suspended in a glass matrix, the interface layer separating the piezoresistor from the electrical-insulating layer and inhibiting diffusion into the piezoresistor of constituents in the electrical-insulating layer.
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Abstract
A thick-film strain-sensing structure for a media-compatible, high-pressure sensor. The strain-sensing structure generally includes a metal diaphragm, at least one electrical-insulating layer on the diaphragm, an interface layer on the electrical-insulating layer, and at least one thick-film piezoresistor on the interface layer for sensing deflection of the diaphragm. The interface layer and the electrical-insulating layers are preferably formed by thick-film processing, as done for the piezoresistors. For compatibility with the metal diaphragm, the electrical-insulating layer has a CTE near that of the diaphragm. The interface layer is formulated to inhibit and control diffusion of the electrical-insulating layers into the piezoresistors. For this purpose, the interface layer is formed from a composition that contains, in addition to a suitable organic media, alumina, zinc oxide, and at least one glass frit mixture comprising lead oxide, a source of boron oxide such as boric acid, silica and alumina. Additional constituents of the interface layer preferably include titania, cupric oxide, manganese carbonate as a source for manganese monoxide, and cobalt carbonate as a source of cobalt oxide.
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Citations
20 Claims
- 1. A sensing structure comprising a substrate, at least one electrical-insulating layer on the substrate, an interface layer on the electrical-insulating layer, and a thick-film piezoresistor on the interface layer, the interface layer having a composition comprising particulate alumina and particulate zinc oxide closely divided and suspended in a glass matrix, the interface layer separating the piezoresistor from the electrical-insulating layer and inhibiting diffusion into the piezoresistor of constituents in the electrical-insulating layer.
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11. A sensing structure of a pressure sensor, the sensing structure comprising:
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a steel alloy diaphragm; at least one dielectric layer on the substrate, the dielectric layer having a composition comprising metal oxides; an interface dielectric layer on and contacting the dielectric layer, the interface dielectric layer comprising particulate alumina and particulate zinc oxide closely divided and suspended in a glass matrix comprising lead oxide, alumina, boron oxide and silica; and a thick-film piezoresistor on the interface dielectric layer for sensing a deflection of the diaphragm; wherein the interface dielectric layer separates the piezoresistor from the dielectric layers and inhibits diffusion into the piezoresistor of constituents in the dielectric layers. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification