Compositions – Electrically conductive or emissive compositions – Metal compound containing
Patent
1990-08-08
1992-12-29
Lieberman, Paul
Compositions
Electrically conductive or emissive compositions
Metal compound containing
252 629, 501135, 505 1, 505775, C01F 1102, C01F 1700, C01G 3500, C04B 3500
Patent
active
051749262
ABSTRACT:
A piezoresistive pressure transducer employing a sapphire force collector diaphragm having piezoresistive films of silicon epitaxially formed on a major surface thereof, preferably in a Wheatstone bridge pattern. The silicon piezoresistive film is preferably of a thickness of from 1,000 to 60,000 angstroms and is doped with boron in the range of from 5.times.10.sup.17 to 9.times.10.sup.20 atoms/cc. Electrical lead traces and electrical contact pads are also formed on the major surface of the force collector diaphragm. The diaphragm is mounted on a pressure cell base having a cavity in the upper surface thereof, the diaphragm enclosing the cavity so as to form a chamber with the piezoresistive silicon films within said chamber. The diaphragm is hermetically bonded by a ceramic glass to the base in a vacuum such that the chamber provides a vacuum pressure reference. The contact pads are positioned over a matching number of feed through tubes in the pressure cell base and electrical leads are fed through the tubes for carrying electrical signals from the piezoresistive film within the chamber. A pressure cell fitting encloses the upper surface of the pressure cell base including the sapphire diaphragm with a port providing the medium to be pressure monitored to the exposed surface of the sapphire diaphragm. A shell encloses the remainder of the pressure cell thereby insulating it from external shock or pressure. The pressure cell base, fitting and sapphire diaphragm are all of matching thermal expansion characteristics.
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Boyd John
Lieberman Paul
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