Texas Instruments Corporation

Allan J Siuzdak

Vishwa N Shukla

Stanley J Lukasiewicz

Robert P Bishop

Paul L Hainey

Robert E Luminello, Jr

A capacitive fluid pressure transducer is shown formed of a monolithic ceramic body (10) having a cavity located between a diaphragm portion (12) and a base portion (14). Opposed capacitor plates (22, 24) are disposed on opposed surfaces of the diaphragm portion and the base portion. The capacitor plates (22, 24) are formed of palladium oxide/silver having a ratio selected to create a fluid pressure level in the cavity as a result of oxygen evolution incident to the reduction of palladium oxide during the sintering cycle to offset the tendency of the diaphragm to bow inwardly due to shrinkage mismatch of the metal and ceramic materials.

Method for making a fluid pressure transducer

A monolithic capacitive pressure transducer (12) is shown composed of ceramic material having a first closed cavity (12) separated from a surface thereof by a flexible wall member and a second closed cavity (16) defined by rigid wall members. Capacitor plates (32, 36; 40, 44) are formed on two opposed surfaces defining each cavity. Vias (33, 37; 41, 45) are formed extending from the capacitor plates to permit electrical connection therewith. The transducer is made by separately forming under pressure a diaphragm (20) and first and second base portions (22, 30) having recesses (24) in the top and bottom surfaces using ceramic powder coated with an organic binder. A metal layer is deposited on the pieces which are then joined together to form a single unit. A spacer (26) may be inserted in the recesses to ensure that a predetermined gap is maintained in each cavity during the joining operation. The parts are then debinderized by heating to a first temperature level to allow the binder organics, as well as the spacer organics if a spacer is employed, to be vaporized and/or decomposed and removed through the open pores of the diaphragm and base. The unit is then brought up to a sintering temperature to change it into a monolithic body and to convert the metallized layer into a conductive layer bonded to the ceramic.

Pressure transducer apparatus with monolithic body of ceramic material

An array of raised lands disposed in columns and rows formed of ceramic material, particularly barium strontium titanate, is formed by making a die of resist material having a negative image pattern of the array on a ceramic substrate and then forming a slurry having a high solid content of the ceramic material, filling the pattern with the slurry and firing the filled die to produce a sintered array of pixels. In a modified embodiment a pressing pad 18 of deformable ceramic tape is formed and pressed into the die after the die has been filled with slurry 16 in order to compact the material and wipe the ceramic material from the sidewalls 12. In another embodiment a ceramic tape of the type used for the pressing pad is pressed into the die and after a short time removed from the die with the pixel array formed in the tape which is then fired to sinter the array. In a modification of this embodiment that portion of the tape extending out of the die beyond the sidewalls 12 can be removed and the die then fired to form a pixel array which is confined essentially to vertical shrinkage upon firing.

Process for forming ceramic pixel array and pixel array formed thereby

The bond of a layer of glass dielectric material applied to metal substrates of the type which are capable of forming solid solutions with copper is enhanced by first coating the substrate with a layer of thick film copper, curing the thick film at a temperature which results in the formation of the solid solution at the interface between the substrate and the thick film copper and then applying the dielectric layer to the thick film copper and curing the dielectric layer. Circuit patterns and components can then be built on the dielectric layer.

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Cumberland, RI, United States of America

Allan J Siuzdak