Texas Instruments Corporation

Paul L Hainey

Robert P Bishop

Vishwa N Shukla

Stanley J Lukasiewicz

Allan J Siuzdak

Robert E Luminello, Jr

A monolithic capacitive pressure transducer (12, 12') is made by separately forming under pressure a diaphragm (22, 22') and a base (24, 24') having a recess (26) in the top surface using ceramic powder coated with an organic binder. Metal layers are deposited on the two pieces and the pieces are then joined together to form a single unit. A spacer (36) may be inserted in the recess to ensure that a predetermined gap is maintained between the two parts during the joining operation. The parts are then heated 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 and then sintered to change the parts into a monolithic body and to convert the metallized layer into a conductive layer bonded to the ceramic. In one embodiment the metal layers include terminal pads (18b, 19c, 20c) formed on the diaphragm and joinder pads (19b, 20b) formed on the base around terminal receiving bores (34, 32) each in alignment with a terminal pad. In a second embodiment terminal pads (18b', 19d', 20d') are formed on the diaphragm with vias extending radially inwardly from terminal pads (19d', 20d') to respective connecting pads (19c', 20c') which are aligned with joinder pads (19b', 20b') formed on the base. The base has a recessed portion (24b') in its outer wall providing access to terminal pads (18b', 19d', 20d').

Method for making a 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

A monolithic capacitive pressure transducer (12, 12') is made by separately forming under pressure a diaphragm (22, 22') and a base (24, 24') having a recess (14) in the top surface using ceramic powder coated with an organic binder. Metal layers are deposited on the two pieces and the pieces are then joined together to form a single unit. A spacer (36) may be inserted in the recess to ensure that a predetermined gap is maintained between the two parts during the joining operation. The parts are then heated 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 and then sintered to change the parts into a monolithic body and to convert the metallized layer into a conductive layer bonded to the ceramic. In one embodiment the metal layers include terminal pads (18b, 19c, 20c) formed on the diaphragm and joinder pads (19b, 20b) formed on the base around terminal receiving bores (34, 32) each in alignment with a terminal pad. In a second embodiment terminal pads (18b', 19d', 20d') are formed on the diaphragm with vias extending radially inwardly from terminal pads (19d', 20d') to respective connecting pads (19c', 20c') which are aligned with joinder pads (19b', 20b') formed on the base. The base has a recessed portion (24b') in its outer wall providing access to terminal pads (18b', 19d', 20d').

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Douglas, MA, United States of America

Paul L Hainey