Abstract: A process for manufacturing a pressure transducer of a pressure sensor is disclosed. Initially, a capacitive pressure transducer is formed by bonding a silicon diaphragm to a glass base such that the transducer produces different capacitances in response to different diaphragm deflections provided in response to sensed pressures. The sensitivity of the capacitive pressure transducer is adjusted by etching the silicon diaphragm while it is bonded to the base substrate in accordance with capacitance values of the transducer which were previously obtained at various predetermined pressures. In this manner, the thickness of the silicon diaphragm is selectively reduced to obtain an accurate desired sensitivity for the transducer and handling of very thin silicon diaphragms prior to their assembly to associated transducer bases is eliminated.

Abstract: The undesired temperature variation of a capacitive pressure sensing element (10) having a positive temperature coefficient of capacitance (TCC) is compensated by a series resistor R and compensating capacitor (C.sub.c) connected in parallel to the pressure sensing capacitor (C.sub.x). The compensating capacitor and presssure sensing element have opposite polarity temperature coefficients of capacitance, and the magnitude of the resistor is selected such that its resistive impedance is nonnegligible and is comparable to the magnitude of the capacitive reactance of the pressure sensing capacitor or compensating capacitor at a predetermined operative frequency of an electrical signal applied to and/or determined by the pressure sensing and compensating capacitors.

Abstract: A technique for metallizing a substrate while providing stress relief for the metallization on the substrate is disclosed. Chrome conductive metallization (22) is deposited on a top surface (21) of an insulating glass substrate (20). An interior gold conductive metallization (23) is deposited on the chrome, and metallization (24) having a substantial nickel composition is deposited on the gold. Subsequently, an additional outer gold metallization (25) is provided on the nickel, and solder is provided on the additional gold metallization. Prior to the application of solder to the outer gold layer 25, the metallization layers are subjected to anodic bonding temperatures and voltage potentials. The gold layer between the nickel and chrome layers diffuses along the grain boundaries of the nickel and chrome layers, thus reducing the ability to transmit stress through these metallizations induced by the solder.

Abstract: A capacitive pressure transducer 10 with an analog output voltage which varies linearly as a function of sensed pressure is provided. A capacitive pressure sensor C.sub.x provides a pressure variable capacitance that determines the frequency of a sensor oscillator 11. The oscillator frequency is combined with a reference frequency by a pair of D-type flip-flops 18 and 19 to provide a resultant signal having a duty cycle related to the sensed pressure. The resultant signal is integrated to provide a first analog signal as an input to a controllable gain amplifier 24 which receives gain control information from a non-linear gain control circuit 40 that receives an analog control signal as an input. The analog control signal varies as a function of sensed pressure in an opposite manner to said first analog signal. Said non-linear circuit provides for non-linearly varying the gain of amplifier 24 as a function of sensed pressure. Preferably the non-linear circuit 40 includes temperature compensating diodes 47.

Abstract: A method of utilizing anodic bonding to bond a conductive semiconductor wafer to a metallized dielectric glass plate so as to form a capacitive pressure sensing element is disclosed. The method includes positioning the semiconductor wafer in contact with the glass plate, heating the wafer and glass plate and applying a substantial positive DC potential to the semiconductor wafer and metallization on the glass plate while applying a negative DC voltage potential to the glass plate. The glass plate metallization forms one capacitor plate of the capacitive pressure sensing element while the semiconductor wafer forms the other capacitor plate.

Abstract: A pressure sensor assembly (10, 10') is disclosed in which a pressure sensing element (11, 11', 11") is protected from external contaminants in an externally-applied pressure (P) to be sensed. This is accomplished by filling an external cavity (36) of a tubular portion (32) of a cover member (30) which fits over the pressure sensing element that has previously been mounted on a metallized substrate (14). The external cavity (36) is totally filled with an incompressibel liquid (35), such as silicon oil, and a thin diaphragm (40), preferably comprising a polyimide film, seals this external cavity and provides a compliant barrier between the externally-applied pressure (P) and the imcompressible fluid (35) and pressure sensing element (11).